r360308 - [c++20] Implement P0846R0: allow (ADL-only) calls to template-ids whose

Alex L via cfe-commits cfe-commits at lists.llvm.org
Wed Aug 14 16:43:10 PDT 2019


Thanks for the fix! I'll test it on our code bases as soon as I get a
chance (hopefully we don't have any code that has the V4 regression you
showed).

On Wed, 14 Aug 2019 at 16:08, Richard Smith <richard at metafoo.co.uk> wrote:

> Interesting. This is a pre-existing bug that started showing up more after
> this change. For example, we've always rejected this related example:
>
> typedef __attribute__((__ext_vector_type__(4))) float vector_float4;
> template<typename T> struct xyzw {};
> vector_float4 foo123(vector_float4 &A, vector_float4 &B) {
>   return A.xyzw < B.x && B.y > A.y;
> }
>
> and similarly (and more problematically) we reject this after
> typo-correcting from something valid to something invalid:
>
> typedef __attribute__((__ext_vector_type__(4))) float vector_float4;
> template<typename T> struct xyzv {};
> vector_float4 foo123(vector_float4 &A, vector_float4 &B) {
>   return A.xyzw < B.x && B.y > A.y; // typo-corrected to xyzv and then
> rejected
> }
>
> All that is fixed in r368940. However, that change regresses this:
>
> template<typename T> using V4 = T __attribute__((ext_vector_type(4)));
> void f(V4<int> v) { v.V4<int>::~V4<int>(); }
>
> ... because we no longer look for a template named 'V4' here and instead
> interpret 'V4' as a vector swizzle name. But it's not obvious to me whether
> that's actually wrong; it seems somewhat more consistent to say that we
> behave as if all identifiers are valid "member" names for a vector, but
> some of them might name invalid vector components and thus be ill-formed.
> (Presumably the alternative would be to allow cases such as the above but
> only if V4 is spelled in a way that's not a valid swizzle for the vector,
> which seems like an unfortunate choice for extensibility of the swizzle
> syntax if nothing else.)
>
> The OpenCL/C++ specification doesn't appear to give any hints as to how to
> handle this.
>
> On Tue, 13 Aug 2019 at 19:29, Richard Smith <richard at metafoo.co.uk> wrote:
>
>> On Tue, 13 Aug 2019 at 18:09, Alex L via cfe-commits <
>> cfe-commits at lists.llvm.org> wrote:
>>
>>> Hi Richard,
>>>
>>> Did you get a chance to look at the issue that was reported by Akira?
>>> It's causing a lot of pain on our end.
>>>
>>
>> Sorry, I missed that email. I'll take a look tomorrow.
>>
>>
>>> Thanks,
>>> Alex
>>>
>>>
>>>
>>> On Mon, 8 Jul 2019 at 18:27, Akira Hatanaka via cfe-commits <
>>> cfe-commits at lists.llvm.org> wrote:
>>>
>>>> Hi Richard,
>>>>
>>>> It looks like this patch is causing clang to reject the following code,
>>>> which used to compile fine:
>>>>
>>>> $ cat test.cpp
>>>> typedef __attribute__((__ext_vector_type__(2))) float vector_float2;
>>>>
>>>> bool foo123(vector_float2 &A, vector_float2 &B)
>>>> {
>>>>   return A.x < B.x && B.y > A.y;
>>>> }
>>>>
>>>> On May 8, 2019, at 8:31 PM, Richard Smith via cfe-commits <
>>>> cfe-commits at lists.llvm.org> wrote:
>>>>
>>>> Author: rsmith
>>>> Date: Wed May  8 20:31:27 2019
>>>> New Revision: 360308
>>>>
>>>> URL: http://llvm.org/viewvc/llvm-project?rev=360308&view=rev
>>>> Log:
>>>> [c++20] Implement P0846R0: allow (ADL-only) calls to template-ids whose
>>>> template name is not visible to unqualified lookup.
>>>>
>>>> In order to support this without a severe degradation in our ability to
>>>> diagnose typos in template names, this change significantly restructures
>>>> the way we handle template-id-shaped syntax for which lookup of the
>>>> template name finds nothing.
>>>>
>>>> Instead of eagerly diagnosing an undeclared template name, we now form a
>>>> placeholder template-name representing a name that is known to not find
>>>> any templates. When the parser sees such a name, it attempts to
>>>> disambiguate whether we have a less-than comparison or a template-id.
>>>> Any diagnostics or typo-correction for the name are delayed until its
>>>> point of use.
>>>>
>>>> The upshot should be a small improvement of our diagostic quality
>>>> overall: we now take more syntactic context into account when trying to
>>>> resolve an undeclared identifier on the left hand side of a '<'. In
>>>> fact, this works well enough that the backwards-compatible portion (for
>>>> an undeclared identifier rather than a lookup that finds functions but
>>>> no function templates) is enabled in all language modes.
>>>>
>>>> Added:
>>>>    cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp
>>>> Modified:
>>>>    cfe/trunk/include/clang/AST/ASTContext.h
>>>>    cfe/trunk/include/clang/AST/DeclarationName.h
>>>>    cfe/trunk/include/clang/AST/TemplateName.h
>>>>    cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
>>>>    cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>>    cfe/trunk/include/clang/Basic/TemplateKinds.h
>>>>    cfe/trunk/include/clang/Parse/Parser.h
>>>>    cfe/trunk/include/clang/Sema/Sema.h
>>>>    cfe/trunk/lib/AST/ASTContext.cpp
>>>>    cfe/trunk/lib/AST/ASTImporter.cpp
>>>>    cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
>>>>    cfe/trunk/lib/AST/ItaniumMangle.cpp
>>>>    cfe/trunk/lib/AST/ODRHash.cpp
>>>>    cfe/trunk/lib/AST/TemplateName.cpp
>>>>    cfe/trunk/lib/Parse/ParseDecl.cpp
>>>>    cfe/trunk/lib/Parse/ParseDeclCXX.cpp
>>>>    cfe/trunk/lib/Parse/ParseExprCXX.cpp
>>>>    cfe/trunk/lib/Parse/ParseTemplate.cpp
>>>>    cfe/trunk/lib/Parse/ParseTentative.cpp
>>>>    cfe/trunk/lib/Parse/Parser.cpp
>>>>    cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp
>>>>    cfe/trunk/lib/Sema/SemaDecl.cpp
>>>>    cfe/trunk/lib/Sema/SemaDeclCXX.cpp
>>>>    cfe/trunk/lib/Sema/SemaExpr.cpp
>>>>    cfe/trunk/lib/Sema/SemaExprCXX.cpp
>>>>    cfe/trunk/lib/Sema/SemaOverload.cpp
>>>>    cfe/trunk/lib/Sema/SemaTemplate.cpp
>>>>    cfe/trunk/lib/Serialization/ASTReader.cpp
>>>>    cfe/trunk/lib/Serialization/ASTWriter.cpp
>>>>    cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp
>>>>    cfe/trunk/test/CXX/drs/dr2xx.cpp
>>>>    cfe/trunk/test/CXX/drs/dr6xx.cpp
>>>>    cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp
>>>>    cfe/trunk/test/FixIt/typo-crash.cpp
>>>>    cfe/trunk/test/Misc/diag-template-diffing.cpp
>>>>    cfe/trunk/test/Modules/module-private.cpp
>>>>    cfe/trunk/test/Modules/submodules-merge-defs.cpp
>>>>    cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp
>>>>    cfe/trunk/test/Parser/cxx-template-argument.cpp
>>>>    cfe/trunk/test/Parser/cxx-template-decl.cpp
>>>>    cfe/trunk/test/SemaCXX/alias-template.cpp
>>>>    cfe/trunk/test/SemaCXX/class.cpp
>>>>    cfe/trunk/test/SemaCXX/destructor.cpp
>>>>    cfe/trunk/test/SemaCXX/invalid-member-expr.cpp
>>>>    cfe/trunk/test/SemaCXX/typo-correction.cpp
>>>>    cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp
>>>>    cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp
>>>>    cfe/trunk/test/SemaTemplate/rdar9173693.cpp
>>>>    cfe/trunk/test/SemaTemplate/recovery-crash.cpp
>>>>    cfe/trunk/tools/libclang/CIndex.cpp
>>>>    cfe/trunk/www/cxx_status.html
>>>>
>>>> Modified: cfe/trunk/include/clang/AST/ASTContext.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/ASTContext.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/AST/ASTContext.h (original)
>>>> +++ cfe/trunk/include/clang/AST/ASTContext.h Wed May  8 20:31:27 2019
>>>> @@ -1977,6 +1977,7 @@ public:
>>>>
>>>>   TemplateName getOverloadedTemplateName(UnresolvedSetIterator Begin,
>>>>                                          UnresolvedSetIterator End)
>>>> const;
>>>> +  TemplateName getAssumedTemplateName(DeclarationName Name) const;
>>>>
>>>>   TemplateName getQualifiedTemplateName(NestedNameSpecifier *NNS,
>>>>                                         bool TemplateKeyword,
>>>>
>>>> Modified: cfe/trunk/include/clang/AST/DeclarationName.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/DeclarationName.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/AST/DeclarationName.h (original)
>>>> +++ cfe/trunk/include/clang/AST/DeclarationName.h Wed May  8 20:31:27
>>>> 2019
>>>> @@ -863,4 +863,24 @@ struct DenseMapInfo<clang::DeclarationNa
>>>>
>>>> } // namespace llvm
>>>>
>>>> +// The definition of AssumedTemplateStorage is factored out of
>>>> TemplateName to
>>>> +// resolve a cyclic dependency between it and DeclarationName (via
>>>> Type).
>>>> +namespace clang {
>>>> +
>>>> +/// A structure for storing the information associated with a name
>>>> that has
>>>> +/// been assumed to be a template name (despite finding no
>>>> TemplateDecls).
>>>> +class AssumedTemplateStorage : public UncommonTemplateNameStorage {
>>>> +  friend class ASTContext;
>>>> +
>>>> +  AssumedTemplateStorage(DeclarationName Name)
>>>> +      : UncommonTemplateNameStorage(Assumed, 0), Name(Name) {}
>>>> +  DeclarationName Name;
>>>> +
>>>> +public:
>>>> +  /// Get the name of the template.
>>>> +  DeclarationName getDeclName() const { return Name; }
>>>> +};
>>>> +
>>>> +} // namespace clang
>>>> +
>>>> #endif // LLVM_CLANG_AST_DECLARATIONNAME_H
>>>>
>>>> Modified: cfe/trunk/include/clang/AST/TemplateName.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/TemplateName.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/AST/TemplateName.h (original)
>>>> +++ cfe/trunk/include/clang/AST/TemplateName.h Wed May  8 20:31:27 2019
>>>> @@ -31,6 +31,7 @@ class NamedDecl;
>>>> class NestedNameSpecifier;
>>>> enum OverloadedOperatorKind : int;
>>>> class OverloadedTemplateStorage;
>>>> +class AssumedTemplateStorage;
>>>> class PartialDiagnostic;
>>>> struct PrintingPolicy;
>>>> class QualifiedTemplateName;
>>>> @@ -46,6 +47,7 @@ class UncommonTemplateNameStorage {
>>>> protected:
>>>>   enum Kind {
>>>>     Overloaded,
>>>> +    Assumed, // defined in DeclarationName.h
>>>>     SubstTemplateTemplateParm,
>>>>     SubstTemplateTemplateParmPack
>>>>   };
>>>> @@ -78,6 +80,12 @@ public:
>>>>              : nullptr;
>>>>   }
>>>>
>>>> +  AssumedTemplateStorage *getAsAssumedTemplateName()  {
>>>> +    return Bits.Kind == Assumed
>>>> +             ? reinterpret_cast<AssumedTemplateStorage *>(this)
>>>> +             : nullptr;
>>>> +  }
>>>> +
>>>>   SubstTemplateTemplateParmStorage *getAsSubstTemplateTemplateParm() {
>>>>     return Bits.Kind == SubstTemplateTemplateParm
>>>>              ? reinterpret_cast<SubstTemplateTemplateParmStorage
>>>> *>(this)
>>>> @@ -194,6 +202,10 @@ public:
>>>>     /// A set of overloaded template declarations.
>>>>     OverloadedTemplate,
>>>>
>>>> +    /// An unqualified-id that has been assumed to name a function
>>>> template
>>>> +    /// that will be found by ADL.
>>>> +    AssumedTemplate,
>>>> +
>>>>     /// A qualified template name, where the qualification is kept
>>>>     /// to describe the source code as written.
>>>>     QualifiedTemplate,
>>>> @@ -215,6 +227,7 @@ public:
>>>>   TemplateName() = default;
>>>>   explicit TemplateName(TemplateDecl *Template);
>>>>   explicit TemplateName(OverloadedTemplateStorage *Storage);
>>>> +  explicit TemplateName(AssumedTemplateStorage *Storage);
>>>>   explicit TemplateName(SubstTemplateTemplateParmStorage *Storage);
>>>>   explicit TemplateName(SubstTemplateTemplateParmPackStorage *Storage);
>>>>   explicit TemplateName(QualifiedTemplateName *Qual);
>>>> @@ -236,7 +249,7 @@ public:
>>>>   TemplateDecl *getAsTemplateDecl() const;
>>>>
>>>>   /// Retrieve the underlying, overloaded function template
>>>> -  // declarations that this template name refers to, if known.
>>>> +  /// declarations that this template name refers to, if known.
>>>>   ///
>>>>   /// \returns The set of overloaded function templates that this
>>>> template
>>>>   /// name refers to, if known. If the template name does not refer to a
>>>> @@ -244,6 +257,10 @@ public:
>>>>   /// refers to a single template, returns NULL.
>>>>   OverloadedTemplateStorage *getAsOverloadedTemplate() const;
>>>>
>>>> +  /// Retrieve information on a name that has been assumed to be a
>>>> +  /// template-name in order to permit a call via ADL.
>>>> +  AssumedTemplateStorage *getAsAssumedTemplateName() const;
>>>> +
>>>>   /// Retrieve the substituted template template parameter, if
>>>>   /// known.
>>>>   ///
>>>>
>>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td (original)
>>>> +++ cfe/trunk/include/clang/Basic/DiagnosticParseKinds.td Wed May  8
>>>> 20:31:27 2019
>>>> @@ -744,7 +744,8 @@ def err_typename_refers_to_non_type_temp
>>>> def err_expected_type_name_after_typename : Error<
>>>>   "expected an identifier or template-id after '::'">;
>>>> def err_explicit_spec_non_template : Error<
>>>> -  "explicit %select{specialization|instantiation}0 of non-template %1
>>>> %2">;
>>>> +  "explicit %select{specialization|instantiation}0 of "
>>>> +  "%select{non-|undeclared }3template %1 %2">;
>>>>
>>>> def err_default_template_template_parameter_not_template : Error<
>>>>   "default template argument for a template template parameter must be
>>>> a class "
>>>>
>>>> Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
>>>> +++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Wed May  8
>>>> 20:31:27 2019
>>>> @@ -3963,6 +3963,15 @@ def err_template_member_noparams : Error
>>>> def err_template_tag_noparams : Error<
>>>>   "extraneous 'template<>' in declaration of %0 %1">;
>>>>
>>>> +def warn_cxx17_compat_adl_only_template_id : Warning<
>>>> +  "use of function template name with no prior function template "
>>>> +  "declaration in function call with explicit template arguments "
>>>> +  "is incompatible with C++ standards before C++2a">,
>>>> +  InGroup<CXXPre2aCompat>, DefaultIgnore;
>>>> +def ext_adl_only_template_id : ExtWarn<
>>>> +  "use of function template name with no prior declaration in function
>>>> call "
>>>> +  "with explicit template arguments is a C++2a extension">,
>>>> InGroup<CXX2a>;
>>>> +
>>>> // C++ Template Argument Lists
>>>> def err_template_missing_args : Error<
>>>>   "use of "
>>>>
>>>> Modified: cfe/trunk/include/clang/Basic/TemplateKinds.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/TemplateKinds.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Basic/TemplateKinds.h (original)
>>>> +++ cfe/trunk/include/clang/Basic/TemplateKinds.h Wed May  8 20:31:27
>>>> 2019
>>>> @@ -21,7 +21,8 @@ enum TemplateNameKind {
>>>>   /// The name does not refer to a template.
>>>>   TNK_Non_template = 0,
>>>>   /// The name refers to a function template or a set of overloaded
>>>> -  /// functions that includes at least one function template.
>>>> +  /// functions that includes at least one function template, or (in
>>>> C++20)
>>>> +  /// refers to a set of non-template functions but is followed by a
>>>> '<'.
>>>>   TNK_Function_template,
>>>>   /// The name refers to a template whose specialization produces a
>>>>   /// type. The template itself could be a class template, template
>>>> @@ -42,7 +43,11 @@ enum TemplateNameKind {
>>>>   /// whether the template name is assumed to refer to a type template
>>>> or a
>>>>   /// function template depends on the context in which the template
>>>>   /// name occurs.
>>>> -  TNK_Dependent_template_name
>>>> +  TNK_Dependent_template_name,
>>>> +  /// Lookup for the name failed, but we're assuming it was a template
>>>> name
>>>> +  /// anyway. In C++20, this is mandatory in order to parse ADL-only
>>>> function
>>>> +  /// template specialization calls.
>>>> +  TNK_Undeclared_template,
>>>> };
>>>>
>>>> }
>>>>
>>>> Modified: cfe/trunk/include/clang/Parse/Parser.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Parse/Parser.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Parse/Parser.h (original)
>>>> +++ cfe/trunk/include/clang/Parse/Parser.h Wed May  8 20:31:27 2019
>>>> @@ -2303,13 +2303,18 @@ private:
>>>>   /// Doesn't consume tokens.
>>>>   TPResult
>>>>   isCXXDeclarationSpecifier(TPResult BracedCastResult = TPResult::False,
>>>> -                            bool *HasMissingTypename = nullptr);
>>>> +                            bool *InvalidAsDeclSpec = nullptr);
>>>>
>>>>   /// Given that isCXXDeclarationSpecifier returns \c TPResult::True or
>>>>   /// \c TPResult::Ambiguous, determine whether the decl-specifier
>>>> would be
>>>>   /// a type-specifier other than a cv-qualifier.
>>>>   bool isCXXDeclarationSpecifierAType();
>>>>
>>>> +  /// Determine whether the current token sequence might be
>>>> +  ///   '<' template-argument-list '>'
>>>> +  /// rather than a less-than expression.
>>>> +  TPResult isTemplateArgumentList(unsigned TokensToSkip);
>>>> +
>>>>   /// Determine whether an identifier has been tentatively declared as a
>>>>   /// non-type. Such tentative declarations should not be found to name
>>>> a type
>>>>   /// during a tentative parse, but also should not be annotated as a
>>>> non-type.
>>>> @@ -2994,7 +2999,6 @@ private:
>>>>                                UnqualifiedId &TemplateName,
>>>>                                bool AllowTypeAnnotation = true);
>>>>   void AnnotateTemplateIdTokenAsType(bool IsClassName = false);
>>>> -  bool IsTemplateArgumentList(unsigned Skip = 0);
>>>>   bool ParseTemplateArgumentList(TemplateArgList &TemplateArgs);
>>>>   ParsedTemplateArgument ParseTemplateTemplateArgument();
>>>>   ParsedTemplateArgument ParseTemplateArgument();
>>>>
>>>> Modified: cfe/trunk/include/clang/Sema/Sema.h
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/include/clang/Sema/Sema.h (original)
>>>> +++ cfe/trunk/include/clang/Sema/Sema.h Wed May  8 20:31:27 2019
>>>> @@ -1823,7 +1823,8 @@ public:
>>>>     NC_NestedNameSpecifier,
>>>>     NC_TypeTemplate,
>>>>     NC_VarTemplate,
>>>> -    NC_FunctionTemplate
>>>> +    NC_FunctionTemplate,
>>>> +    NC_UndeclaredTemplate,
>>>>   };
>>>>
>>>>   class NameClassification {
>>>> @@ -1871,6 +1872,12 @@ public:
>>>>       return Result;
>>>>     }
>>>>
>>>> +    static NameClassification UndeclaredTemplate(TemplateName Name) {
>>>> +      NameClassification Result(NC_UndeclaredTemplate);
>>>> +      Result.Template = Name;
>>>> +      return Result;
>>>> +    }
>>>> +
>>>>     NameClassificationKind getKind() const { return Kind; }
>>>>
>>>>     ParsedType getType() const {
>>>> @@ -1885,7 +1892,7 @@ public:
>>>>
>>>>     TemplateName getTemplateName() const {
>>>>       assert(Kind == NC_TypeTemplate || Kind == NC_FunctionTemplate ||
>>>> -             Kind == NC_VarTemplate);
>>>> +             Kind == NC_VarTemplate || Kind == NC_UndeclaredTemplate);
>>>>       return Template;
>>>>     }
>>>>
>>>> @@ -1897,6 +1904,8 @@ public:
>>>>         return TNK_Function_template;
>>>>       case NC_VarTemplate:
>>>>         return TNK_Var_template;
>>>> +      case NC_UndeclaredTemplate:
>>>> +        return TNK_Undeclared_template;
>>>>       default:
>>>>         llvm_unreachable("unsupported name classification.");
>>>>       }
>>>> @@ -6256,7 +6265,8 @@ public:
>>>>                                      bool AllowDependent = true);
>>>>   bool hasAnyAcceptableTemplateNames(LookupResult &R,
>>>>                                      bool AllowFunctionTemplates = true,
>>>> -                                     bool AllowDependent = true);
>>>> +                                     bool AllowDependent = true,
>>>> +                                     bool AllowNonTemplateFunctions =
>>>> false);
>>>>   /// Try to interpret the lookup result D as a template-name.
>>>>   ///
>>>>   /// \param D A declaration found by name lookup.
>>>> @@ -6268,10 +6278,20 @@ public:
>>>>                                    bool AllowFunctionTemplates = true,
>>>>                                    bool AllowDependent = true);
>>>>
>>>> +  enum class AssumedTemplateKind {
>>>> +    /// This is not assumed to be a template name.
>>>> +    None,
>>>> +    /// This is assumed to be a template name because lookup found
>>>> nothing.
>>>> +    FoundNothing,
>>>> +    /// This is assumed to be a template name because lookup found one
>>>> or more
>>>> +    /// functions (but no function templates).
>>>> +    FoundFunctions,
>>>> +  };
>>>>   bool LookupTemplateName(LookupResult &R, Scope *S, CXXScopeSpec &SS,
>>>>                           QualType ObjectType, bool EnteringContext,
>>>>                           bool &MemberOfUnknownSpecialization,
>>>> -                          SourceLocation TemplateKWLoc =
>>>> SourceLocation());
>>>> +                          SourceLocation TemplateKWLoc =
>>>> SourceLocation(),
>>>> +                          AssumedTemplateKind *ATK = nullptr);
>>>>
>>>>   TemplateNameKind isTemplateName(Scope *S,
>>>>                                   CXXScopeSpec &SS,
>>>> @@ -6282,6 +6302,20 @@ public:
>>>>                                   TemplateTy &Template,
>>>>                                   bool &MemberOfUnknownSpecialization);
>>>>
>>>> +  /// Try to resolve an undeclared template name as a type template.
>>>> +  ///
>>>> +  /// Sets II to the identifier corresponding to the template name,
>>>> and updates
>>>> +  /// Name to a corresponding (typo-corrected) type template name and
>>>> TNK to
>>>> +  /// the corresponding kind, if possible.
>>>> +  void ActOnUndeclaredTypeTemplateName(Scope *S, TemplateTy &Name,
>>>> +                                       TemplateNameKind &TNK,
>>>> +                                       SourceLocation NameLoc,
>>>> +                                       IdentifierInfo *&II);
>>>> +
>>>> +  bool resolveAssumedTemplateNameAsType(Scope *S, TemplateName &Name,
>>>> +                                        SourceLocation NameLoc,
>>>> +                                        bool Diagnose = true);
>>>> +
>>>>   /// Determine whether a particular identifier might be the name in a
>>>> C++1z
>>>>   /// deduction-guide declaration.
>>>>   bool isDeductionGuideName(Scope *S, const IdentifierInfo &Name,
>>>> @@ -6391,14 +6425,11 @@ public:
>>>>                               TemplateArgumentListInfo &TemplateArgs);
>>>>
>>>>   TypeResult
>>>> -  ActOnTemplateIdType(CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
>>>> +  ActOnTemplateIdType(Scope *S, CXXScopeSpec &SS, SourceLocation
>>>> TemplateKWLoc,
>>>>                       TemplateTy Template, IdentifierInfo *TemplateII,
>>>> -                      SourceLocation TemplateIILoc,
>>>> -                      SourceLocation LAngleLoc,
>>>> -                      ASTTemplateArgsPtr TemplateArgs,
>>>> -                      SourceLocation RAngleLoc,
>>>> -                      bool IsCtorOrDtorName = false,
>>>> -                      bool IsClassName = false);
>>>> +                      SourceLocation TemplateIILoc, SourceLocation
>>>> LAngleLoc,
>>>> +                      ASTTemplateArgsPtr TemplateArgs, SourceLocation
>>>> RAngleLoc,
>>>> +                      bool IsCtorOrDtorName = false, bool IsClassName
>>>> = false);
>>>>
>>>>   /// Parsed an elaborated-type-specifier that refers to a template-id,
>>>>   /// such as \c class T::template apply<U>.
>>>>
>>>> Modified: cfe/trunk/lib/AST/ASTContext.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTContext.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/ASTContext.cpp (original)
>>>> +++ cfe/trunk/lib/AST/ASTContext.cpp Wed May  8 20:31:27 2019
>>>> @@ -5226,6 +5226,11 @@ ASTContext::getNameForTemplate(TemplateN
>>>>     return DeclarationNameInfo((*Storage->begin())->getDeclName(),
>>>> NameLoc);
>>>>   }
>>>>
>>>> +  case TemplateName::AssumedTemplate: {
>>>> +    AssumedTemplateStorage *Storage = Name.getAsAssumedTemplateName();
>>>> +    return DeclarationNameInfo(Storage->getDeclName(), NameLoc);
>>>> +  }
>>>> +
>>>>   case TemplateName::DependentTemplate: {
>>>>     DependentTemplateName *DTN = Name.getAsDependentTemplateName();
>>>>     DeclarationName DName;
>>>> @@ -5273,7 +5278,8 @@ TemplateName ASTContext::getCanonicalTem
>>>>   }
>>>>
>>>>   case TemplateName::OverloadedTemplate:
>>>> -    llvm_unreachable("cannot canonicalize overloaded template");
>>>> +  case TemplateName::AssumedTemplate:
>>>> +    llvm_unreachable("cannot canonicalize unresolved template");
>>>>
>>>>   case TemplateName::DependentTemplate: {
>>>>     DependentTemplateName *DTN = Name.getAsDependentTemplateName();
>>>> @@ -7620,6 +7626,13 @@ ASTContext::getOverloadedTemplateName(Un
>>>>   return TemplateName(OT);
>>>> }
>>>>
>>>> +/// Retrieve a template name representing an unqualified-id that has
>>>> been
>>>> +/// assumed to name a template for ADL purposes.
>>>> +TemplateName ASTContext::getAssumedTemplateName(DeclarationName Name)
>>>> const {
>>>> +  auto *OT = new (*this) AssumedTemplateStorage(Name);
>>>> +  return TemplateName(OT);
>>>> +}
>>>> +
>>>> /// Retrieve the template name that represents a qualified
>>>> /// template name such as \c std::vector.
>>>> TemplateName
>>>>
>>>> Modified: cfe/trunk/lib/AST/ASTImporter.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTImporter.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/ASTImporter.cpp (original)
>>>> +++ cfe/trunk/lib/AST/ASTImporter.cpp Wed May  8 20:31:27 2019
>>>> @@ -8126,6 +8126,14 @@ Expected<TemplateName> ASTImporter::Impo
>>>>                                                ToTemplates.end());
>>>>   }
>>>>
>>>> +  case TemplateName::AssumedTemplate: {
>>>> +    AssumedTemplateStorage *FromStorage =
>>>> From.getAsAssumedTemplateName();
>>>> +    auto DeclNameOrErr = Import_New(FromStorage->getDeclName());
>>>> +    if (!DeclNameOrErr)
>>>> +      return DeclNameOrErr.takeError();
>>>> +    return ToContext.getAssumedTemplateName(*DeclNameOrErr);
>>>> +  }
>>>> +
>>>>   case TemplateName::QualifiedTemplate: {
>>>>     QualifiedTemplateName *QTN = From.getAsQualifiedTemplateName();
>>>>     auto QualifierOrErr = Import_New(QTN->getQualifier());
>>>>
>>>> Modified: cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp (original)
>>>> +++ cfe/trunk/lib/AST/ASTStructuralEquivalence.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -180,6 +180,12 @@ static bool IsStructurallyEquivalent(Str
>>>>     return I1 == E1 && I2 == E2;
>>>>   }
>>>>
>>>> +  case TemplateName::AssumedTemplate: {
>>>> +    AssumedTemplateStorage *TN1 = N1.getAsAssumedTemplateName(),
>>>> +                           *TN2 = N1.getAsAssumedTemplateName();
>>>> +    return TN1->getDeclName() == TN2->getDeclName();
>>>> +  }
>>>> +
>>>>   case TemplateName::QualifiedTemplate: {
>>>>     QualifiedTemplateName *QN1 = N1.getAsQualifiedTemplateName(),
>>>>                           *QN2 = N2.getAsQualifiedTemplateName();
>>>>
>>>> Modified: cfe/trunk/lib/AST/ItaniumMangle.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ItaniumMangle.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/ItaniumMangle.cpp (original)
>>>> +++ cfe/trunk/lib/AST/ItaniumMangle.cpp Wed May  8 20:31:27 2019
>>>> @@ -1891,6 +1891,7 @@ void CXXNameMangler::mangleType(Template
>>>>     break;
>>>>
>>>>   case TemplateName::OverloadedTemplate:
>>>> +  case TemplateName::AssumedTemplate:
>>>>     llvm_unreachable("can't mangle an overloaded template name as a
>>>> <type>");
>>>>
>>>>   case TemplateName::DependentTemplate: {
>>>> @@ -2030,6 +2031,7 @@ bool CXXNameMangler::mangleUnresolvedTyp
>>>>     }
>>>>
>>>>     case TemplateName::OverloadedTemplate:
>>>> +    case TemplateName::AssumedTemplate:
>>>>     case TemplateName::DependentTemplate:
>>>>       llvm_unreachable("invalid base for a template specialization
>>>> type");
>>>>
>>>>
>>>> Modified: cfe/trunk/lib/AST/ODRHash.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ODRHash.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/ODRHash.cpp (original)
>>>> +++ cfe/trunk/lib/AST/ODRHash.cpp Wed May  8 20:31:27 2019
>>>> @@ -140,6 +140,7 @@ void ODRHash::AddTemplateName(TemplateNa
>>>>     break;
>>>>   // TODO: Support these cases.
>>>>   case TemplateName::OverloadedTemplate:
>>>> +  case TemplateName::AssumedTemplate:
>>>>   case TemplateName::QualifiedTemplate:
>>>>   case TemplateName::DependentTemplate:
>>>>   case TemplateName::SubstTemplateTemplateParm:
>>>>
>>>> Modified: cfe/trunk/lib/AST/TemplateName.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/TemplateName.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/AST/TemplateName.cpp (original)
>>>> +++ cfe/trunk/lib/AST/TemplateName.cpp Wed May  8 20:31:27 2019
>>>> @@ -66,6 +66,8 @@ TemplateName::TemplateName(void *Ptr) {
>>>> TemplateName::TemplateName(TemplateDecl *Template) : Storage(Template)
>>>> {}
>>>> TemplateName::TemplateName(OverloadedTemplateStorage *Storage)
>>>>     : Storage(Storage) {}
>>>> +TemplateName::TemplateName(AssumedTemplateStorage *Storage)
>>>> +    : Storage(Storage) {}
>>>> TemplateName::TemplateName(SubstTemplateTemplateParmStorage *Storage)
>>>>     : Storage(Storage) {}
>>>> TemplateName::TemplateName(SubstTemplateTemplateParmPackStorage
>>>> *Storage)
>>>> @@ -87,6 +89,8 @@ TemplateName::NameKind TemplateName::get
>>>>     = Storage.get<UncommonTemplateNameStorage*>();
>>>>   if (uncommon->getAsOverloadedStorage())
>>>>     return OverloadedTemplate;
>>>> +  if (uncommon->getAsAssumedTemplateName())
>>>> +    return AssumedTemplate;
>>>>   if (uncommon->getAsSubstTemplateTemplateParm())
>>>>     return SubstTemplateTemplateParm;
>>>>   return SubstTemplateTemplateParmPack;
>>>> @@ -113,6 +117,14 @@ OverloadedTemplateStorage *TemplateName:
>>>>   return nullptr;
>>>> }
>>>>
>>>> +AssumedTemplateStorage *TemplateName::getAsAssumedTemplateName() const
>>>> {
>>>> +  if (UncommonTemplateNameStorage *Uncommon =
>>>> +          Storage.dyn_cast<UncommonTemplateNameStorage *>())
>>>> +    return Uncommon->getAsAssumedTemplateName();
>>>> +
>>>> +  return nullptr;
>>>> +}
>>>> +
>>>> SubstTemplateTemplateParmStorage *
>>>> TemplateName::getAsSubstTemplateTemplateParm() const {
>>>>   if (UncommonTemplateNameStorage *uncommon =
>>>> @@ -230,7 +242,9 @@ TemplateName::print(raw_ostream &OS, con
>>>>   } else if (SubstTemplateTemplateParmPackStorage *SubstPack
>>>>                                         =
>>>> getAsSubstTemplateTemplateParmPack())
>>>>     OS << *SubstPack->getParameterPack();
>>>> -  else {
>>>> +  else if (AssumedTemplateStorage *Assumed =
>>>> getAsAssumedTemplateName()) {
>>>> +    Assumed->getDeclName().print(OS, Policy);
>>>> +  } else {
>>>>     OverloadedTemplateStorage *OTS = getAsOverloadedTemplate();
>>>>     (*OTS->begin())->printName(OS);
>>>>   }
>>>>
>>>> Modified: cfe/trunk/lib/Parse/ParseDecl.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseDecl.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/ParseDecl.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/ParseDecl.cpp Wed May  8 20:31:27 2019
>>>> @@ -2916,6 +2916,7 @@ Parser::DiagnoseMissingSemiAfterTagDefin
>>>>       case Sema::NC_Expression:
>>>>       case Sema::NC_VarTemplate:
>>>>       case Sema::NC_FunctionTemplate:
>>>> +      case Sema::NC_UndeclaredTemplate:
>>>>         // Might be a redeclaration of a prior entity.
>>>>         break;
>>>>       }
>>>> @@ -3386,7 +3387,8 @@ void Parser::ParseDeclarationSpecifiers(
>>>>       // type-name
>>>>     case tok::annot_template_id: {
>>>>       TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
>>>> -      if (TemplateId->Kind != TNK_Type_template) {
>>>> +      if (TemplateId->Kind != TNK_Type_template &&
>>>> +          TemplateId->Kind != TNK_Undeclared_template) {
>>>>         // This template-id does not refer to a type name, so we're
>>>>         // done with the type-specifiers.
>>>>         goto DoneWithDeclSpec;
>>>>
>>>> Modified: cfe/trunk/lib/Parse/ParseDeclCXX.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseDeclCXX.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/ParseDeclCXX.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/ParseDeclCXX.cpp Wed May  8 20:31:27 2019
>>>> @@ -597,10 +597,11 @@ bool Parser::ParseUsingDeclarator(Declar
>>>>
>>>>   // Parse nested-name-specifier.
>>>>   IdentifierInfo *LastII = nullptr;
>>>> -  ParseOptionalCXXScopeSpecifier(D.SS, nullptr,
>>>> /*EnteringContext=*/false,
>>>> -                                 /*MayBePseudoDtor=*/nullptr,
>>>> -                                 /*IsTypename=*/false,
>>>> -                                 /*LastII=*/&LastII);
>>>> +  if (ParseOptionalCXXScopeSpecifier(D.SS, nullptr,
>>>> /*EnteringContext=*/false,
>>>> +                                     /*MayBePseudoDtor=*/nullptr,
>>>> +                                     /*IsTypename=*/false,
>>>> +                                     /*LastII=*/&LastII))
>>>> +    return true;
>>>>   if (D.SS.isInvalid())
>>>>     return true;
>>>>
>>>> @@ -1111,7 +1112,8 @@ TypeResult Parser::ParseBaseTypeSpecifie
>>>>
>>>>   // Parse optional nested-name-specifier
>>>>   CXXScopeSpec SS;
>>>> -  ParseOptionalCXXScopeSpecifier(SS, nullptr,
>>>> /*EnteringContext=*/false);
>>>> +  if (ParseOptionalCXXScopeSpecifier(SS, nullptr,
>>>> /*EnteringContext=*/false))
>>>> +    return true;
>>>>
>>>>   BaseLoc = Tok.getLocation();
>>>>
>>>> @@ -1135,7 +1137,8 @@ TypeResult Parser::ParseBaseTypeSpecifie
>>>>   if (Tok.is(tok::annot_template_id)) {
>>>>     TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
>>>>     if (TemplateId->Kind == TNK_Type_template ||
>>>> -        TemplateId->Kind == TNK_Dependent_template_name) {
>>>> +        TemplateId->Kind == TNK_Dependent_template_name ||
>>>> +        TemplateId->Kind == TNK_Undeclared_template) {
>>>>       AnnotateTemplateIdTokenAsType(/*IsClassName*/true);
>>>>
>>>>       assert(Tok.is(tok::annot_typename) && "template-id -> type
>>>> failed");
>>>> @@ -1554,6 +1557,36 @@ void Parser::ParseClassSpecifier(tok::To
>>>>
>>>>   TemplateParameterLists *TemplateParams = TemplateInfo.TemplateParams;
>>>>
>>>> +  auto RecoverFromUndeclaredTemplateName = [&](IdentifierInfo *Name,
>>>> +                                               SourceLocation NameLoc,
>>>> +                                               SourceRange
>>>> TemplateArgRange,
>>>> +                                               bool KnownUndeclared) {
>>>> +    Diag(NameLoc, diag::err_explicit_spec_non_template)
>>>> +        << (TemplateInfo.Kind ==
>>>> ParsedTemplateInfo::ExplicitInstantiation)
>>>> +        << TagTokKind << Name << TemplateArgRange << KnownUndeclared;
>>>> +
>>>> +    // Strip off the last template parameter list if it was empty,
>>>> since
>>>> +    // we've removed its template argument list.
>>>> +    if (TemplateParams && TemplateInfo.LastParameterListWasEmpty) {
>>>> +      if (TemplateParams->size() > 1) {
>>>> +        TemplateParams->pop_back();
>>>> +      } else {
>>>> +        TemplateParams = nullptr;
>>>> +        const_cast<ParsedTemplateInfo &>(TemplateInfo).Kind =
>>>> +            ParsedTemplateInfo::NonTemplate;
>>>> +      }
>>>> +    } else if (TemplateInfo.Kind ==
>>>> ParsedTemplateInfo::ExplicitInstantiation) {
>>>> +      // Pretend this is just a forward declaration.
>>>> +      TemplateParams = nullptr;
>>>> +      const_cast<ParsedTemplateInfo &>(TemplateInfo).Kind =
>>>> +          ParsedTemplateInfo::NonTemplate;
>>>> +      const_cast<ParsedTemplateInfo &>(TemplateInfo).TemplateLoc =
>>>> +          SourceLocation();
>>>> +      const_cast<ParsedTemplateInfo &>(TemplateInfo).ExternLoc =
>>>> +          SourceLocation();
>>>> +    }
>>>> +  };
>>>> +
>>>>   // Parse the (optional) class name or simple-template-id.
>>>>   IdentifierInfo *Name = nullptr;
>>>>   SourceLocation NameLoc;
>>>> @@ -1574,38 +1607,26 @@ void Parser::ParseClassSpecifier(tok::To
>>>>         // try to give any location information for the list.
>>>>         LAngleLoc = RAngleLoc = SourceLocation();
>>>>       }
>>>> -
>>>> -      Diag(NameLoc, diag::err_explicit_spec_non_template)
>>>> -          << (TemplateInfo.Kind ==
>>>> ParsedTemplateInfo::ExplicitInstantiation)
>>>> -          << TagTokKind << Name << SourceRange(LAngleLoc, RAngleLoc);
>>>> -
>>>> -      // Strip off the last template parameter list if it was empty,
>>>> since
>>>> -      // we've removed its template argument list.
>>>> -      if (TemplateParams && TemplateInfo.LastParameterListWasEmpty) {
>>>> -        if (TemplateParams->size() > 1) {
>>>> -          TemplateParams->pop_back();
>>>> -        } else {
>>>> -          TemplateParams = nullptr;
>>>> -          const_cast<ParsedTemplateInfo&>(TemplateInfo).Kind
>>>> -            = ParsedTemplateInfo::NonTemplate;
>>>> -        }
>>>> -      } else if (TemplateInfo.Kind
>>>> -                                ==
>>>> ParsedTemplateInfo::ExplicitInstantiation) {
>>>> -        // Pretend this is just a forward declaration.
>>>> -        TemplateParams = nullptr;
>>>> -        const_cast<ParsedTemplateInfo&>(TemplateInfo).Kind
>>>> -          = ParsedTemplateInfo::NonTemplate;
>>>> -        const_cast<ParsedTemplateInfo&>(TemplateInfo).TemplateLoc
>>>> -          = SourceLocation();
>>>> -        const_cast<ParsedTemplateInfo&>(TemplateInfo).ExternLoc
>>>> -          = SourceLocation();
>>>> -      }
>>>> +      RecoverFromUndeclaredTemplateName(
>>>> +          Name, NameLoc, SourceRange(LAngleLoc, RAngleLoc), false);
>>>>     }
>>>>   } else if (Tok.is(tok::annot_template_id)) {
>>>>     TemplateId = takeTemplateIdAnnotation(Tok);
>>>>     NameLoc = ConsumeAnnotationToken();
>>>>
>>>> -    if (TemplateId->Kind != TNK_Type_template &&
>>>> +    if (TemplateId->Kind == TNK_Undeclared_template) {
>>>> +      // Try to resolve the template name to a type template.
>>>> +      Actions.ActOnUndeclaredTypeTemplateName(getCurScope(),
>>>> TemplateId->Template,
>>>> +                                              TemplateId->Kind,
>>>> NameLoc, Name);
>>>> +      if (TemplateId->Kind == TNK_Undeclared_template) {
>>>> +        RecoverFromUndeclaredTemplateName(
>>>> +            Name, NameLoc,
>>>> +            SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc),
>>>> true);
>>>> +        TemplateId = nullptr;
>>>> +      }
>>>> +    }
>>>> +
>>>> +    if (TemplateId && TemplateId->Kind != TNK_Type_template &&
>>>>         TemplateId->Kind != TNK_Dependent_template_name) {
>>>>       // The template-name in the simple-template-id refers to
>>>>       // something other than a class template. Give an appropriate
>>>> @@ -1616,7 +1637,7 @@ void Parser::ParseClassSpecifier(tok::To
>>>>
>>>>       // FIXME: Name may be null here.
>>>>       Diag(TemplateId->LAngleLoc,
>>>> diag::err_template_spec_syntax_non_template)
>>>> -        << TemplateId->Name << static_cast<int>(TemplateId->Kind) <<
>>>> Range;
>>>> +          << TemplateId->Name << static_cast<int>(TemplateId->Kind) <<
>>>> Range;
>>>>
>>>>       DS.SetTypeSpecError();
>>>>       SkipUntil(tok::semi, StopBeforeMatch);
>>>> @@ -3451,7 +3472,8 @@ void Parser::ParseConstructorInitializer
>>>> MemInitResult Parser::ParseMemInitializer(Decl *ConstructorDecl) {
>>>>   // parse '::'[opt] nested-name-specifier[opt]
>>>>   CXXScopeSpec SS;
>>>> -  ParseOptionalCXXScopeSpecifier(SS, nullptr,
>>>> /*EnteringContext=*/false);
>>>> +  if (ParseOptionalCXXScopeSpecifier(SS, nullptr,
>>>> /*EnteringContext=*/false))
>>>> +    return true;
>>>>
>>>>   // : identifier
>>>>   IdentifierInfo *II = nullptr;
>>>> @@ -3477,11 +3499,14 @@ MemInitResult Parser::ParseMemInitialize
>>>>                                            ?
>>>> takeTemplateIdAnnotation(Tok)
>>>>                                            : nullptr;
>>>>     if (TemplateId && (TemplateId->Kind == TNK_Type_template ||
>>>> -                       TemplateId->Kind ==
>>>> TNK_Dependent_template_name)) {
>>>> +                       TemplateId->Kind == TNK_Dependent_template_name
>>>> ||
>>>> +                       TemplateId->Kind == TNK_Undeclared_template)) {
>>>>       AnnotateTemplateIdTokenAsType(/*IsClassName*/true);
>>>>       assert(Tok.is(tok::annot_typename) && "template-id -> type
>>>> failed");
>>>>       TemplateTypeTy = getTypeAnnotation(Tok);
>>>>       ConsumeAnnotationToken();
>>>> +      if (!TemplateTypeTy)
>>>> +        return true;
>>>>     } else {
>>>>       Diag(Tok, diag::err_expected_member_or_base_name);
>>>>       return true;
>>>>
>>>> Modified: cfe/trunk/lib/Parse/ParseExprCXX.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseExprCXX.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/ParseExprCXX.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/ParseExprCXX.cpp Wed May  8 20:31:27 2019
>>>> @@ -487,6 +487,14 @@ bool Parser::ParseOptionalCXXScopeSpecif
>>>>                                                         EnteringContext,
>>>>                                                         Template,
>>>>                                               MemberOfUnknownSpecialization))
>>>> {
>>>> +        // If lookup didn't find anything, we treat the name as a
>>>> template-name
>>>> +        // anyway. C++20 requires this, and in prior language modes it
>>>> improves
>>>> +        // error recovery. But before we commit to this, check that we
>>>> actually
>>>> +        // have something that looks like a template-argument-list
>>>> next.
>>>> +        if (!IsTypename && TNK == TNK_Undeclared_template &&
>>>> +            isTemplateArgumentList(1) == TPResult::False)
>>>> +          break;
>>>> +
>>>>         // We have found a template name, so annotate this token
>>>>         // with a template-id annotation. We do not permit the
>>>>         // template-id to be translated into a type annotation,
>>>> @@ -501,7 +509,7 @@ bool Parser::ParseOptionalCXXScopeSpecif
>>>>       }
>>>>
>>>>       if (MemberOfUnknownSpecialization && (ObjectType || SS.isSet()) &&
>>>> -          (IsTypename || IsTemplateArgumentList(1))) {
>>>> +          (IsTypename || isTemplateArgumentList(1) == TPResult::True))
>>>> {
>>>>         // We have something like t::getAs<T>, where getAs is a
>>>>         // member of an unknown specialization. However, this will only
>>>>         // parse correctly as a template, so suggest the keyword
>>>> 'template'
>>>> @@ -2138,9 +2146,15 @@ bool Parser::ParseUnqualifiedIdTemplateI
>>>>                                    TemplateKWLoc.isValid(), Id,
>>>>                                    ObjectType, EnteringContext,
>>>> Template,
>>>>                                    MemberOfUnknownSpecialization);
>>>> +      // If lookup found nothing but we're assuming that this is a
>>>> template
>>>> +      // name, double-check that makes sense syntactically before
>>>> committing
>>>> +      // to it.
>>>> +      if (TNK == TNK_Undeclared_template &&
>>>> +          isTemplateArgumentList(0) == TPResult::False)
>>>> +        return false;
>>>>
>>>>       if (TNK == TNK_Non_template && MemberOfUnknownSpecialization &&
>>>> -          ObjectType && IsTemplateArgumentList()) {
>>>> +          ObjectType && isTemplateArgumentList(0) == TPResult::True) {
>>>>         // We have something like t->getAs<T>(), where getAs is a
>>>>         // member of an unknown specialization. However, this will only
>>>>         // parse correctly as a template, so suggest the keyword
>>>> 'template'
>>>> @@ -2244,11 +2258,9 @@ bool Parser::ParseUnqualifiedIdTemplateI
>>>>   ASTTemplateArgsPtr TemplateArgsPtr(TemplateArgs);
>>>>
>>>>   // Constructor and destructor names.
>>>> -  TypeResult Type
>>>> -    = Actions.ActOnTemplateIdType(SS, TemplateKWLoc,
>>>> -                                  Template, Name, NameLoc,
>>>> -                                  LAngleLoc, TemplateArgsPtr,
>>>> RAngleLoc,
>>>> -                                  /*IsCtorOrDtorName=*/true);
>>>> +  TypeResult Type = Actions.ActOnTemplateIdType(
>>>> +      getCurScope(), SS, TemplateKWLoc, Template, Name, NameLoc,
>>>> LAngleLoc,
>>>> +      TemplateArgsPtr, RAngleLoc, /*IsCtorOrDtorName=*/true);
>>>>   if (Type.isInvalid())
>>>>     return true;
>>>>
>>>>
>>>> Modified: cfe/trunk/lib/Parse/ParseTemplate.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseTemplate.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/ParseTemplate.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/ParseTemplate.cpp Wed May  8 20:31:27 2019
>>>> @@ -1031,6 +1031,8 @@ bool Parser::AnnotateTemplateIdToken(Tem
>>>>     // If we failed to parse the template ID but skipped ahead to a >,
>>>> we're not
>>>>     // going to be able to form a token annotation.  Eat the '>' if
>>>> present.
>>>>     TryConsumeToken(tok::greater);
>>>> +    // FIXME: Annotate the token stream so we don't produce the same
>>>> errors
>>>> +    // again if we're doing this annotation as part of a tentative
>>>> parse.
>>>>     return true;
>>>>   }
>>>>
>>>> @@ -1039,13 +1041,15 @@ bool Parser::AnnotateTemplateIdToken(Tem
>>>>   // Build the annotation token.
>>>>   if (TNK == TNK_Type_template && AllowTypeAnnotation) {
>>>>     TypeResult Type = Actions.ActOnTemplateIdType(
>>>> -        SS, TemplateKWLoc, Template, TemplateName.Identifier,
>>>> +        getCurScope(), SS, TemplateKWLoc, Template,
>>>> TemplateName.Identifier,
>>>>         TemplateNameLoc, LAngleLoc, TemplateArgsPtr, RAngleLoc);
>>>>     if (Type.isInvalid()) {
>>>>       // If we failed to parse the template ID but skipped ahead to a
>>>> >, we're
>>>>       // not going to be able to form a token annotation.  Eat the '>'
>>>> if
>>>>       // present.
>>>>       TryConsumeToken(tok::greater);
>>>> +      // FIXME: Annotate the token stream so we don't produce the same
>>>> errors
>>>> +      // again if we're doing this annotation as part of a tentative
>>>> parse.
>>>>       return true;
>>>>     }
>>>>
>>>> @@ -1108,14 +1112,16 @@ void Parser::AnnotateTemplateIdTokenAsTy
>>>>
>>>>   TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
>>>>   assert((TemplateId->Kind == TNK_Type_template ||
>>>> -          TemplateId->Kind == TNK_Dependent_template_name) &&
>>>> +          TemplateId->Kind == TNK_Dependent_template_name ||
>>>> +          TemplateId->Kind == TNK_Undeclared_template) &&
>>>>          "Only works for type and dependent templates");
>>>>
>>>>   ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
>>>>                                      TemplateId->NumArgs);
>>>>
>>>>   TypeResult Type
>>>> -    = Actions.ActOnTemplateIdType(TemplateId->SS,
>>>> +    = Actions.ActOnTemplateIdType(getCurScope(),
>>>> +                                  TemplateId->SS,
>>>>                                   TemplateId->TemplateKWLoc,
>>>>                                   TemplateId->Template,
>>>>                                   TemplateId->Name,
>>>> @@ -1272,36 +1278,6 @@ ParsedTemplateArgument Parser::ParseTemp
>>>>                                 ExprArg.get(), Loc);
>>>> }
>>>>
>>>> -/// Determine whether the current tokens can only be parsed as a
>>>> -/// template argument list (starting with the '<') and never as a '<'
>>>> -/// expression.
>>>> -bool Parser::IsTemplateArgumentList(unsigned Skip) {
>>>> -  struct AlwaysRevertAction : TentativeParsingAction {
>>>> -    AlwaysRevertAction(Parser &P) : TentativeParsingAction(P) { }
>>>> -    ~AlwaysRevertAction() { Revert(); }
>>>> -  } Tentative(*this);
>>>> -
>>>> -  while (Skip) {
>>>> -    ConsumeAnyToken();
>>>> -    --Skip;
>>>> -  }
>>>> -
>>>> -  // '<'
>>>> -  if (!TryConsumeToken(tok::less))
>>>> -    return false;
>>>> -
>>>> -  // An empty template argument list.
>>>> -  if (Tok.is(tok::greater))
>>>> -    return true;
>>>> -
>>>> -  // See whether we have declaration specifiers, which indicate a type.
>>>> -  while (isCXXDeclarationSpecifier() == TPResult::True)
>>>> -    ConsumeAnyToken();
>>>> -
>>>> -  // If we have a '>' or a ',' then this is a template argument list.
>>>> -  return Tok.isOneOf(tok::greater, tok::comma);
>>>> -}
>>>> -
>>>> /// ParseTemplateArgumentList - Parse a C++ template-argument-list
>>>> /// (C++ [temp.names]). Returns true if there was an error.
>>>> ///
>>>>
>>>> Modified: cfe/trunk/lib/Parse/ParseTentative.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseTentative.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/ParseTentative.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/ParseTentative.cpp Wed May  8 20:31:27 2019
>>>> @@ -1178,12 +1178,17 @@ public:
>>>> /// be either a decl-specifier or a function-style cast, and
>>>> TPResult::Error
>>>> /// if a parsing error was found and reported.
>>>> ///
>>>> -/// If HasMissingTypename is provided, a name with a dependent scope
>>>> specifier
>>>> -/// will be treated as ambiguous if the 'typename' keyword is missing.
>>>> If this
>>>> -/// happens, *HasMissingTypename will be set to 'true'. This will also
>>>> be used
>>>> -/// as an indicator that undeclared identifiers (which will trigger a
>>>> later
>>>> -/// parse error) should be treated as types. Returns
>>>> TPResult::Ambiguous in
>>>> -/// such cases.
>>>> +/// If InvalidAsDeclSpec is not null, some cases that would be
>>>> ill-formed as
>>>> +/// declaration specifiers but possibly valid as some other kind of
>>>> construct
>>>> +/// return TPResult::Ambiguous instead of TPResult::False. When this
>>>> happens,
>>>> +/// the intent is to keep trying to disambiguate, on the basis that we
>>>> might
>>>> +/// find a better reason to treat this construct as a declaration
>>>> later on.
>>>> +/// When this happens and the name could possibly be valid in some
>>>> other
>>>> +/// syntactic context, *InvalidAsDeclSpec is set to 'true'. The
>>>> current cases
>>>> +/// that trigger this are:
>>>> +///
>>>> +///   * When parsing X::Y (with no 'typename') where X is dependent
>>>> +///   * When parsing X<Y> where X is undeclared
>>>> ///
>>>> ///         decl-specifier:
>>>> ///           storage-class-specifier
>>>> @@ -1281,7 +1286,7 @@ public:
>>>> ///
>>>> Parser::TPResult
>>>> Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
>>>> -                                  bool *HasMissingTypename) {
>>>> +                                  bool *InvalidAsDeclSpec) {
>>>>   switch (Tok.getKind()) {
>>>>   case tok::identifier: {
>>>>     // Check for need to substitute AltiVec __vector keyword
>>>> @@ -1321,7 +1326,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>         // argument is an error, and was probably intended to be a type.
>>>>         return GreaterThanIsOperator ? TPResult::True : TPResult::False;
>>>>       case ANK_Unresolved:
>>>> -        return HasMissingTypename ? TPResult::Ambiguous :
>>>> TPResult::False;
>>>> +        return InvalidAsDeclSpec ? TPResult::Ambiguous :
>>>> TPResult::False;
>>>>       case ANK_Success:
>>>>         break;
>>>>       }
>>>> @@ -1342,7 +1347,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>     }
>>>>
>>>>     // We annotated this token as something. Recurse to handle whatever
>>>> we got.
>>>> -    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> HasMissingTypename);
>>>> +    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> InvalidAsDeclSpec);
>>>>   }
>>>>
>>>>   case tok::kw_typename:  // typename T::type
>>>> @@ -1350,7 +1355,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>     // recurse to handle whatever we get.
>>>>     if (TryAnnotateTypeOrScopeToken())
>>>>       return TPResult::Error;
>>>> -    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> HasMissingTypename);
>>>> +    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> InvalidAsDeclSpec);
>>>>
>>>>   case tok::coloncolon: {    // ::foo::bar
>>>>     const Token &Next = NextToken();
>>>> @@ -1365,7 +1370,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>     // recurse to handle whatever we get.
>>>>     if (TryAnnotateTypeOrScopeToken())
>>>>       return TPResult::Error;
>>>> -    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> HasMissingTypename);
>>>> +    return isCXXDeclarationSpecifier(BracedCastResult,
>>>> InvalidAsDeclSpec);
>>>>
>>>>     // decl-specifier:
>>>>     //   storage-class-specifier
>>>> @@ -1471,6 +1476,16 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>
>>>>   case tok::annot_template_id: {
>>>>     TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
>>>> +    // If lookup for the template-name found nothing, don't assume we
>>>> have a
>>>> +    // definitive disambiguation result yet.
>>>> +    if (TemplateId->Kind == TNK_Undeclared_template &&
>>>> InvalidAsDeclSpec) {
>>>> +      // 'template-id(' can be a valid expression but not a valid decl
>>>> spec if
>>>> +      // the template-name is not declared, but we don't consider this
>>>> to be a
>>>> +      // definitive disambiguation. In any other context, it's an
>>>> error either
>>>> +      // way.
>>>> +      *InvalidAsDeclSpec = NextToken().is(tok::l_paren);
>>>> +      return TPResult::Ambiguous;
>>>> +    }
>>>>     if (TemplateId->Kind != TNK_Type_template)
>>>>       return TPResult::False;
>>>>     CXXScopeSpec SS;
>>>> @@ -1499,19 +1514,19 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>           TPResult TPR = TPResult::False;
>>>>           if (!isIdentifier)
>>>>             TPR = isCXXDeclarationSpecifier(BracedCastResult,
>>>> -                                            HasMissingTypename);
>>>> +                                            InvalidAsDeclSpec);
>>>>
>>>>           if (isIdentifier ||
>>>>               TPR == TPResult::True || TPR == TPResult::Error)
>>>>             return TPResult::Error;
>>>>
>>>> -          if (HasMissingTypename) {
>>>> +          if (InvalidAsDeclSpec) {
>>>>             // We can't tell whether this is a missing 'typename' or a
>>>> valid
>>>>             // expression.
>>>> -            *HasMissingTypename = true;
>>>> +            *InvalidAsDeclSpec = true;
>>>>             return TPResult::Ambiguous;
>>>>           } else {
>>>> -            // In MS mode, if HasMissingTypename is not provided, and
>>>> the tokens
>>>> +            // In MS mode, if InvalidAsDeclSpec is not provided, and
>>>> the tokens
>>>>             // are or the form *) or &) *> or &> &&>, this can't be an
>>>> expression.
>>>>             // The typename must be missing.
>>>>             if (getLangOpts().MSVCCompat) {
>>>> @@ -1547,8 +1562,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>                        ? TPResult::True
>>>>                        : TPResult::False;
>>>>           case ANK_Unresolved:
>>>> -            return HasMissingTypename ? TPResult::Ambiguous
>>>> -                                      : TPResult::False;
>>>> +            return InvalidAsDeclSpec ? TPResult::Ambiguous :
>>>> TPResult::False;
>>>>           case ANK_Success:
>>>>             break;
>>>>           }
>>>> @@ -1556,8 +1570,7 @@ Parser::isCXXDeclarationSpecifier(Parser
>>>>           // Annotated it, check again.
>>>>           assert(Tok.isNot(tok::annot_cxxscope) ||
>>>>                  NextToken().isNot(tok::identifier));
>>>> -          return isCXXDeclarationSpecifier(BracedCastResult,
>>>> -                                           HasMissingTypename);
>>>> +          return isCXXDeclarationSpecifier(BracedCastResult,
>>>> InvalidAsDeclSpec);
>>>>         }
>>>>       }
>>>>       return TPResult::False;
>>>> @@ -2029,3 +2042,56 @@ Parser::TPResult Parser::TryParseBracket
>>>>
>>>>   return TPResult::Ambiguous;
>>>> }
>>>> +
>>>> +/// Determine whether we might be looking at the '<'
>>>> template-argument-list '>'
>>>> +/// of a template-id or simple-template-id, rather than a less-than
>>>> comparison.
>>>> +/// This will often fail and produce an ambiguity, but should never be
>>>> wrong
>>>> +/// if it returns True or False.
>>>> +Parser::TPResult Parser::isTemplateArgumentList(unsigned TokensToSkip)
>>>> {
>>>> +  if (!TokensToSkip) {
>>>> +    if (Tok.isNot(tok::less))
>>>> +      return TPResult::False;
>>>> +    if (NextToken().is(tok::greater))
>>>> +      return TPResult::True;
>>>> +  }
>>>> +
>>>> +  RevertingTentativeParsingAction PA(*this);
>>>> +
>>>> +  while (TokensToSkip) {
>>>> +    ConsumeAnyToken();
>>>> +    --TokensToSkip;
>>>> +  }
>>>> +
>>>> +  if (!TryConsumeToken(tok::less))
>>>> +    return TPResult::False;
>>>> +
>>>> +  bool InvalidAsTemplateArgumentList = false;
>>>> +  while (true) {
>>>> +    // We can't do much to tell an expression apart from a
>>>> template-argument,
>>>> +    // but one good distinguishing factor is that a "decl-specifier"
>>>> not
>>>> +    // followed by '(' or '{' can't appear in an expression.
>>>> +    if (isCXXDeclarationSpecifier(
>>>> +            TPResult::False, &InvalidAsTemplateArgumentList) ==
>>>> TPResult::True)
>>>> +      return TPResult::True;
>>>> +
>>>> +    // That didn't help, try the next template-argument.
>>>> +    SkipUntil({tok::comma, tok::greater, tok::greatergreater,
>>>> +               tok::greatergreatergreater},
>>>> +              StopAtSemi | StopBeforeMatch);
>>>> +    switch (Tok.getKind()) {
>>>> +    case tok::comma:
>>>> +      ConsumeToken();
>>>> +      break;
>>>> +
>>>> +    case tok::greater:
>>>> +    case tok::greatergreater:
>>>> +    case tok::greatergreatergreater:
>>>> +      if (InvalidAsTemplateArgumentList)
>>>> +        return TPResult::False;
>>>> +      return TPResult::Ambiguous;
>>>> +
>>>> +    default:
>>>> +      return TPResult::False;
>>>> +    }
>>>> +  }
>>>> +}
>>>>
>>>> Modified: cfe/trunk/lib/Parse/Parser.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/Parser.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Parse/Parser.cpp (original)
>>>> +++ cfe/trunk/lib/Parse/Parser.cpp Wed May  8 20:31:27 2019
>>>> @@ -315,6 +315,14 @@ bool Parser::SkipUntil(ArrayRef<tok::Tok
>>>>       else
>>>>         SkipUntil(tok::r_brace);
>>>>       break;
>>>> +    case tok::question:
>>>> +      // Recursively skip ? ... : pairs; these function as brackets.
>>>> But
>>>> +      // still stop at a semicolon if requested.
>>>> +      ConsumeToken();
>>>> +      SkipUntil(tok::colon,
>>>> +                SkipUntilFlags(unsigned(Flags) &
>>>> +                               unsigned(StopAtCodeCompletion |
>>>> StopAtSemi)));
>>>> +      break;
>>>>
>>>>     // Okay, we found a ']' or '}' or ')', which we think should be
>>>> balanced.
>>>>     // Since the user wasn't looking for this token (if they were, it
>>>> would
>>>> @@ -1600,6 +1608,20 @@ Parser::TryAnnotateName(bool IsAddressOf
>>>>       Actions.ClassifyName(getCurScope(), SS, Name, NameLoc, Next,
>>>>                            IsAddressOfOperand, SS.isEmpty() ? CCC :
>>>> nullptr);
>>>>
>>>> +  // If name lookup found nothing and we guessed that this was a
>>>> template name,
>>>> +  // double-check before committing to that interpretation. C++20
>>>> requires that
>>>> +  // we interpret this as a template-id if it can be, but if it can't
>>>> be, then
>>>> +  // this is an error recovery case.
>>>> +  if (Classification.getKind() == Sema::NC_UndeclaredTemplate &&
>>>> +      isTemplateArgumentList(1) == TPResult::False) {
>>>> +    // It's not a template-id; re-classify without the '<' as a hint.
>>>> +    Token FakeNext = Next;
>>>> +    FakeNext.setKind(tok::unknown);
>>>> +    Classification =
>>>> +        Actions.ClassifyName(getCurScope(), SS, Name, NameLoc,
>>>> FakeNext,
>>>> +                             IsAddressOfOperand, SS.isEmpty() ? CCC :
>>>> nullptr);
>>>> +  }
>>>> +
>>>>   switch (Classification.getKind()) {
>>>>   case Sema::NC_Error:
>>>>     return ANK_Error;
>>>> @@ -1668,7 +1690,8 @@ Parser::TryAnnotateName(bool IsAddressOf
>>>>     }
>>>>     LLVM_FALLTHROUGH;
>>>>   case Sema::NC_VarTemplate:
>>>> -  case Sema::NC_FunctionTemplate: {
>>>> +  case Sema::NC_FunctionTemplate:
>>>> +  case Sema::NC_UndeclaredTemplate: {
>>>>     // We have a type, variable or function template followed by '<'.
>>>>     ConsumeToken();
>>>>     UnqualifiedId Id;
>>>> @@ -1791,7 +1814,8 @@ bool Parser::TryAnnotateTypeOrScopeToken
>>>>     } else if (Tok.is(tok::annot_template_id)) {
>>>>       TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
>>>>       if (TemplateId->Kind != TNK_Type_template &&
>>>> -          TemplateId->Kind != TNK_Dependent_template_name) {
>>>> +          TemplateId->Kind != TNK_Dependent_template_name &&
>>>> +          TemplateId->Kind != TNK_Undeclared_template) {
>>>>         Diag(Tok, diag::err_typename_refers_to_non_type_template)
>>>>           << Tok.getAnnotationRange();
>>>>         return true;
>>>> @@ -1890,6 +1914,8 @@ bool Parser::TryAnnotateTypeOrScopeToken
>>>>     }
>>>>
>>>>     // If this is a template-id, annotate with a template-id or type
>>>> token.
>>>> +    // FIXME: This appears to be dead code. We already have formed
>>>> template-id
>>>> +    // tokens when parsing the scope specifier; this can never form a
>>>> new one.
>>>>     if (NextToken().is(tok::less)) {
>>>>       TemplateTy Template;
>>>>       UnqualifiedId TemplateName;
>>>> @@ -1900,14 +1926,19 @@ bool Parser::TryAnnotateTypeOrScopeToken
>>>>               /*hasTemplateKeyword=*/false, TemplateName,
>>>>               /*ObjectType=*/nullptr, /*EnteringContext*/false,
>>>> Template,
>>>>               MemberOfUnknownSpecialization)) {
>>>> -        // Consume the identifier.
>>>> -        ConsumeToken();
>>>> -        if (AnnotateTemplateIdToken(Template, TNK, SS,
>>>> SourceLocation(),
>>>> -                                    TemplateName)) {
>>>> -          // If an unrecoverable error occurred, we need to return
>>>> true here,
>>>> -          // because the token stream is in a damaged state.  We may
>>>> not return
>>>> -          // a valid identifier.
>>>> -          return true;
>>>> +        // Only annotate an undeclared template name as a template-id
>>>> if the
>>>> +        // following tokens have the form of a template argument list.
>>>> +        if (TNK != TNK_Undeclared_template ||
>>>> +            isTemplateArgumentList(1) != TPResult::False) {
>>>> +          // Consume the identifier.
>>>> +          ConsumeToken();
>>>> +          if (AnnotateTemplateIdToken(Template, TNK, SS,
>>>> SourceLocation(),
>>>> +                                      TemplateName)) {
>>>> +            // If an unrecoverable error occurred, we need to return
>>>> true here,
>>>> +            // because the token stream is in a damaged state.  We may
>>>> not
>>>> +            // return a valid identifier.
>>>> +            return true;
>>>> +          }
>>>>         }
>>>>       }
>>>>     }
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaCXXScopeSpec.cpp Wed May  8 20:31:27 2019
>>>> @@ -888,7 +888,7 @@ bool Sema::IsInvalidUnlessNestedName(Sco
>>>> bool Sema::ActOnCXXNestedNameSpecifier(Scope *S,
>>>>                                        CXXScopeSpec &SS,
>>>>                                        SourceLocation TemplateKWLoc,
>>>> -                                       TemplateTy Template,
>>>> +                                       TemplateTy OpaqueTemplate,
>>>>                                        SourceLocation TemplateNameLoc,
>>>>                                        SourceLocation LAngleLoc,
>>>>                                        ASTTemplateArgsPtr
>>>> TemplateArgsIn,
>>>> @@ -898,11 +898,13 @@ bool Sema::ActOnCXXNestedNameSpecifier(S
>>>>   if (SS.isInvalid())
>>>>     return true;
>>>>
>>>> +  TemplateName Template = OpaqueTemplate.get();
>>>> +
>>>>   // Translate the parser's template argument list in our AST format.
>>>>   TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
>>>>   translateTemplateArguments(TemplateArgsIn, TemplateArgs);
>>>>
>>>> -  DependentTemplateName *DTN =
>>>> Template.get().getAsDependentTemplateName();
>>>> +  DependentTemplateName *DTN = Template.getAsDependentTemplateName();
>>>>   if (DTN && DTN->isIdentifier()) {
>>>>     // Handle a dependent template specialization for which we cannot
>>>> resolve
>>>>     // the template name.
>>>> @@ -930,23 +932,28 @@ bool Sema::ActOnCXXNestedNameSpecifier(S
>>>>     return false;
>>>>   }
>>>>
>>>> -  TemplateDecl *TD = Template.get().getAsTemplateDecl();
>>>> -  if (Template.get().getAsOverloadedTemplate() || DTN ||
>>>> +  // If we assumed an undeclared identifier was a template name, try to
>>>> +  // typo-correct it now.
>>>> +  if (Template.getAsAssumedTemplateName() &&
>>>> +      resolveAssumedTemplateNameAsType(S, Template, TemplateNameLoc))
>>>> +    return true;
>>>> +
>>>> +  TemplateDecl *TD = Template.getAsTemplateDecl();
>>>> +  if (Template.getAsOverloadedTemplate() || DTN ||
>>>>       isa<FunctionTemplateDecl>(TD) || isa<VarTemplateDecl>(TD)) {
>>>>     SourceRange R(TemplateNameLoc, RAngleLoc);
>>>>     if (SS.getRange().isValid())
>>>>       R.setBegin(SS.getRange().getBegin());
>>>>
>>>>     Diag(CCLoc, diag::err_non_type_template_in_nested_name_specifier)
>>>> -      << (TD && isa<VarTemplateDecl>(TD)) << Template.get() << R;
>>>> -    NoteAllFoundTemplates(Template.get());
>>>> +      << (TD && isa<VarTemplateDecl>(TD)) << Template << R;
>>>> +    NoteAllFoundTemplates(Template);
>>>>     return true;
>>>>   }
>>>>
>>>>   // We were able to resolve the template name to an actual template.
>>>>   // Build an appropriate nested-name-specifier.
>>>> -  QualType T =
>>>> -      CheckTemplateIdType(Template.get(), TemplateNameLoc,
>>>> TemplateArgs);
>>>> +  QualType T = CheckTemplateIdType(Template, TemplateNameLoc,
>>>> TemplateArgs);
>>>>   if (T.isNull())
>>>>     return true;
>>>>
>>>> @@ -954,7 +961,7 @@ bool Sema::ActOnCXXNestedNameSpecifier(S
>>>>   // nested name specifiers.
>>>>   if (!T->isDependentType() && !T->getAs<TagType>()) {
>>>>     Diag(TemplateNameLoc, diag::err_nested_name_spec_non_tag) << T;
>>>> -    NoteAllFoundTemplates(Template.get());
>>>> +    NoteAllFoundTemplates(Template);
>>>>     return true;
>>>>   }
>>>>
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaDecl.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDecl.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaDecl.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaDecl.cpp Wed May  8 20:31:27 2019
>>>> @@ -917,6 +917,16 @@ Corrected:
>>>>       }
>>>>     }
>>>>
>>>> +    if (getLangOpts().CPlusPlus2a && !SS.isSet() && NextToken.is(tok::less))
>>>> {
>>>> +      // In C++20 onwards, this could be an ADL-only call to a function
>>>> +      // template, and we're required to assume that this is a
>>>> template name.
>>>> +      //
>>>> +      // FIXME: Find a way to still do typo correction in this case.
>>>> +      TemplateName Template =
>>>> +          Context.getAssumedTemplateName(NameInfo.getName());
>>>> +      return NameClassification::UndeclaredTemplate(Template);
>>>> +    }
>>>> +
>>>>     // In C, we first see whether there is a tag type by the same name,
>>>> in
>>>>     // which case it's likely that the user just forgot to write "enum",
>>>>     // "struct", or "union".
>>>> @@ -1045,52 +1055,62 @@ Corrected:
>>>>
>>>>   if (getLangOpts().CPlusPlus && NextToken.is(tok::less) &&
>>>>       (IsFilteredTemplateName ||
>>>> -       hasAnyAcceptableTemplateNames(Result,
>>>> /*AllowFunctionTemplates=*/true,
>>>> -                                     /*AllowDependent=*/false))) {
>>>> +       hasAnyAcceptableTemplateNames(
>>>> +           Result, /*AllowFunctionTemplates=*/true,
>>>> +           /*AllowDependent=*/false,
>>>> +           /*AllowNonTemplateFunctions*/ !SS.isSet() &&
>>>> +               getLangOpts().CPlusPlus2a))) {
>>>>     // C++ [temp.names]p3:
>>>>     //   After name lookup (3.4) finds that a name is a template-name
>>>> or that
>>>>     //   an operator-function-id or a literal- operator-id refers to a
>>>> set of
>>>>     //   overloaded functions any member of which is a function
>>>> template if
>>>>     //   this is followed by a <, the < is always taken as the
>>>> delimiter of a
>>>>     //   template-argument-list and never as the less-than operator.
>>>> +    // C++2a [temp.names]p2:
>>>> +    //   A name is also considered to refer to a template if it is an
>>>> +    //   unqualified-id followed by a < and name lookup finds either
>>>> one
>>>> +    //   or more functions or finds nothing.
>>>>     if (!IsFilteredTemplateName)
>>>>       FilterAcceptableTemplateNames(Result);
>>>>
>>>> -    if (!Result.empty()) {
>>>> -      bool IsFunctionTemplate;
>>>> -      bool IsVarTemplate;
>>>> -      TemplateName Template;
>>>> -      if (Result.end() - Result.begin() > 1) {
>>>> -        IsFunctionTemplate = true;
>>>> -        Template = Context.getOverloadedTemplateName(Result.begin(),
>>>> -                                                     Result.end());
>>>> -      } else {
>>>> -        auto *TD = cast<TemplateDecl>(getAsTemplateNameDecl(
>>>> -            *Result.begin(), /*AllowFunctionTemplates=*/true,
>>>> -            /*AllowDependent=*/false));
>>>> -        IsFunctionTemplate = isa<FunctionTemplateDecl>(TD);
>>>> -        IsVarTemplate = isa<VarTemplateDecl>(TD);
>>>> -
>>>> -        if (SS.isSet() && !SS.isInvalid())
>>>> -          Template =
>>>> -              Context.getQualifiedTemplateName(SS.getScopeRep(),
>>>> -
>>>>                                               /*TemplateKeyword=*/false,
>>>> TD);
>>>> -        else
>>>> -          Template = TemplateName(TD);
>>>> -      }
>>>> -
>>>> -      if (IsFunctionTemplate) {
>>>> -        // Function templates always go through overload resolution,
>>>> at which
>>>> -        // point we'll perform the various checks (e.g.,
>>>> accessibility) we need
>>>> -        // to based on which function we selected.
>>>> -        Result.suppressDiagnostics();
>>>> +    bool IsFunctionTemplate;
>>>> +    bool IsVarTemplate;
>>>> +    TemplateName Template;
>>>> +    if (Result.end() - Result.begin() > 1) {
>>>> +      IsFunctionTemplate = true;
>>>> +      Template = Context.getOverloadedTemplateName(Result.begin(),
>>>> +                                                   Result.end());
>>>> +    } else if (!Result.empty()) {
>>>> +      auto *TD = cast<TemplateDecl>(getAsTemplateNameDecl(
>>>> +          *Result.begin(), /*AllowFunctionTemplates=*/true,
>>>> +          /*AllowDependent=*/false));
>>>> +      IsFunctionTemplate = isa<FunctionTemplateDecl>(TD);
>>>> +      IsVarTemplate = isa<VarTemplateDecl>(TD);
>>>> +
>>>> +      if (SS.isSet() && !SS.isInvalid())
>>>> +        Template =
>>>> +            Context.getQualifiedTemplateName(SS.getScopeRep(),
>>>> +
>>>>                                             /*TemplateKeyword=*/false, TD);
>>>> +      else
>>>> +        Template = TemplateName(TD);
>>>> +    } else {
>>>> +      // All results were non-template functions. This is a function
>>>> template
>>>> +      // name.
>>>> +      IsFunctionTemplate = true;
>>>> +      Template = Context.getAssumedTemplateName(NameInfo.getName());
>>>> +    }
>>>>
>>>> -        return NameClassification::FunctionTemplate(Template);
>>>> -      }
>>>> +    if (IsFunctionTemplate) {
>>>> +      // Function templates always go through overload resolution, at
>>>> which
>>>> +      // point we'll perform the various checks (e.g., accessibility)
>>>> we need
>>>> +      // to based on which function we selected.
>>>> +      Result.suppressDiagnostics();
>>>>
>>>> -      return IsVarTemplate ? NameClassification::VarTemplate(Template)
>>>> -                           :
>>>> NameClassification::TypeTemplate(Template);
>>>> +      return NameClassification::FunctionTemplate(Template);
>>>>     }
>>>> +
>>>> +    return IsVarTemplate ? NameClassification::VarTemplate(Template)
>>>> +                         : NameClassification::TypeTemplate(Template);
>>>>   }
>>>>
>>>>   NamedDecl *FirstDecl = (*Result.begin())->getUnderlyingDecl();
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaDeclCXX.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaDeclCXX.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaDeclCXX.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaDeclCXX.cpp Wed May  8 20:31:27 2019
>>>> @@ -3881,6 +3881,8 @@ Sema::BuildMemInitializer(Decl *Construc
>>>>
>>>>   if (TemplateTypeTy) {
>>>>     BaseType = GetTypeFromParser(TemplateTypeTy, &TInfo);
>>>> +    if (BaseType.isNull())
>>>> +      return true;
>>>>   } else if (DS.getTypeSpecType() == TST_decltype) {
>>>>     BaseType = BuildDecltypeType(DS.getRepAsExpr(),
>>>> DS.getTypeSpecTypeLoc());
>>>>   } else if (DS.getTypeSpecType() == TST_decltype_auto) {
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaExpr.cpp Wed May  8 20:31:27 2019
>>>> @@ -2065,11 +2065,12 @@ bool Sema::DiagnoseEmptyLookup(Scope *S,
>>>>       // is in the wrong place to recover. Suggest the typo
>>>>       // correction, but don't make it a fix-it since we're not going
>>>>       // to recover well anyway.
>>>> -      AcceptableWithoutRecovery =
>>>> -          isa<TypeDecl>(UnderlyingND) ||
>>>> isa<ObjCInterfaceDecl>(UnderlyingND);
>>>> +      AcceptableWithoutRecovery = isa<TypeDecl>(UnderlyingND) ||
>>>> +                                  getAsTypeTemplateDecl(UnderlyingND)
>>>> ||
>>>> +                                  isa<ObjCInterfaceDecl>(UnderlyingND);
>>>>     } else {
>>>> -      // FIXME: We found a keyword or a type. Suggest it, but don't
>>>> provide a
>>>> -      // fix-it because we aren't able to recover.
>>>> +      // FIXME: We found a keyword. Suggest it, but don't provide a
>>>> fix-it
>>>> +      // because we aren't able to recover.
>>>>       AcceptableWithoutRecovery = true;
>>>>     }
>>>>
>>>> @@ -2221,8 +2222,10 @@ Sema::ActOnIdExpression(Scope *S, CXXSco
>>>>     // this becomes a performance hit, we can work harder to preserve
>>>> those
>>>>     // results until we get here but it's likely not worth it.
>>>>     bool MemberOfUnknownSpecialization;
>>>> +    AssumedTemplateKind AssumedTemplate;
>>>>     if (LookupTemplateName(R, S, SS, QualType(),
>>>> /*EnteringContext=*/false,
>>>> -                           MemberOfUnknownSpecialization,
>>>> TemplateKWLoc))
>>>> +                           MemberOfUnknownSpecialization,
>>>> TemplateKWLoc,
>>>> +                           &AssumedTemplate))
>>>>       return ExprError();
>>>>
>>>>     if (MemberOfUnknownSpecialization ||
>>>> @@ -5518,7 +5521,24 @@ tryImplicitlyCaptureThisIfImplicitMember
>>>> ExprResult Sema::ActOnCallExpr(Scope *Scope, Expr *Fn, SourceLocation
>>>> LParenLoc,
>>>>                                MultiExprArg ArgExprs, SourceLocation
>>>> RParenLoc,
>>>>                                Expr *ExecConfig) {
>>>> -  return BuildCallExpr(Scope, Fn, LParenLoc, ArgExprs, RParenLoc,
>>>> ExecConfig);
>>>> +  ExprResult Call =
>>>> +      BuildCallExpr(Scope, Fn, LParenLoc, ArgExprs, RParenLoc,
>>>> ExecConfig);
>>>> +  if (Call.isInvalid())
>>>> +    return Call;
>>>> +
>>>> +  // Diagnose uses of the C++20 "ADL-only template-id call" feature in
>>>> earlier
>>>> +  // language modes.
>>>> +  if (auto *ULE = dyn_cast<UnresolvedLookupExpr>(Fn)) {
>>>> +    if (ULE->hasExplicitTemplateArgs() &&
>>>> +        ULE->decls_begin() == ULE->decls_end()) {
>>>> +      Diag(Fn->getExprLoc(), getLangOpts().CPlusPlus2a
>>>> +                                 ?
>>>> diag::warn_cxx17_compat_adl_only_template_id
>>>> +                                 : diag::ext_adl_only_template_id)
>>>> +          << ULE->getName();
>>>> +    }
>>>> +  }
>>>> +
>>>> +  return Call;
>>>> }
>>>>
>>>> /// BuildCallExpr - Handle a call to Fn with the specified array of
>>>> arguments.
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaExprCXX.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExprCXX.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaExprCXX.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaExprCXX.cpp Wed May  8 20:31:27 2019
>>>> @@ -7074,7 +7074,8 @@ ExprResult Sema::ActOnPseudoDestructorEx
>>>>     TemplateIdAnnotation *TemplateId = SecondTypeName.TemplateId;
>>>>     ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
>>>>                                        TemplateId->NumArgs);
>>>> -    TypeResult T = ActOnTemplateIdType(TemplateId->SS,
>>>> +    TypeResult T = ActOnTemplateIdType(S,
>>>> +                                       TemplateId->SS,
>>>>                                        TemplateId->TemplateKWLoc,
>>>>                                        TemplateId->Template,
>>>>                                        TemplateId->Name,
>>>> @@ -7126,7 +7127,8 @@ ExprResult Sema::ActOnPseudoDestructorEx
>>>>       TemplateIdAnnotation *TemplateId = FirstTypeName.TemplateId;
>>>>       ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
>>>>                                          TemplateId->NumArgs);
>>>> -      TypeResult T = ActOnTemplateIdType(TemplateId->SS,
>>>> +      TypeResult T = ActOnTemplateIdType(S,
>>>> +                                         TemplateId->SS,
>>>>                                          TemplateId->TemplateKWLoc,
>>>>                                          TemplateId->Template,
>>>>                                          TemplateId->Name,
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaOverload.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaOverload.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaOverload.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaOverload.cpp Wed May  8 20:31:27 2019
>>>> @@ -12017,7 +12017,8 @@ bool Sema::buildOverloadedCallSet(Scope
>>>>     // We don't perform ADL for implicit declarations of builtins.
>>>>     // Verify that this was correctly set up.
>>>>     FunctionDecl *F;
>>>> -    if (ULE->decls_begin() + 1 == ULE->decls_end() &&
>>>> +    if (ULE->decls_begin() != ULE->decls_end() &&
>>>> +        ULE->decls_begin() + 1 == ULE->decls_end() &&
>>>>         (F = dyn_cast<FunctionDecl>(*ULE->decls_begin())) &&
>>>>         F->getBuiltinID() && F->isImplicit())
>>>>       llvm_unreachable("performing ADL for builtin");
>>>> @@ -12201,10 +12202,9 @@ ExprResult Sema::BuildOverloadedCallExpr
>>>>   OverloadingResult OverloadResult =
>>>>       CandidateSet.BestViableFunction(*this, Fn->getBeginLoc(), Best);
>>>>
>>>> -  return FinishOverloadedCallExpr(*this, S, Fn, ULE, LParenLoc, Args,
>>>> -                                  RParenLoc, ExecConfig, &CandidateSet,
>>>> -                                  &Best, OverloadResult,
>>>> -                                  AllowTypoCorrection);
>>>> +  return FinishOverloadedCallExpr(*this, S, Fn, ULE, LParenLoc, Args,
>>>> RParenLoc,
>>>> +                                  ExecConfig, &CandidateSet, &Best,
>>>> +                                  OverloadResult, AllowTypoCorrection);
>>>> }
>>>>
>>>> static bool IsOverloaded(const UnresolvedSetImpl &Functions) {
>>>>
>>>> Modified: cfe/trunk/lib/Sema/SemaTemplate.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplate.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Sema/SemaTemplate.cpp (original)
>>>> +++ cfe/trunk/lib/Sema/SemaTemplate.cpp Wed May  8 20:31:27 2019
>>>> @@ -130,10 +130,15 @@ void Sema::FilterAcceptableTemplateNames
>>>>
>>>> bool Sema::hasAnyAcceptableTemplateNames(LookupResult &R,
>>>>                                          bool AllowFunctionTemplates,
>>>> -                                         bool AllowDependent) {
>>>> -  for (LookupResult::iterator I = R.begin(), IEnd = R.end(); I !=
>>>> IEnd; ++I)
>>>> +                                         bool AllowDependent,
>>>> +                                         bool
>>>> AllowNonTemplateFunctions) {
>>>> +  for (LookupResult::iterator I = R.begin(), IEnd = R.end(); I !=
>>>> IEnd; ++I) {
>>>>     if (getAsTemplateNameDecl(*I, AllowFunctionTemplates,
>>>> AllowDependent))
>>>>       return true;
>>>> +    if (AllowNonTemplateFunctions &&
>>>> +        isa<FunctionDecl>((*I)->getUnderlyingDecl()))
>>>> +      return true;
>>>> +  }
>>>>
>>>>   return false;
>>>> }
>>>> @@ -171,11 +176,25 @@ TemplateNameKind Sema::isTemplateName(Sc
>>>>
>>>>   QualType ObjectType = ObjectTypePtr.get();
>>>>
>>>> +  AssumedTemplateKind AssumedTemplate;
>>>>   LookupResult R(*this, TName, Name.getBeginLoc(), LookupOrdinaryName);
>>>>   if (LookupTemplateName(R, S, SS, ObjectType, EnteringContext,
>>>> -                         MemberOfUnknownSpecialization))
>>>> +                         MemberOfUnknownSpecialization,
>>>> SourceLocation(),
>>>> +                         &AssumedTemplate))
>>>> +    return TNK_Non_template;
>>>> +
>>>> +  if (AssumedTemplate != AssumedTemplateKind::None) {
>>>> +    TemplateResult =
>>>> TemplateTy::make(Context.getAssumedTemplateName(TName));
>>>> +    // Let the parser know whether we found nothing or found
>>>> functions; if we
>>>> +    // found nothing, we want to more carefully check whether this is
>>>> actually
>>>> +    // a function template name versus some other kind of undeclared
>>>> identifier.
>>>> +    return AssumedTemplate == AssumedTemplateKind::FoundNothing
>>>> +               ? TNK_Undeclared_template
>>>> +               : TNK_Function_template;
>>>> +  }
>>>> +
>>>> +  if (R.empty())
>>>>     return TNK_Non_template;
>>>> -  if (R.empty()) return TNK_Non_template;
>>>>
>>>>   NamedDecl *D = nullptr;
>>>>   if (R.isAmbiguous()) {
>>>> @@ -325,7 +344,11 @@ bool Sema::LookupTemplateName(LookupResu
>>>>                               QualType ObjectType,
>>>>                               bool EnteringContext,
>>>>                               bool &MemberOfUnknownSpecialization,
>>>> -                              SourceLocation TemplateKWLoc) {
>>>> +                              SourceLocation TemplateKWLoc,
>>>> +                              AssumedTemplateKind *ATK) {
>>>> +  if (ATK)
>>>> +    *ATK = AssumedTemplateKind::None;
>>>> +
>>>>   Found.setTemplateNameLookup(true);
>>>>
>>>>   // Determine where to perform name lookup
>>>> @@ -405,6 +428,32 @@ bool Sema::LookupTemplateName(LookupResu
>>>>   if (Found.isAmbiguous())
>>>>     return false;
>>>>
>>>> +  if (ATK && !SS.isSet() && ObjectType.isNull() &&
>>>> TemplateKWLoc.isInvalid()) {
>>>> +    // C++2a [temp.names]p2:
>>>> +    //   A name is also considered to refer to a template if it is an
>>>> +    //   unqualified-id followed by a < and name lookup finds either
>>>> one or more
>>>> +    //   functions or finds nothing.
>>>> +    //
>>>> +    // To keep our behavior consistent, we apply the "finds nothing"
>>>> part in
>>>> +    // all language modes, and diagnose the empty lookup in
>>>> ActOnCallExpr if we
>>>> +    // successfully form a call to an undeclared template-id.
>>>> +    bool AllFunctions =
>>>> +        getLangOpts().CPlusPlus2a &&
>>>> +        std::all_of(Found.begin(), Found.end(), [](NamedDecl *ND) {
>>>> +          return isa<FunctionDecl>(ND->getUnderlyingDecl());
>>>> +        });
>>>> +    if (AllFunctions || (Found.empty() && !IsDependent)) {
>>>> +      // If lookup found any functions, or if this is a name that can
>>>> only be
>>>> +      // used for a function, then strongly assume this is a function
>>>> +      // template-id.
>>>> +      *ATK = (Found.empty() && Found.getLookupName().isIdentifier())
>>>> +                 ? AssumedTemplateKind::FoundNothing
>>>> +                 : AssumedTemplateKind::FoundFunctions;
>>>> +      Found.clear();
>>>> +      return false;
>>>> +    }
>>>> +  }
>>>> +
>>>>   if (Found.empty() && !IsDependent) {
>>>>     // If we did not find any names, attempt to correct any typos.
>>>>     DeclarationName Name = Found.getLookupName();
>>>> @@ -418,13 +467,13 @@ bool Sema::LookupTemplateName(LookupResu
>>>>     if (TypoCorrection Corrected =
>>>>             CorrectTypo(Found.getLookupNameInfo(),
>>>> Found.getLookupKind(), S,
>>>>                         &SS, FilterCCC, CTK_ErrorRecovery, LookupCtx)) {
>>>> -      Found.setLookupName(Corrected.getCorrection());
>>>>       if (auto *ND = Corrected.getFoundDecl())
>>>>         Found.addDecl(ND);
>>>>       FilterAcceptableTemplateNames(Found);
>>>>       if (Found.isAmbiguous()) {
>>>>         Found.clear();
>>>>       } else if (!Found.empty()) {
>>>> +        Found.setLookupName(Corrected.getCorrection());
>>>>         if (LookupCtx) {
>>>>           std::string
>>>> CorrectedStr(Corrected.getAsString(getLangOpts()));
>>>>           bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
>>>> @@ -436,8 +485,6 @@ bool Sema::LookupTemplateName(LookupResu
>>>>           diagnoseTypo(Corrected, PDiag(diag::err_no_template_suggest)
>>>> << Name);
>>>>         }
>>>>       }
>>>> -    } else {
>>>> -      Found.setLookupName(Name);
>>>>     }
>>>>   }
>>>>
>>>> @@ -3348,14 +3395,65 @@ QualType Sema::CheckTemplateIdType(Templ
>>>>   return Context.getTemplateSpecializationType(Name, TemplateArgs,
>>>> CanonType);
>>>> }
>>>>
>>>> -TypeResult
>>>> -Sema::ActOnTemplateIdType(CXXScopeSpec &SS, SourceLocation
>>>> TemplateKWLoc,
>>>> -                          TemplateTy TemplateD, IdentifierInfo
>>>> *TemplateII,
>>>> -                          SourceLocation TemplateIILoc,
>>>> -                          SourceLocation LAngleLoc,
>>>> -                          ASTTemplateArgsPtr TemplateArgsIn,
>>>> -                          SourceLocation RAngleLoc,
>>>> -                          bool IsCtorOrDtorName, bool IsClassName) {
>>>> +void Sema::ActOnUndeclaredTypeTemplateName(Scope *S, TemplateTy
>>>> &ParsedName,
>>>> +                                           TemplateNameKind &TNK,
>>>> +                                           SourceLocation NameLoc,
>>>> +                                           IdentifierInfo *&II) {
>>>> +  assert(TNK == TNK_Undeclared_template && "not an undeclared template
>>>> name");
>>>> +
>>>> +  TemplateName Name = ParsedName.get();
>>>> +  auto *ATN = Name.getAsAssumedTemplateName();
>>>> +  assert(ATN && "not an assumed template name");
>>>> +  II = ATN->getDeclName().getAsIdentifierInfo();
>>>> +
>>>> +  if (!resolveAssumedTemplateNameAsType(S, Name, NameLoc,
>>>> /*Diagnose*/false)) {
>>>> +    // Resolved to a type template name.
>>>> +    ParsedName = TemplateTy::make(Name);
>>>> +    TNK = TNK_Type_template;
>>>> +  }
>>>> +}
>>>> +
>>>> +bool Sema::resolveAssumedTemplateNameAsType(Scope *S, TemplateName
>>>> &Name,
>>>> +                                            SourceLocation NameLoc,
>>>> +                                            bool Diagnose) {
>>>> +  // We assumed this undeclared identifier to be an (ADL-only) function
>>>> +  // template name, but it was used in a context where a type was
>>>> required.
>>>> +  // Try to typo-correct it now.
>>>> +  AssumedTemplateStorage *ATN = Name.getAsAssumedTemplateName();
>>>> +  assert(ATN && "not an assumed template name");
>>>> +
>>>> +  LookupResult R(*this, ATN->getDeclName(), NameLoc,
>>>> LookupOrdinaryName);
>>>> +  struct CandidateCallback : CorrectionCandidateCallback {
>>>> +    bool ValidateCandidate(const TypoCorrection &TC) override {
>>>> +      return TC.getCorrectionDecl() &&
>>>> +             getAsTypeTemplateDecl(TC.getCorrectionDecl());
>>>> +    }
>>>> +    std::unique_ptr<CorrectionCandidateCallback> clone() override {
>>>> +      return llvm::make_unique<CandidateCallback>(*this);
>>>> +    }
>>>> +  } FilterCCC;
>>>> +
>>>> +  TypoCorrection Corrected =
>>>> +      CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, nullptr,
>>>> +                  FilterCCC, CTK_ErrorRecovery);
>>>> +  if (Corrected && Corrected.getFoundDecl()) {
>>>> +    diagnoseTypo(Corrected, PDiag(diag::err_no_template_suggest)
>>>> +                                << ATN->getDeclName());
>>>> +    Name = TemplateName(Corrected.getCorrectionDeclAs<TemplateDecl>());
>>>> +    return false;
>>>> +  }
>>>> +
>>>> +  if (Diagnose)
>>>> +    Diag(R.getNameLoc(), diag::err_no_template) << R.getLookupName();
>>>> +  return true;
>>>> +}
>>>> +
>>>> +TypeResult Sema::ActOnTemplateIdType(
>>>> +    Scope *S, CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
>>>> +    TemplateTy TemplateD, IdentifierInfo *TemplateII,
>>>> +    SourceLocation TemplateIILoc, SourceLocation LAngleLoc,
>>>> +    ASTTemplateArgsPtr TemplateArgsIn, SourceLocation RAngleLoc,
>>>> +    bool IsCtorOrDtorName, bool IsClassName) {
>>>>   if (SS.isInvalid())
>>>>     return true;
>>>>
>>>> @@ -3396,6 +3494,9 @@ Sema::ActOnTemplateIdType(CXXScopeSpec &
>>>>   }
>>>>
>>>>   TemplateName Template = TemplateD.get();
>>>> +  if (Template.getAsAssumedTemplateName() &&
>>>> +      resolveAssumedTemplateNameAsType(S, Template, TemplateIILoc))
>>>> +    return true;
>>>>
>>>>   // Translate the parser's template argument list in our AST format.
>>>>   TemplateArgumentListInfo TemplateArgs(LAngleLoc, RAngleLoc);
>>>> @@ -4141,7 +4242,6 @@ ExprResult Sema::BuildTemplateIdExpr(con
>>>>   //       vs template<class T, class U> void f(U);
>>>>
>>>>   // These should be filtered out by our callers.
>>>> -  assert(!R.empty() && "empty lookup results when building
>>>> templateid");
>>>>   assert(!R.isAmbiguous() && "ambiguous lookup when building
>>>> templateid");
>>>>
>>>>   // Non-function templates require a template argument list.
>>>>
>>>> Modified: cfe/trunk/lib/Serialization/ASTReader.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTReader.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Serialization/ASTReader.cpp (original)
>>>> +++ cfe/trunk/lib/Serialization/ASTReader.cpp Wed May  8 20:31:27 2019
>>>> @@ -8745,6 +8745,11 @@ ASTReader::ReadTemplateName(ModuleFile &
>>>>     return Context.getOverloadedTemplateName(Decls.begin(),
>>>> Decls.end());
>>>>   }
>>>>
>>>> +  case TemplateName::AssumedTemplate: {
>>>> +    DeclarationName Name = ReadDeclarationName(F, Record, Idx);
>>>> +    return Context.getAssumedTemplateName(Name);
>>>> +  }
>>>> +
>>>>   case TemplateName::QualifiedTemplate: {
>>>>     NestedNameSpecifier *NNS = ReadNestedNameSpecifier(F, Record, Idx);
>>>>     bool hasTemplKeyword = Record[Idx++];
>>>>
>>>> Modified: cfe/trunk/lib/Serialization/ASTWriter.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Serialization/ASTWriter.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/lib/Serialization/ASTWriter.cpp (original)
>>>> +++ cfe/trunk/lib/Serialization/ASTWriter.cpp Wed May  8 20:31:27 2019
>>>> @@ -5877,6 +5877,12 @@ void ASTRecordWriter::AddTemplateName(Te
>>>>     break;
>>>>   }
>>>>
>>>> +  case TemplateName::AssumedTemplate: {
>>>> +    AssumedTemplateStorage *ADLT = Name.getAsAssumedTemplateName();
>>>> +    AddDeclarationName(ADLT->getDeclName());
>>>> +    break;
>>>> +  }
>>>> +
>>>>   case TemplateName::QualifiedTemplate: {
>>>>     QualifiedTemplateName *QualT = Name.getAsQualifiedTemplateName();
>>>>     AddNestedNameSpecifier(QualT->getQualifier());
>>>>
>>>> Modified:
>>>> cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp
>>>> (original)
>>>> +++ cfe/trunk/test/CXX/basic/basic.lookup/basic.lookup.unqual/p3.cpp
>>>> Wed May  8 20:31:27 2019
>>>> @@ -1,25 +1,67 @@
>>>> // RUN: %clang_cc1 -fsyntax-only -verify %s
>>>> -// expected-no-diagnostics
>>>> +// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s
>>>> +// RUN: %clang_cc1 -std=c++2a -fsyntax-only -verify %s
>>>>
>>>> -typedef int f;
>>>> +typedef int fn;
>>>>
>>>> namespace N0 {
>>>> -  struct A {
>>>> -    friend void f();
>>>> +  struct A {
>>>> +    friend void fn();
>>>>     void g() {
>>>> -      int i = f(1);
>>>> +      int i = fn(1);
>>>>     }
>>>>   };
>>>> }
>>>>
>>>> namespace N1 {
>>>> -  struct A {
>>>> -    friend void f(A &);
>>>> +  struct A {
>>>> +    friend void fn(A &);
>>>>     operator int();
>>>>     void g(A a) {
>>>> -      // ADL should not apply to the lookup of 'f', it refers to the
>>>> typedef
>>>> +      // ADL should not apply to the lookup of 'fn', it refers to the
>>>> typedef
>>>>       // above.
>>>> -      int i = f(a);
>>>> +      int i = fn(a);
>>>>     }
>>>>   };
>>>> }
>>>> +
>>>> +namespace std_example {
>>>> +  int h; // expected-note {{non-template declaration}}
>>>> +  void g();
>>>> +#if __cplusplus <= 201703L
>>>> +  // expected-note at -2 {{non-template declaration}}
>>>> +#endif
>>>> +  namespace N {
>>>> +    struct A {};
>>>> +    template<class T> int f(T);
>>>> +    template<class T> int g(T);
>>>> +#if __cplusplus <= 201703L
>>>> +    // expected-note at -2 {{here}}
>>>> +#endif
>>>> +    template<class T> int h(T); // expected-note {{here}}
>>>> +  }
>>>> +
>>>> +  int x = f<N::A>(N::A());
>>>> +#if __cplusplus <= 201703L
>>>> +  // expected-warning at -2 {{C++2a extension}}
>>>> +#endif
>>>> +  int y = g<N::A>(N::A());
>>>> +#if __cplusplus <= 201703L
>>>> +  // expected-error at -2 {{'g' does not name a template but is followed
>>>> by template arguments; did you mean 'N::g'?}}
>>>> +#endif
>>>> +  int z = h<N::A>(N::A()); // expected-error {{'h' does not name a
>>>> template but is followed by template arguments; did you mean 'N::h'?}}
>>>> +}
>>>> +
>>>> +namespace AnnexD_example {
>>>> +  struct A {};
>>>> +  void operator<(void (*fp)(), A);
>>>> +  void f() {}
>>>> +  int main() {
>>>> +    A a;
>>>> +    f < a;
>>>> +#if __cplusplus > 201703L
>>>> +    // expected-error at -2 {{expected '>'}}
>>>> +#endif
>>>> +    (f) < a;
>>>> +  }
>>>> +}
>>>>
>>>> Modified: cfe/trunk/test/CXX/drs/dr2xx.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr2xx.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/CXX/drs/dr2xx.cpp (original)
>>>> +++ cfe/trunk/test/CXX/drs/dr2xx.cpp Wed May  8 20:31:27 2019
>>>> @@ -2,6 +2,7 @@
>>>> // RUN: %clang_cc1 -std=c++11 %s -verify -fexceptions -fcxx-exceptions
>>>> -pedantic-errors
>>>> // RUN: %clang_cc1 -std=c++14 %s -verify -fexceptions -fcxx-exceptions
>>>> -pedantic-errors
>>>> // RUN: %clang_cc1 -std=c++17 %s -verify -fexceptions -fcxx-exceptions
>>>> -pedantic-errors
>>>> +// RUN: %clang_cc1 -std=c++2a %s -verify -fexceptions -fcxx-exceptions
>>>> -pedantic-errors
>>>>
>>>> // PR13819 -- __SIZE_TYPE__ is incompatible.
>>>> typedef __SIZE_TYPE__ size_t; // expected-error 0-1 {{extension}}
>>>> @@ -434,7 +435,7 @@ namespace dr239 { // dr239: yes
>>>> namespace dr241 { // dr241: yes
>>>>   namespace A {
>>>>     struct B {};
>>>> -    template <int X> void f(); // expected-note 2{{candidate}}
>>>> +    template <int X> void f(); // expected-note 3{{candidate}}
>>>>     template <int X> void g(B);
>>>>   }
>>>>   namespace C {
>>>> @@ -442,8 +443,8 @@ namespace dr241 { // dr241: yes
>>>>     template <class T> void g(T t); // expected-note {{candidate}}
>>>>   }
>>>>   void h(A::B b) {
>>>> -    f<3>(b); // expected-error {{undeclared identifier}}
>>>> -    g<3>(b); // expected-error {{undeclared identifier}}
>>>> +    f<3>(b); // expected-error 0-1{{C++2a extension}} expected-error
>>>> {{no matching}}
>>>> +    g<3>(b); // expected-error 0-1{{C++2a extension}}
>>>>     A::f<3>(b); // expected-error {{no matching}}
>>>>     A::g<3>(b);
>>>>     C::f<3>(b); // expected-error {{no matching}}
>>>>
>>>> Modified: cfe/trunk/test/CXX/drs/dr6xx.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr6xx.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/CXX/drs/dr6xx.cpp (original)
>>>> +++ cfe/trunk/test/CXX/drs/dr6xx.cpp Wed May  8 20:31:27 2019
>>>> @@ -1048,10 +1048,13 @@ namespace dr686 { // dr686: yes
>>>>   template<struct R {} *> struct Y; // expected-error {{cannot be
>>>> defined in a type specifier}}
>>>> }
>>>>
>>>> -namespace dr687 { // dr687 still open
>>>> +namespace dr687 { // dr687 (9 c++20, but the issue is still considered
>>>> open)
>>>>   template<typename T> void f(T a) {
>>>> -    // FIXME: This is valid in C++20.
>>>> -    g<int>(a); // expected-error {{undeclared}} expected-error {{'('}}
>>>> +    // This is valid in C++20.
>>>> +    g<int>(a);
>>>> +#if __cplusplus <= 201703L
>>>> +    // expected-error at -2 {{C++2a extension}}
>>>> +#endif
>>>>
>>>>     // This is not.
>>>>     template g<int>(a); // expected-error {{expected expression}}
>>>>
>>>> Modified: cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp (original)
>>>> +++ cfe/trunk/test/CXX/temp/temp.spec/temp.explicit/p5.cpp Wed May  8
>>>> 20:31:27 2019
>>>> @@ -8,7 +8,10 @@ namespace N {
>>>>   };
>>>> }
>>>>
>>>> -template class Z<int>; // expected-error{{explicit instantiation of
>>>> non-template class 'Z'}}
>>>> +template class Z<int>; // expected-error{{explicit instantiation of
>>>> undeclared template class 'Z'}}
>>>> +
>>>> +struct Q;
>>>> +template class Q<int>; // expected-error{{explicit instantiation of
>>>> non-template class 'Q'}}
>>>>
>>>> // FIXME: This example from the standard is wrong; note posted to CWG
>>>> reflector
>>>> // on 10/27/2009
>>>>
>>>> Modified: cfe/trunk/test/FixIt/typo-crash.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/FixIt/typo-crash.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/FixIt/typo-crash.cpp (original)
>>>> +++ cfe/trunk/test/FixIt/typo-crash.cpp Wed May  8 20:31:27 2019
>>>> @@ -1,14 +1,8 @@
>>>> // RUN: %clang_cc1 -fsyntax-only -verify %s
>>>>
>>>> -// FIXME: The diagnostics and recovery here are very, very poor.
>>>> -
>>>> // PR10355
>>>> -template<typename T> void template_id1() { // expected-note
>>>> {{'template_id1' declared here}} \
>>>> -  // expected-note {{possible target for call}}
>>>> -  template_id2<> t; // expected-error {{no template named
>>>> 'template_id2'; did you mean 'template_id1'?}} \
>>>> -  // expected-error {{expected ';' after expression}} \
>>>> -  // expected-error {{reference to overloaded function could not be
>>>> resolved; did you mean to call it?}} \
>>>> -  // expected-error {{use of undeclared identifier 't'}}
>>>> +template<typename T> void template_id1() {
>>>> +  template_id2<> t; // expected-error-re {{no template named
>>>> 'template_id2'{{$}}}}
>>>>  }
>>>>
>>>> // FIXME: It would be nice if we could get this correction right.
>>>>
>>>> Modified: cfe/trunk/test/Misc/diag-template-diffing.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Misc/diag-template-diffing.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Misc/diag-template-diffing.cpp (original)
>>>> +++ cfe/trunk/test/Misc/diag-template-diffing.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -394,7 +394,7 @@ template<double* ...A> class class_ptrs
>>>> void set13(class_ptrs<&a13, &b13>) {}
>>>> void test13() {
>>>>   set13(class_ptrs<&c13>());
>>>> -  set13(class_ptrss<&a13, &b13, &d13>());
>>>> +  set13(class_ptrs<&a13, &b13, &d13>());
>>>> }
>>>> // CHECK-ELIDE-NOTREE: no matching function for call to 'set13'
>>>> // CHECK-ELIDE-NOTREE: candidate function not viable: no known
>>>> conversion from 'class_ptrs<&c13, (no argument)>' to 'class_ptrs<&a13,
>>>> &b13>' for 1st argument
>>>>
>>>> Modified: cfe/trunk/test/Modules/module-private.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/module-private.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Modules/module-private.cpp (original)
>>>> +++ cfe/trunk/test/Modules/module-private.cpp Wed May  8 20:31:27 2019
>>>> @@ -18,9 +18,7 @@ int test_broken() {
>>>>   int *ip = 0;
>>>>   f1(ip); // expected-error{{use of undeclared identifier 'f1'}}
>>>>
>>>> -  vector<int> vec; // expected-error{{use of undeclared identifier
>>>> 'vector'}} \
>>>> -  // expected-error{{expected '(' for function-style cast or type
>>>> construction}} \
>>>> -  // expected-error{{use of undeclared identifier 'vec'}}
>>>> +  vector<int> vec; // expected-error{{no template named 'vector'}}
>>>>
>>>>   VisibleStruct vs;
>>>>   vs.field = 0; // expected-error{{no member named 'field' in
>>>> 'VisibleStruct'}}
>>>>
>>>> Modified: cfe/trunk/test/Modules/submodules-merge-defs.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Modules/submodules-merge-defs.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Modules/submodules-merge-defs.cpp (original)
>>>> +++ cfe/trunk/test/Modules/submodules-merge-defs.cpp Wed May  8
>>>> 20:31:27 2019
>>>> @@ -29,7 +29,7 @@ B::Inner2 pre_bi; // expected-error +{{m
>>>> // expected-note at defs.h:4 +{{here}}
>>>> // expected-note at defs.h:17 +{{here}}
>>>> void pre_bfi(B b) { // expected-error +{{must be imported}}
>>>> -  b.f<int>(); // expected-error +{{}}
>>>> +  b.f<int>();
>>>> }
>>>>
>>>> C_Base<1> pre_cb1; // expected-error +{{must be imported}}
>>>> @@ -48,7 +48,7 @@ int pre_e = E(0); // expected-error {{mu
>>>> // expected-note at defs.h:32 +{{here}}
>>>>
>>>> int pre_ff = F<int>().f(); // expected-error +{{must be imported}}
>>>> -int pre_fg = F<int>().g<int>(); // expected-error +{{must be
>>>> imported}} expected-error 2{{expected}}
>>>> +int pre_fg = F<int>().g<int>(); // expected-error +{{must be imported}}
>>>> // expected-note at defs.h:34 +{{here}}
>>>>
>>>> G::A pre_ga // expected-error +{{must be imported}}
>>>>
>>>> Modified: cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp (original)
>>>> +++ cfe/trunk/test/Parser/cxx-ambig-init-templ.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -31,7 +31,7 @@ struct S {
>>>>
>>>>   void f2a(
>>>>     // T3<int> here is a parameter type, so must be declared before it
>>>> is used.
>>>> -    int k1 = c < b, T3 < int > x = 0 // expected-error {{unexpected
>>>> end of default argument expression}}
>>>> +    int k1 = c < b, T3 < int > x = 0 // expected-error {{no template
>>>> named 'T3'}}
>>>>   );
>>>>
>>>>   template<typename, int=0> struct T3 { T3(int); operator int(); };
>>>>
>>>> Modified: cfe/trunk/test/Parser/cxx-template-argument.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx-template-argument.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Parser/cxx-template-argument.cpp (original)
>>>> +++ cfe/trunk/test/Parser/cxx-template-argument.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -60,33 +60,32 @@ namespace pr16225add {
>>>>   template<int N1, int N2> struct ABC2 {};
>>>>
>>>>   template<class T1, typename T2> struct foo :
>>>> -    UnknownBase<T1,T2> // expected-error {{unknown template name
>>>> 'UnknownBase'}}
>>>> +    UnknownBase<T1,T2> // expected-error {{no template named
>>>> 'UnknownBase'}}
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo2 :
>>>> -    UnknownBase<T1,T2>, // expected-error {{unknown template name
>>>> 'UnknownBase'}}
>>>> +    UnknownBase<T1,T2>, // expected-error {{no template named
>>>> 'UnknownBase'}}
>>>>     Known<T1>  // expected-error {{too few template arguments for class
>>>> template 'Known'}}
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo3 :
>>>> -    UnknownBase<T1,T2,ABC<T2,T1> > // expected-error {{unknown
>>>> template name 'UnknownBase'}}
>>>> +    UnknownBase<T1,T2,ABC<T2,T1> > // expected-error {{no template
>>>> named 'UnknownBase'}}
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo4 :
>>>> -    UnknownBase<T1,ABC<T2> >, // expected-error {{unknown template
>>>> name 'UnknownBase'}} \
>>>> -                              // expected-error {{too few template
>>>> arguments for class template 'ABC'}}
>>>> +    UnknownBase<T1,ABC<T2> >, // expected-error {{too few template
>>>> arguments for class template 'ABC'}}
>>>>     Known<T1>  // expected-error {{too few template arguments for class
>>>> template 'Known'}}
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo5 :
>>>> -    UnknownBase<T1,T2,ABC<T2,T1>> // expected-error {{unknown template
>>>> name 'UnknownBase'}}
>>>> +    UnknownBase<T1,T2,ABC<T2,T1>> // expected-error {{no template
>>>> named 'UnknownBase'}}
>>>> #if __cplusplus <= 199711L
>>>>     // expected-error at -2 {{use '> >'}}
>>>> #endif
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo6 :
>>>> -    UnknownBase<T1,ABC<T2,T1>>, // expected-error {{unknown template
>>>> name 'UnknownBase'}}
>>>> +    UnknownBase<T1,ABC<T2,T1>>, // expected-error {{no template named
>>>> 'UnknownBase'}}
>>>> #if __cplusplus <= 199711L
>>>>     // expected-error at -2 {{use '> >'}}
>>>> #endif
>>>> @@ -94,32 +93,32 @@ namespace pr16225add {
>>>>   { };
>>>>
>>>>   template<class T1, typename T2, int N> struct foo7 :
>>>> -    UnknownBase<T1,T2,(N>1)> // expected-error {{unknown template name
>>>> 'UnknownBase'}}
>>>> +    UnknownBase<T1,T2,(N>1)> // expected-error {{no template named
>>>> 'UnknownBase'}}
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo8 :
>>>> -    UnknownBase<X<int,int>,X<int,int>> // expected-error {{unknown
>>>> template name 'UnknownBase'}}
>>>> +    UnknownBase<X<int,int>,X<int,int>> // expected-error {{no template
>>>> named 'UnknownBase'}}
>>>> #if __cplusplus <= 199711L
>>>>     // expected-error at -2 {{use '> >'}}
>>>> #endif
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo9 :
>>>> -    UnknownBase<Known<int,int>,X<int,int>> // expected-error {{unknown
>>>> template name 'UnknownBase'}}
>>>> +    UnknownBase<Known<int,int>,X<int,int>> // expected-error {{no
>>>> template named 'UnknownBase'}}
>>>> #if __cplusplus <= 199711L
>>>>     // expected-error at -2 {{use '> >'}}
>>>> #endif
>>>>   { };
>>>>
>>>>   template<class T1, typename T2> struct foo10 :
>>>> -    UnknownBase<Known<int,int>,X<int,X<int,int>>> // expected-error
>>>> {{unknown template name 'UnknownBase'}}
>>>> +    UnknownBase<Known<int,int>,X<int,X<int,int>>> // expected-error
>>>> {{no template named 'UnknownBase'}}
>>>> #if __cplusplus <= 199711L
>>>>     // expected-error at -2 {{use '> >'}}
>>>> #endif
>>>>   { };
>>>>
>>>>   template<int N1, int N2> struct foo11 :
>>>> -    UnknownBase<2<N1,N2<4> // expected-error {{unknown template name
>>>> 'UnknownBase'}}
>>>> +    UnknownBase<2<N1,N2<4> // expected-error {{no template named
>>>> 'UnknownBase'}}
>>>>   { };
>>>>
>>>> }
>>>>
>>>> Modified: cfe/trunk/test/Parser/cxx-template-decl.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Parser/cxx-template-decl.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/Parser/cxx-template-decl.cpp (original)
>>>> +++ cfe/trunk/test/Parser/cxx-template-decl.cpp Wed May  8 20:31:27 2019
>>>> @@ -128,8 +128,13 @@ void f2() {
>>>>
>>>>
>>>> // PR3844
>>>> -template <> struct S<int> { }; // expected-error{{explicit
>>>> specialization of non-template struct 'S'}}
>>>> -template <> union U<int> { }; // expected-error{{explicit
>>>> specialization of non-template union 'U'}}
>>>> +template <> struct S<int> { }; // expected-error{{explicit
>>>> specialization of undeclared template struct 'S'}}
>>>> +template <> union U<int> { }; // expected-error{{explicit
>>>> specialization of undeclared template union 'U'}}
>>>> +
>>>> +struct SS;
>>>> +union UU;
>>>> +template <> struct SS<int> { }; // expected-error{{explicit
>>>> specialization of non-template struct 'SS'}}
>>>> +template <> union UU<int> { }; // expected-error{{explicit
>>>> specialization of non-template union 'UU'}}
>>>>
>>>> namespace PR6184 {
>>>>   namespace N {
>>>> @@ -230,11 +235,11 @@ struct base { };
>>>>
>>>> struct t1 : base<int,
>>>>   public:  // expected-error {{expected expression}}
>>>> -};  // expected-error {{expected class name}}
>>>> +};
>>>> // expected-error at -1 {{expected '{' after base class list}}
>>>> struct t2 : base<int,
>>>>   public  // expected-error {{expected expression}}
>>>> -};  // expected-error {{expected class name}}
>>>> +};
>>>> // expected-error at -1 {{expected '{' after base class list}}
>>>>
>>>> }
>>>>
>>>> Modified: cfe/trunk/test/SemaCXX/alias-template.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/alias-template.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/alias-template.cpp (original)
>>>> +++ cfe/trunk/test/SemaCXX/alias-template.cpp Wed May  8 20:31:27 2019
>>>> @@ -112,11 +112,8 @@ namespace StdExample {
>>>>   template<typename T> using handler_t = void (*)(T);
>>>>   extern handler_t<int> ignore;
>>>>   extern void (*ignore)(int);
>>>> -  // FIXME: we recover as if cell is an undeclared variable. the
>>>> diagnostics are terrible!
>>>> -  template<typename T> using cell = pair<T*, cell<T>*>; //
>>>> expected-error {{use of undeclared identifier 'cell'}} \
>>>> -
>>>>                                                           expected-error
>>>> {{'T' does not refer to a value}} \
>>>> -
>>>>                                                           expected-note
>>>> {{declared here}} \
>>>> -
>>>>                                                           expected-error
>>>> {{expected ';' after alias declaration}}
>>>> +  // FIXME: we recover as if cell is an undeclared variable template
>>>> +  template<typename T> using cell = pair<T*, cell<T>*>; //
>>>> expected-error {{use of undeclared identifier 'cell'}} expected-error
>>>> {{expected expression}}
>>>> }
>>>>
>>>> namespace Access {
>>>>
>>>> Modified: cfe/trunk/test/SemaCXX/class.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/class.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/class.cpp (original)
>>>> +++ cfe/trunk/test/SemaCXX/class.cpp Wed May  8 20:31:27 2019
>>>> @@ -138,7 +138,7 @@ struct S
>>>> // Don't crash on this bogus code.
>>>> namespace pr6629 {
>>>>   template<class T1, class T2> struct foo :
>>>> -    bogus<foo<T1,T2> > // expected-error {{unknown template name
>>>> 'bogus'}}
>>>> +    bogus<foo<T1,T2> > // expected-error {{no template named 'bogus'}}
>>>>   { };
>>>>
>>>>   template<> struct foo<unknown,unknown> { // expected-error
>>>> {{undeclared identifier 'unknown'}}
>>>>
>>>> Added: cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp?rev=360308&view=auto
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp (added)
>>>> +++ cfe/trunk/test/SemaCXX/cxx2a-adl-only-template-id.cpp Wed May  8
>>>> 20:31:27 2019
>>>> @@ -0,0 +1,67 @@
>>>> +// RUN: %clang_cc1 -std=c++2a -verify %s
>>>> +
>>>> +namespace N {
>>>> +  struct Q {};
>>>> +  template<typename> int f(Q);
>>>> +  template<int> int f(Q);
>>>> +  template<typename> int g(Q);
>>>> +  template<int> int g(Q);
>>>> +
>>>> +  template<int> int some_long_name(Q); // expected-note {{here}}
>>>> +}
>>>> +N::Q q;
>>>> +int g();
>>>> +
>>>> +int h();
>>>> +template<int> int h(...);
>>>> +int h(int);
>>>> +
>>>> +// OK, these find the above functions by ADL.
>>>> +int a = f<int>(q);
>>>> +int b(f<int>(q));
>>>> +int c(f<0>(q));
>>>> +int d = g<int>(q);
>>>> +
>>>> +int e = h<0>(q); // ok, found by unqualified lookup
>>>> +
>>>> +void fn() {
>>>> +  f<0>(q);
>>>> +  int f;
>>>> +  f<0>(q); // expected-error {{invalid operands to binary expression}}
>>>> +}
>>>> +
>>>> +void disambig() {
>>>> +  // FIXME: It's unclear whether ending the template argument at the >
>>>> inside the ?: is correct here (see DR579).
>>>> +  f<true ? 1 > 2 : 3>(q); // expected-error {{expected ':'}}
>>>> expected-note {{to match}} expected-error {{expected expression}}
>>>> +
>>>> +  f < 1 + 3 > (q); // ok, function call
>>>> +}
>>>> +
>>>> +bool typo(int something) { // expected-note 4{{declared here}}
>>>> +  // FIXME: We shouldn't suggest the N:: for an ADL call if the
>>>> candidate can be found by ADL.
>>>> +  some_logn_name<3>(q); // expected-error {{did you mean
>>>> 'N::some_long_name'?}}
>>>> +  somethign < 3 ? h() > 4 : h(0); // expected-error {{did you mean
>>>> 'something'}}
>>>> +  // This is parsed as a comparison on the left of a ?: expression.
>>>> +  somethign < 3 ? h() + 4 : h(0); // expected-error {{did you mean
>>>> 'something'}}
>>>> +  // This is parsed as an ADL-only template-id call.
>>>> +  somethign < 3 ? h() + 4 : h(0) >(0); // expected-error {{undeclared
>>>> identifier 'somethign'}}
>>>> +  bool k(somethign < 3); // expected-error {{did you mean 'something'}}
>>>> +  return somethign < 3; // expected-error {{did you mean 'something'}}
>>>> +}
>>>> +
>>>> +// Ensure that treating undeclared identifiers as template names
>>>> doesn't cause
>>>> +// problems.
>>>> +struct W<int> {}; // expected-error {{undeclared template struct 'W'}}
>>>> +X<int>::Y xy; // expected-error {{no template named 'X'}}
>>>> +void xf(X<int> x); // expected-error {{no template named 'X'}}
>>>> +struct A : X<int> { // expected-error {{no template named 'X'}}
>>>> +  A() : X<int>() {} // expected-error {{no template named 'X'}}
>>>> +};
>>>> +
>>>> +// Similarly for treating overload sets of functions as template names.
>>>> +struct g<int> {}; // expected-error {{'g' refers to a function
>>>> template}}
>>>> +g<int>::Y xy; // expected-error {{no template named 'g'}} FIXME lies
>>>> +void xf(g<int> x); // expected-error {{variable has incomplete type
>>>> 'void'}} expected-error 1+{{}} expected-note {{}}
>>>> +struct B : g<int> { // expected-error {{expected class name}}
>>>> +  B() : g<int>() {} // expected-error {{expected class member or base
>>>> class name}}
>>>> +};
>>>>
>>>> Modified: cfe/trunk/test/SemaCXX/destructor.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/destructor.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/destructor.cpp (original)
>>>> +++ cfe/trunk/test/SemaCXX/destructor.cpp Wed May  8 20:31:27 2019
>>>> @@ -99,7 +99,7 @@ struct Y {
>>>> namespace PR6421 {
>>>>   class T; // expected-note{{forward declaration}}
>>>>
>>>> -  class QGenericArgument // expected-note{{declared here}}
>>>> +  class QGenericArgument
>>>>   {
>>>>     template<typename U>
>>>>     void foo(T t) // expected-error{{variable has incomplete type}}
>>>> @@ -108,8 +108,7 @@ namespace PR6421 {
>>>>     void disconnect()
>>>>     {
>>>>       T* t;
>>>> -      bob<QGenericArgument>(t); // expected-error{{undeclared
>>>> identifier 'bob'}} \
>>>> -      // expected-error{{does not refer to a value}}
>>>> +      bob<QGenericArgument>(t); // expected-error{{undeclared
>>>> identifier 'bob'}}
>>>>     }
>>>>   };
>>>> }
>>>>
>>>> Modified: cfe/trunk/test/SemaCXX/invalid-member-expr.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/invalid-member-expr.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/invalid-member-expr.cpp (original)
>>>> +++ cfe/trunk/test/SemaCXX/invalid-member-expr.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -53,7 +53,10 @@ namespace test3 {
>>>> namespace rdar11293995 {
>>>>
>>>> struct Length {
>>>> -  explicit Length(PassRefPtr<CalculationValue>); // expected-error
>>>> {{no template named 'PassRefPtr}} expected-error {{undeclared identifier
>>>> 'CalculationValue'}}
>>>> +  // FIXME: We try to annotate the template-id here during tentative
>>>> parsing,
>>>> +  // and fail, then try again during the actual parse. This results in
>>>> the same
>>>> +  // diagnostic being produced twice. :(
>>>> +  explicit Length(PassRefPtr<CalculationValue>); // expected-error
>>>> 2{{undeclared identifier 'CalculationValue'}}
>>>> };
>>>>
>>>> struct LengthSize {
>>>>
>>>> Modified: cfe/trunk/test/SemaCXX/typo-correction.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/typo-correction.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaCXX/typo-correction.cpp (original)
>>>> +++ cfe/trunk/test/SemaCXX/typo-correction.cpp Wed May  8 20:31:27 2019
>>>> @@ -438,7 +438,7 @@ namespace PR17394 {
>>>>     long zzzzzzzzzz;
>>>>   };
>>>>   class B : private A {};
>>>> -  B zzzzzzzzzy<>; // expected-error {{expected ';' after top level
>>>> declarator}}{}
>>>> +  B zzzzzzzzzy<>; // expected-error {{template specialization requires
>>>> 'template<>'}} expected-error {{no variable template matches
>>>> specialization}}
>>>> }
>>>>
>>>> namespace correct_fields_in_member_funcs {
>>>>
>>>> Modified: cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp (original)
>>>> +++ cfe/trunk/test/SemaTemplate/dependent-base-classes.cpp Wed May  8
>>>> 20:31:27 2019
>>>> @@ -9,7 +9,7 @@ template<typename T, typename U>
>>>> struct X1 : T::apply<U> { }; // expected-error{{use 'template' keyword
>>>> to treat 'apply' as a dependent template name}}
>>>>
>>>> template<typename T>
>>>> -struct X2 : vector<T> { }; // expected-error{{unknown template name
>>>> 'vector'}}
>>>> +struct X2 : vector<T> { }; // expected-error{{no template named
>>>> 'vector'}}
>>>>
>>>> namespace PR6031 {
>>>>   template<typename T>
>>>>
>>>> Modified: cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp
>>>> (original)
>>>> +++ cfe/trunk/test/SemaTemplate/dependent-template-recover.cpp Wed May
>>>>  8 20:31:27 2019
>>>> @@ -7,7 +7,7 @@ struct X {
>>>>
>>>>     t->operator+<U const, 1>(1); // expected-error{{use 'template'
>>>> keyword to treat 'operator +' as a dependent template name}}
>>>>     t->f1<int const, 2>(1); // expected-error{{use 'template' keyword
>>>> to treat 'f1' as a dependent template name}}
>>>> -    t->f1<3, int const>(1); // expected-error{{missing 'template'
>>>> keyword prior to dependent template name 'f1'}}
>>>> +    t->f1<3, int const>(1); // expected-error{{use 'template' keyword
>>>> to treat 'f1' as a dependent template name}}
>>>>
>>>>     T::getAs<U>(); // expected-error{{use 'template' keyword to treat
>>>> 'getAs' as a dependent template name}}
>>>>     t->T::getAs<U>(); // expected-error{{use 'template' keyword to
>>>> treat 'getAs' as a dependent template name}}
>>>> @@ -15,7 +15,7 @@ struct X {
>>>>     (*t).f2<N>(); // expected-error{{missing 'template' keyword prior
>>>> to dependent template name 'f2'}}
>>>>     (*t).f2<0>(); // expected-error{{missing 'template' keyword prior
>>>> to dependent template name 'f2'}}
>>>>     T::f2<0>(); // expected-error{{missing 'template' keyword prior to
>>>> dependent template name 'f2'}}
>>>> -    T::f2<0, int>(0); // expected-error{{missing 'template' keyword
>>>> prior to dependent template name 'f2'}}
>>>> +    T::f2<0, int>(0); // expected-error{{use 'template' keyword to
>>>> treat 'f2' as a dependent template name}}
>>>>
>>>>     T::foo<N < 2 || N >= 4>(); // expected-error{{missing 'template'
>>>> keyword prior to dependent template name 'foo'}}
>>>>
>>>> @@ -24,7 +24,7 @@ struct X {
>>>>     T::foo<T::bar < 1>(); // expected-error{{missing 'template' keyword
>>>> prior to dependent template name 'foo'}}
>>>>     T::foo < T::bar<1>(); // expected-error{{missing 'template' keyword
>>>> prior to dependent template name 'bar'}}
>>>>
>>>> -    // Prefer to diagonse a missing 'template' keyword rather than
>>>> finding a non-template name.
>>>> +    // Prefer to diagnose a missing 'template' keyword rather than
>>>> finding a non-template name.
>>>>     xyz < T::foo < 1 > (); // expected-error{{missing 'template'
>>>> keyword prior to dependent template name 'foo'}}
>>>>     T::foo < xyz < 1 > (); // expected-error{{missing 'template'
>>>> keyword prior to dependent template name 'foo'}}
>>>>
>>>> @@ -83,12 +83,12 @@ template<int N, typename T> void f(T t)
>>>>   T::g<mb>(0);
>>>>
>>>>   // ... but this one must be a template-id.
>>>> -  T::g<mb, int>(0); // expected-error {{missing 'template' keyword
>>>> prior to dependent template name 'g'}}
>>>> +  T::g<mb, int>(0); // expected-error {{use 'template' keyword to
>>>> treat 'g' as a dependent template name}} expected-error {{no matching
>>>> function}}
>>>> }
>>>>
>>>> struct Y {
>>>>   template <int> void f(int);
>>>> -  template <int = 0> static void g(int); // expected-warning
>>>> 0-1{{extension}}
>>>> +  template <int = 0> static void g(int); // expected-warning
>>>> 0-1{{extension}} expected-note {{candidate}}
>>>> };
>>>> void q() { void (*p)(int) = Y::g; }
>>>> template void f<0>(Y); // expected-note {{in instantiation of}}
>>>>
>>>> Modified: cfe/trunk/test/SemaTemplate/rdar9173693.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/rdar9173693.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaTemplate/rdar9173693.cpp (original)
>>>> +++ cfe/trunk/test/SemaTemplate/rdar9173693.cpp Wed May  8 20:31:27 2019
>>>> @@ -2,5 +2,8 @@
>>>>
>>>> // <rdar://problem/9173693>
>>>> template< bool C > struct assert { };
>>>> -template< bool > struct assert_arg_pred_impl { }; // expected-note 3
>>>> {{declared here}}
>>>> -template< typename Pred > assert<false> assert_not_arg( void
>>>> (*)(Pred), typename assert_arg_pred<Pred>::type ); // expected-error 5 {{}}
>>>> +// FIXME: We diagnose the same problem multiple times here because we
>>>> have no
>>>> +// way to indicate in the token stream that we already tried to
>>>> annotate a
>>>> +// template-id and we failed.
>>>> +template< bool > struct assert_arg_pred_impl { }; // expected-note 4
>>>> {{declared here}}
>>>> +template< typename Pred > assert<false> assert_not_arg( void
>>>> (*)(Pred), typename assert_arg_pred<Pred>::type ); // expected-error 6 {{}}
>>>>
>>>> Modified: cfe/trunk/test/SemaTemplate/recovery-crash.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/recovery-crash.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/test/SemaTemplate/recovery-crash.cpp (original)
>>>> +++ cfe/trunk/test/SemaTemplate/recovery-crash.cpp Wed May  8 20:31:27
>>>> 2019
>>>> @@ -28,12 +28,12 @@ namespace PR16134 {
>>>> namespace PR16225 {
>>>>   template <typename T> void f();
>>>>   template <typename C> void g(C*) {
>>>> -    struct LocalStruct : UnknownBase<Mumble, C> { };  //
>>>> expected-error {{unknown template name 'UnknownBase'}} \
>>>> -                                                      //
>>>> expected-error {{use of undeclared identifier 'Mumble'}}
>>>> +    struct LocalStruct : UnknownBase<Mumble, C> { };  //
>>>> expected-error {{use of undeclared identifier 'Mumble'}}
>>>>     f<LocalStruct>();
>>>> #if __cplusplus <= 199711L
>>>>     // expected-warning at -2 {{template argument uses local type
>>>> 'LocalStruct'}}
>>>> #endif
>>>> +    struct LocalStruct2 : UnknownBase<C> { };  // expected-error {{no
>>>> template named 'UnknownBase'}}
>>>>   }
>>>>   struct S;
>>>>   void h() {
>>>>
>>>> Modified: cfe/trunk/tools/libclang/CIndex.cpp
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/tools/libclang/CIndex.cpp?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/tools/libclang/CIndex.cpp (original)
>>>> +++ cfe/trunk/tools/libclang/CIndex.cpp Wed May  8 20:31:27 2019
>>>> @@ -1430,6 +1430,10 @@ bool CursorVisitor::VisitTemplateName(Te
>>>>
>>>>     return false;
>>>>
>>>> +  case TemplateName::AssumedTemplate:
>>>> +    // FIXME: Visit DeclarationName?
>>>> +    return false;
>>>> +
>>>>   case TemplateName::DependentTemplate:
>>>>     // FIXME: Visit nested-name-specifier.
>>>>     return false;
>>>>
>>>> Modified: cfe/trunk/www/cxx_status.html
>>>> URL:
>>>> http://llvm.org/viewvc/llvm-project/cfe/trunk/www/cxx_status.html?rev=360308&r1=360307&r2=360308&view=diff
>>>>
>>>> ==============================================================================
>>>> --- cfe/trunk/www/cxx_status.html (original)
>>>> +++ cfe/trunk/www/cxx_status.html Wed May  8 20:31:27 2019
>>>> @@ -893,7 +893,7 @@ as the draft C++2a standard evolves.
>>>>     <tr>
>>>>       <td>ADL and function templates that are not visible</td>
>>>>       <td><a href="http://wg21.link/p0846r0">P0846R0</a></td>
>>>> -      <td class="none" align="center">No</td>
>>>> +      <td class="svn" align="center">SVN</td>
>>>>     </tr>
>>>>     <tr>
>>>>       <td><tt>const</tt> mismatch with defaulted copy constructor</td>
>>>>
>>>>
>>>> _______________________________________________
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>>>> cfe-commits at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>
>>>>
>>>> _______________________________________________
>>>> cfe-commits mailing list
>>>> cfe-commits at lists.llvm.org
>>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>>>>
>>> _______________________________________________
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>>
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