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

Alex L via cfe-commits cfe-commits at lists.llvm.org
Tue Aug 13 18:08:55 PDT 2019


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.

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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