[clang] [Clang][Sema] Explicit template arguments are not substituted into the exception specification of a function (PR #90760)
Krystian Stasiowski via cfe-commits
cfe-commits at lists.llvm.org
Wed May 1 11:54:21 PDT 2024
https://github.com/sdkrystian created https://github.com/llvm/llvm-project/pull/90760
[[temp.deduct.general] p6](eel.is/c++draft/temp.deduct.general#6) states:
> At certain points in the template argument deduction process it is necessary to take a function type that makes use of template parameters and replace those template parameters with the corresponding template arguments.
This is done at the beginning of template argument deduction when any explicitly specified template arguments are substituted into the function type, and again at the end of template argument deduction when any template arguments that were deduced or obtained from default arguments are substituted.
[[temp.deduct.general] p7](eel.is/c++draft/temp.deduct.general#7) goes on to say:
> The _deduction substitution loci_ are
> - the function type outside of the _noexcept-specifier_,
> - the explicit-specifier,
> - the template parameter declarations, and
> - the template argument list of a partial specialization
>
> The substitution occurs in all types and expressions that are used in the deduction substitution loci. [...]
Currently, `Sema::SubstituteExplicitTemplateArguments` will substitute into the _noexcept-specifier_ when deducing template arguments from a function declaration or when deducing template arguments for taking the address of a function template (and the substitution is treated as happening in a SFINAE context). This behavior is incorrect ([note 4](http://eel.is/c++draft/temp.deduct.general#note-4) says as much), and this patch corrects it by deferring all substitution into the _noexcept-specifier_ until it is instantiated.
As part of the necessary changes to make this patch work, the instantiation of the exception specification of a function template specialization when taking the address of a function template is changed to only occur for the function selected by overload resolution per [[except.spec] p13.1](http://eel.is/c++draft/except.spec#13.1) (as opposed to being instantiated for every candidate).
>From 5086c9801842b22dbc99393d52a02f35d1fcfdfc Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Wed, 1 May 2024 10:54:12 -0400
Subject: [PATCH 1/2] [Clang][Sema] Explicit template arguments are not
substituted into the exception specification of a function
---
clang/lib/Sema/SemaTemplateDeduction.cpp | 17 -----------------
clang/test/CXX/temp/temp.deduct/p7.cpp | 14 ++++++++++++++
2 files changed, 14 insertions(+), 17 deletions(-)
create mode 100644 clang/test/CXX/temp/temp.deduct/p7.cpp
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index e93f7bd842e444..1f67cf0dd3f6d2 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -3414,23 +3414,6 @@ TemplateDeductionResult Sema::SubstituteExplicitTemplateArguments(
if (FunctionType) {
auto EPI = Proto->getExtProtoInfo();
EPI.ExtParameterInfos = ExtParamInfos.getPointerOrNull(ParamTypes.size());
-
- // In C++1z onwards, exception specifications are part of the function type,
- // so substitution into the type must also substitute into the exception
- // specification.
- SmallVector<QualType, 4> ExceptionStorage;
- if (getLangOpts().CPlusPlus17 &&
- SubstExceptionSpec(
- Function->getLocation(), EPI.ExceptionSpec, ExceptionStorage,
- getTemplateInstantiationArgs(
- FunctionTemplate, nullptr, /*Final=*/true,
- /*Innermost=*/SugaredExplicitArgumentList->asArray(),
- /*RelativeToPrimary=*/false,
- /*Pattern=*/nullptr,
- /*ForConstraintInstantiation=*/false,
- /*SkipForSpecialization=*/true)))
- return TemplateDeductionResult::SubstitutionFailure;
-
*FunctionType = BuildFunctionType(ResultType, ParamTypes,
Function->getLocation(),
Function->getDeclName(),
diff --git a/clang/test/CXX/temp/temp.deduct/p7.cpp b/clang/test/CXX/temp/temp.deduct/p7.cpp
new file mode 100644
index 00000000000000..cf6d17fc51ac95
--- /dev/null
+++ b/clang/test/CXX/temp/temp.deduct/p7.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -verify %s
+
+struct A {
+ static constexpr bool x = true;
+};
+
+template<typename T, typename U>
+void f(T, U) noexcept(T::x);
+
+template<typename T, typename U>
+void f(T, U*) noexcept(T::y); // expected-error {{no member named 'y' in 'A'}}
+
+template<>
+void f<A>(A, int*); // expected-note {{in instantiation of exception specification}}
>From 2bc18f45560f607a09c756bb9ebca0b7ad5d1bb4 Mon Sep 17 00:00:00 2001
From: Krystian Stasiowski <sdkrystian at gmail.com>
Date: Wed, 1 May 2024 14:14:28 -0400
Subject: [PATCH 2/2] [FOLD]
---
clang/lib/Sema/SemaInit.cpp | 20 +++++++++++++------
clang/lib/Sema/SemaTemplateDeduction.cpp | 11 ++--------
clang/test/CXX/drs/dr13xx.cpp | 13 +++++-------
.../SemaCXX/cxx1z-noexcept-function-type.cpp | 4 ++--
clang/test/SemaTemplate/temp_arg_type.cpp | 10 ++++------
5 files changed, 27 insertions(+), 31 deletions(-)
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 7d9eaf6720461d..2c1c7affbc13a4 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -6576,12 +6576,10 @@ void InitializationSequence::InitializeFrom(Sema &S,
AddPassByIndirectCopyRestoreStep(DestType, ShouldCopy);
} else if (ICS.isBad()) {
- DeclAccessPair dap;
- if (isLibstdcxxPointerReturnFalseHack(S, Entity, Initializer)) {
+ if (isLibstdcxxPointerReturnFalseHack(S, Entity, Initializer))
AddZeroInitializationStep(Entity.getType());
- } else if (Initializer->getType() == Context.OverloadTy &&
- !S.ResolveAddressOfOverloadedFunction(Initializer, DestType,
- false, dap))
+ else if (DeclAccessPair Found; Initializer->getType() == Context.OverloadTy &&
+ !S.ResolveAddressOfOverloadedFunction(Initializer, DestType, /*Complain=*/false, Found))
SetFailed(InitializationSequence::FK_AddressOfOverloadFailed);
else if (Initializer->getType()->isFunctionType() &&
isExprAnUnaddressableFunction(S, Initializer))
@@ -9641,6 +9639,8 @@ bool InitializationSequence::Diagnose(Sema &S,
if (!Failed())
return false;
+ QualType DestType = Entity.getType();
+
// When we want to diagnose only one element of a braced-init-list,
// we need to factor it out.
Expr *OnlyArg;
@@ -9650,11 +9650,19 @@ bool InitializationSequence::Diagnose(Sema &S,
OnlyArg = List->getInit(0);
else
OnlyArg = Args[0];
+
+ if (OnlyArg->getType() == S.Context.OverloadTy) {
+ DeclAccessPair Found;
+ if (FunctionDecl *FD = S.ResolveAddressOfOverloadedFunction(
+ OnlyArg, DestType.getNonReferenceType(), /*Complain=*/false, Found)) {
+ if (Expr *Resolved = S.FixOverloadedFunctionReference(OnlyArg, Found, FD).get())
+ OnlyArg = Resolved;
+ }
+ }
}
else
OnlyArg = nullptr;
- QualType DestType = Entity.getType();
switch (Failure) {
case FK_TooManyInitsForReference:
// FIXME: Customize for the initialized entity?
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index 1f67cf0dd3f6d2..fc8a645e733926 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -1231,11 +1231,11 @@ bool Sema::isSameOrCompatibleFunctionType(QualType P, QualType A) {
// Noreturn and noexcept adjustment.
QualType AdjustedParam;
if (IsFunctionConversion(P, A, AdjustedParam))
- return Context.hasSameType(AdjustedParam, A);
+ return Context.hasSameFunctionTypeIgnoringExceptionSpec(AdjustedParam, A);
// FIXME: Compatible calling conventions.
- return Context.hasSameType(P, A);
+ return Context.hasSameFunctionTypeIgnoringExceptionSpec(P, A);
}
/// Get the index of the first template parameter that was originally from the
@@ -4593,13 +4593,6 @@ TemplateDeductionResult Sema::DeduceTemplateArguments(
Info.getLocation()))
return TemplateDeductionResult::MiscellaneousDeductionFailure;
- auto *SpecializationFPT =
- Specialization->getType()->castAs<FunctionProtoType>();
- if (IsAddressOfFunction && getLangOpts().CPlusPlus17 &&
- isUnresolvedExceptionSpec(SpecializationFPT->getExceptionSpecType()) &&
- !ResolveExceptionSpec(Info.getLocation(), SpecializationFPT))
- return TemplateDeductionResult::MiscellaneousDeductionFailure;
-
// Adjust the exception specification of the argument to match the
// substituted and resolved type we just formed. (Calling convention and
// noreturn can't be dependent, so we don't actually need this for them
diff --git a/clang/test/CXX/drs/dr13xx.cpp b/clang/test/CXX/drs/dr13xx.cpp
index dad82c4e2829f0..a334b6d01acf51 100644
--- a/clang/test/CXX/drs/dr13xx.cpp
+++ b/clang/test/CXX/drs/dr13xx.cpp
@@ -281,13 +281,10 @@ namespace cwg1330 { // cwg1330: 4 c++11
decltype(f<char>()) f2; // #cwg1330-f-char
bool f3 = noexcept(f<float>()); /// #cwg1330-f-float
#endif
- // In C++17 onwards, substituting explicit template arguments into the
- // function type substitutes into the exception specification (because it's
- // part of the type). In earlier languages, we don't notice there's a problem
- // until we've already started to instantiate.
template int f<short>(); // #cwg1330-f-short
- // since-cxx17-error at -1 {{explicit instantiation of 'f' does not refer to a function template, variable template, member function, member class, or static data member}}
- // since-cxx17-note@#cwg1330-f {{candidate template ignored: substitution failure [with T = short]: type 'short' cannot be used prior to '::' because it has no members}}
+ // since-cxx17-error@#cwg1330-f {{type 'short' cannot be used prior to '::' because it has no members}}
+ // since-cxx17-note@#cwg1330-f {{in instantiation of exception specification for 'f<short>' requested here}}
+ // since-cxx17-note@#cwg1330-f-short {{in instantiation of function template specialization 'cwg1330::f<short>' requested here}}
template<typename T> struct C {
C() throw(typename T::type); // #cwg1330-C
@@ -500,7 +497,7 @@ namespace cwg1359 { // cwg1359: 3.5
union B { constexpr B() = default; int a; }; // #cwg1359-B
// cxx11-17-error at -1 {{defaulted definition of default constructor cannot be marked constexpr before C++23}}
union C { constexpr C() = default; int a, b; }; // #cwg1359-C
- // cxx11-17-error at -1 {{defaulted definition of default constructor cannot be marked constexpr}}
+ // cxx11-17-error at -1 {{defaulted definition of default constructor cannot be marked constexpr}}
struct X { constexpr X() = default; union {}; };
// since-cxx11-error at -1 {{declaration does not declare anything}}
struct Y { constexpr Y() = default; union { int a; }; }; // #cwg1359-Y
@@ -720,7 +717,7 @@ struct A {
} // namespace cwg1397
namespace cwg1399 { // cwg1399: dup 1388
- template<typename ...T> void f(T..., int, T...) {} // #cwg1399-f
+ template<typename ...T> void f(T..., int, T...) {} // #cwg1399-f
// cxx98-error at -1 {{variadic templates are a C++11 extension}}
void g() {
f(0);
diff --git a/clang/test/SemaCXX/cxx1z-noexcept-function-type.cpp b/clang/test/SemaCXX/cxx1z-noexcept-function-type.cpp
index 5e56f19477d6ca..c8204c21523a37 100644
--- a/clang/test/SemaCXX/cxx1z-noexcept-function-type.cpp
+++ b/clang/test/SemaCXX/cxx1z-noexcept-function-type.cpp
@@ -18,7 +18,7 @@ template<typename A, typename B> void redecl3() throw(B); // expected-error {{do
typedef int I;
template<bool B> void redecl4(I) noexcept(B);
-template<bool B> void redecl4(I) noexcept(B); // expected-note {{could not match 'void (I) noexcept(false)' (aka 'void (int) noexcept(false)') against 'void (int) noexcept'}}
+template<bool B> void redecl4(I) noexcept(B);
void (*init_with_exact_type_a)(int) noexcept = redecl4<true>;
void (*init_with_mismatched_type_a)(int) = redecl4<true>;
@@ -27,7 +27,7 @@ using DeducedType_a = decltype(deduce_auto_from_noexcept_function_ptr_a);
using DeducedType_a = void (*)(int) noexcept;
void (*init_with_exact_type_b)(int) = redecl4<false>;
-void (*init_with_mismatched_type_b)(int) noexcept = redecl4<false>; // expected-error {{does not match required type}}
+void (*init_with_mismatched_type_b)(int) noexcept = redecl4<false>; // expected-error {{cannot initialize a variable of type}}
auto deduce_auto_from_noexcept_function_ptr_b = redecl4<false>;
using DeducedType_b = decltype(deduce_auto_from_noexcept_function_ptr_b);
using DeducedType_b = void (*)(int);
diff --git a/clang/test/SemaTemplate/temp_arg_type.cpp b/clang/test/SemaTemplate/temp_arg_type.cpp
index 9069f63e0224fe..cdbcf281125efd 100644
--- a/clang/test/SemaTemplate/temp_arg_type.cpp
+++ b/clang/test/SemaTemplate/temp_arg_type.cpp
@@ -11,7 +11,7 @@ A<0> *a1; // expected-error{{template argument for template type parameter must
A<A> *a2; // expected-error{{use of class template 'A' requires template arguments}}
A<int> *a3;
-A<int()> *a4;
+A<int()> *a4;
A<int(float)> *a5;
A<A<int> > *a6;
@@ -95,15 +95,13 @@ namespace deduce_noexcept {
template void dep() noexcept(true); // expected-error {{does not refer to a function template}}
template void dep() noexcept(false); // expected-error {{does not refer to a function template}}
- // FIXME: It's also not clear whether this should be valid: do we substitute
- // into the function type (including the exception specification) or not?
- template<typename T> typename T::type1 f() noexcept(T::a);
- template<typename T> typename T::type2 f() noexcept(T::b) {}
+ template<typename T> typename T::type1 f() noexcept(T::a); // expected-note {{candidate}}
+ template<typename T> typename T::type2 f() noexcept(T::b) {} // expected-note {{candidate}}
struct X {
static constexpr bool b = true;
using type1 = void;
using type2 = void;
};
- template void f<X>();
+ template void f<X>(); // expected-error {{partial ordering for explicit instantiation of 'f' is ambiguous}}
}
#endif
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