From 0e3246e46820df6d13ea623e20c8226c571d4f9a Mon Sep 17 00:00:00 2001 From: Matheus Izvekov Date: Mon, 27 Jan 2025 00:04:59 -0300 Subject: [PATCH] [clang] fix nondeduced mismatch with nullptr template arguments In deduction, when comparing template arguments of value kind, we should check if the value matches. Values of different types can still match. For example, `short(0)` matches `int(0)`. Values of nullptr kind always match each other, since there is only one such possible value. Similarly to integrals, the type does not matter. --- clang/docs/ReleaseNotes.rst | 1 + clang/lib/Sema/SemaTemplateDeduction.cpp | 7 ++++--- clang/test/SemaTemplate/cwg2398.cpp | 4 ---- 3 files changed, 5 insertions(+), 7 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index c1bf2dc1c33aa..d8a94703bd9c5 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -1037,6 +1037,7 @@ Bug Fixes to C++ Support - Fix template argument checking so that converted template arguments are converted again. This fixes some issues with partial ordering involving template template parameters with non-type template parameters. +- Fix nondeduced mismatch with nullptr template arguments. - Clang now rejects declaring an alias template with the same name as its template parameter. (#GH123423) - Fixed the rejection of valid code when referencing an enumerator of an unscoped enum member with a prior declaration. (#GH124405) - Fixed immediate escalation of non-dependent expressions. (#GH123405) diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp index 2b96692727a7c..1e1fce10e7c01 100644 --- a/clang/lib/Sema/SemaTemplateDeduction.cpp +++ b/clang/lib/Sema/SemaTemplateDeduction.cpp @@ -2541,10 +2541,9 @@ DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams, return TemplateDeductionResult::NonDeducedMismatch; case TemplateArgument::NullPtr: - if (A.getKind() == TemplateArgument::NullPtr && - S.Context.hasSameType(P.getNullPtrType(), A.getNullPtrType())) + // 'nullptr' has only one possible value, so it always matches. + if (A.getKind() == TemplateArgument::NullPtr) return TemplateDeductionResult::Success; - Info.FirstArg = P; Info.SecondArg = A; return TemplateDeductionResult::NonDeducedMismatch; @@ -2559,6 +2558,8 @@ DeduceTemplateArguments(Sema &S, TemplateParameterList *TemplateParams, return TemplateDeductionResult::NonDeducedMismatch; case TemplateArgument::StructuralValue: + // FIXME: structural equality will also compare types, + // but they should match iff they have the same value. if (A.getKind() == TemplateArgument::StructuralValue && A.structurallyEquals(P)) return TemplateDeductionResult::Success; diff --git a/clang/test/SemaTemplate/cwg2398.cpp b/clang/test/SemaTemplate/cwg2398.cpp index 137b94ba2641d..dccb17c48d325 100644 --- a/clang/test/SemaTemplate/cwg2398.cpp +++ b/clang/test/SemaTemplate/cwg2398.cpp @@ -697,15 +697,11 @@ namespace nttp_partial_order { template void f(B<&A::m>); } // namespace t5 namespace t6 { - // FIXME: This should pick the second overload. struct A {}; using nullptr_t = decltype(nullptr); template class TT2> void f(TT2); - // new-note@-1 {{here}} template class TT1> void f(TT1) {} - // new-note@-1 {{here}} template struct B {}; template void f(B); - // new-error@-1 {{ambiguous}} } // namespace t6 } // namespace nttp_partial_order