From 4e1c487004a29ec9bc56fd47fc30336d033c57dd Mon Sep 17 00:00:00 2001 From: Adam Czachorowski Date: Thu, 4 Mar 2021 18:01:06 +0100 Subject: [PATCH] [clang] Fix crash when creating deduction guide. We used to trigger assertion when transforming c-tor with unparsed default argument. Now we ignore such constructors for this purpose. Differential Revision: https://reviews.llvm.org/D97965 --- clang/lib/Sema/SemaTemplate.cpp | 6 ++++++ .../cxx1z-class-template-argument-deduction.cpp | 11 +++++++++++ 2 files changed, 17 insertions(+) diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index 12880b95b9c6..7a65c2a6fe2c 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -2494,6 +2494,12 @@ void Sema::DeclareImplicitDeductionGuides(TemplateDecl *Template, if (!CD || (!FTD && CD->isFunctionTemplateSpecialization())) continue; + // Cannot make a deduction guide when unparsed arguments are present. + if (std::any_of(CD->param_begin(), CD->param_end(), [](ParmVarDecl *P) { + return !P || P->hasUnparsedDefaultArg(); + })) + continue; + Transform.transformConstructor(FTD, CD); AddedAny = true; } diff --git a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp index 305cc3e976b0..161944f9e64f 100644 --- a/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp +++ b/clang/test/SemaCXX/cxx1z-class-template-argument-deduction.cpp @@ -416,6 +416,17 @@ B b(0, {}); } +namespace no_crash_on_default_arg { +class A { + template class B { + B(int c = 1); + }; + // This used to crash due to unparsed default arg above. The diagnostic could + // be improved, but the point of this test is to simply check we do not crash. + B(); // expected-error {{deduction guide declaration without trailing return type}} +}; +} // namespace no_crash_on_default_arg + #pragma clang diagnostic push #pragma clang diagnostic warning "-Wctad-maybe-unsupported" namespace test_implicit_ctad_warning {