https://github.com/a-tarasyuk updated https://github.com/llvm/llvm-project/pull/173776
>From 0e6bc4ff732cfcaf5d2ba445dd25f8064da128e3 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Sun, 28 Dec 2025 14:15:42 +0200 Subject: [PATCH 1/2] [Clang] prevent assertion failure by avoiding always-dependent lambdas in constraint-related nested scopes --- clang/docs/ReleaseNotes.rst | 1 + clang/lib/Sema/SemaLambda.cpp | 14 +++++++++----- clang/test/SemaCXX/lambda-unevaluated.cpp | 9 ++++++++- 3 files changed, 18 insertions(+), 6 deletions(-) diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 2319ff13f7864..1ae44bf610221 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -623,6 +623,7 @@ Bug Fixes to C++ Support - Fix the result of ``__is_pointer_interconvertible_base_of`` when arguments are qualified and passed via template parameters. (#GH135273) - Fixed a crash when evaluating nested requirements in requires-expressions that reference invented parameters. (#GH166325) - Fixed a crash when standard comparison categories (e.g. ``std::partial_ordering``) are defined with incorrect static member types. (#GH170015) (#GH56571) +- Fixed an assertion failure triggered by nested lambdas during capture handling. (#GH172814) Bug Fixes to AST Handling ^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp index 81ec0b18dedfd..53f2612a46bf4 100644 --- a/clang/lib/Sema/SemaLambda.cpp +++ b/clang/lib/Sema/SemaLambda.cpp @@ -1102,7 +1102,7 @@ void Sema::ActOnLambdaExpressionAfterIntroducer(LambdaIntroducer &Intro, CXXRecordDecl::LDK_Unknown; if (CurScope->getTemplateParamParent() != nullptr) { LambdaDependencyKind = CXXRecordDecl::LDK_AlwaysDependent; - } else if (Scope *P = CurScope->getParent()) { + } else if (Scope *ParentScope = CurScope->getParent()) { // Given a lambda defined inside a requires expression, // // struct S { @@ -1113,10 +1113,14 @@ void Sema::ActOnLambdaExpressionAfterIntroducer(LambdaIntroducer &Intro, // The parameter var is not injected into the function Decl at the point of // parsing lambda. In such scenarios, perceiving it as dependent could // result in the constraint being evaluated, which matches what GCC does. - while (P->getEntity() && P->getEntity()->isRequiresExprBody()) - P = P->getParent(); - if (P->isFunctionDeclarationScope() && - llvm::any_of(P->decls(), [](Decl *D) { + Scope *LookupScope = ParentScope; + while (LookupScope->getEntity() && + LookupScope->getEntity()->isRequiresExprBody()) + LookupScope = LookupScope->getParent(); + + if (LookupScope != ParentScope && + LookupScope->isFunctionDeclarationScope() && + llvm::any_of(LookupScope->decls(), [](Decl *D) { return isa<ParmVarDecl>(D) && cast<ParmVarDecl>(D)->getType()->isTemplateTypeParmType(); })) diff --git a/clang/test/SemaCXX/lambda-unevaluated.cpp b/clang/test/SemaCXX/lambda-unevaluated.cpp index 9289fc9ec1243..e3dffa00cd39a 100644 --- a/clang/test/SemaCXX/lambda-unevaluated.cpp +++ b/clang/test/SemaCXX/lambda-unevaluated.cpp @@ -1,7 +1,6 @@ // RUN: %clang_cc1 -std=c++20 %s -Wno-c++23-extensions -verify // RUN: %clang_cc1 -std=c++23 %s -verify - template <auto> struct Nothing {}; Nothing<[]() { return 0; }()> nothing; @@ -282,3 +281,11 @@ static_assert(__is_same_as(int, helper<int>)); } // namespace GH138018 + +namespace GH172814 { +auto t() { + int x = 0; + return [](auto w=[&] { x += w(); }); // expected-error {{lambda expression in default argument cannot capture any entity}} \ + // expected-error {{expected body of lambda expression}} +}; +} >From d50bbaa5f931829961d6b5c24c4bfbe22645b541 Mon Sep 17 00:00:00 2001 From: Oleksandr Tarasiuk <[email protected]> Date: Mon, 29 Dec 2025 11:23:51 +0200 Subject: [PATCH 2/2] add additional test case --- clang/test/SemaCXX/lambda-unevaluated.cpp | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/clang/test/SemaCXX/lambda-unevaluated.cpp b/clang/test/SemaCXX/lambda-unevaluated.cpp index e3dffa00cd39a..d02eabf11edb4 100644 --- a/clang/test/SemaCXX/lambda-unevaluated.cpp +++ b/clang/test/SemaCXX/lambda-unevaluated.cpp @@ -283,9 +283,13 @@ static_assert(__is_same_as(int, helper<int>)); } // namespace GH138018 namespace GH172814 { -auto t() { +auto t1() { int x = 0; return [](auto w=[&] { x += w(); }); // expected-error {{lambda expression in default argument cannot capture any entity}} \ // expected-error {{expected body of lambda expression}} }; +auto t2() { + int x = 0; + return [](auto w = [&] { return x; }) { }; // expected-error {{lambda expression in default argument cannot capture any entity}} +}; } _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
