https://github.com/anirudhmathur12 updated https://github.com/llvm/llvm-project/pull/221440
>From d507501ab7b106f7bf9e42a4094cbf8374f6b0f0 Mon Sep 17 00:00:00 2001 From: AnirudhMathur12 <[email protected]> Date: Sat, 5 Sep 2026 16:22:58 +0530 Subject: [PATCH 1/4] [Clang][Sema] Don't treat error-recovery dependence as genuine template dependence in ActOnTag When a template argument fails to resolve (e.g. a namespace name used where a value is expected), Sema substitutes a RecoveryExpr with a dependent type so downstream code can recover gracefully. This error-induced dependence was being conflated with genuine template parameter dependence in ActOnTag's handling of TagUseKind::Reference/ Friend, causing computeDeclContext to report failure the same way it would for an actually-dependent nested-name-specifier. This tripped an assert in ActOnExplicitInstantiation that assumes dependent names can't reach explicit instantiation, when in fact the diagnostic had already been emitted at the point the RecoveryExpr was created. Fixes #220525 --- clang/lib/Sema/SemaDecl.cpp | 10 +++++++++- clang/test/SemaCXX/GH220525.cpp | 7 +++++++ 2 files changed, 16 insertions(+), 1 deletion(-) create mode 100644 clang/test/SemaCXX/GH220525.cpp diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index d6114ccbae7fe..7f22701376770 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -18356,7 +18356,15 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc, if (TUK == TagUseKind::Friend || TUK == TagUseKind::Reference) { DC = computeDeclContext(SS, false); if (!DC) { - IsDependent = true; + if (SS.getScopeRep().getAsType() && + !SS.getScopeRep().getAsType()->containsErrors()) { + // This is a genuinely dependent nested-name-specifier (e.g. it + // depends on an uninstantiated template parameter), not one that + // merely appears dependent because of an embedded error-recovery + // placeholder. Only in that genuine case should we defer/treat this + // as a dependent name for the caller to handle. + IsDependent = true; + } return true; } } else { diff --git a/clang/test/SemaCXX/GH220525.cpp b/clang/test/SemaCXX/GH220525.cpp new file mode 100644 index 0000000000000..5f34e67d70886 --- /dev/null +++ b/clang/test/SemaCXX/GH220525.cpp @@ -0,0 +1,7 @@ +// RUN: %clang_cc1 -std=c++17 -fsyntax-only -verify %s + +namespace foo { + template<typename T> struct S {}; // expected-note {{template parameter is declared here}} +} +template struct foo::S<foo>::bar; // expected-error {{template argument for template type parameter must be a type}} \ + // expected-error {{unexpected namespace name 'foo': expected expression}} >From 5e74ba80882b499d0defe13bb76580c60dfb8d44 Mon Sep 17 00:00:00 2001 From: AnirudhMathur12 <[email protected]> Date: Mon, 7 Sep 2026 16:04:51 +0530 Subject: [PATCH 2/4] Updates ReleaseNotes.md --- clang/docs/ReleaseNotes.md | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md index db9220d43936a..97548a5ca308e 100644 --- a/clang/docs/ReleaseNotes.md +++ b/clang/docs/ReleaseNotes.md @@ -614,6 +614,11 @@ features cannot lower the translation-unit ABI level; in a token that was lexed and cached before the first occurrence was parsed. (#GH214128) +- Fixed an assertion failure when explicitly instantiating a nested member + through a nested-name-specifier whose template argument was ill-formed. The + resulting error-recovery placeholder was being treated as a genuinely + dependent name instead of an already-diagnosed error. (#GH220525) + #### Bug Fixes to AST Handling - Fixed a non-deterministic ordering of unused local typedefs that made >From 3ca71415b4082313967d4ce038acbbdfcc9c5c5f Mon Sep 17 00:00:00 2001 From: AnirudhMathur12 <[email protected]> Date: Tue, 8 Sep 2026 22:15:22 +0530 Subject: [PATCH 3/4] use isDependentScopeSpecifier --- clang/lib/Sema/SemaDecl.cpp | 17 ++++++++--------- 1 file changed, 8 insertions(+), 9 deletions(-) diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index 7f22701376770..d52df8192afce 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -18356,15 +18356,14 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc, if (TUK == TagUseKind::Friend || TUK == TagUseKind::Reference) { DC = computeDeclContext(SS, false); if (!DC) { - if (SS.getScopeRep().getAsType() && - !SS.getScopeRep().getAsType()->containsErrors()) { - // This is a genuinely dependent nested-name-specifier (e.g. it - // depends on an uninstantiated template parameter), not one that - // merely appears dependent because of an embedded error-recovery - // placeholder. Only in that genuine case should we defer/treat this - // as a dependent name for the caller to handle. - IsDependent = true; - } + // This is a genuinely dependent nested-name-specifier (e.g. it + // depends on an uninstantiated template parameter), not one that + // merely appears dependent because of an embedded error-recovery + // placeholder. Only in that genuine case should we defer/treat this + // as a dependent name for the caller to handle. + const Type *T = SS.getScopeRep().getAsType(); + IsDependent = + isDependentScopeSpecifier(SS) && (!T || !T->containsErrors()); return true; } } else { >From 17e75d93e7c928bb5c26352774428e88f0100cf4 Mon Sep 17 00:00:00 2001 From: AnirudhMathur12 <[email protected]> Date: Sat, 19 Sep 2026 15:09:24 +0530 Subject: [PATCH 4/4] Reverted changes in SemaDecl.cpp and moved TagD nullptr check above assert --- clang/lib/Sema/SemaDecl.cpp | 9 +-------- clang/lib/Sema/SemaTemplate.cpp | 4 +++- 2 files changed, 4 insertions(+), 9 deletions(-) diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp index d52df8192afce..d6114ccbae7fe 100644 --- a/clang/lib/Sema/SemaDecl.cpp +++ b/clang/lib/Sema/SemaDecl.cpp @@ -18356,14 +18356,7 @@ Sema::ActOnTag(Scope *S, unsigned TagSpec, TagUseKind TUK, SourceLocation KWLoc, if (TUK == TagUseKind::Friend || TUK == TagUseKind::Reference) { DC = computeDeclContext(SS, false); if (!DC) { - // This is a genuinely dependent nested-name-specifier (e.g. it - // depends on an uninstantiated template parameter), not one that - // merely appears dependent because of an embedded error-recovery - // placeholder. Only in that genuine case should we defer/treat this - // as a dependent name for the caller to handle. - const Type *T = SS.getScopeRep().getAsType(); - IsDependent = - isDependentScopeSpecifier(SS) && (!T || !T->containsErrors()); + IsDependent = true; return true; } } else { diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp index dd17f9365a5a1..4a405fb3021a2 100644 --- a/clang/lib/Sema/SemaTemplate.cpp +++ b/clang/lib/Sema/SemaTemplate.cpp @@ -10600,11 +10600,13 @@ Sema::ActOnExplicitInstantiation(Scope *S, SourceLocation ExternLoc, false, TypeResult(), /*IsTypeSpecifier*/ false, /*IsTemplateParamOrArg*/ false, /*OOK=*/OffsetOfKind::Outside) .get(); - assert(!IsDependent && "explicit instantiation of dependent name not yet handled"); if (!TagD) return true; + assert(!IsDependent && + "explicit instantiation of dependent name not yet handled"); + TagDecl *Tag = cast<TagDecl>(TagD); assert(!Tag->isEnum() && "shouldn't see enumerations here"); _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
