Author: Younan Zhang Date: 2026-08-24T18:39:54+08:00 New Revision: f3fd5b2dd911bedad05e316d2857fdbe3a5486ba
URL: https://github.com/llvm/llvm-project/commit/f3fd5b2dd911bedad05e316d2857fdbe3a5486ba DIFF: https://github.com/llvm/llvm-project/commit/f3fd5b2dd911bedad05e316d2857fdbe3a5486ba.diff LOG: [Clang] Clear outer SubstIndex when normalizing PackIndexingType (#218257) When we instantiate a fold-expression concept we expand the template arguments outside of the TreeTransform. However a PackIndexingType should gain its own index from the index expression, not the outer SubstIndex. The bug occurs because we don't support rewrite of PackIndexingType, which the default transform unexpectedly expands the pattern in the normalization so that the instantiation picks up the outer SubstIndex that is set up for a fold expression. This is identical to 410d6350ed, and in fact we're unnecessarily transforming the pattern of PackIndexingType repeatedly. This is a regression since #161671, so no release note for backporting. Fixes #218035 Added: Modified: clang/lib/Sema/TreeTransform.h clang/test/SemaCXX/cxx2c-fold-exprs.cpp Removed: ################################################################################ diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h index 4799f72dd6177..b0c836325a971 100644 --- a/clang/lib/Sema/TreeTransform.h +++ b/clang/lib/Sema/TreeTransform.h @@ -7124,6 +7124,10 @@ TreeTransform<Derived>::TransformPackIndexingType(TypeLocBuilder &TLB, for (QualType T : Types) { if (!T->containsUnexpandedParameterPack()) { + // A pack indexing type can appear in a larger pack expansion, + // e.g. `Pack...[pack_of_indexes]...` + // so we need to temporarily disable substitution of pack elements + Sema::ArgPackSubstIndexRAII SubstIndex(getSema(), std::nullopt); QualType Transformed = getDerived().TransformType(T); if (Transformed.isNull()) return QualType(); diff --git a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp index bd9dff73cb640..79d57a6f94d58 100644 --- a/clang/test/SemaCXX/cxx2c-fold-exprs.cpp +++ b/clang/test/SemaCXX/cxx2c-fold-exprs.cpp @@ -629,3 +629,15 @@ static_assert(MutabilityAlias<Constant::alias>); static_assert(MutabilityAlias<Mutable::alias>); } + +namespace GH218035 { + +template <class T, class UnusedParam> +concept same_as_impl = sizeof(T) == 8; +template <typename... P> +void f() + requires(same_as_impl<P...[0], P> && ...) +{} +void g() { f<long long, float>(); } + +} _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
