[clang] CTAD: Remove an incorrect assertion in BuildDeductionGuideForTypeAlias #126532
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@llvm/pr-subscribers-clang Author: Haojian Wu (hokein) ChangesFixes #125821 The assertion was too strict, as Clang can reach this code path when recursively generating deduction guides for alias templates. See the detailed explanation here. No release notes needed, as there is no behavior change in release builds. Full diff: https://github.com/llvm/llvm-project/pull/126532.diff 2 Files Affected:
diff --git a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
index e5931f4684a57d..b789824d970208 100644
--- a/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
+++ b/clang/lib/Sema/SemaTemplateDeductionGuide.cpp
@@ -998,8 +998,6 @@ getRHSTemplateDeclAndArgs(Sema &SemaRef, TypeAliasTemplateDecl *AliasTemplate) {
Template = CTSD->getSpecializedTemplate();
AliasRhsTemplateArgs = CTSD->getTemplateArgs().asArray();
}
- } else {
- assert(false && "unhandled RHS type of the alias");
}
return {Template, AliasRhsTemplateArgs};
}
diff --git a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
index 37dca2215af6ba..832ce15e662508 100644
--- a/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
+++ b/clang/test/SemaCXX/cxx20-ctad-type-alias.cpp
@@ -525,3 +525,17 @@ template <ArrayType<int>::Array array> void test() {}
void foo() { test<{1, 2, 3}>(); }
} // namespace GH113518
+
+namespace GH125821 {
+template<typename T>
+struct A { A(T){} };
+
+template<typename T>
+using Proxy = T;
+
+template<typename T>
+using C = Proxy< A<T> >;
+
+C test{ 42 }; // expected-error {{no viable constructor or deduction guide for deduction of template arguments}}
+
+} // namespace GH125821
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flovent
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Feb 13, 2025
…TypeAlias (llvm#126532) Fixes llvm#125821 The assertion was too strict, as Clang can reach this code path when recursively generating deduction guides for alias templates. See the detailed explanation [here](llvm#125821 (comment)). No release notes needed, as there is no behavior change in release builds.
joaosaffran
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Feb 14, 2025
…TypeAlias (llvm#126532) Fixes llvm#125821 The assertion was too strict, as Clang can reach this code path when recursively generating deduction guides for alias templates. See the detailed explanation [here](llvm#125821 (comment)). No release notes needed, as there is no behavior change in release builds.
sivan-shani
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Feb 24, 2025
…TypeAlias (llvm#126532) Fixes llvm#125821 The assertion was too strict, as Clang can reach this code path when recursively generating deduction guides for alias templates. See the detailed explanation [here](llvm#125821 (comment)). No release notes needed, as there is no behavior change in release builds.
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Fixes #125821
The assertion was too strict, as Clang can reach this code path when recursively generating deduction guides for alias templates. See the detailed explanation here.
No release notes needed, as there is no behavior change in release builds.