release/21.x: [Clang] Fix a partial ordering bug involving CTAD injected template arguments (#149782) #151075
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@shafik What do you think about merging this PR to the release branch? |
llvmbot
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clang
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@llvm/pr-subscribers-clang Author: None (llvmbot) ChangesBackport 07faafe Requested by: @zyn0217 Full diff: https://github.com/llvm/llvm-project/pull/151075.diff 2 Files Affected:
diff --git a/clang/lib/Sema/SemaTemplateDeduction.cpp b/clang/lib/Sema/SemaTemplateDeduction.cpp
index d09a72b71b805..ce78ecc2d4a2d 100644
--- a/clang/lib/Sema/SemaTemplateDeduction.cpp
+++ b/clang/lib/Sema/SemaTemplateDeduction.cpp
@@ -5525,6 +5525,15 @@ static TemplateDeductionResult CheckDeductionConsistency(
// FIXME: A substitution can be incomplete on a non-structural part of the
// type. Use the canonical type for now, until the TemplateInstantiator can
// deal with that.
+
+ // Workaround: Implicit deduction guides use InjectedClassNameTypes, whereas
+ // the explicit guides don't. The substitution doesn't transform these types,
+ // so let it transform their specializations instead.
+ bool IsDeductionGuide = isa<CXXDeductionGuideDecl>(FTD->getTemplatedDecl());
+ if (IsDeductionGuide) {
+ if (auto *Injected = P->getAs<InjectedClassNameType>())
+ P = Injected->getInjectedSpecializationType();
+ }
QualType InstP = S.SubstType(P.getCanonicalType(), MLTAL, FTD->getLocation(),
FTD->getDeclName(), &IsIncompleteSubstitution);
if (InstP.isNull() && !IsIncompleteSubstitution)
@@ -5539,9 +5548,15 @@ static TemplateDeductionResult CheckDeductionConsistency(
if (auto *PA = dyn_cast<PackExpansionType>(A);
PA && !isa<PackExpansionType>(InstP))
A = PA->getPattern();
- if (!S.Context.hasSameType(
- S.Context.getUnqualifiedArrayType(InstP.getNonReferenceType()),
- S.Context.getUnqualifiedArrayType(A.getNonReferenceType())))
+ auto T1 = S.Context.getUnqualifiedArrayType(InstP.getNonReferenceType());
+ auto T2 = S.Context.getUnqualifiedArrayType(A.getNonReferenceType());
+ if (IsDeductionGuide) {
+ if (auto *Injected = T1->getAs<InjectedClassNameType>())
+ T1 = Injected->getInjectedSpecializationType();
+ if (auto *Injected = T2->getAs<InjectedClassNameType>())
+ T2 = Injected->getInjectedSpecializationType();
+ }
+ if (!S.Context.hasSameType(T1, T2))
return TemplateDeductionResult::NonDeducedMismatch;
return TemplateDeductionResult::Success;
}
diff --git a/clang/test/SemaTemplate/deduction-guide.cpp b/clang/test/SemaTemplate/deduction-guide.cpp
index 0953f647426fa..f6bc6ee3673c2 100644
--- a/clang/test/SemaTemplate/deduction-guide.cpp
+++ b/clang/test/SemaTemplate/deduction-guide.cpp
@@ -966,3 +966,19 @@ Expand<Type, Invocable<>> _{};
// CHECK-NEXT: | `-ParmVarDecl {{.+}} 'T...' pack
}
+
+namespace GH134613 {
+template <typename R> struct Foo {
+ using value_type = R;
+
+ Foo() = default;
+ Foo(Foo<Foo<R>> &&rhs) {}
+};
+
+void main() {
+ auto r1 = Foo(Foo<Foo<int>>{});
+
+ static_assert(__is_same(decltype(r1)::value_type, int));
+}
+
+}
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cor3ntin
approved these changes
Jul 29, 2025
github-project-automation
bot
moved this from Needs Review
to Needs Merge
in LLVM Release Status
…rguments (llvm#149782) The synthesized deduction guides use injected template arguments for distinguishment of explicit and implicit deduction guides. In partial ordering, we may substitute into these injected types when checking consistency. Properly substituting them needs the instantiated class template specializations which isn't the case at that point. So instead, we check their template specialization types. No release note because I think we want a backport, after baking it for a couple of days. Fixes llvm#134613 (cherry picked from commit 07faafe)
github-project-automation
bot
moved this from Needs Merge
to Done
in LLVM Release Status
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@zyn0217 (or anyone else). If you would like to add a note about this fix in the release notes (completely optional). Please reply to this comment with a one or two sentence description of the fix. When you are done, please add the release:note label to this PR. |
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Backport 07faafe
Requested by: @zyn0217