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[Clang][Concepts] Fix a constraint comparison regression for out-of-line ClassTemplateDecls #102587

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[Clang][Concepts] Fix a constraint comparison regression for out-of-line ClassTemplateDecls #102587

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[Clang][Concepts] Fix a constraint comparison regression for out-of-l…
zyn0217 Aug 9, 2024
23bc937
Don't visit out-of-line specializations
zyn0217 Aug 10, 2024
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2 changes: 2 additions & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -186,6 +186,8 @@ Bug Fixes to C++ Support
substitutions in concepts, so it doesn't incorrectly complain of missing
module imports in those situations. (#GH60336)
- Fix init-capture packs having a size of one before being instantiated. (#GH63677)
- Clang now properly compares constraints on an out of line class template
declaration definition. (#GH102320)

Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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11 changes: 7 additions & 4 deletions clang/lib/Sema/SemaConcept.cpp
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Expand Up @@ -948,7 +948,7 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
Sema &S, const Sema::TemplateCompareNewDeclInfo &DeclInfo,
const Expr *ConstrExpr) {
MultiLevelTemplateArgumentList MLTAL = S.getTemplateInstantiationArgs(
DeclInfo.getDecl(), DeclInfo.getLexicalDeclContext(), /*Final=*/false,
DeclInfo.getDecl(), DeclInfo.getDeclContext(), /*Final=*/false,
/*Innermost=*/std::nullopt,
/*RelativeToPrimary=*/true,
/*Pattern=*/nullptr, /*ForConstraintInstantiation=*/true,
Expand All @@ -971,9 +971,12 @@ static const Expr *SubstituteConstraintExpressionWithoutSatisfaction(
// this may happen while we're comparing two templates' constraint
// equivalence.
LocalInstantiationScope ScopeForParameters(S);
if (auto *FD = DeclInfo.getDecl()->getAsFunction())
for (auto *PVD : FD->parameters())
ScopeForParameters.InstantiatedLocal(PVD, PVD);
if (const NamedDecl *D = DeclInfo.getDecl()) {
const FunctionDecl *FD = D->getAsFunction();
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When is D null?

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(I roughly explained in the comment.)
This function SubstituteConstraintExpressionWithoutSatisfaction would be called in the context where a template parameter list is getting parsed, when the template declaration that the template parameter list would attach to is not yet available.

if (FD)
for (auto *PVD : FD->parameters())
ScopeForParameters.InstantiatedLocal(PVD, PVD);
}

std::optional<Sema::CXXThisScopeRAII> ThisScope;

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21 changes: 21 additions & 0 deletions clang/test/SemaTemplate/concepts-out-of-line-def.cpp
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Expand Up @@ -599,3 +599,24 @@ template <class DerT>
unsigned long DerivedCollection<DerTs...>::index() {}

} // namespace GH72557

namespace GH102320 {

template <class, class>
concept Constrained = true;

template <class T> class C {
template <Constrained<T>> class D;
template <class U>
requires Constrained<T, U>
class E;
};

template <class T> template <Constrained<T>> class C<T>::D {};

template <class T>
template <class U>
requires Constrained<T, U>
class C<T>::E {};

} // namespace GH102320
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