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[Clang][Sema] Diagnose function/variable templates that shadow their own template parameters #78274

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Jan 17, 2024
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[Clang][Sema] Diagnose function/variable templates that shadow their own template parameters #78274

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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -568,6 +568,7 @@ Improvements to Clang's diagnostics
- Clang now diagnoses the requirement that non-template friend declarations with requires clauses
and template friend declarations with a constraint that depends on a template parameter from an
enclosing template must be a definition.
- Clang now diagnoses function/variable templates that shadow their own template parameters, e.g. ``template<class T> void T();``.


Improvements to Clang's time-trace
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12 changes: 6 additions & 6 deletions clang/lib/Sema/SemaDecl.cpp
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Expand Up @@ -6377,12 +6377,6 @@ NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
} else if (DiagnoseUnexpandedParameterPack(NameInfo, UPPC_DeclarationType))
return nullptr;

// The scope passed in may not be a decl scope. Zip up the scope tree until
// we find one that is.
while ((S->getFlags() & Scope::DeclScope) == 0 ||
(S->getFlags() & Scope::TemplateParamScope) != 0)
S = S->getParent();

DeclContext *DC = CurContext;
if (D.getCXXScopeSpec().isInvalid())
D.setInvalidType();
Expand Down Expand Up @@ -6535,6 +6529,12 @@ NamedDecl *Sema::HandleDeclarator(Scope *S, Declarator &D,
if (getLangOpts().CPlusPlus)
CheckExtraCXXDefaultArguments(D);

// The scope passed in may not be a decl scope. Zip up the scope tree until
// we find one that is.
while ((S->getFlags() & Scope::DeclScope) == 0 ||
(S->getFlags() & Scope::TemplateParamScope) != 0)
S = S->getParent();

NamedDecl *New;

bool AddToScope = true;
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20 changes: 17 additions & 3 deletions clang/test/CXX/temp/temp.res/temp.local/p6.cpp
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Expand Up @@ -127,16 +127,30 @@ template<int T> struct Z { // expected-note 16{{declared here}}
template<typename T> // expected-note {{declared here}}
void f(int T) {} // expected-error {{declaration of 'T' shadows template parameter}}

// FIXME: These are ill-formed: a template-parameter shall not have the same name as the template name.
namespace A {
template<typename T> struct T {}; // expected-error{{declaration of 'T' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}
template<typename T> struct U {
template<typename V> struct V {}; // expected-error{{declaration of 'V' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}
};
}
namespace B {
template<typename T> void T() {}
template<typename T> void T() {} // expected-error{{declaration of 'T' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}

template<typename T> struct U {
template<typename V> void V(); // expected-error{{declaration of 'V' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}
};
}
namespace C {
template<typename T> int T;
template<typename T> int T; // expected-error{{declaration of 'T' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}
template<typename T> struct U {
template<typename V> static int V; // expected-error{{declaration of 'V' shadows template parameter}}
// expected-note@-1{{template parameter is declared here}}
};
}

namespace PR28023 {
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