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[Clang] Fix evaluation context of lambdas appearing in discarded statements #146857

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Merged
merged 2 commits into from
Jul 3, 2025
Merged

[Clang] Fix evaluation context of lambdas appearing in discarded statements #146857

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4ee72df
[Clang] Fix evaluation context of lambdas appearing in discarded stat…
cor3ntin Jul 3, 2025
34b4b5e
Update clang/lib/Sema/SemaExpr.cpp
cor3ntin Jul 3, 2025
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5 changes: 5 additions & 0 deletions clang/lib/Sema/SemaExpr.cpp
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Expand Up @@ -18252,6 +18252,11 @@ static bool isImplicitlyDefinableConstexprFunction(FunctionDecl *Func) {

if (Func->isImplicitlyInstantiable() || !Func->isUserProvided())
return true;

// Lambda conversion operators are never user provided
if (CXXConversionDecl *Conv = dyn_cast<CXXConversionDecl>(Func))
return isLambdaConversionOperator(Conv);

auto *CCD = dyn_cast<CXXConstructorDecl>(Func);
return CCD && CCD->getInheritedConstructor();
}
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10 changes: 3 additions & 7 deletions clang/lib/Sema/TreeTransform.h
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Expand Up @@ -15723,13 +15723,9 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {

// FIXME: Sema's lambda-building mechanism expects us to push an expression
// evaluation context even if we're not transforming the function body.
getSema().PushExpressionEvaluationContext(
E->getCallOperator()->isConsteval() ?
Sema::ExpressionEvaluationContext::ImmediateFunctionContext :
Sema::ExpressionEvaluationContext::PotentiallyEvaluated);
getSema().currentEvaluationContext().InImmediateEscalatingFunctionContext =
getSema().getLangOpts().CPlusPlus20 &&
E->getCallOperator()->isImmediateEscalating();
getSema().PushExpressionEvaluationContextForFunction(
Sema::ExpressionEvaluationContext::PotentiallyEvaluated,
E->getCallOperator());

Sema::CodeSynthesisContext C;
C.Kind = clang::Sema::CodeSynthesisContext::LambdaExpressionSubstitution;
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22 changes: 22 additions & 0 deletions clang/test/CXX/stmt.stmt/stmt.select/stmt.if/p2.cpp
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Expand Up @@ -218,4 +218,26 @@ void regression() {

}

namespace GH146063 {
template <typename>
struct A {
static_assert([]() constexpr { return true; }());
};

void f1() {
if constexpr (false) {
A<int> a;
}
}

void f2() {
if constexpr (false) {
static_assert([]{});
// expected-warning@-1 {{address of lambda function pointer conversion operator will always evaluate to 'true'}}
}
}

}


#endif
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