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Don't mark lambda non-dependent if nested in a generic lambda. #149121

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Merged
zyn0217 merged 3 commits into from
Nov 23, 2025
Merged

Don't mark lambda non-dependent if nested in a generic lambda. #149121

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438c368
Don't mark lambda non-dependent if nested in a generic lambda.
katzdm Jul 16, 2025
17a98f9
Adding test from #156579.
katzdm Nov 22, 2025
cbd6475
Add other issue.
katzdm Nov 22, 2025
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1 change: 1 addition & 0 deletions clang/docs/ReleaseNotes.rst
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Expand Up @@ -557,6 +557,7 @@ Bug Fixes to C++ Support
- Diagnose unresolved overload sets in non-dependent compound requirements. (#GH51246) (#GH97753)
- Fix a crash when extracting unavailable member type from alias in template deduction. (#GH165560)
- Fix incorrect diagnostics for lambdas with init-captures inside braced initializers. (#GH163498)
- Fixed spurious diagnoses of certain nested lambda expressions. (#GH149121) (#GH156579)

Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
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2 changes: 2 additions & 0 deletions clang/lib/Sema/TreeTransform.h
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Expand Up @@ -15628,6 +15628,8 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr *E) {
DC = DC->getParent();
if ((getSema().isUnevaluatedContext() ||
getSema().isConstantEvaluatedContext()) &&
!(dyn_cast_or_null<CXXRecordDecl>(DC->getParent()) &&
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@erichkeane erichkeane Jul 16, 2025

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We'd want to use isa_and_present (or isa_and_nonnull or w/e it is called) in this case.

That said, we probably would prefer to do something like extracting above the if a const auto *RD = dyn_cast_if_present<CXXRecordDecl>(DC->getParent()); then changing the check to RD && RD->isGenericLambda()` (or perhaps BETTER, pulling that whole thing out to a separate boolean with a reasonable name, so you have a place to put a comment).

Which brings me to the last thing, I'd like a comment explaining WHY this check should be here, it looks enough out of place as to why this cannot be dependent.

cast<CXXRecordDecl>(DC->getParent())->isGenericLambda()) &&
(DC->isFileContext() || !DC->getParent()->isDependentContext()))
DependencyKind = CXXRecordDecl::LDK_NeverDependent;

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23 changes: 22 additions & 1 deletion clang/test/SemaCXX/cxx2a-consteval.cpp
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Expand Up @@ -1319,6 +1319,27 @@ namespace GH139160{
B result = (B){10, get_value(make_struct())}; // expected-error {{initializer element is not a compile-time constant}}
// expected-error@-1 {{call to consteval function 'GH139160::get_value' is not a constant expression}}
// expected-note@-2 {{non-constexpr function 'make_struct' cannot be used in a constant expression}}
};
} // namespace GH139160

namespace GH118187 {

template <typename T> int t() {
return []<typename U>() consteval {
return [](U v) { return v; }(123);
}.template operator()<int>();
}

int v = t<int>();
} // namespace GH118187

namespace GH156579 {
template <class>
auto f{[] (auto...) {
if constexpr ([] (auto) { return true; }(0))
return 0;
}};

void g() {
f<int>();
}
} // namespace GH156579