================
@@ -14636,6 +14645,20 @@ TreeTransform<Derived>::TransformLambdaExpr(LambdaExpr
*E) {
/*IsInstantiation*/ true);
SavedContext.pop();
+ // Parts other than the capture e.g. the lambda body might still contain a
+ // pattern that an outer fold expression would expand.
+ //
+ // We don't have a way to propagate up the ContainsUnexpandedParameterPack
+ // flag from a Stmt, so we have to revisit the lambda.
+ if (!LSICopy.ContainsUnexpandedParameterPack) {
+ llvm::SmallVector<UnexpandedParameterPack> UnexpandedPacks;
+ getSema().collectUnexpandedParameterPacksFromLambda(NewCallOperator,
+ UnexpandedPacks);
+ // FIXME: Should we call Sema::DiagnoseUnexpandedParameterPacks() instead?
+ // Unfortunately, that requires the LambdaScopeInfo to exist, which has
been
+ // removed by ActOnFinishFunctionBody().
+ LSICopy.ContainsUnexpandedParameterPack = !UnexpandedPacks.empty();
+ }
----------------
zyn0217 wrote:
Despite these, I have another concern on performance issue after some
deliberation. This is actually a workaround given that we don't have any flags
on a `Stmt` to tell whether it contains unexpanded expressions - what we do now
leads to visiting the lambda body twice, which might cause some impact in
lambda instantiation, if the body is large enough.
A compromise is, we remove this traversal in this patch and *leave it for
future fixes*. (Sigh!)
https://github.com/llvm/llvm-project/pull/86265
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