================
@@ -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:
That function attracts me because we seem to 1. always call it after collecting
unexpanded packs; 2. also set the `LSI->ContainsUnexpandedParameterPack` flag
there. However, this would probably be unnecessary if we called it during
parsing.
> Also, I am not sure what you mean by leaving it as an NFC.
I was wondering if we could add an additional flag to
`ActOnFinishFunctionBody()` so that we remove the scope info on the caller's
own. (e.g. we could do that at the end of `TransformLambdaExpr`.) This way, we
could also avoid copying LSI around the lines above. (I had intended to call
`ContainsUnexpandedParameterPack()` afterward; again, even if the call is
unnecessary, we still could benefit from the refactoring because we don't need
to copy LSI.)
> but I don't think the solution is to simply teach ActOnFinishFunctionBody not
> to pop the function scope.
Can you say more? I think the FIXME is suggesting another way to avoid copying
LSI, but that doesn't necessarily mean tweaking `ActOnFinishFunctionBody` is
impossible?
https://github.com/llvm/llvm-project/pull/86265
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