rsmith added inline comments.
================
Comment at: clang/lib/Sema/TreeTransform.h:12162
for (unsigned I = 0, NumParams = NewCallOperator->getNumParams();
I != NumParams; ++I) {
----------------
rsmith wrote:
> This logic shouldn't even be here in the first place.. this should all be
> handled by `SubstParmVarDecl` in `SemaTemplateInstantiate`. It's wrong for
> `TreeTransform` to be assuming that `TransformFunctionProtoType` will have
> built new function parameters -- it doesn't do so by default, so in the
> non-template-instantiation case, this is clobbering the default argument
> information on the original lambda. And in the template instantiation case,
> this is clobbering the default argument information (including
> initialization) that `SubstParmVarDecl` already did.
>
> Please try deleting this loop entirely. If there are still problems (and I
> think there are: I don't think we handle delayed instantiation for default
> argument in generic lambdas properly), we should address them by changing how
> we do default argument instantiation in `SubstParmVarDecl`. In particular,
> where that function calls `SetParamDefaultArgument` after calling
> `SubstExpr`, we should presumably instead be calling
> `setUninstantiatedDefaultArg` on the parameter if it's a parameter of a
> generic lambda (we still need to instantiate the default argument with the
> template arguments of the actual lambda call operator).
Hmm, what I wrote above isn't entirely true -- `TreeTransform` does create new
parameters by default. But nonetheless, it's the responsibility of
`TransformFunctionTypeParam` to set up the default argument, not the
responsibility of this code, so we shouldn't be partially overwriting its
results here. (Perhaps we should move the substitution into default arguments
from `SubstParmVarDecl` into `TreeTransform::TransformFunctionTypeParam`,
though I think that can be done separately from this bugfix.)
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D76038/new/
https://reviews.llvm.org/D76038
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