[PATCH] D73208: [objc_direct] fix codegen for mismatched Decl/Impl return types

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith added a comment.

In D73208#1835264 <https://reviews.llvm.org/D73208#1835264>, @MadCoder wrote:

> In D73208#1835051 <https://reviews.llvm.org/D73208#1835051>, @dexonsmith wrote:
>
> > Why isn't a similar dance needed for non-direct methods?
>
>
> because non direct methods do not need an `llvm::Function` to be synthesized at the call-site. direct methods do, and they form one with the type of the declaration they see. Then that same `llvm::Function` is used when you CodeGen the Implementation, so if there's a mismatch, sadness ensues because the LLVM IR verifier will notice the discrepancy between the declared return type of the function and the actual types coming out of the `ret` codepaths.
>
> Regular obj-C methods use the _implementation_ types for the codegen (the declaration(s) aren't even consulted) and I want to stick at what obj-c does as much as I can.
>
> (as a data point: If you use obj-C types with C functions, the type of the first declaration seen is used instead).


Okay, that makes sense to me.

Another solution would be to change IRGen for the implementation: if the declaration already exists (`getFunction`), do a bitcast + RAUW dance to fix it up (and update the `DirectMethodDefinitions` table).  WDYT?


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https://reviews.llvm.org/D73208