[Sema] Set __builtin_wasm placeholder type to v* instead of i (#181146)
The `rewriteBuiltinFunctionDecl` was unconditionally rewriting
BuiltinFnTy to FunctionTy, by taking the type from the FDecl instead of
copying it from the Fn. That confused BuildResolvedCallExpr immediately
afterward, which sets `ResultTy = Context.BoolTy` if the type is
declared to be Function rather than BuiltinFn. Thus this only usually
matters when also using custom type checking, since otherwise this
eventually extracts the type from the FuncT and overwrites the type
extracted from the builtin, but that ability is disabled for builtins
with custom type checking marked. Either change here is sufficient alone
for the current __builtin_wasm declarations, but doing both changes
seemed more conservative for possible future builtins.
This was introduced originally in
b919c7d9eb8598b7f631c1edcd0b874bbdaf99d6.
Analysis assisted by Claude Sonnet 4.5
llvm-project
e0477ce1 - [Sema] Set __builtin_wasm placeholder type to v* instead of i (#181146)
