rjmccall added inline comments.
================
Comment at: lib/Sema/SemaDeclObjC.cpp:4131-4133
+ if (!getLangOpts().ObjCRuntime.allowsClassStubs()) {
+ Diag(IntfDecl->getLocation(), diag::err_class_stub_not_supported);
+ }
----------------
aaron.ballman wrote:
> This should be done in Attr.td. You'll need to add a new LangOpt subclass
> (around line 298 or so are examples), and then add it to the `LangOpts` array
> when defining the attribute. Then you can remove this code as well as the new
> diagnostic.
I don't think there's a way to run arbitrary code in a `LangOpt` right now, but
it should be relatively straightforward to generalize `ClangAttrEmitter` to
handle this. Just add an optional `Code` property to `LangOpt` that's
expressed in terms of an assumed variable `LangOpts`, so that `Attr.td` could
have a line like:
```
def ObjCClassStubsAllowed : LangOpt<"ObjCClassStubsAllowed",
"LangOpts.ObjCRuntime.allowsClassStubs()">;
```
`ClangAttrEmitter` would take that expression, parenthesize it, and use it
where it currently expands to `"LangOpts." + Name`. It should be possible to
remove the `Negated` field in favor of this.
I guess that's probably worth doing vs. just having some hard-coded logic.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59628/new/
https://reviews.llvm.org/D59628
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