[clang-tools-extra] Add support for renaming objc methods, even those with multiple selector pieces (PR #76466)

[Alex Hoppen via cfe-commits]

================
@@ -538,11 +564,222 @@ std::optional<InvalidName> checkName(const NamedDecl &RenameDecl,
             Conflict->getLocation().printToString(ASTCtx.getSourceManager())};
     }
   }
-  if (Result)
+  if (Result) {
     InvalidNameMetric.record(1, toString(Result->K));
+    return makeError(*Result);
+  }
+  return llvm::Error::success();
+}
+
+bool isSelectorLike(const syntax::Token &Cur, const syntax::Token &Next) {
+  return Cur.kind() == tok::identifier && Next.kind() == tok::colon &&
+         // We require the selector name and : to be contiguous.
+         // e.g. support `foo:` but not `foo :`.
+         Cur.endLocation() == Next.location();
+}
+
+bool isMatchingSelectorName(const syntax::Token &Cur, const syntax::Token &Next,
+                            const SourceManager &SM,
+                            llvm::StringRef SelectorName) {
+  if (SelectorName.empty())
+    return Cur.kind() == tok::colon;
+  return isSelectorLike(Cur, Next) && Cur.text(SM) == SelectorName;
+}
+
+// Scan through Tokens to find ranges for each selector fragment in Sel at the
+// top level (not nested in any () or {} or []). The search will terminate upon
----------------
ahoppen wrote:

I think the `not nested in any () or {} or []` is quite misleading. Based on this comment, I would have expected `doStuff` in `[someObject someArgLabel: [foo doStuff: 1]]` or 

```objectivec
- (void) test {
  [foo doStuff: 1];
}
```

to not be found because it’s nested in `{}` or `[]`.

https://github.com/llvm/llvm-project/pull/76466