[clang] [clang-format] Fix '!Scopes.empty()' assertion in parseBrace (PR #199098)

[Björn Schäpers via cfe-commits]

================
@@ -1214,9 +1214,11 @@ class AnnotatingParser {
 
     unsigned CommaCount = 0;
     while (CurrentToken) {
-      assert(!Scopes.empty());
+      if (Scopes.empty())
+        return false;
       if (CurrentToken->is(tok::r_brace)) {
-        assert(Scopes.back() == getScopeType(OpeningBrace));
+        if (Scopes.back() != getScopeType(OpeningBrace))
----------------
HazardyKnusperkeks wrote:

> Yes, it happens — it's not just a defensive change.
> 
> hit by `enum E { { ? } a }` , outer `{` pushes ST_Enum, inner `{` pushes ST_Other. The stray `}` inside the `?` gets eaten by consumeToken's r_brace branch and pops the inner ST_Other. So when the inner parseBrace reaches its real `}`, the top is ST_Enum — wrong type, not empty — and the second assert trips.

Thanks for the reply and the analysis.

If we add to `parseConditional`
``` c++
if (CurrentToken->is(tok::r_brace))
  return false;
```

That should also fix the issue and the assert can stay, right? I'd prefer that.


https://github.com/llvm/llvm-project/pull/199098