[clang] [clang][Parser] Warn when the body of expansion statement is not a compound statement (PR #209229)

[Corentin Jabot via cfe-commits]

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@@ -2379,6 +2382,11 @@ StmtResult Parser::ParseForStatement(SourceLocation *TrailingElseLoc,
       return StmtError();
     }
 
+    // attribute-specifier without attribute (`[[]]`) isn't in AST.
+    // `__declspec()` is only applied to declarations, so we can ignore it.
+    if (!isa<CompoundStmt>(Body.get()) || BodyStartsWithAttr)
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cor3ntin wrote:

I mean, our logic could actually warn by checking the next token is `{` - that cover all the cases, i think 
https://eel.is/c++draft/stmt.block#nt:compound-statement

https://github.com/llvm/llvm-project/pull/209229