[clang] [clang-repl] Extend the C support. (PR #89804)

[Aaron Ballman via cfe-commits]

================
@@ -2282,7 +2282,8 @@ void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
 
     // Remove this name from our lexical scope, and warn on it if we haven't
     // already.
-    IdResolver.RemoveDecl(D);
+    if (!PP.isIncrementalProcessingEnabled())
+      IdResolver.RemoveDecl(D);
----------------
AaronBallman wrote:

so in incremental processing mode, we never remove declarations from the id resolver, so they always stay available? e.g.,
```
{
  int i = 12;
}
printf("%d", i); // Fine?
```


https://github.com/llvm/llvm-project/pull/89804