Merge pull request RustPython#4338 from yt2b/fix_symbol_scope

Fix panic about warlus operator inside mutiple comprehensions.

Author: DimitrisJim

compiler/codegen/src/symboltable.rs

@@ -483,7 +483,7 @@ impl SymbolTableAnalyzer {
                     };
                 } else {
                     let mut cloned_sym = symbol.clone();
-                    cloned_sym.scope = SymbolScope::Local;
+                    cloned_sym.scope = SymbolScope::Cell;
                     last.0.insert(cloned_sym.name.to_owned(), cloned_sym);
                 }
             }

extra_tests/snippets/syntax_comprehension.py

@@ -41,3 +41,8 @@
 assert 'c' not in locals()
 assert 'b' not in globals()
 assert 'c' not in globals()
+
+
+def f():
+    # Test no panic occured.
+    [[x := 1 for j in range(5)] for i in range(5)]