Fix scan_expression not to mark sequence as Load

compiler/src/symboltable.rs

@@ -585,7 +585,7 @@ impl SymbolTableBuilder {
             }
             Bytes { .. } => {}
             Tuple { elements } | Set { elements } | List { elements } | Slice { elements } => {
-                self.scan_expressions(elements, &ExpressionContext::Load)?;
+                self.scan_expressions(elements, context)?;
             }
             Comprehension { kind, generators } => {
                 match **kind {

tests/snippets/comprehensions.py

@@ -27,3 +27,17 @@ z = [(9,), (10,)]
 w = [x for x, in z]
 assert w == [9, 10]
 
+# generator targets shouldn't affect scopes out of comprehensions
+[a for a in range(5)]
+assert 'a' not in locals()
+assert 'a' not in globals()
+
+[b for a, b in [(1, 1), (2, 2)]]
+assert 'b' not in locals()
+assert 'b' not in globals()
+
+{b: c for b, c in {1: 2}.items()}
+assert 'b' not in locals()
+assert 'c' not in locals()
+assert 'b' not in globals()
+assert 'c' not in globals()