Fix match subject ignoring redefinitions (#15306)

Fixes #14746

Author: VincentVanlaer

mypy/renaming.py

@@ -182,6 +182,7 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
             self.analyze_lvalue(lvalue)
 
     def visit_match_stmt(self, s: MatchStmt) -> None:
+        s.subject.accept(self)
         for i in range(len(s.patterns)):
             with self.enter_block():
                 s.patterns[i].accept(self)

test-data/unit/check-python310.test

@@ -1933,3 +1933,28 @@ def match_stmt_error5(x: Optional[str]) -> None:
             pass
     nested()
 [builtins fixtures/tuple.pyi]
+
+[case testMatchSubjectRedefinition]
+# flags: --allow-redefinition
+def transform1(a: str) -> int:
+    ...
+
+def transform2(a: int) -> str:
+    ...
+
+def redefinition_good(a: str):
+    a = transform1(a)
+
+    match (a + 1):
+        case _:
+            ...
+
+
+def redefinition_bad(a: int):
+    a = transform2(a)
+
+    match (a + 1):  # E: Unsupported operand types for + ("str" and "int")
+        case _:
+            ...
+
+[builtins fixtures/primitives.pyi]