Bugfix

Author: cdce8p

mypy/fastparse.py

@@ -461,6 +461,8 @@ def fix_function_overloads(self, stmts: List[Statement]) -> List[Statement]:
                 current_overload_name is not None
                 and isinstance(stmt, IfStmt)
                 and len(stmt.body[0].body) == 1
+                and isinstance(stmt.else_body, Block)
+                and len(stmt.else_body.body) == 0
                 and isinstance(
                     stmt.body[0].body[0], (Decorator, FuncDef, OverloadedFuncDef))
                 and stmt.body[0].body[0].name == current_overload_name
@@ -518,6 +520,8 @@ def fix_function_overloads(self, stmts: List[Statement]) -> List[Statement]:
             ret.append(current_overload[0])
         elif len(current_overload) > 1:
             ret.append(OverloadedFuncDef(current_overload))
+        elif last_if_stmt is not None:
+            ret.append(last_if_stmt)
         return ret
 
     def in_method_scope(self) -> bool:

test-data/unit/check-overloading.test

@@ -5330,3 +5330,34 @@ def f2(g: Any) -> Any: ...
 reveal_type(f2(42))  # N: Revealed type is "__main__.A"
 reveal_type(f2("Hello"))  # N: Revealed type is "__main__.A" \
                           # E: Argument 1 to "f2" has incompatible type "str"; expected "int"
+
+[case testOverloadIfOldStyle]
+# flags: --always-false var_false --always-true var_true
+from typing import overload, Any
+
+class A: ...
+class B: ...
+
+var_true = True
+var_false = False
+
+if var_false:
+    @overload
+    def f1(g: int) -> A: ...
+    @overload
+    def f1(g: str) -> B: ...
+    def f1(g: Any) -> Any: ...
+elif var_true:
+    @overload
+    def f1(g: int) -> A: ...
+    @overload
+    def f1(g: str) -> B: ...
+    def f1(g: Any) -> Any: ...
+else:
+    @overload
+    def f1(g: int) -> A: ...
+    @overload
+    def f1(g: str) -> B: ...
+    def f1(g: Any) -> Any: ...
+reveal_type(f1(42))  # N: Revealed type is "__main__.A"
+reveal_type(f1("Hello"))  # N: Revealed type is "__main__.B"