Attempt to fix bool re-narrowing

mypy/binder.py

@@ -135,14 +135,17 @@ def _get(self, key: Key, index: int = -1) -> Optional[Type]:
                 return self.frames[i].types[key]
         return None
 
-    def put(self, expr: Expression, typ: Type) -> None:
+    def put(self, expr: Expression, typ: Type, *, redeclare: bool = False) -> None:
         if not isinstance(expr, (IndexExpr, MemberExpr, AssignmentExpr, NameExpr)):
             return
         if not literal(expr):
             return
         key = literal_hash(expr)
         assert key is not None, 'Internal error: binder tried to put non-literal'
-        if key not in self.declarations:
+        proper = get_proper_type(typ)
+        if redeclare and proper:
+            self.declarations[key] = proper
+        elif key not in self.declarations:
             self.declarations[key] = get_declaration(expr)
             self._add_dependencies(key)
         self._put(key, typ)

mypy/checker.py

@@ -3479,7 +3479,9 @@ def visit_assert_stmt(self, s: AssertStmt) -> None:
         true_map, else_map = self.find_isinstance_check(s.expr)
         if s.msg is not None:
             self.expr_checker.analyze_cond_branch(else_map, s.msg, None)
-        self.push_type_map(true_map)
+        # We want to redeclare the type in type_map, because it was refined
+        # for the rest of the frame.
+        self.push_type_map(true_map, redeclare=True)
 
     def visit_raise_stmt(self, s: RaiseStmt) -> None:
         """Type check a raise statement."""
@@ -5244,12 +5246,12 @@ def iterable_item_type(self, instance: Instance) -> Type:
     def function_type(self, func: FuncBase) -> FunctionLike:
         return function_type(func, self.named_type('builtins.function'))
 
-    def push_type_map(self, type_map: 'TypeMap') -> None:
+    def push_type_map(self, type_map: 'TypeMap', *, redeclare: bool = False) -> None:
         if type_map is None:
             self.binder.unreachable()
         else:
             for expr, type in type_map.items():
-                self.binder.put(expr, type)
+                self.binder.put(expr, type, redeclare=redeclare)
 
     def infer_issubclass_maps(self, node: CallExpr,
                               expr: Expression,

test-data/unit/check-narrowing.test

@@ -1245,3 +1245,17 @@ def two_type_vars(x: Union[str, Dict[str, int], Dict[bool, object], int]) -> Non
     else:
         reveal_type(x)  # N: Revealed type is "builtins.int"
 [builtins fixtures/dict.pyi]
+
+[case testBoolNarrowingAfterLiterallFallback]
+# https://github.com/python/mypy/issues/11839
+from typing import Any
+
+var: Any
+reveal_type(var)  # N: Revealed type is "Any"
+assert isinstance(var, bool)
+reveal_type(var)  # N: Revealed type is "builtins.bool"
+
+if var:
+    reveal_type(var)  # N: Revealed type is "Literal[True]"
+reveal_type(var)  # N: Revealed type is "builtins.bool"
+[builtins fixtures/isinstance.pyi]