1 files changed, 26 insertions, 10 deletions

diff --git a/lib/sqlalchemy/ext/mypy/apply.py b/lib/sqlalchemy/ext/mypy/apply.py
index 0f4bb1fd9..366260437 100644
--- a/lib/sqlalchemy/ext/mypy/apply.py
+++ b/lib/sqlalchemy/ext/mypy/apply.py
@@ -24,9 +24,12 @@ from mypy.nodes import Var
 from mypy.plugin import SemanticAnalyzerPluginInterface
 from mypy.plugins.common import add_method_to_class
 from mypy.types import AnyType
+from mypy.types import get_proper_type
 from mypy.types import Instance
 from mypy.types import NoneTyp
+from mypy.types import ProperType
 from mypy.types import TypeOfAny
+from mypy.types import UnboundType
 from mypy.types import UnionType
 
 from . import util
@@ -37,7 +40,7 @@ def _apply_mypy_mapped_attr(
     api: SemanticAnalyzerPluginInterface,
     item: Union[NameExpr, StrExpr],
     cls_metadata: util.DeclClassApplied,
-):
+) -> None:
     if isinstance(item, NameExpr):
         name = item.name
     elif isinstance(item, StrExpr):
@@ -46,7 +49,11 @@ def _apply_mypy_mapped_attr(
         return
 
     for stmt in cls.defs.body:
-        if isinstance(stmt, AssignmentStmt) and stmt.lvalues[0].name == name:
+        if (
+            isinstance(stmt, AssignmentStmt)
+            and isinstance(stmt.lvalues[0], NameExpr)
+            and stmt.lvalues[0].name == name
+        ):
             break
     else:
         util.fail(api, "Can't find mapped attribute {}".format(name), cls)
@@ -61,7 +68,10 @@ def _apply_mypy_mapped_attr(
         )
         return
 
-    left_hand_explicit_type = stmt.type
+    left_hand_explicit_type = get_proper_type(stmt.type)
+    assert isinstance(
+        left_hand_explicit_type, (Instance, UnionType, UnboundType)
+    )
 
     cls_metadata.mapped_attr_names.append((name, left_hand_explicit_type))
 
@@ -74,7 +84,7 @@ def _re_apply_declarative_assignments(
     cls: ClassDef,
     api: SemanticAnalyzerPluginInterface,
     cls_metadata: util.DeclClassApplied,
-):
+) -> None:
     """For multiple class passes, re-apply our left-hand side types as mypy
     seems to reset them in place.
 
@@ -90,7 +100,9 @@ def _re_apply_declarative_assignments(
         # will change).
         if (
             isinstance(stmt, AssignmentStmt)
+            and isinstance(stmt.lvalues[0], NameExpr)
             and stmt.lvalues[0].name in mapped_attr_lookup
+            and isinstance(stmt.lvalues[0].node, Var)
         ):
             typ = mapped_attr_lookup[stmt.lvalues[0].name]
             left_node = stmt.lvalues[0].node
@@ -102,8 +114,8 @@ def _apply_type_to_mapped_statement(
     api: SemanticAnalyzerPluginInterface,
     stmt: AssignmentStmt,
     lvalue: NameExpr,
-    left_hand_explicit_type: Optional[Union[Instance, UnionType]],
-    python_type_for_type: Union[Instance, UnionType],
+    left_hand_explicit_type: Optional[ProperType],
+    python_type_for_type: Optional[ProperType],
 ) -> None:
     """Apply the Mapped[<type>] annotation and right hand object to a
     declarative assignment statement.
@@ -124,6 +136,7 @@ def _apply_type_to_mapped_statement(
 
     """
     left_node = lvalue.node
+    assert isinstance(left_node, Var)
 
     if left_hand_explicit_type is not None:
         left_node.type = api.named_type(
@@ -131,7 +144,10 @@ def _apply_type_to_mapped_statement(
         )
     else:
         lvalue.is_inferred_def = False
-        left_node.type = api.named_type("__sa_Mapped", [python_type_for_type])
+        left_node.type = api.named_type(
+            "__sa_Mapped",
+            [] if python_type_for_type is None else [python_type_for_type],
+        )
 
     # so to have it skip the right side totally, we can do this:
     # stmt.rvalue = TempNode(AnyType(TypeOfAny.special_form))
@@ -146,7 +162,7 @@ def _apply_type_to_mapped_statement(
     # the original right-hand side is maintained so it gets type checked
     # internally
     column_descriptor = nodes.NameExpr("__sa_Mapped")
-    column_descriptor.fullname = "sqlalchemy.orm.Mapped"
+    column_descriptor.fullname = "sqlalchemy.orm.attributes.Mapped"
     mm = nodes.MemberExpr(column_descriptor, "_empty_constructor")
     orig_call_expr = stmt.rvalue
     stmt.rvalue = CallExpr(mm, [orig_call_expr], [nodes.ARG_POS], ["arg1"])
@@ -199,11 +215,11 @@ def _apply_placeholder_attr_to_class(
     cls: ClassDef,
     qualified_name: str,
     attrname: str,
-):
+) -> None:
     sym = api.lookup_fully_qualified_or_none(qualified_name)
     if sym:
         assert isinstance(sym.node, TypeInfo)
-        type_: Union[Instance, AnyType] = Instance(sym.node, [])
+        type_: ProperType = Instance(sym.node, [])
     else:
         type_ = AnyType(TypeOfAny.special_form)
     var = Var(attrname)