1 files changed, 37 insertions, 3 deletions
diff --git a/lib/sqlalchemy/ext/mypy/infer.py b/lib/sqlalchemy/ext/mypy/infer.py
index 3cd946e04..6a5e99e48 100644
--- a/lib/sqlalchemy/ext/mypy/infer.py
+++ b/lib/sqlalchemy/ext/mypy/infer.py
@@ -42,11 +42,13 @@ def infer_type_from_right_hand_nameexpr(
     left_hand_explicit_type: Optional[ProperType],
     infer_from_right_side: RefExpr,
 ) -> Optional[ProperType]:
-
     type_id = names.type_id_for_callee(infer_from_right_side)
-
     if type_id is None:
         return None
+    elif type_id is names.MAPPED:
+        python_type_for_type = _infer_type_from_mapped(
+            api, stmt, node, left_hand_explicit_type, infer_from_right_side
+        )
     elif type_id is names.COLUMN:
         python_type_for_type = _infer_type_from_decl_column(
             api, stmt, node, left_hand_explicit_type
@@ -245,7 +247,7 @@ def _infer_type_from_decl_composite_property(
     node: Var,
     left_hand_explicit_type: Optional[ProperType],
 ) -> Optional[ProperType]:
-    """Infer the type of mapping from a CompositeProperty."""
+    """Infer the type of mapping from a Composite."""
 
     assert isinstance(stmt.rvalue, CallExpr)
     target_cls_arg = stmt.rvalue.args[0]
@@ -271,6 +273,38 @@ def _infer_type_from_decl_composite_property(
         return python_type_for_type
 
 
+def _infer_type_from_mapped(
+    api: SemanticAnalyzerPluginInterface,
+    stmt: AssignmentStmt,
+    node: Var,
+    left_hand_explicit_type: Optional[ProperType],
+    infer_from_right_side: RefExpr,
+) -> Optional[ProperType]:
+    """Infer the type of mapping from a right side expression
+    that returns Mapped.
+
+
+    """
+    assert isinstance(stmt.rvalue, CallExpr)
+
+    # (Pdb) print(stmt.rvalue.callee)
+    # NameExpr(query_expression [sqlalchemy.orm._orm_constructors.query_expression])  # noqa: E501
+    # (Pdb) stmt.rvalue.callee.node
+    # <mypy.nodes.FuncDef object at 0x7f8d92fb5940>
+    # (Pdb) stmt.rvalue.callee.node.type
+    # def [_T] (default_expr: sqlalchemy.sql.elements.ColumnElement[_T`-1] =) -> sqlalchemy.orm.base.Mapped[_T`-1]  # noqa: E501
+    # sqlalchemy.orm.base.Mapped[_T`-1]
+    # the_mapped_type = stmt.rvalue.callee.node.type.ret_type
+
+    # TODO: look at generic ref and either use that,
+    # or reconcile w/ what's present, etc.
+    the_mapped_type = util.type_for_callee(infer_from_right_side)  # noqa
+
+    return infer_type_from_left_hand_type_only(
+        api, node, left_hand_explicit_type
+    )
+
+
 def _infer_type_from_decl_column_property(
     api: SemanticAnalyzerPluginInterface,
     stmt: AssignmentStmt,