pep-484: the pep-484ening, SQL part three

hitting DML which is causing us to open up the
ColumnCollection structure a bit, as we do put anonymous
column expressions with None here.  However, we still want
Table /TableClause to have named column collections that
don't return None, so parametrize the "key" in this
collection also.

* rename some "immutable" elements to "readonly".  we change
  the contents of immutablecolumncollection underneath, so it's
  not "immutable"

Change-Id: I2593995a4e5c6eae874bed5bf76117198be8ae97

1 files changed, 27 insertions, 0 deletions

diff --git a/lib/sqlalchemy/sql/coercions.py b/lib/sqlalchemy/sql/coercions.py
index 35cd33a18..ccc8fba8d 100644
--- a/lib/sqlalchemy/sql/coercions.py
+++ b/lib/sqlalchemy/sql/coercions.py
@@ -46,6 +46,7 @@ if typing.TYPE_CHECKING:
     from . import schema
     from . import selectable
     from . import traversals
+    from ._typing import _ColumnsClauseArgument
     from .elements import ClauseElement
     from .elements import ColumnClause
     from .elements import ColumnElement
@@ -166,6 +167,32 @@ def expect(
 
 @overload
 def expect(
+    role: Type[roles.DMLTableRole],
+    element: Any,
+    *,
+    apply_propagate_attrs: Optional[ClauseElement] = None,
+    argname: Optional[str] = None,
+    post_inspect: bool = False,
+    **kw: Any,
+) -> roles.DMLTableRole:
+    ...
+
+
+@overload
+def expect(
+    role: Type[roles.ColumnsClauseRole],
+    element: Any,
+    *,
+    apply_propagate_attrs: Optional[ClauseElement] = None,
+    argname: Optional[str] = None,
+    post_inspect: bool = False,
+    **kw: Any,
+) -> roles.ColumnsClauseRole:
+    ...
+
+
+@overload
+def expect(
     role: Type[_SR],
     element: Any,
     *,