Use roles for ORM alias() conversion

as SELECT statements will have subquery() and not alias(),
start getting ready for the places where the ORM coerces SELECTs
into subqueries and be ready to warn about it

Change-Id: I90d4b6cae2c72816c6b192016ce074589caf4731

1 files changed, 12 insertions, 0 deletions

diff --git a/test/sql/test_deprecations.py b/test/sql/test_deprecations.py
index 8e8591aec..90646c41d 100644
--- a/test/sql/test_deprecations.py
+++ b/test/sql/test_deprecations.py
@@ -486,6 +486,18 @@ class SubqueryCoercionsTest(fixtures.TestBase, AssertsCompiledSQL):
 
         is_true(stmt.compare(select([table1.c.myid]).scalar_subquery()))
 
+    def test_fromclause_subquery(self):
+        stmt = select([table1.c.myid])
+        with testing.expect_deprecated(
+            "Implicit coercion of SELECT and textual SELECT constructs "
+            "into FROM clauses is deprecated"
+        ):
+            coerced = coercions.expect(
+                roles.StrictFromClauseRole, stmt, allow_select=True
+            )
+
+        is_true(coerced.compare(stmt.subquery()))
+
 
 class TextTest(fixtures.TestBase, AssertsCompiledSQL):
     __dialect__ = "default"