Ensure float are not implemented as numeric

Fixed the base class for dialect-specific float/double types; Oracle
:class:`_oracle.BINARY_DOUBLE` now subclasses :class:`_sqltypes.Double`,
and internal types for :class:`_sqltypes.Float` for asyncpg and pg8000 now
correctly subclass :class:`_sqltypes.Float`.

Added suite tests to ensure that floating point types, such as
class:`_types.Float` and :class:`_types.Double` are not resolved as
class:`_types.Numeric` in the dialect, since it may not compatible in
all cases, such as when casting a value.

Change-Id: I20b814e8e029d57921d9728a55f2570f74c35c87

2 files changed, 17 insertions, 0 deletions

diff --git a/lib/sqlalchemy/testing/requirements.py b/lib/sqlalchemy/testing/requirements.py
index b59cce374..c1d6a14aa 100644
--- a/lib/sqlalchemy/testing/requirements.py
+++ b/lib/sqlalchemy/testing/requirements.py
@@ -1241,6 +1241,12 @@ class SuiteRequirements(Requirements):
         return exclusions.open()
 
     @property
+    def float_is_numeric(self):
+        """target backend uses Numeric for Float/Dual"""
+
+        return exclusions.open()
+
+    @property
     def text_type(self):
         """Target database must support an unbounded Text() "
         "type such as TEXT or CLOB"""
diff --git a/lib/sqlalchemy/testing/suite/test_types.py b/lib/sqlalchemy/testing/suite/test_types.py
index 72f1e8c10..92781cc1b 100644
--- a/lib/sqlalchemy/testing/suite/test_types.py
+++ b/lib/sqlalchemy/testing/suite/test_types.py
@@ -13,6 +13,7 @@ from .. import fixtures
 from .. import mock
 from ..assertions import eq_
 from ..assertions import is_
+from ..assertions import ne_
 from ..config import requirements
 from ..schema import Column
 from ..schema import Table
@@ -47,6 +48,7 @@ from ... import UUID
 from ... import Uuid
 from ...orm import declarative_base
 from ...orm import Session
+from ...sql import sqltypes
 from ...sql.sqltypes import LargeBinary
 from ...sql.sqltypes import PickleType
 
@@ -1090,6 +1092,15 @@ class NumericTest(_LiteralRoundTripFixture, fixtures.TestBase):
             Numeric(precision=5, scale=3), numbers, numbers, check_scale=True
         )
 
+    @testing.combinations(sqltypes.Float, sqltypes.Double, argnames="cls_")
+    @testing.requires.float_is_numeric
+    def test_float_is_not_numeric(self, connection, cls_):
+        target_type = cls_().dialect_impl(connection.dialect)
+        numeric_type = sqltypes.Numeric().dialect_impl(connection.dialect)
+
+        ne_(target_type.__visit_name__, numeric_type.__visit_name__)
+        ne_(target_type.__class__, numeric_type.__class__)
+
 
 class BooleanTest(_LiteralRoundTripFixture, fixtures.TablesTest):
     __backend__ = True