refactor(datatypes): remove Enum

Enum types are now aliased to String. There was no functionality
provided by Enums, and in every backend that we implement that supports
them they are restricted to Strings.

BREAKING CHANGE: Enums are now strings. Likely no action needed since no functionality existed.

ibis/expr/datatypes/core.py

@@ -752,17 +752,6 @@ def _pretty_piece(self) -> str:
         return f"<{self.value_type}>"
 
 
-@public
-class Enum(DataType):
-    """Enumeration values."""
-
-    rep_type = datatype
-    value_type = datatype
-
-    scalar = ir.EnumScalar
-    column = ir.EnumColumn
-
-
 @public
 class Map(Variadic):
     """Associative array values."""
@@ -959,6 +948,8 @@ class INET(String):
 inet = INET()
 decimal = Decimal()
 
+Enum = String
+
 public(
     null=null,
     boolean=boolean,
@@ -995,4 +986,5 @@ class INET(String):
     macaddr=macaddr,
     inet=inet,
     decimal=decimal,
+    Enum=Enum,
 )

ibis/expr/datatypes/value.py

@@ -175,8 +175,8 @@ def infer_integer(value: int, prefer_unsigned: bool = False) -> dt.Integer:
 
 
 @infer.register(enum.Enum)
-def infer_enum(value: enum.Enum) -> dt.Enum:
-    return dt.Enum(infer(value.name), infer(value.value))
+def infer_enum(_: enum.Enum) -> dt.String:
+    return dt.string
 
 
 @infer.register(bool)

ibis/expr/types/collections.py

@@ -3,21 +3,6 @@
 from ibis.expr.types.generic import Column, Scalar, Value
 
 
-@public
-class EnumValue(Value):
-    pass  # noqa: E701,E302
-
-
-@public
-class EnumScalar(Scalar, EnumValue):
-    pass  # noqa: E701,E302
-
-
-@public
-class EnumColumn(Column, EnumValue):
-    pass  # noqa: E701,E302
-
-
 @public
 class SetValue(Value):
     pass  # noqa: E701,E302

ibis/tests/expr/test_datatypes.py

@@ -444,7 +444,7 @@ class Foo(enum.Enum):
                 ]
             ),
         ),
-        (Foo.a, dt.Enum(dt.string, dt.int8)),
+        (Foo.a, dt.Enum()),
     ],
 )
 def test_infer_dtype(value, expected_dtype):