Blow away IsSubsimilar (#79)

The view seems to be that the real thing needs to be full python
typing assignability, and the runtime will just need to do some the
best it can.

I merged some code from issubsimilar back into issubtype

Author: msullivan

README.md

@@ -1,6 +1,6 @@
 # Computed Types in Python
 
-See [pep.rst](pep.rst) for the PEP draft and [design-qs.rst](design-qs.rst) for some design discussion not yet merged into the PEP.
+See [pep.rst](pep.rst) for the PEP draft.
 
 ## Development
 

design-qs.rst

@@ -33,7 +33,6 @@
     GetSpecialAttr,
     GetType,
     GetAnnotations,
-    IsSubtype,
     IsSub,
     Iter,
     Length,
@@ -1408,16 +1407,6 @@ def test_eval_bool_literal_07():
     d = eval_typing(IsSub[Literal[False], _BoolLiteral[False]])
     assert d == _BoolLiteral[True]
 
-    d = eval_typing(IsSubtype[_BoolLiteral[True], Literal[True]])
-    assert d == _BoolLiteral[True]
-    d = eval_typing(IsSubtype[_BoolLiteral[False], Literal[False]])
-    assert d == _BoolLiteral[True]
-
-    d = eval_typing(IsSubtype[Literal[True], _BoolLiteral[True]])
-    assert d == _BoolLiteral[True]
-    d = eval_typing(IsSubtype[Literal[False], _BoolLiteral[False]])
-    assert d == _BoolLiteral[True]
-
     d = eval_typing(Matches[_BoolLiteral[True], Literal[True]])
     assert d == _BoolLiteral[True]
     d = eval_typing(Matches[_BoolLiteral[False], Literal[False]])

tests/test_type_eval.py

@@ -9,7 +9,6 @@
 # XXX: this needs to go second due to nasty circularity -- try to fix that!!
 from ._eval_call import eval_call, eval_call_with_types
 from ._subtype import issubtype
-from ._subsim import issubsimilar
 
 # This one is imported for registering handlers
 from . import _eval_operators  # noqa
@@ -24,7 +23,6 @@
     "eval_call_with_types",
     "flatten_class",
     "issubtype",
-    "issubsimilar",
     "TypeMapError",
     "_EvalProxy",
     "_get_current_context",

typemap/type_eval/__init__.py

@@ -29,8 +29,7 @@
     GetMemberType,
     GetSpecialAttr,
     InitField,
-    IsSubSimilar,
-    IsSubtype,
+    IsSub,
     Iter,
     Length,
     Lowercase,
@@ -236,23 +235,17 @@ def _eval_Iter(tp, *, ctx):
 # N.B: These handle unions on their own
 
 
-@type_eval.register_evaluator(IsSubtype)
+@type_eval.register_evaluator(IsSub)
 @_lift_evaluated
-def _eval_IsSubtype(lhs, rhs, *, ctx):
+def _eval_IsSub(lhs, rhs, *, ctx):
     return _BoolLiteral[type_eval.issubtype(lhs, rhs)]
 
 
-@type_eval.register_evaluator(IsSubSimilar)
-@_lift_evaluated
-def _eval_IsSubSimilar(lhs, rhs, *, ctx):
-    return _BoolLiteral[type_eval.issubsimilar(lhs, rhs)]
-
-
 @type_eval.register_evaluator(Matches)
 @_lift_evaluated
 def _eval_Matches(lhs, rhs, *, ctx):
     return _BoolLiteral[
-        type_eval.issubsimilar(lhs, rhs) and type_eval.issubsimilar(rhs, lhs)
+        type_eval.issubtype(lhs, rhs) and type_eval.issubtype(rhs, lhs)
     ]
 
 
@@ -262,8 +255,8 @@ def _eval_bool_tp(tp, ctx):
     else:
         return _BoolLiteral[
             any(
-                type_eval.issubsimilar(arg, typing.Literal[True])
-                and not type_eval.issubsimilar(arg, typing.Never)
+                type_eval.issubtype(arg, typing.Literal[True])
+                and not type_eval.issubtype(arg, typing.Never)
                 for arg in _union_elems(tp, ctx)
             )
         ]
@@ -1032,7 +1025,7 @@ def _eval_RaiseError(msg, *extra_types, ctx):
 
 def _add_quals(typ, quals):
     for qual in (typing.ClassVar, typing.Final):
-        if type_eval.issubsimilar(typing.Literal[qual.__name__], quals):
+        if type_eval.issubtype(typing.Literal[qual.__name__], quals):
             typ = qual[typ]
     return typ
 
@@ -1079,7 +1072,7 @@ def _eval_NewProtocol(*etyps: Member, ctx):
         typ = _eval_types(typ, ctx)
         tquals = _eval_types(quals, ctx)
 
-        if type_eval.issubsimilar(
+        if type_eval.issubtype(
             typing.Literal["ClassVar"], tquals
         ) and _is_method_like(typ):
             dct[name] = _callable_type_to_method(name, typ)

typemap/type_eval/_eval_operators.py

@@ -1,9 +1,3 @@
-# XXX: This is the start of an implementation of issubtype, but
-# honestly it is still mostly the same as issubsimilar. I'm preserving
-# it for now and might still expand it some.
-# Largely the value of it is in the TODO comments I guess.
-
-
 import typing
 
 
@@ -15,14 +9,24 @@
 
 def issubtype(lhs: typing.Any, rhs: typing.Any) -> bool:
     # TODO: Need to handle a lot of cases!
+    # This is explicitly "best-effort", though.
 
     # TODO: We will probably need to carry a context around,
     # and maybe recursively invoke eval_typing?
 
     # N.B: All of the 'bool's in these are because black otherwise
     # formats the two-conditional chains in an unconscionably bad way.
 
+    if lhs is None:
+        lhs = type(None)
+    if rhs is None:
+        rhs = type(None)
+
     # Unions first
+    if lhs is typing.Never:
+        return True
+    elif rhs is typing.Never:
+        return False
     if _typing_inspect.is_union_type(rhs):
         return any(issubtype(lhs, r) for r in typing.get_args(rhs))
     elif _typing_inspect.is_union_type(lhs):
@@ -43,11 +47,11 @@ def issubtype(lhs: typing.Any, rhs: typing.Any) -> bool:
         return issubclass(lhs, rhs)
 
     # literal <:? literal
-    elif bool(
-        _typing_inspect.is_literal(lhs) and _typing_inspect.is_literal(rhs)
-    ):
-        rhs_args = set(typing.get_args(rhs))
-        return all(lv in rhs_args for lv in typing.get_args(lhs))
+    elif _typing_inspect.is_literal(lhs) and _typing_inspect.is_literal(rhs):
+        # We need to check both value and type, since True == 1 but
+        # Literal[True] should not be a subtype of Literal[1]
+        rhs_args = {(t, type(t)) for t in typing.get_args(rhs)}
+        return all((lv, type(lv)) in rhs_args for lv in typing.get_args(lhs))
 
     # XXX: This case is kind of a hack, to support NoLiterals.
     elif rhs is typing.Literal:
@@ -71,14 +75,23 @@ def issubtype(lhs: typing.Any, rhs: typing.Any) -> bool:
     ):
         return issubtype(lhs, _typing_inspect.get_origin(rhs))
 
+    # C[A] <:? D[B] -- just match the heads!
+    # Super wrong!
+    # TODO: What to do about C[A] <:? D[B]???
+    # TODO: and we will we need to infer variance ourselves with the new syntax
+    elif bool(
+        _typing_inspect.is_generic_alias(lhs)
+        and _typing_inspect.is_generic_alias(rhs)
+    ):
+        return issubtype(
+            _typing_inspect.get_origin(lhs), _typing_inspect.get_origin(rhs)
+        )
+
     # XXX: I think this is probably wrong, but a test currently has
     # an unbound type variable...
     elif _typing_inspect.is_type_var(lhs):
         return lhs is rhs
 
-    # TODO: What to do about C[A] <:? D[B]???
-    # TODO: and we will we need to infer variance ourselves with the new syntax
-
     # TODO: Protocols???
 
     # TODO: tuple
@@ -97,4 +110,7 @@ def issubtype(lhs: typing.Any, rhs: typing.Any) -> bool:
     # We could have restrictions if we are willing to document them.
 
     # This will probably fail
-    return issubclass(lhs, rhs)
+    try:
+        return issubclass(lhs, rhs)
+    except TypeError as e:
+        raise TypeError(*e.args, lhs, rhs)

typemap/type_eval/_subsim.py

@@ -280,12 +280,7 @@ def __bool__(self):
 
 
 @_SpecialForm
-def IsSubtype(self, tps):
-    return _BoolGenericAlias(self, tps)
-
-
-@_SpecialForm
-def IsSubSimilar(self, tps):
+def IsSub(self, tps):
     return _BoolGenericAlias(self, tps)
 
 
@@ -294,9 +289,6 @@ def Matches(self, tps):
     return _BoolGenericAlias(self, tps)
 
 
-IsSub = IsSubSimilar
-
-
 @_SpecialForm
 def Bool(self, tp):
     return _BoolGenericAlias(self, tp)