[mypyc] Support type narrowing of native int types using "int" (#14524)

Now `isinstance(x, int)` can be used to narrow a union type that
includes a native int type. In mypyc unions there is no runtime
distinction between different integer types -- everything is represented
at runtime as boxed `int` values anyway.

Also test narrowing a native int using the same native int type.

Work on mypyc/mypyc#837.

mypy/checker.py

@@ -178,6 +178,7 @@
 )
 from mypy.types import (
  ANY_STRATEGY,
+ MYPYC_NATIVE_INT_NAMES,
  OVERLOAD_NAMES,
  AnyType,
  BoolTypeQuery,
@@ -4517,10 +4518,7 @@ def analyze_range_native_int_type(self, expr: Expression) -> Type | None:
  ok = True
  for arg in expr.args:
  argt = get_proper_type(self.lookup_type(arg))
- if isinstance(argt, Instance) and argt.type.fullname in (
- "mypy_extensions.i64",
- "mypy_extensions.i32",
- ):
+ if isinstance(argt, Instance) and argt.type.fullname in MYPYC_NATIVE_INT_NAMES:
  if native_int is None:
  native_int = argt
  elif argt != native_int:

mypy/meet.py

@@ -15,6 +15,7 @@
 )
 from mypy.typeops import is_recursive_pair, make_simplified_union, tuple_fallback
 from mypy.types import (
+ MYPYC_NATIVE_INT_NAMES,
  AnyType,
  CallableType,
  DeletedType,
@@ -475,6 +476,9 @@ def _type_object_overlap(left: Type, right: Type) -> bool:
  ):
  return True
 
+ if right.type.fullname == "builtins.int" and left.type.fullname in MYPYC_NATIVE_INT_NAMES:
+ return True
+
  # Two unrelated types cannot be partially overlapping: they're disjoint.
  if left.type.has_base(right.type.fullname):
  left = map_instance_to_supertype(left, right.type)

mypy/semanal_classprop.py

@@ -22,7 +22,7 @@
  Var,
 )
 from mypy.options import Options
-from mypy.types import Instance, ProperType
+from mypy.types import MYPYC_NATIVE_INT_NAMES, Instance, ProperType
 
 # Hard coded type promotions (shared between all Python versions).
 # These add extra ad-hoc edges to the subtyping relation. For example,
@@ -177,7 +177,7 @@ def add_type_promotion(
  # Special case the promotions between 'int' and native integer types.
  # These have promotions going both ways, such as from 'int' to 'i64'
  # and 'i64' to 'int', for convenience.
- if defn.fullname == "mypy_extensions.i64" or defn.fullname == "mypy_extensions.i32":
+ if defn.fullname in MYPYC_NATIVE_INT_NAMES:
  int_sym = builtin_names["int"]
  assert isinstance(int_sym.node, TypeInfo)
  int_sym.node._promote.append(Instance(defn.info, []))

mypy/subtypes.py

@@ -27,6 +27,7 @@
 from mypy.options import Options
 from mypy.state import state
 from mypy.types import (
+ MYPYC_NATIVE_INT_NAMES,
  TUPLE_LIKE_INSTANCE_NAMES,
  TYPED_NAMEDTUPLE_NAMES,
  AnyType,
@@ -1793,14 +1794,19 @@ def covers_at_runtime(item: Type, supertype: Type) -> bool:
  erase_type(item), supertype, ignore_promotions=True, erase_instances=True
  ):
  return True
- if isinstance(supertype, Instance) and supertype.type.is_protocol:
- # TODO: Implement more robust support for runtime isinstance() checks, see issue #3827.
- if is_proper_subtype(item, supertype, ignore_promotions=True):
- return True
- if isinstance(item, TypedDictType) and isinstance(supertype, Instance):
- # Special case useful for selecting TypedDicts from unions using isinstance(x, dict).
- if supertype.type.fullname == "builtins.dict":
- return True
+ if isinstance(supertype, Instance):
+ if supertype.type.is_protocol:
+ # TODO: Implement more robust support for runtime isinstance() checks, see issue #3827.
+ if is_proper_subtype(item, supertype, ignore_promotions=True):
+ return True
+ if isinstance(item, TypedDictType):
+ # Special case useful for selecting TypedDicts from unions using isinstance(x, dict).
+ if supertype.type.fullname == "builtins.dict":
+ return True
+ elif isinstance(item, Instance) and supertype.type.fullname == "builtins.int":
+ # "int" covers all native int types
+ if item.type.fullname in MYPYC_NATIVE_INT_NAMES:
+ return True
  # TODO: Add more special cases.
  return False
 

mypy/types.py

@@ -150,6 +150,9 @@
  "typing_extensions.Never",
 )
 
+# Mypyc fixed-width native int types (compatible with builtins.int)
+MYPYC_NATIVE_INT_NAMES: Final = ("mypy_extensions.i64", "mypy_extensions.i32")
+
 DATACLASS_TRANSFORM_NAMES: Final = (
  "typing.dataclass_transform",
  "typing_extensions.dataclass_transform",

mypyc/test-data/irbuild-i64.test

@@ -1834,3 +1834,67 @@ L0:
  r0 = CPyLong_FromFloat(x)
  r1 = unbox(int64, r0)
  return r1
+
+[case testI64IsinstanceNarrowing]
+from typing import Union
+from mypy_extensions import i64
+
+class C:
+ a: i64
+
+def narrow1(x: Union[C, i64]) -> i64:
+ if isinstance(x, i64):
+ return x
+ return x.a
+
+def narrow2(x: Union[C, i64]) -> i64:
+ if isinstance(x, int):
+ return x
+ return x.a
+[out]
+def narrow1(x):
+ x :: union[__main__.C, int64]
+ r0 :: object
+ r1 :: int32
+ r2 :: bit
+ r3 :: bool
+ r4 :: int64
+ r5 :: __main__.C
+ r6 :: int64
+L0:
+ r0 = load_address PyLong_Type
+ r1 = PyObject_IsInstance(x, r0)
+ r2 = r1 >= 0 :: signed
+ r3 = truncate r1: int32 to builtins.bool
+ if r3 goto L1 else goto L2 :: bool
+L1:
+ r4 = unbox(int64, x)
+ return r4
+L2:
+ r5 = borrow cast(__main__.C, x)
+ r6 = r5.a
+ keep_alive x
+ return r6
+def narrow2(x):
+ x :: union[__main__.C, int64]
+ r0 :: object
+ r1 :: int32
+ r2 :: bit
+ r3 :: bool
+ r4 :: int64
+ r5 :: __main__.C
+ r6 :: int64
+L0:
+ r0 = load_address PyLong_Type
+ r1 = PyObject_IsInstance(x, r0)
+ r2 = r1 >= 0 :: signed
+ r3 = truncate r1: int32 to builtins.bool
+ if r3 goto L1 else goto L2 :: bool
+L1:
+ r4 = unbox(int64, x)
+ return r4
+L2:
+ r5 = borrow cast(__main__.C, x)
+ r6 = r5.a
+ keep_alive x
+ return r6

mypyc/test-data/run-i64.test

@@ -1,5 +1,5 @@
 [case testI64BasicOps]
-from typing import List, Any, Tuple
+from typing import List, Any, Tuple, Union
 
 MYPY = False
 if MYPY:
@@ -497,6 +497,22 @@ def test_for_loop() -> None:
  assert n == 9
  assert sum([x * x for x in range(i64(4 + int()))]) == 1 + 4 + 9
 
+def narrow1(x: Union[str, i64]) -> i64:
+ if isinstance(x, i64):
+ return x
+ return len(x)
+
+def narrow2(x: Union[str, i64]) -> i64:
+ if isinstance(x, int):
+ return x
+ return len(x)
+
+def test_isinstance() -> None:
+ assert narrow1(123) == 123
+ assert narrow1("foobar") == 6
+ assert narrow2(123) == 123
+ assert narrow2("foobar") == 6
+
 [case testI64ErrorValuesAndUndefined]
 from typing import Any, Tuple
 import sys

test-data/unit/check-native-int.test

@@ -184,3 +184,47 @@ from mypy_extensions import i64, i32
 reveal_type([a for a in range(i64(5))]) # N: Revealed type is "builtins.list[mypy_extensions.i64]"
 [reveal_type(a) for a in range(0, i32(5))] # N: Revealed type is "mypy_extensions.i32"
 [builtins fixtures/primitives.pyi]
+
+[case testNativeIntNarrowing]
+from typing import Union
+from mypy_extensions import i64, i32
+
+def narrow_i64(x: Union[str, i64]) -> None:
+ if isinstance(x, i64):
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i64"
+ else:
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i64]"
+
+ if isinstance(x, str):
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ else:
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i64"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i64]"
+
+ if isinstance(x, int):
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i64"
+ else:
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i64]"
+
+def narrow_i32(x: Union[str, i32]) -> None:
+ if isinstance(x, i32):
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i32"
+ else:
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i32]"
+
+ if isinstance(x, str):
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ else:
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i32"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i32]"
+
+ if isinstance(x, int):
+ reveal_type(x) # N: Revealed type is "mypy_extensions.i32"
+ else:
+ reveal_type(x) # N: Revealed type is "builtins.str"
+ reveal_type(x) # N: Revealed type is "Union[builtins.str, mypy_extensions.i32]"
+
+[builtins fixtures/primitives.pyi]