Added future flag check

Author: cdce8p

mypy/fastparse.py

@@ -1430,7 +1430,8 @@ def visit_BinOp(self, n: ast3.BinOp) -> Type:
         right = self.visit(n.right)
         return UnionType([left, right],
                          line=self.line,
-                         column=self.convert_column(n.col_offset))
+                         column=self.convert_column(n.col_offset),
+                         is_binary_op=True)
 
     def visit_NameConstant(self, n: NameConstant) -> Type:
         if isinstance(n.value, bool):

mypy/typeanal.py

@@ -605,6 +605,11 @@ def visit_star_type(self, t: StarType) -> Type:
         return StarType(self.anal_type(t.type), t.line)
 
     def visit_union_type(self, t: UnionType) -> Type:
+        if (t.is_binary_op is True
+                and self.api.is_stub_file is False
+                and self.options.python_version < (3, 10)
+                and self.api.is_future_flag_set('annotations') is False):
+            self.fail("Alternative syntax for unions requires Python 3.10 or newer", t)
         return UnionType(self.anal_array(t.items), t.line)
 
     def visit_partial_type(self, t: PartialType) -> Type:

mypy/types.py

@@ -1724,11 +1724,13 @@ class UnionType(ProperType):
 
     __slots__ = ('items',)
 
-    def __init__(self, items: Sequence[Type], line: int = -1, column: int = -1) -> None:
+    def __init__(self, items: Sequence[Type], line: int = -1, column: int = -1,
+                 is_binary_op: bool = False) -> None:
         super().__init__(line, column)
         self.items = flatten_nested_unions(items)
         self.can_be_true = any(item.can_be_true for item in items)
         self.can_be_false = any(item.can_be_false for item in items)
+        self.is_binary_op = is_binary_op
 
     def __hash__(self) -> int:
         return hash(frozenset(self.items))

test-data/unit/check-union-or-syntax.test

@@ -1,16 +1,18 @@
 -- Type checking of union types with '|' syntax
 
 [case testUnionOrSyntaxWithTwoBuiltinsTypes]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
+from __future__ import annotations
 def f(x: int | str) -> int | str:
     reveal_type(x)  # N: Revealed type is 'Union[builtins.int, builtins.str]'
     z: int | str = 0
     reveal_type(z)  # N: Revealed type is 'Union[builtins.int, builtins.str]'
     return x
 reveal_type(f)  # N: Revealed type is 'def (x: Union[builtins.int, builtins.str]) -> Union[builtins.int, builtins.str]'
+[builtins fixtures/tuple.pyi]
 
 [case testUnionOrSyntaxWithThreeBuiltinsTypes]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 def f(x: int | str | float) -> int | str | float:
     reveal_type(x)  # N: Revealed type is 'Union[builtins.int, builtins.str, builtins.float]'
     z: int | str | float = 0
@@ -20,7 +22,7 @@ def f(x: int | str | float) -> int | str | float:
 reveal_type(f)  # N: Revealed type is 'def (x: Union[builtins.int, builtins.str, builtins.float]) -> Union[builtins.int, builtins.str, builtins.float]'
 
 [case testUnionOrSyntaxWithTwoTypes]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 class A: pass
 class B: pass
 def f(x: A | B) -> A | B:
@@ -31,7 +33,7 @@ def f(x: A | B) -> A | B:
 reveal_type(f)  # N: Revealed type is 'def (x: Union[__main__.A, __main__.B]) -> Union[__main__.A, __main__.B]'
 
 [case testUnionOrSyntaxWithThreeTypes]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 class A: pass
 class B: pass
 class C: pass
@@ -43,21 +45,37 @@ def f(x: A | B | C) -> A | B | C:
 reveal_type(f)  # N: Revealed type is 'def (x: Union[__main__.A, __main__.B, __main__.C]) -> Union[__main__.A, __main__.B, __main__.C]'
 
 [case testUnionOrSyntaxWithLiteral]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 from typing_extensions import Literal
 reveal_type(Literal[4] | str)  # N: Revealed type is 'Any'
 [builtins fixtures/tuple.pyi]
 
 [case testUnionOrSyntaxWithBadOperator]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 x: 1 + 2  # E: Invalid type comment or annotation
 
 [case testUnionOrSyntaxWithBadOperands]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 x: int | 42  # E: Invalid type: try using Literal[42] instead?
 y: 42 | int  # E: Invalid type: try using Literal[42] instead?
 z: str | 42 | int  # E: Invalid type: try using Literal[42] instead?
 
 [case testUnionOrSyntaxInComment]
-# flags: --python-version 3.9
+# flags: --python-version 3.10
 x = 1  # type: int | str
+
+[case testUnionOrSyntaxFutureImport]
+# flags: --python-version 3.7
+from __future__ import annotations
+x: int | None
+[builtins fixtures/tuple.pyi]
+
+[case testUnionOrSyntaxMissingFutureImport]
+# flags: --python-version 3.9
+x: int | None  # E: Alternative syntax for unions requires Python 3.10 or newer
+
+[case testUnionOrSyntaxInStubFile]
+# flags: --python-version 3.6
+from lib import x
+[file lib.pyi]
+x: int | None