Basic support for typing_extensions.NamedTuple

mypy/nodes.py

@@ -2417,7 +2417,7 @@ class NamedTupleExpr(Expression):
     # The class representation of this named tuple (its tuple_type attribute contains
     # the tuple item types)
     info: "TypeInfo"
-    is_typed: bool  # whether this class was created with typing.NamedTuple
+    is_typed: bool  # whether this class was created with typing(_extensions).NamedTuple
 
     def __init__(self, info: 'TypeInfo', is_typed: bool = False) -> None:
         super().__init__()

mypy/semanal.py

@@ -99,7 +99,7 @@
     TypeTranslator, TypeOfAny, TypeType, NoneType, PlaceholderType, TPDICT_NAMES, ProperType,
     get_proper_type, get_proper_types, TypeAliasType, TypeVarLikeType, Parameters, ParamSpecType,
     PROTOCOL_NAMES, TYPE_ALIAS_NAMES, FINAL_TYPE_NAMES, FINAL_DECORATOR_NAMES, REVEAL_TYPE_NAMES,
-    ASSERT_TYPE_NAMES, OVERLOAD_NAMES, is_named_instance,
+    ASSERT_TYPE_NAMES, OVERLOAD_NAMES, TYPED_NAMEDTUPLE_NAMES, is_named_instance,
 )
 from mypy.typeops import function_type, get_type_vars
 from mypy.type_visitor import TypeQuery
@@ -1529,7 +1529,7 @@ def analyze_base_classes(
         bases = []
         for base_expr in base_type_exprs:
             if (isinstance(base_expr, RefExpr) and
-                    base_expr.fullname in ('typing.NamedTuple',) + TPDICT_NAMES):
+                    base_expr.fullname in TYPED_NAMEDTUPLE_NAMES + TPDICT_NAMES):
                 # Ignore magic bases for now.
                 continue
 

mypy/semanal_namedtuple.py

@@ -9,7 +9,7 @@
 
 from mypy.types import (
     Type, TupleType, AnyType, TypeOfAny, CallableType, TypeType, TypeVarType,
-    UnboundType, LiteralType,
+    UnboundType, LiteralType, TYPED_NAMEDTUPLE_NAMES
 )
 from mypy.semanal_shared import (
     SemanticAnalyzerInterface, set_callable_name, calculate_tuple_fallback, PRIORITY_FALLBACKS
@@ -65,7 +65,7 @@ def analyze_namedtuple_classdef(self, defn: ClassDef, is_stub_file: bool,
         for base_expr in defn.base_type_exprs:
             if isinstance(base_expr, RefExpr):
                 self.api.accept(base_expr)
-                if base_expr.fullname == 'typing.NamedTuple':
+                if base_expr.fullname in TYPED_NAMEDTUPLE_NAMES:
                     result = self.check_namedtuple_classdef(defn, is_stub_file)
                     if result is None:
                         # This is a valid named tuple, but some types are incomplete.
@@ -175,7 +175,7 @@ def check_namedtuple(self,
         fullname = callee.fullname
         if fullname == 'collections.namedtuple':
             is_typed = False
-        elif fullname == 'typing.NamedTuple':
+        elif fullname in TYPED_NAMEDTUPLE_NAMES:
             is_typed = True
         else:
             return None, None
@@ -270,7 +270,7 @@ def parse_namedtuple_args(self, call: CallExpr, fullname: str
 
         Return None if the definition didn't typecheck.
         """
-        type_name = 'NamedTuple' if fullname == 'typing.NamedTuple' else 'namedtuple'
+        type_name = 'NamedTuple' if fullname in TYPED_NAMEDTUPLE_NAMES else 'namedtuple'
         # TODO: Share code with check_argument_count in checkexpr.py?
         args = call.args
         if len(args) < 2:
@@ -279,7 +279,7 @@ def parse_namedtuple_args(self, call: CallExpr, fullname: str
         defaults: List[Expression] = []
         if len(args) > 2:
             # Typed namedtuple doesn't support additional arguments.
-            if fullname == 'typing.NamedTuple':
+            if fullname in TYPED_NAMEDTUPLE_NAMES:
                 self.fail('Too many arguments for "NamedTuple()"', call)
                 return None
             for i, arg_name in enumerate(call.arg_names[2:], 2):

mypy/subtypes.py

@@ -8,7 +8,7 @@
     Instance, TypeVarType, CallableType, TupleType, TypedDictType, UnionType, Overloaded,
     ErasedType, PartialType, DeletedType, UninhabitedType, TypeType, is_named_instance,
     FunctionLike, TypeOfAny, LiteralType, get_proper_type, TypeAliasType, ParamSpecType,
-    Parameters, UnpackType, TUPLE_LIKE_INSTANCE_NAMES, TypeVarTupleType,
+    Parameters, UnpackType, TUPLE_LIKE_INSTANCE_NAMES, TYPED_NAMEDTUPLE_NAMES, TypeVarTupleType,
 )
 import mypy.applytype
 import mypy.constraints
@@ -286,7 +286,7 @@ def visit_instance(self, left: Instance) -> bool:
             # in `TypeInfo.mro`, so when `(a: NamedTuple) -> None` is used,
             # we need to check for `is_named_tuple` property
             if ((left.type.has_base(rname) or rname == 'builtins.object'
-                    or (rname == 'typing.NamedTuple'
+                    or (rname in TYPED_NAMEDTUPLE_NAMES
                         and any(l.is_named_tuple for l in left.type.mro)))
                     and not self.ignore_declared_variance):
                 # Map left type to corresponding right instances.

mypy/types.py

@@ -66,6 +66,11 @@
         SyntheticTypeVisitor as SyntheticTypeVisitor,
     )
 
+TYPED_NAMEDTUPLE_NAMES: Final = (
+    "typing.NamedTuple",
+    "typing_extensions.NamedTuple"
+)
+
 # Supported names of TypedDict type constructors.
 TPDICT_NAMES: Final = (
     "typing.TypedDict",

test-data/unit/check-class-namedtuple.test

@@ -709,3 +709,21 @@ class HasStaticMethod(NamedTuple):
         return 4
 
 [builtins fixtures/property.pyi]
+
+[case testTypingExtensionsNamedTuple]
+from typing_extensions import NamedTuple
+
+class Point(NamedTuple):
+    x: int
+    y: int
+
+bad_point = Point('foo') # E: Missing positional argument "y" in call to "Point" \
+                         # E: Argument 1 to "Point" has incompatible type "str"; expected "int"
+point = Point(1, 2)
+x, y = point
+x = point.x
+reveal_type(x) # N: Revealed type is "builtins.int"
+reveal_type(y) # N: Revealed type is "builtins.int"
+point.y = 6 # E: Property "y" defined in "Point" is read-only
+
+[builtins fixtures/tuple.pyi]

test-data/unit/lib-stub/typing_extensions.pyi

@@ -10,6 +10,7 @@ class _SpecialForm:
     def __getitem__(self, typeargs: Any) -> Any:
         pass
 
+NamedTuple = 0
 Protocol: _SpecialForm = ...
 def runtime_checkable(x: _T) -> _T: pass
 runtime = runtime_checkable