Add TypeVarTupleType type node (#12632)

This adds the TypeVarTupleType type node and basic semanal/glue.

Type checking involving it will be added in a subsequent PR to keep each PR smaller.

This PR is mostly consisting of modifying all the visitors, but not all of them are implemented.

mypy/constraints.py

@@ -8,7 +8,7 @@
     TupleType, TypedDictType, UnionType, Overloaded, ErasedType, PartialType, DeletedType,
     UninhabitedType, TypeType, TypeVarId, TypeQuery, is_named_instance, TypeOfAny, LiteralType,
     ProperType, ParamSpecType, get_proper_type, TypeAliasType, is_union_with_any,
-    UnpackType, callable_with_ellipsis, Parameters, TUPLE_LIKE_INSTANCE_NAMES,
+    UnpackType, callable_with_ellipsis, Parameters, TUPLE_LIKE_INSTANCE_NAMES, TypeVarTupleType,
 )
 from mypy.maptype import map_instance_to_supertype
 import mypy.subtypes
@@ -403,6 +403,9 @@ def visit_param_spec(self, template: ParamSpecType) -> List[Constraint]:
         # Can't infer ParamSpecs from component values (only via Callable[P, T]).
         return []
 
+    def visit_type_var_tuple(self, template: TypeVarTupleType) -> List[Constraint]:
+        raise NotImplementedError
+
     def visit_unpack_type(self, template: UnpackType) -> List[Constraint]:
         raise NotImplementedError
 

mypy/erasetype.py

@@ -4,7 +4,8 @@
     Type, TypeVisitor, UnboundType, AnyType, NoneType, TypeVarId, Instance, TypeVarType,
     CallableType, TupleType, TypedDictType, UnionType, Overloaded, ErasedType, PartialType,
     DeletedType, TypeTranslator, UninhabitedType, TypeType, TypeOfAny, LiteralType, ProperType,
-    get_proper_type, get_proper_types, TypeAliasType, ParamSpecType, Parameters, UnpackType
+    get_proper_type, get_proper_types, TypeAliasType, ParamSpecType, Parameters, UnpackType,
+    TypeVarTupleType
 )
 from mypy.nodes import ARG_STAR, ARG_STAR2
 
@@ -62,8 +63,11 @@ def visit_param_spec(self, t: ParamSpecType) -> ProperType:
     def visit_parameters(self, t: Parameters) -> ProperType:
         raise RuntimeError("Parameters should have been bound to a class")
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        return AnyType(TypeOfAny.special_form)
+
     def visit_unpack_type(self, t: UnpackType) -> ProperType:
-        raise NotImplementedError
+        return AnyType(TypeOfAny.special_form)
 
     def visit_callable_type(self, t: CallableType) -> ProperType:
         # We must preserve the fallback type for overload resolution to work.

mypy/expandtype.py

@@ -6,7 +6,7 @@
     ErasedType, PartialType, DeletedType, UninhabitedType, TypeType, TypeVarId,
     FunctionLike, TypeVarType, LiteralType, get_proper_type, ProperType,
     TypeAliasType, ParamSpecType, TypeVarLikeType, Parameters, ParamSpecFlavor,
-    UnpackType
+    UnpackType, TypeVarTupleType
 )
 
 
@@ -131,6 +131,9 @@ def visit_param_spec(self, t: ParamSpecType) -> Type:
             # TODO: should this branch be removed? better not to fail silently
             return repl
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
+        raise NotImplementedError
+
     def visit_unpack_type(self, t: UnpackType) -> Type:
         raise NotImplementedError
 

mypy/fixup.py

@@ -11,7 +11,7 @@
     CallableType, Instance, Overloaded, TupleType, TypedDictType,
     TypeVarType, UnboundType, UnionType, TypeVisitor, LiteralType,
     TypeType, NOT_READY, TypeAliasType, AnyType, TypeOfAny, ParamSpecType,
-    Parameters, UnpackType,
+    Parameters, UnpackType, TypeVarTupleType
 )
 from mypy.visitor import NodeVisitor
 from mypy.lookup import lookup_fully_qualified
@@ -252,6 +252,9 @@ def visit_type_var(self, tvt: TypeVarType) -> None:
     def visit_param_spec(self, p: ParamSpecType) -> None:
         p.upper_bound.accept(self)
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> None:
+        t.upper_bound.accept(self)
+
     def visit_unpack_type(self, u: UnpackType) -> None:
         u.type.accept(self)
 

mypy/indirection.py

@@ -67,6 +67,9 @@ def visit_type_var(self, t: types.TypeVarType) -> Set[str]:
     def visit_param_spec(self, t: types.ParamSpecType) -> Set[str]:
         return set()
 
+    def visit_type_var_tuple(self, t: types.TypeVarTupleType) -> Set[str]:
+        return self._visit(t.upper_bound)
+
     def visit_unpack_type(self, t: types.UnpackType) -> Set[str]:
         return t.type.accept(self)
 

mypy/join.py

@@ -8,7 +8,7 @@
     TupleType, TypedDictType, ErasedType, UnionType, FunctionLike, Overloaded, LiteralType,
     PartialType, DeletedType, UninhabitedType, TypeType, TypeOfAny, get_proper_type,
     ProperType, get_proper_types, TypeAliasType, PlaceholderType, ParamSpecType, Parameters,
-    UnpackType
+    UnpackType, TypeVarTupleType,
 )
 from mypy.maptype import map_instance_to_supertype
 from mypy.subtypes import (
@@ -257,6 +257,11 @@ def visit_param_spec(self, t: ParamSpecType) -> ProperType:
             return t
         return self.default(self.s)
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        if self.s == t:
+            return t
+        return self.default(self.s)
+
     def visit_unpack_type(self, t: UnpackType) -> UnpackType:
         raise NotImplementedError
 

mypy/meet.py

@@ -6,7 +6,7 @@
     TupleType, TypedDictType, ErasedType, UnionType, PartialType, DeletedType,
     UninhabitedType, TypeType, TypeOfAny, Overloaded, FunctionLike, LiteralType,
     ProperType, get_proper_type, get_proper_types, TypeAliasType, TypeGuardedType,
-    ParamSpecType, Parameters, UnpackType,
+    ParamSpecType, Parameters, UnpackType, TypeVarTupleType,
 )
 from mypy.subtypes import is_equivalent, is_subtype, is_callable_compatible, is_proper_subtype
 from mypy.erasetype import erase_type
@@ -536,6 +536,12 @@ def visit_param_spec(self, t: ParamSpecType) -> ProperType:
         else:
             return self.default(self.s)
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> ProperType:
+        if self.s == t:
+            return self.s
+        else:
+            return self.default(self.s)
+
     def visit_unpack_type(self, t: UnpackType) -> ProperType:
         raise NotImplementedError
 

mypy/sametypes.py

@@ -4,7 +4,8 @@
     Type, UnboundType, AnyType, NoneType, TupleType, TypedDictType,
     UnionType, CallableType, TypeVarType, Instance, TypeVisitor, ErasedType,
     Overloaded, PartialType, DeletedType, UninhabitedType, TypeType, LiteralType,
-    ProperType, get_proper_type, TypeAliasType, ParamSpecType, Parameters, UnpackType
+    ProperType, get_proper_type, TypeAliasType, ParamSpecType, Parameters,
+    UnpackType, TypeVarTupleType,
 )
 from mypy.typeops import tuple_fallback, make_simplified_union, is_simple_literal
 
@@ -118,6 +119,10 @@ def visit_param_spec(self, left: ParamSpecType) -> bool:
         return (isinstance(self.right, ParamSpecType) and
                 left.id == self.right.id and left.flavor == self.right.flavor)
 
+    def visit_type_var_tuple(self, left: TypeVarTupleType) -> bool:
+        return (isinstance(self.right, TypeVarTupleType) and
+                left.id == self.right.id)
+
     def visit_unpack_type(self, left: UnpackType) -> bool:
         return (isinstance(self.right, UnpackType) and
                 is_same_type(left.type, self.right.type))

mypy/semanal_typeargs.py

@@ -10,7 +10,7 @@
 from mypy.nodes import TypeInfo, Context, MypyFile, FuncItem, ClassDef, Block, FakeInfo
 from mypy.types import (
     Type, Instance, TypeVarType, AnyType, get_proper_types, TypeAliasType, ParamSpecType,
-    UnpackType, TupleType, get_proper_type
+    UnpackType, TupleType, TypeVarTupleType, TypeOfAny, get_proper_type
 )
 from mypy.mixedtraverser import MixedTraverserVisitor
 from mypy.subtypes import is_subtype
@@ -99,8 +99,15 @@ def visit_unpack_type(self, typ: UnpackType) -> None:
         proper_type = get_proper_type(typ.type)
         if isinstance(proper_type, TupleType):
             return
+        if isinstance(proper_type, TypeVarTupleType):
+            return
         if isinstance(proper_type, Instance) and proper_type.type.fullname == "builtins.tuple":
             return
+        if isinstance(proper_type, AnyType) and proper_type.type_of_any == TypeOfAny.from_error:
+            return
+
+        # TODO: Infer something when it can't be unpacked to allow rest of
+        # typechecking to work.
         self.fail(message_registry.INVALID_UNPACK.format(proper_type), typ)
 
     def check_type_var_values(self, type: TypeInfo, actuals: List[Type], arg_name: str,

mypy/server/astdiff.py

@@ -60,7 +60,7 @@ class level -- these are handled at attribute level (say, 'mod.Cls.method'
     Type, TypeVisitor, UnboundType, AnyType, NoneType, UninhabitedType,
     ErasedType, DeletedType, Instance, TypeVarType, CallableType, TupleType, TypedDictType,
     UnionType, Overloaded, PartialType, TypeType, LiteralType, TypeAliasType, ParamSpecType,
-    Parameters, UnpackType,
+    Parameters, UnpackType, TypeVarTupleType,
 )
 from mypy.util import get_prefix
 
@@ -318,6 +318,12 @@ def visit_param_spec(self, typ: ParamSpecType) -> SnapshotItem:
                 typ.flavor,
                 snapshot_type(typ.upper_bound))
 
+    def visit_type_var_tuple(self, typ: TypeVarTupleType) -> SnapshotItem:
+        return ('TypeVarTupleType',
+                typ.id.raw_id,
+                typ.id.meta_level,
+                snapshot_type(typ.upper_bound))
+
     def visit_unpack_type(self, typ: UnpackType) -> SnapshotItem:
         return ('UnpackType', snapshot_type(typ.type))
 

mypy/server/astmerge.py

@@ -60,7 +60,7 @@
     TupleType, TypeType, TypedDictType, UnboundType, UninhabitedType, UnionType,
     Overloaded, TypeVarType, TypeList, CallableArgument, EllipsisType, StarType, LiteralType,
     RawExpressionType, PartialType, PlaceholderType, TypeAliasType, ParamSpecType, Parameters,
-    UnpackType
+    UnpackType, TypeVarTupleType,
 )
 from mypy.util import get_prefix, replace_object_state
 from mypy.typestate import TypeState
@@ -416,6 +416,9 @@ def visit_type_var(self, typ: TypeVarType) -> None:
     def visit_param_spec(self, typ: ParamSpecType) -> None:
         pass
 
+    def visit_type_var_tuple(self, typ: TypeVarTupleType) -> None:
+        typ.upper_bound.accept(self)
+
     def visit_unpack_type(self, typ: UnpackType) -> None:
         typ.type.accept(self)
 

mypy/server/deps.py

@@ -100,7 +100,7 @@ class 'mod.Cls'. This can also refer to an attribute inherited from a
     Type, Instance, AnyType, NoneType, TypeVisitor, CallableType, DeletedType, PartialType,
     TupleType, TypeType, TypeVarType, TypedDictType, UnboundType, UninhabitedType, UnionType,
     FunctionLike, Overloaded, TypeOfAny, LiteralType, ErasedType, get_proper_type, ProperType,
-    TypeAliasType, ParamSpecType, Parameters, UnpackType
+    TypeAliasType, ParamSpecType, Parameters, UnpackType, TypeVarTupleType,
 )
 from mypy.server.trigger import make_trigger, make_wildcard_trigger
 from mypy.util import correct_relative_import
@@ -966,6 +966,13 @@ def visit_param_spec(self, typ: ParamSpecType) -> List[str]:
         triggers.extend(self.get_type_triggers(typ.upper_bound))
         return triggers
 
+    def visit_type_var_tuple(self, typ: TypeVarTupleType) -> List[str]:
+        triggers = []
+        if typ.fullname:
+            triggers.append(make_trigger(typ.fullname))
+        triggers.extend(self.get_type_triggers(typ.upper_bound))
+        return triggers
+
     def visit_unpack_type(self, typ: UnpackType) -> List[str]:
         return typ.type.accept(self)
 

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,
+    Parameters, UnpackType, TUPLE_LIKE_INSTANCE_NAMES, TypeVarTupleType,
 )
 import mypy.applytype
 import mypy.constraints
@@ -340,6 +340,15 @@ def visit_param_spec(self, left: ParamSpecType) -> bool:
             return True
         return self._is_subtype(left.upper_bound, self.right)
 
+    def visit_type_var_tuple(self, left: TypeVarTupleType) -> bool:
+        right = self.right
+        if (
+            isinstance(right, TypeVarTupleType)
+            and right.id == left.id
+        ):
+            return True
+        return self._is_subtype(left.upper_bound, self.right)
+
     def visit_unpack_type(self, left: UnpackType) -> bool:
         raise NotImplementedError
 
@@ -1463,6 +1472,15 @@ def visit_param_spec(self, left: ParamSpecType) -> bool:
             return True
         return self._is_proper_subtype(left.upper_bound, self.right)
 
+    def visit_type_var_tuple(self, left: TypeVarTupleType) -> bool:
+        right = self.right
+        if (
+            isinstance(right, TypeVarTupleType)
+            and right.id == left.id
+        ):
+            return True
+        return self._is_proper_subtype(left.upper_bound, self.right)
+
     def visit_unpack_type(self, left: UnpackType) -> bool:
         raise NotImplementedError
 

mypy/tvar_scope.py

@@ -1,6 +1,10 @@
 from typing import Optional, Dict, Union
-from mypy.types import TypeVarLikeType, TypeVarType, ParamSpecType, ParamSpecFlavor, TypeVarId
-from mypy.nodes import ParamSpecExpr, TypeVarExpr, TypeVarLikeExpr, SymbolTableNode
+from mypy.types import (
+    TypeVarLikeType, TypeVarType, ParamSpecType, ParamSpecFlavor, TypeVarId, TypeVarTupleType,
+)
+from mypy.nodes import (
+    ParamSpecExpr, TypeVarExpr, TypeVarLikeExpr, SymbolTableNode, TypeVarTupleExpr,
+)
 
 
 class TypeVarLikeScope:
@@ -88,6 +92,15 @@ def bind_new(self, name: str, tvar_expr: TypeVarLikeExpr) -> TypeVarLikeType:
                 line=tvar_expr.line,
                 column=tvar_expr.column
             )
+        elif isinstance(tvar_expr, TypeVarTupleExpr):
+            tvar_def = TypeVarTupleType(
+                name,
+                tvar_expr.fullname,
+                i,
+                upper_bound=tvar_expr.upper_bound,
+                line=tvar_expr.line,
+                column=tvar_expr.column
+            )
         else:
             assert False
         self.scope[tvar_expr.fullname] = tvar_def

mypy/type_visitor.py

@@ -23,7 +23,8 @@
     Parameters, RawExpressionType, Instance, NoneType, TypeType,
     UnionType, TypeVarType, PartialType, DeletedType, UninhabitedType, TypeVarLikeType,
     UnboundType, ErasedType, StarType, EllipsisType, TypeList, CallableArgument,
-    PlaceholderType, TypeAliasType, ParamSpecType, UnpackType, get_proper_type
+    PlaceholderType, TypeAliasType, ParamSpecType, UnpackType, TypeVarTupleType,
+    get_proper_type
 )
 
 
@@ -71,6 +72,10 @@ def visit_param_spec(self, t: ParamSpecType) -> T:
     def visit_parameters(self, t: Parameters) -> T:
         pass
 
+    @abstractmethod
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> T:
+        pass
+
     @abstractmethod
     def visit_instance(self, t: Instance) -> T:
         pass
@@ -197,6 +202,9 @@ def visit_param_spec(self, t: ParamSpecType) -> Type:
     def visit_parameters(self, t: Parameters) -> Type:
         return t.copy_modified(arg_types=self.translate_types(t.arg_types))
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> Type:
+        return t
+
     def visit_partial_type(self, t: PartialType) -> Type:
         return t
 
@@ -315,6 +323,9 @@ def visit_type_var(self, t: TypeVarType) -> T:
     def visit_param_spec(self, t: ParamSpecType) -> T:
         return self.strategy([])
 
+    def visit_type_var_tuple(self, t: TypeVarTupleType) -> T:
+        return self.strategy([])
+
     def visit_unpack_type(self, t: UnpackType) -> T:
         return self.query_types([t.type])