Change tuple[] repr to tuple[()] (#15783)

Closes #15782

mypy/messages.py

@@ -2507,10 +2507,11 @@ def format_literal_value(typ: LiteralType) -> str:
         # Prefer the name of the fallback class (if not tuple), as it's more informative.
         if typ.partial_fallback.type.fullname != "builtins.tuple":
             return format(typ.partial_fallback)
+        type_items = format_list(typ.items) or "()"
         if options.use_lowercase_names():
-            s = f"tuple[{format_list(typ.items)}]"
+            s = f"tuple[{type_items}]"
         else:
-            s = f"Tuple[{format_list(typ.items)}]"
+            s = f"Tuple[{type_items}]"
         return s
     elif isinstance(typ, TypedDictType):
         # If the TypedDictType is named, return the name

mypy/test/testtypes.py

@@ -129,10 +129,10 @@ def test_callable_type_with_var_args(self) -> None:
         )
         assert_equal(str(c3), "def (X? =, *Y?) -> Any")
 
-    def test_tuple_type(self) -> None:
+    def test_tuple_type_upper(self) -> None:
         options = Options()
         options.force_uppercase_builtins = True
-        assert_equal(TupleType([], self.fx.std_tuple).str_with_options(options), "Tuple[]")
+        assert_equal(TupleType([], self.fx.std_tuple).str_with_options(options), "Tuple[()]")
         assert_equal(TupleType([self.x], self.fx.std_tuple).str_with_options(options), "Tuple[X?]")
         assert_equal(
             TupleType(

mypy/types.py

@@ -3197,7 +3197,7 @@ def visit_overloaded(self, t: Overloaded) -> str:
         return f"Overload({', '.join(a)})"
 
     def visit_tuple_type(self, t: TupleType) -> str:
-        s = self.list_str(t.items)
+        s = self.list_str(t.items) or "()"
         tuple_name = "tuple" if self.options.use_lowercase_names() else "Tuple"
         if t.partial_fallback and t.partial_fallback.type:
             fallback_name = t.partial_fallback.type.fullname

test-data/unit/check-async-await.test

@@ -475,7 +475,7 @@ async def gen() -> AsyncGenerator[int, str]:
 
 async def h() -> None:
     g = gen()
-    await g.asend(())  # E: Argument 1 to "asend" of "AsyncGenerator" has incompatible type "Tuple[]"; expected "str"
+    await g.asend(())  # E: Argument 1 to "asend" of "AsyncGenerator" has incompatible type "Tuple[()]"; expected "str"
     reveal_type(await g.asend('hello'))  # N: Revealed type is "builtins.int"
 
 [builtins fixtures/dict.pyi]

test-data/unit/check-dataclasses.test

@@ -1896,7 +1896,7 @@ reveal_type(t.__match_args__)  # N: Revealed type is "Tuple[Literal['bar']]"
 class Empty:
     ...
 e: Empty
-reveal_type(e.__match_args__)  # N: Revealed type is "Tuple[]"
+reveal_type(e.__match_args__)  # N: Revealed type is "Tuple[()]"
 [builtins fixtures/dataclasses.pyi]
 
 [case testDataclassWithoutMatchArgs]

test-data/unit/check-namedtuple.test

@@ -931,6 +931,16 @@ reveal_type(A().b)  # N: Revealed type is "typing.NamedTuple"
 [builtins fixtures/tuple.pyi]
 [typing fixtures/typing-namedtuple.pyi]
 
+
+[case testEmptyNamedTupleTypeRepr]
+from typing import NamedTuple
+
+N = NamedTuple('N', [])
+n: N
+reveal_type(N)  # N: Revealed type is "def () -> Tuple[(), fallback=__main__.N]"
+reveal_type(n)  # N: Revealed type is "Tuple[(), fallback=__main__.N]"
+[builtins fixtures/tuple.pyi]
+
 [case testNamedTupleWrongfile]
 from typing import NamedTuple
 from b import Type1
@@ -1036,7 +1046,7 @@ def good6() -> NamedTuple:
 def bad1() -> NamedTuple:
     return 1  # E: Incompatible return value type (got "int", expected "NamedTuple")
 def bad2() -> NamedTuple:
-    return ()  # E: Incompatible return value type (got "Tuple[]", expected "NamedTuple")
+    return ()  # E: Incompatible return value type (got "Tuple[()]", expected "NamedTuple")
 def bad3() -> NamedTuple:
     return (1, 2)  # E: Incompatible return value type (got "Tuple[int, int]", expected "NamedTuple")
 

test-data/unit/check-overloading.test

@@ -1145,7 +1145,7 @@ def f(x: str) -> None: pass
 f(1.1)
 f('')
 f(1)
-f(()) # E: No overload variant of "f" matches argument type "Tuple[]" \
+f(()) # E: No overload variant of "f" matches argument type "Tuple[()]" \
       # N: Possible overload variants: \
       # N:     def f(x: float) -> None \
       # N:     def f(x: str) -> None

test-data/unit/check-python310.test

@@ -1568,8 +1568,8 @@ class AnnAssign(stmt):
    value: str
    simple: int
 
-reveal_type(AST.__match_args__)  # N: Revealed type is "Tuple[]"
-reveal_type(stmt.__match_args__)  # N: Revealed type is "Tuple[]"
+reveal_type(AST.__match_args__)  # N: Revealed type is "Tuple[()]"
+reveal_type(stmt.__match_args__)  # N: Revealed type is "Tuple[()]"
 reveal_type(AnnAssign.__match_args__)  # N: Revealed type is "Tuple[Literal['target']?, Literal['annotation']?, Literal['value']?, Literal['simple']?]"
 
 AnnAssign.__match_args__ = ('a', 'b', 'c', 'd')  # E: Cannot assign to "__match_args__"

test-data/unit/check-tuples.test

@@ -143,7 +143,7 @@ t3 = None # type: Tuple[A, B]
 a, b, c = None, None, None # type: (A, B, C)
 
 if int():
-    t2 = ()        # E: Incompatible types in assignment (expression has type "Tuple[]", variable has type "Tuple[A]")
+    t2 = ()        # E: Incompatible types in assignment (expression has type "Tuple[()]", variable has type "Tuple[A]")
 if int():
     t2 = (a, a)    # E: Incompatible types in assignment (expression has type "Tuple[A, A]", variable has type "Tuple[A]")
 if int():
@@ -1244,9 +1244,9 @@ f(0)  # E: Argument 1 to "f" has incompatible type "int"; expected "Tuple[Any, .
 from typing import Tuple
 def f(a: Tuple[()]) -> None: pass
 f(())
-f((1,))  # E: Argument 1 to "f" has incompatible type "Tuple[int]"; expected "Tuple[]"
-f(('', ''))  # E: Argument 1 to "f" has incompatible type "Tuple[str, str]"; expected "Tuple[]"
-f(0)  # E: Argument 1 to "f" has incompatible type "int"; expected "Tuple[]"
+f((1,))  # E: Argument 1 to "f" has incompatible type "Tuple[int]"; expected "Tuple[()]"
+f(('', ''))  # E: Argument 1 to "f" has incompatible type "Tuple[str, str]"; expected "Tuple[()]"
+f(0)  # E: Argument 1 to "f" has incompatible type "int"; expected "Tuple[()]"
 [builtins fixtures/tuple.pyi]
 
 [case testNonliteralTupleIndex]
@@ -1467,20 +1467,29 @@ from typing import Tuple
 t = ('',) * 2
 reveal_type(t)  # N: Revealed type is "Tuple[builtins.str, builtins.str]"
 t2 = ('',) * -1
-reveal_type(t2)  # N: Revealed type is "Tuple[]"
+reveal_type(t2)  # N: Revealed type is "Tuple[()]"
 t3 = ('', 1) * 2
 reveal_type(t3)  # N: Revealed type is "Tuple[builtins.str, builtins.int, builtins.str, builtins.int]"
 def f() -> Tuple[str, ...]:
     return ('', )
 reveal_type(f() * 2)  # N: Revealed type is "builtins.tuple[builtins.str, ...]"
 [builtins fixtures/tuple.pyi]
 
+[case testEmptyTupleTypeRepr]
+from typing import Tuple
+
+def f() -> Tuple[()]: ...
+
+reveal_type(f)    # N: Revealed type is "def () -> Tuple[()]"
+reveal_type(f())  # N: Revealed type is "Tuple[()]"
+[builtins fixtures/tuple.pyi]
+
 [case testMultiplyTupleByIntegerLiteralReverse]
 from typing import Tuple
 t = 2 * ('',)
 reveal_type(t)  # N: Revealed type is "Tuple[builtins.str, builtins.str]"
 t2 = -1 * ('',)
-reveal_type(t2)  # N: Revealed type is "Tuple[]"
+reveal_type(t2)  # N: Revealed type is "Tuple[()]"
 t3 = 2 * ('', 1)
 reveal_type(t3)  # N: Revealed type is "Tuple[builtins.str, builtins.int, builtins.str, builtins.int]"
 def f() -> Tuple[str, ...]:

test-data/unit/check-type-aliases.test

@@ -12,7 +12,7 @@ U = Union[int, str]
 def f(x: U) -> None: pass
 f(1)
 f('')
-f(()) # E: Argument 1 to "f" has incompatible type "Tuple[]"; expected "Union[int, str]"
+f(()) # E: Argument 1 to "f" has incompatible type "Tuple[()]"; expected "Union[int, str]"
 [targets __main__, __main__.f]
 [builtins fixtures/tuple.pyi]
 
@@ -64,7 +64,7 @@ from _m import U
 def f(x: U) -> None: pass
 f(1)
 f('x')
-f(()) # E: Argument 1 to "f" has incompatible type "Tuple[]"; expected "Union[int, str]"
+f(()) # E: Argument 1 to "f" has incompatible type "Tuple[()]"; expected "Union[int, str]"
 [file _m.py]
 from typing import Union
 U = Union[int, str]
@@ -170,11 +170,11 @@ f(1) # E: Argument 1 to "f" has incompatible type "int"; expected "str"
 from typing import Tuple, Callable
 EmptyTuple = Tuple[()]
 x: EmptyTuple
-reveal_type(x)  # N: Revealed type is "Tuple[]"
+reveal_type(x)  # N: Revealed type is "Tuple[()]"
 
 EmptyTupleCallable = Callable[[Tuple[()]], None]
 f: EmptyTupleCallable
-reveal_type(f)  # N: Revealed type is "def (Tuple[])"
+reveal_type(f)  # N: Revealed type is "def (Tuple[()])"
 [builtins fixtures/list.pyi]
 
 [case testForwardTypeAlias]

test-data/unit/check-typevar-tuple.test

@@ -58,7 +58,7 @@ f_args3: Tuple[int, str, bool]
 reveal_type(f(f_args))  # N: Revealed type is "Tuple[builtins.str, builtins.str]"
 reveal_type(f(f_args2))  # N: Revealed type is "Tuple[builtins.str]"
 reveal_type(f(f_args3))  # N: Revealed type is "Tuple[builtins.str, builtins.str, builtins.bool]"
-f(empty)  # E: Argument 1 to "f" has incompatible type "Tuple[]"; expected "Tuple[int]"
+f(empty)  # E: Argument 1 to "f" has incompatible type "Tuple[()]"; expected "Tuple[int]"
 f(bad_args)  # E: Argument 1 to "f" has incompatible type "Tuple[str, str]"; expected "Tuple[int, str]"
 # TODO: This hits a crash where we assert len(templates.items) == 1. See visit_tuple_type
 # in mypy/constraints.py.

test-data/unit/fine-grained.test

@@ -8026,7 +8026,7 @@ A = NamedTuple('A', F)  # type: ignore
 [builtins fixtures/list.pyi]
 [out]
 ==
-b.py:3: note: Revealed type is "Tuple[, fallback=a.A]"
+b.py:3: note: Revealed type is "Tuple[(), fallback=a.A]"
 
 [case testImportOnTopOfAlias1]
 from a import A

test-data/unit/typexport-basic.test

@@ -294,8 +294,8 @@ import typing
 x = ()
 [builtins fixtures/primitives.pyi]
 [out]
-NameExpr(2) : Tuple[]
-TupleExpr(2) : Tuple[]
+NameExpr(2) : Tuple[()]
+TupleExpr(2) : Tuple[()]
 
 [case testInferTwoTypes]
 ## NameExpr
@@ -313,8 +313,8 @@ def f() -> None:
     x = ()
 [builtins fixtures/primitives.pyi]
 [out]
-NameExpr(3) : Tuple[]
-TupleExpr(3) : Tuple[]
+NameExpr(3) : Tuple[()]
+TupleExpr(3) : Tuple[()]
 
 
 -- Basic generics