Make overloaded constructors consistent in error messages (#20483)

This allows to re-enable 7 tests that were skipped in parallel mode.

Note that I changed my opinion on what the representation of overloaded
constructors should actually be. Now I think that the representation
that previously was only used in warm runs is better. Two reasons for
this:
* Having a non-`None` return type for `__init__` would be weird (and
manually tweaking it would introduce some fragile special-casing)
* I found a (very) old test case `testSerializeOverloaded__init__` from
which it looks like using the class name is very much intentional.

Also note that currently logic for determining function name, and for
determining first argument (i.e. `self`/`cls`) are currently entangled.
I refactor this to make these two pieces independent.

Author: ilevkivskyi

mypy/messages.py

@@ -3017,30 +3017,37 @@ def [T <: int] f(self, x: int, y: T) -> None
             s += ", /"
             slash = True
 
-    # If we got a "special arg" (i.e: self, cls, etc...), prepend it to the arg list
     definition = get_func_def(tp)
+
+    # Extract function name, prefer the "human-readable" name if available.
+    func_name = None
+    if tp.name:
+        func_name = tp.name.split()[0]  # skip "of Class" part
+    elif isinstance(definition, FuncDef):
+        func_name = definition.name
+
+    # If we got a "special arg" (i.e: self, cls, etc...), prepend it to the arg list
+    first_arg = None
     if (
         isinstance(definition, FuncDef)
         and hasattr(definition, "arguments")
         and not tp.from_concatenate
     ):
         definition_arg_names = [arg.variable.name for arg in definition.arguments]
-        if (
-            len(definition_arg_names) > len(tp.arg_names)
-            and definition_arg_names[0]
-            and not skip_self
-        ):
-            if s:
-                s = ", " + s
-            s = definition_arg_names[0] + s
-        s = f"{definition.name}({s})"
-    elif tp.name:
+        if len(definition_arg_names) > len(tp.arg_names) and definition_arg_names[0]:
+            first_arg = definition_arg_names[0]
+    else:
+        # TODO: avoid different logic for incremental runs.
         first_arg = get_first_arg(tp)
-        if first_arg:
-            if s:
-                s = ", " + s
-            s = first_arg + s
-        s = f"{tp.name.split()[0]}({s})"  # skip "of Class" part
+
+    if tp.is_type_obj():
+        skip_self = True
+    if first_arg and not skip_self:
+        if s:
+            s = ", " + s
+        s = first_arg + s
+    if func_name:
+        s = f"{func_name}({s})"
     else:
         s = f"({s})"
 

test-data/unit/check-classes.test

@@ -3492,8 +3492,8 @@ c.a # E: "C" has no attribute "a"
 C('', '')
 C('') # E: No overload variant of "C" matches argument type "str" \
       # N: Possible overload variants: \
-      # N:     def __new__(cls, foo: int) -> C \
-      # N:     def __new__(cls, x: str, y: str) -> C
+      # N:     def C(foo: int) -> C \
+      # N:     def C(x: str, y: str) -> C
 [builtins fixtures/__new__.pyi]
 
 
@@ -3922,8 +3922,8 @@ u = new(User)
 [out]
 tmp/foo.pyi:17: error: No overload variant of "User" matches argument type "str"
 tmp/foo.pyi:17: note: Possible overload variants:
-tmp/foo.pyi:17: note:     def __init__(self) -> U
-tmp/foo.pyi:17: note:     def __init__(self, arg: int) -> U
+tmp/foo.pyi:17: note:     def User() -> U
+tmp/foo.pyi:17: note:     def User(arg: int) -> U
 tmp/foo.pyi:18: error: Too many arguments for "foo" of "User"
 
 [case testTypeUsingTypeCInUpperBound]
@@ -8529,7 +8529,7 @@ def identity_wrapper(func: FuncT) -> FuncT:
 def foo(self: Any) -> str:
     return ""
 
-[case testParentClassWithTypeAliasAndSubclassWithMethod_no_parallel]
+[case testParentClassWithTypeAliasAndSubclassWithMethod]
 from typing import Any, Callable, TypeVar
 
 class Parent:
@@ -8548,7 +8548,7 @@ class Child(Parent):
         return val
     def bar(self, val: str) -> str:  # E: Signature of "bar" incompatible with supertype "Parent" \
                                      # N:      Superclass: \
-                                     # N:          def __init__(self) -> bar \
+                                     # N:          def bar() -> bar \
                                      # N:      Subclass: \
                                      # N:          def bar(self, val: str) -> str
         return val

test-data/unit/check-flags.test

@@ -2472,19 +2472,19 @@ cb(lambda x: a)  # OK
 fn = lambda x: a
 cb(fn)
 
-[case testShowErrorCodeLinks_no_parallel]
+[case testShowErrorCodeLinks]
 # flags: --show-error-codes --show-error-code-links
 
 x: int = ""  # E: Incompatible types in assignment (expression has type "str", variable has type "int")  [assignment]
 list(1)  # E: No overload variant of "list" matches argument type "int"  [call-overload] \
          # N: Possible overload variants: \
-         # N:     def [T] __init__(self) -> list[T] \
-         # N:     def [T] __init__(self, x: Iterable[T]) -> list[T] \
+         # N:     def [T] list() -> list[T] \
+         # N:     def [T] list(x: Iterable[T]) -> list[T] \
          # N: See https://mypy.rtfd.io/en/stable/_refs.html#code-call-overload for more info
 list(2)  # E: No overload variant of "list" matches argument type "int"  [call-overload] \
          # N: Possible overload variants: \
-         # N:     def [T] __init__(self) -> list[T] \
-         # N:     def [T] __init__(self, x: Iterable[T]) -> list[T]
+         # N:     def [T] list() -> list[T] \
+         # N:     def [T] list(x: Iterable[T]) -> list[T]
 [builtins fixtures/list.pyi]
 
 [case testNestedGenericInAliasDisallow]

test-data/unit/check-inference.test

@@ -1748,13 +1748,13 @@ def f(blocks: Any): # E: Name "Any" is not defined \
     to_process = list(blocks)
 [builtins fixtures/list.pyi]
 
-[case testSpecialCaseEmptyListInitialization2_no_parallel]
+[case testSpecialCaseEmptyListInitialization2]
 def f(blocks: object):
     to_process = []
     to_process = list(blocks) # E: No overload variant of "list" matches argument type "object" \
                               # N: Possible overload variants: \
-                              # N:     def [T] __init__(self) -> list[T] \
-                              # N:     def [T] __init__(self, x: Iterable[T]) -> list[T]
+                              # N:     def [T] list() -> list[T] \
+                              # N:     def [T] list(x: Iterable[T]) -> list[T]
 [builtins fixtures/list.pyi]
 
 [case testInferListInitializedToEmptyAndAssigned]

test-data/unit/check-overloading.test

@@ -625,8 +625,8 @@ a = A(a)
 a = A(b)
 a = A(object()) # E: No overload variant of "A" matches argument type "object" \
                 # N: Possible overload variants: \
-                # N:     def __init__(self, a: A) -> A \
-                # N:     def __init__(self, b: B) -> A
+                # N:     def A(a: A) -> A \
+                # N:     def A(b: B) -> A
 
 class A:
   @overload

test-data/unit/check-protocols.test

@@ -3609,7 +3609,7 @@ test(C)  # E: Argument 1 to "test" has incompatible type "type[C]"; expected "P"
          # N:     Expected: \
          # N:         def __call__(x: int, y: int) -> Any \
          # N:     Got: \
-         # N:         def __init__(x: int, y: str) -> C \
+         # N:         def C(x: int, y: str) -> C \
          # N: "P.__call__" has type "def __call__(self, x: int, y: int) -> Any"
 
 [case testProtocolClassObjectPureCallback]
@@ -3631,7 +3631,7 @@ test(C)  # E: Argument 1 to "test" has incompatible type "type[C]"; expected "P"
          # N:     Expected: \
          # N:         def __call__(x: int, y: int) -> Any \
          # N:     Got: \
-         # N:         def __init__(x: int, y: str) -> C \
+         # N:         def C(x: int, y: str) -> C \
          # N: "P.__call__" has type "def __call__(self, x: int, y: int) -> Any"
 [builtins fixtures/type.pyi]
 
@@ -3654,7 +3654,7 @@ p: P = C  # E: Incompatible types in assignment (expression has type "type[C]",
           # N:     Expected: \
           # N:         def __call__(app: int) -> Callable[[str], None] \
           # N:     Got: \
-          # N:         def __init__(app: str) -> C \
+          # N:         def C(app: str) -> C \
           # N: "P.__call__" has type "def __call__(self, app: int) -> Callable[[str], None]"
 
 [builtins fixtures/type.pyi]
@@ -3890,7 +3890,7 @@ other_flag = False
 def update() -> str: ...
 [builtins fixtures/module.pyi]
 
-[case testModuleAsProtocolImplementationClassObject_no_parallel]
+[case testModuleAsProtocolImplementationClassObject]
 import runner
 import bad_runner
 from typing import Callable, Protocol
@@ -3909,7 +3909,7 @@ run(bad_runner)  # E: Argument 1 to "run" has incompatible type Module; expected
                  # N:     Expected: \
                  # N:         def (int, /) -> Result \
                  # N:     Got: \
-                 # N:         def __init__(arg: str) -> Run
+                 # N:         def Run(arg: str) -> Run
 
 [file runner.py]
 class Run:
@@ -3922,7 +3922,7 @@ class Run:
     def __init__(self, arg: str) -> None: ...
 [builtins fixtures/module.pyi]
 
-[case testModuleAsProtocolImplementationTypeAlias_no_parallel]
+[case testModuleAsProtocolImplementationTypeAlias]
 import runner
 import bad_runner
 from typing import Callable, Protocol
@@ -3941,7 +3941,7 @@ run(bad_runner)  # E: Argument 1 to "run" has incompatible type Module; expected
                  # N:     Expected: \
                  # N:         def (int, /) -> Result \
                  # N:     Got: \
-                 # N:         def __init__(arg: str) -> Run
+                 # N:         def Run(arg: str) -> Run
 
 [file runner.py]
 class Run:

test-data/unit/check-python311.test

@@ -137,9 +137,9 @@ myclass2 = MyClass(float, float)
 reveal_type(myclass2)  # N: Revealed type is "__main__.MyClass[builtins.float, builtins.float]"
 myclass3 = MyClass(float, float, float)  # E: No overload variant of "MyClass" matches argument types "type[float]", "type[float]", "type[float]" \
                                          # N: Possible overload variants: \
-                                         # N:     def [T1, T2] __init__(self) -> MyClass[None, None] \
-                                         # N:     def [T1, T2] __init__(self, type[T1], /) -> MyClass[T1, None] \
-                                         # N:     def [T1, T2] __init__(type[T1], type[T2], /) -> MyClass[T1, T2]
+                                         # N:     def [T1, T2] MyClass() -> MyClass[None, None] \
+                                         # N:     def [T1, T2] MyClass(type[T1], /) -> MyClass[T1, None] \
+                                         # N:     def [T1, T2] MyClass(type[T1], type[T2], /) -> MyClass[T1, T2]
 reveal_type(myclass3)  # N: Revealed type is "Any"
 [builtins fixtures/tuple.pyi]
 

test-data/unit/check-selftype.test

@@ -749,7 +749,7 @@ def bad(x: str) -> str: ...
 reveal_type(ci.from_item(conv))  # N: Revealed type is "builtins.str"
 ci.from_item(bad)  # E: Argument 1 to "from_item" of "C" has incompatible type "Callable[[str], str]"; expected "Callable[[int], str]"
 
-[case testSelfTypeRestrictedMethodOverloadInit_no_parallel]
+[case testSelfTypeRestrictedMethodOverloadInit]
 from typing import TypeVar
 from lib import P, C
 
@@ -767,8 +767,8 @@ class SubP(P[T]):
 
 SubP('no')  # E: No overload variant of "SubP" matches argument type "str" \
             # N: Possible overload variants: \
-            # N:     def [T] __init__(self, use_str: Literal[True]) -> SubP[T] \
-            # N:     def [T] __init__(self, use_str: Literal[False]) -> SubP[T]
+            # N:     def [T] SubP(use_str: Literal[True]) -> SubP[T] \
+            # N:     def [T] SubP(use_str: Literal[False]) -> SubP[T]
 
 # This is a bit unfortunate: we don't have a way to map the overloaded __init__ to subtype.
 x = SubP(use_str=True)  # E: Need type annotation for "x"

test-data/unit/check-serialize.test

@@ -312,8 +312,8 @@ class A:
 [out2]
 tmp/a.py:2: error: No overload variant of "A" matches argument type "object"
 tmp/a.py:2: note: Possible overload variants:
-tmp/a.py:2: note:     def A(self, x: int) -> A
-tmp/a.py:2: note:     def A(self, x: str) -> A
+tmp/a.py:2: note:     def A(x: int) -> A
+tmp/a.py:2: note:     def A(x: str) -> A
 tmp/a.py:7: error: No overload variant of "__init__" of "A" matches argument type "object"
 tmp/a.py:7: note: Possible overload variants:
 tmp/a.py:7: note:     def __init__(self, x: int) -> None

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

@@ -1339,16 +1339,16 @@ a: A
 reveal_type(a)  # N: Revealed type is "builtins.list[builtins.str]"
 [builtins fixtures/tuple.pyi]
 
-[case testTypeAliasDict_no_parallel]
+[case testTypeAliasDict]
 D = dict[str, int]
 d = D()
 reveal_type(d)  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
 reveal_type(D())  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
 reveal_type(D(x=1))  # N: Revealed type is "builtins.dict[builtins.str, builtins.int]"
 reveal_type(D(x="asdf"))  # E: No overload variant of "dict" matches argument type "str" \
                           # N: Possible overload variants: \
-                          # N:     def __init__(self, **kwargs: int) -> dict[str, int] \
-                          # N:     def __init__(self, arg: Iterable[tuple[str, int]], **kwargs: int) -> dict[str, int] \
+                          # N:     def dict(**kwargs: int) -> dict[str, int] \
+                          # N:     def dict(arg: Iterable[tuple[str, int]], **kwargs: int) -> dict[str, int] \
                           # N: Revealed type is "Any"
 [builtins fixtures/dict.pyi]