Apply arity filter more aggressively

Summary:
If only one overload has a parameter count that is compatible with a call's argument count, we should take that as the matching overload even if the call produces errors.

This gives us more precise return types and better error messages.

In some cases, this increases the number of errors because a single "No matching overload" error is replaced with multiple errors about specific parameters. IMO this is a good change.

Fixes #2833.

Reviewed By: stroxler

Differential Revision: D97394258

fbshipit-source-id: 737258f4a3f2f56d287efd3240bec5c7052a8db3

Author: rchen152

conformance/third_party/conformance.exp

@@ -9073,24 +9073,24 @@
     },
     {
       "code": -2,
-      "column": 11,
-      "concise_description": "No matching overload found for function `example1_1` called with arguments: (Literal[1], Literal[1])",
-      "description": "No matching overload found for function `example1_1` called with arguments: (Literal[1], Literal[1])\n  Possible overloads:\n  (x: int, y: str) -> int [closest match]\n  (x: str) -> str",
+      "column": 15,
+      "concise_description": "Argument `Literal[1]` is not assignable to parameter `y` with type `str` in function `example1_1`",
+      "description": "Argument `Literal[1]` is not assignable to parameter `y` with type `str` in function `example1_1`",
       "line": 46,
-      "name": "no-matching-overload",
+      "name": "bad-argument-type",
       "severity": "error",
-      "stop_column": 17,
+      "stop_column": 16,
       "stop_line": 46
     },
     {
       "code": -2,
-      "column": 11,
-      "concise_description": "No matching overload found for function `example1_1` called with arguments: (Literal[1])",
-      "description": "No matching overload found for function `example1_1` called with arguments: (Literal[1])\n  Possible overloads:\n  (x: int, y: str) -> int\n  (x: str) -> str [closest match]",
+      "column": 12,
+      "concise_description": "Argument `Literal[1]` is not assignable to parameter `x` with type `str` in function `example1_1`",
+      "description": "Argument `Literal[1]` is not assignable to parameter `x` with type `str` in function `example1_1`",
       "line": 51,
-      "name": "no-matching-overload",
+      "name": "bad-argument-type",
       "severity": "error",
-      "stop_column": 14,
+      "stop_column": 13,
       "stop_line": 51
     },
     {
@@ -11738,13 +11738,13 @@
     },
     {
       "code": -2,
-      "column": 11,
-      "concise_description": "No matching overload found for function `ExtraMovie.__init__` called with arguments: (name=Literal['No Country for Old Men'], language=Literal['English'])",
-      "description": "No matching overload found for function `ExtraMovie.__init__` called with arguments: (name=Literal['No Country for Old Men'], language=Literal['English'])\n  Possible overloads:\n  (*, name: str, **int) -> None [closest match]\n  (__map: ExtraMovie, /, *, name: str = ..., **int) -> None",
+      "column": 52,
+      "concise_description": "Keyword argument `language` with type `Literal['English']` is not assignable to kwargs type `int` in function `ExtraMovie.__init__`",
+      "description": "Keyword argument `language` with type `Literal['English']` is not assignable to kwargs type `int` in function `ExtraMovie.__init__`",
       "line": 285,
-      "name": "no-matching-overload",
+      "name": "bad-argument-type",
       "severity": "error",
-      "stop_column": 62,
+      "stop_column": 61,
       "stop_line": 285
     },
     {

pyrefly/lib/alt/overload.rs

@@ -319,7 +319,11 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
                         break;
                     }
                 }
-                (closest_overload, matched)
+                (
+                    closest_overload,
+                    // If there was only one overload with the right arity, it definitely matched.
+                    matched || arity_compatible_overloads.len() == 1,
+                )
             }
         };
 
@@ -364,6 +368,7 @@ impl<'a, Ans: LookupAnswer> AnswersSolver<'a, Ans> {
                     msg,
                 );
             }
+            errors.extend(closest_overload.call_errors);
             (closest_overload.res, closest_overload.func.1.signature)
         } else {
             // Build a string showing the argument types for error messages

pyrefly/lib/test/dataclasses.rs

@@ -660,7 +660,7 @@ testcase!(
     test_bad_keyword,
     r#"
 from dataclasses import dataclass
-@dataclass(flibbertigibbet=True)  # E: No matching overload found
+@dataclass(flibbertigibbet=True)  # E: Unexpected keyword argument `flibbertigibbet`
 class C:
     pass
     "#,

pyrefly/lib/test/dict.rs

@@ -68,16 +68,15 @@ def bar(yes: bool) -> None:
 );
 
 testcase!(
-    bug = "https://github.com/facebook/pyrefly/issues/2833",
     test_get_dict_value_even_with_error,
     r#"
 from typing import assert_type
 d: dict[str, int] = {}
 def f(k: str | None):
     # We should report the mismatch between `str` and `str | None` rather than "No matching overload".
-    v = d.get(k)  # E: No matching overload
+    v = d.get(k)  # E: Argument `str | None` is not assignable to parameter `key` with type `str`
     # Because only one overload of `dict.get` can match based on argument count, we should use its
     # return type of `int | None`.
-    assert_type(v, int | None)  # E: assert_type(Unknown, int | None)
+    assert_type(v, int | None)
     "#,
 );

pyrefly/lib/test/generic_basic.rs

@@ -358,7 +358,7 @@ def f():
 
 def g():
     x: dict[int, int] = {}
-    x.update(a=1) # E: No matching overload
+    x.update(a=1) # E: `dict[int, int]` is not assignable to parameter `self` with type `SupportsGetItem[str, int]`
 "#,
 );
 

pyrefly/lib/test/lsp/hover_type.rs

@@ -443,10 +443,7 @@ Hover Result: `(a: int, b: bool) -> str`
 
 15 | overloaded_func(False)
        ^
-Hover Result: `Overload[
-  (a: str) -> bool
-  (a: int, b: bool) -> str
-]`
+Hover Result: `(a: str) -> bool`
 "#
         .trim(),
         report.trim(),
@@ -488,10 +485,7 @@ Hover Result: `(self: Foo, a: int, b: bool) -> str`
 
 17 | foo.overloaded_meth(False)
              ^
-Hover Result: `Overload[
-  (self: Foo, a: str) -> bool
-  (self: Foo, a: int, b: bool) -> str
-]`
+Hover Result: `(self: Foo, a: str) -> bool`
 "#
         .trim(),
         report.trim(),

pyrefly/lib/test/overload.rs

@@ -1677,7 +1677,6 @@ def g(x):
 );
 
 testcase!(
-    bug = "https://github.com/facebook/pyrefly/issues/2833",
     test_eliminate_overload_using_argument_count_even_with_error,
     r#"
 from typing import assert_type, overload
@@ -1691,9 +1690,9 @@ def f(x, y="") -> int | str: ...
 def g(x: int | None):
     # We should report the mismatch between `int` and `int | None` rather than "No matching overload",
     # since we know only the first overload can match based on argument count.
-    e = f(x)  # E: No matching overload
+    e = f(x)  # E: `int | None` is not assignable to parameter `x` with type `int`
     # Even though the call failed, we know that the second overload cannot match based on argument
     # count, so we should use the return type from the first overload.
-    assert_type(e, int)  # E: assert_type(Unknown, int)
+    assert_type(e, int)
     "#,
 );

pyrefly/lib/test/pydantic/extra.rs

@@ -143,7 +143,7 @@ pydantic_testcase!(
 from pydantic import BaseModel, ConfigDict
 
 class ModelForbid(BaseModel):
-    model_config = ConfigDict(extra=False) # E: No matching overload found for function `pydantic.config.ConfigDict.__init__`
+    model_config = ConfigDict(extra=False) # E: `Literal[False]` is not assignable to parameter `extra`
     x: int
 
 ModelForbid(x=1, y=2)
@@ -156,7 +156,7 @@ pydantic_testcase!(
 from pydantic import BaseModel, ConfigDict
 
 class ModelForbid(BaseModel):
-    model_config = ConfigDict(extra="123") # E: No matching overload found for function `pydantic.config.ConfigDict.__init__`
+    model_config = ConfigDict(extra="123") # E: `Literal['123']` is not assignable to parameter `extra`
     x: int
 
 ModelForbid(x=1, y=2)

pyrefly/lib/test/typed_dict.rs

@@ -386,7 +386,7 @@ v5 = td_o.pop("x", "fallback")
 assert_type(v5, int | str)
 
 v6 = td_m.pop("a") # E:
-assert_type(v6, Any)
+assert_type(v6, int)
 
 v7 = td_m.pop("x")
 assert_type(v7, int)
@@ -748,7 +748,7 @@ class A(TypedDict):
 class B(A):
     y: str
 B(x=0, y='1')  # OK
-B(x=0, y=1)  # E: No matching overload found for function `B.__init__`
+B(x=0, y=1)  # E: `Literal[1]` is not assignable to parameter `y` with type `str`
     "#,
 );
 
@@ -896,7 +896,7 @@ def f(c1: C, c2: C, c3: dict[str, int], d: D, e: E, f: F):
     c1.update([("x", 1), ("y", 2)])
     c1.update([("z", 3)]) # E: No matching overload found for function `C.update`
     c1.update(x=1, y=2)
-    c1.update(z=1) # E: No matching overload found for function `C.update`
+    c1.update(z=1) # E: Unexpected keyword argument `z`
     "#,
 );
 
@@ -945,9 +945,9 @@ class C(TypedDict):
     x: int
 def f(c: C, s: str):
     assert_type(c.setdefault("x", 0), int)
-    c.setdefault("x", 0.0)  # E: No matching overload
+    c.setdefault("x", 0.0)  # E: `float` is not assignable to parameter `default` with type `int`
     c.setdefault("x")  # E: No matching overload
-    c.setdefault(s, 0)  # E: No matching overload
+    c.setdefault(s, 0)  # E: `str` is not assignable to parameter `key` with type `Literal['x']`
     "#,
 );
 
@@ -963,7 +963,7 @@ class D(TypedDict):
 def f(c: C, d: D):
     c.setdefault("x", 0)  # E: `Literal['x']` is not assignable to parameter `k` with type `Never`
     d.setdefault("x", 0)
-    d.setdefault("y", "oops")  # E: No matching overload
+    d.setdefault("y", "oops")  # E: `Literal['y']` is not assignable to parameter `key` with type `Literal['x']`  # E: `Literal['oops']` is not assignable to parameter `default` with type `int`
     "#,
 );
 
@@ -986,7 +986,7 @@ testcase!(
 from typing import TypedDict
 class C(TypedDict):
     x: int
-C(0)  # E: No matching overload found for function `C.__init__`
+C(0)  # E: `Literal[0]` is not assignable to parameter `__map` with type `C`
     "#,
 );
 
@@ -1258,7 +1258,7 @@ from typing import TypedDict
 class Movie(TypedDict, extra_items=int):
     name: str
 good_movie = Movie(name='Toy Story', year=1995)
-bad_movie = Movie(name='Toy Story', studio='Pixar')  # E: No matching overload found for function `Movie.__init__`
+bad_movie = Movie(name='Toy Story', studio='Pixar')  # E: `Literal['Pixar']` is not assignable to kwargs type `int`
     "#,
 );