[red-knot] Handle unions of callables better

crates/red_knot_python_semantic/resources/mdtest/binary/instances.md

@@ -363,7 +363,7 @@ reveal_type(X() + Y())  # revealed: int
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 a = NotBoolable()
 

crates/red_knot_python_semantic/resources/mdtest/call/callable_instance.md

@@ -71,7 +71,7 @@ def _(flag: bool):
 
     a = NonCallable()
     # error: [call-non-callable] "Object of type `Literal[1]` is not callable"
-    reveal_type(a())  # revealed: int | Unknown
+    reveal_type(a())  # revealed: Unknown | int
 ```
 
 ## Call binding errors

crates/red_knot_python_semantic/resources/mdtest/call/union.md

@@ -40,7 +40,7 @@ def _(flag: bool):
         def f() -> int:
             return 1
     x = f()  # error: [call-non-callable] "Object of type `Literal[1]` is not callable"
-    reveal_type(x)  # revealed: int | Unknown
+    reveal_type(x)  # revealed: Unknown | int
 ```
 
 ## Multiple non-callable elements in a union
@@ -58,7 +58,7 @@ def _(flag: bool, flag2: bool):
             return 1
     # TODO we should mention all non-callable elements of the union
     # error: [call-non-callable] "Object of type `Literal[1]` is not callable"
-    # revealed: int | Unknown
+    # revealed: Unknown | int
     reveal_type(f())
 ```
 
@@ -148,3 +148,16 @@ def _(flag: bool):
     x = f(3)
     reveal_type(x)  # revealed: Unknown
 ```
+
+## Union including a special-cased function
+
+```py
+def _(flag: bool):
+    if flag:
+        f = str
+    else:
+        f = repr
+    reveal_type(str("string"))  # revealed: Literal["string"]
+    reveal_type(repr("string"))  # revealed: Literal["'string'"]
+    reveal_type(f("string"))  # revealed: Literal["string", "'string'"]
+```

crates/red_knot_python_semantic/resources/mdtest/comparison/instances/membership_test.md

@@ -191,7 +191,7 @@ It may also be more appropriate to use `unsupported-operator` as the error code.
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 class WithContains:
     def __contains__(self, item) -> NotBoolable:

crates/red_knot_python_semantic/resources/mdtest/comparison/instances/rich_comparison.md

@@ -355,7 +355,7 @@ element) of a chained comparison.
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 class Comparable:
     def __lt__(self, item) -> NotBoolable:

crates/red_knot_python_semantic/resources/mdtest/comparison/tuples.md

@@ -355,7 +355,7 @@ def compute_chained_comparison():
 
 ```py
 class NotBoolable:
-    __bool__ = 5
+    __bool__: int = 5
 
 class Comparable:
     def __lt__(self, other) -> NotBoolable:
@@ -387,7 +387,7 @@ class A:
         return NotBoolable()
 
 class NotBoolable:
-    __bool__ = None
+    __bool__: None = None
 
 # error: [unsupported-bool-conversion]
 (A(),) == (A(),)

crates/red_knot_python_semantic/resources/mdtest/conditional/if_expression.md

@@ -40,7 +40,7 @@ def _(flag: bool):
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
 3 if NotBoolable() else 4

crates/red_knot_python_semantic/resources/mdtest/conditional/if_statement.md

@@ -152,7 +152,7 @@ def _(flag: bool):
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
 if NotBoolable():

crates/red_knot_python_semantic/resources/mdtest/conditional/match.md

@@ -48,7 +48,7 @@ def _(target: int):
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 def _(target: int, flag: NotBoolable):
     y = 1

crates/red_knot_python_semantic/resources/mdtest/expression/assert.md

@@ -2,7 +2,7 @@
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
 assert NotBoolable()

crates/red_knot_python_semantic/resources/mdtest/expression/boolean.md

@@ -121,7 +121,7 @@ if NotBoolable():
 
 ```py
 class NotBoolable:
-    __bool__ = None
+    __bool__: None = None
 
 # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
 if NotBoolable():
@@ -133,9 +133,9 @@ if NotBoolable():
 ```py
 def test(cond: bool):
     class NotBoolable:
-        __bool__ = None if cond else 3
+        __bool__: int | None = None if cond else 3
 
-    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; it incorrectly implements `__bool__`"
+    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
     if NotBoolable():
         ...
 ```
@@ -145,7 +145,7 @@ def test(cond: bool):
 ```py
 def test(cond: bool):
     class NotBoolable:
-        __bool__ = None
+        __bool__: None = None
 
     a = 10 if cond else NotBoolable()
 

crates/red_knot_python_semantic/resources/mdtest/loops/while_loop.md

@@ -121,7 +121,7 @@ def _(flag: bool, flag2: bool):
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
 while NotBoolable():

crates/red_knot_python_semantic/resources/mdtest/snapshots/for.md_-_For_loops_-_Possibly_unbound_`__iter__`_and_possibly_invalid_`__getitem__`.snap

@@ -86,8 +86,7 @@ error: lint:not-iterable
    |
 35 |     # error: [not-iterable]
 36 |     for y in Iterable2():
-   |              ^^^^^^^^^^^ Object of type `Iterable2` may not be iterable because it may not have an `__iter__` method and its `__getitem__` method (with type `<bound method `__getitem__` of `Iterable2`> | <bound method `__getitem__` of `Iterable2`>`)
-                            may have an incorrect signature for the old-style iteration protocol (expected a signature at least as permissive as `def __getitem__(self, key: int): ...`)
+   |              ^^^^^^^^^^^ Object of type `Iterable2` may not be iterable because it may not have an `__iter__` method and its `__getitem__` method (with type `<bound method `__getitem__` of `Iterable2`> | <bound method `__getitem__` of `Iterable2`>`) may have an incorrect signature for the old-style iteration protocol (expected a signature at least as permissive as `def __getitem__(self, key: int): ...`)
 37 |         reveal_type(y)  # revealed: bytes | str | int
    |
 

crates/red_knot_python_semantic/resources/mdtest/snapshots/instances.md_-_Binary_operations_on_instances_-_Operations_involving_types_with_invalid_`__bool__`_methods.snap

@@ -13,7 +13,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/binary/instances.m
 
 ```
 1 | class NotBoolable:
-2 |     __bool__ = 3
+2 |     __bool__: int = 3
 3 | 
 4 | a = NotBoolable()
 5 | 

crates/red_knot_python_semantic/resources/mdtest/snapshots/membership_test.md_-_Comparison___Membership_Test_-_Return_type_that_doesn't_implement_`__bool__`_correctly.snap

@@ -13,7 +13,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/comparison/instanc
 
 ```
  1 | class NotBoolable:
- 2 |     __bool__ = 3
+ 2 |     __bool__: int = 3
  3 | 
  4 | class WithContains:
  5 |     def __contains__(self, item) -> NotBoolable:

crates/red_knot_python_semantic/resources/mdtest/snapshots/not.md_-_Unary_not_-_Object_that_implements_`__bool__`_incorrectly.snap

@@ -13,7 +13,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/unary/not.md
 
 ```
 1 | class NotBoolable:
-2 |     __bool__ = 3
+2 |     __bool__: int = 3
 3 | 
 4 | # error: [unsupported-bool-conversion]
 5 | not NotBoolable()

crates/red_knot_python_semantic/resources/mdtest/snapshots/rich_comparison.md_-_Comparison___Rich_Comparison_-_Chained_comparisons_with_objects_that_don't_implement_`__bool__`_correctly.snap

@@ -13,7 +13,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/comparison/instanc
 
 ```
  1 | class NotBoolable:
- 2 |     __bool__ = 3
+ 2 |     __bool__: int = 3
  3 | 
  4 | class Comparable:
  5 |     def __lt__(self, item) -> NotBoolable:

crates/red_knot_python_semantic/resources/mdtest/snapshots/tuples.md_-_Comparison___Tuples_-_Chained_comparisons_with_elements_that_incorrectly_implement_`__bool__`.snap

@@ -13,7 +13,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/comparison/tuples.
 
 ```
  1 | class NotBoolable:
- 2 |     __bool__ = 5
+ 2 |     __bool__: int = 5
  3 | 
  4 | class Comparable:
  5 |     def __lt__(self, other) -> NotBoolable:

crates/red_knot_python_semantic/resources/mdtest/snapshots/tuples.md_-_Comparison___Tuples_-_Equality_with_elements_that_incorrectly_implement_`__bool__`.snap

@@ -17,7 +17,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/comparison/tuples.
 3 |         return NotBoolable()
 4 | 
 5 | class NotBoolable:
-6 |     __bool__ = None
+6 |     __bool__: None = None
 7 | 
 8 | # error: [unsupported-bool-conversion]
 9 | (A(),) == (A(),)

crates/red_knot_python_semantic/resources/mdtest/unary/not.md

@@ -210,7 +210,7 @@ reveal_type(not PossiblyUnboundBool())
 
 ```py
 class NotBoolable:
-    __bool__ = 3
+    __bool__: int = 3
 
 # error: [unsupported-bool-conversion]
 not NotBoolable()

crates/red_knot_python_semantic/src/symbol.rs

@@ -15,7 +15,7 @@ use crate::{resolve_module, Db, KnownModule, Module, Program};
 
 pub(crate) use implicit_globals::module_type_implicit_global_symbol;
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
 pub(crate) enum Boundness {
     Bound,
     PossiblyUnbound,