red_knot_python_semantic: improve diagnostics for unsupported boolean conversions

This mostly only improves things for incorrect arguments and for an
incorrect return type. It doesn't do much to improve the case where
`__bool__` isn't callable and leaves the union/other cases untouched
completely.

I picked this one because, at first glance, this _looked_ like a lower
hanging fruit. The conceptual improvement here is pretty
straight-forward: add annotations for relevant data. But it took me a
bit to figure out how to connect all of the pieces.

Author: BurntSushi

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

@@ -42,6 +42,6 @@ def _(flag: bool):
 class NotBoolable:
     __bool__: int = 3
 
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 3 if NotBoolable() else 4
 ```

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

@@ -154,10 +154,10 @@ def _(flag: bool):
 class NotBoolable:
     __bool__: int = 3
 
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 if NotBoolable():
     ...
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 elif NotBoolable():
     ...
 ```

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

@@ -292,7 +292,7 @@ class NotBoolable:
 def _(target: int, flag: NotBoolable):
     y = 1
     match target:
-        # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+        # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
         case 1 if flag:
             y = 2
         case 2:

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

@@ -4,6 +4,6 @@
 class NotBoolable:
     __bool__: int = 3
 
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 assert NotBoolable()
 ```

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

@@ -123,7 +123,7 @@ if NotBoolable():
 class NotBoolable:
     __bool__: None = None
 
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 if NotBoolable():
     ...
 ```
@@ -135,7 +135,7 @@ def test(cond: bool):
     class NotBoolable:
         __bool__: int | None = None if cond else 3
 
-    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
     if NotBoolable():
         ...
 ```
@@ -149,7 +149,7 @@ def test(cond: bool):
 
     a = 10 if cond else NotBoolable()
 
-    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `Literal[10] | NotBoolable`; its `__bool__` method isn't callable"
+    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `Literal[10] | NotBoolable`"
     if a:
         ...
 ```

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

@@ -123,7 +123,7 @@ def _(flag: bool, flag2: bool):
 class NotBoolable:
     __bool__: int = 3
 
-# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable"
+# error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `NotBoolable`"
 while NotBoolable():
     ...
 ```

crates/red_knot_python_semantic/resources/mdtest/narrow/truthiness.md

@@ -270,7 +270,7 @@ def _(
     if af:
         reveal_type(af)  # revealed: type[AmbiguousClass] & ~AlwaysFalsy
 
-    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `MetaDeferred`; the return type of its bool method (`MetaAmbiguous`) isn't assignable to `bool"
+    # error: [unsupported-bool-conversion] "Boolean conversion is unsupported for type `MetaDeferred`"
     if d:
         # TODO: Should be `Unknown`
         reveal_type(d)  # revealed: type[DeferredClass] & ~AlwaysFalsy

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

@@ -24,12 +24,13 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/binary/instances.m
 # Diagnostics
 
 ```
-error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable
+error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`
  --> /src/mdtest_snippet.py:7:8
   |
 6 | # error: [unsupported-bool-conversion]
 7 | 10 and a and True
   |        ^
   |
+info: `__bool__` on `NotBoolable` must be callable
 
 ```

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

@@ -28,7 +28,7 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/comparison/instanc
 # Diagnostics
 
 ```
-error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable
+error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`
   --> /src/mdtest_snippet.py:9:1
    |
  8 | # error: [unsupported-bool-conversion]
@@ -37,17 +37,19 @@ error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for t
 10 | # error: [unsupported-bool-conversion]
 11 | 10 not in WithContains()
    |
+info: `__bool__` on `NotBoolable` must be callable
 
 ```
 
 ```
-error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable
+error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`
   --> /src/mdtest_snippet.py:11:1
    |
  9 | 10 in WithContains()
 10 | # error: [unsupported-bool-conversion]
 11 | 10 not in WithContains()
    | ^^^^^^^^^^^^^^^^^^^^^^^^
    |
+info: `__bool__` on `NotBoolable` must be callable
 
 ```

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

@@ -22,12 +22,13 @@ mdtest path: crates/red_knot_python_semantic/resources/mdtest/unary/not.md
 # Diagnostics
 
 ```
-error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`; its `__bool__` method isn't callable
+error: lint:unsupported-bool-conversion: Boolean conversion is unsupported for type `NotBoolable`
  --> /src/mdtest_snippet.py:5:1
   |
 4 | # error: [unsupported-bool-conversion]
 5 | not NotBoolable()
   | ^^^^^^^^^^^^^^^^^
   |
+info: `__bool__` on `NotBoolable` must be callable
 
 ```