[ty] Delegate truthiness inference of an enum `Literal` type to its enum-instance supertype (#21060)

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

@@ -78,6 +78,7 @@ python-version = "3.11"
 ```
 
 ```py
+import enum
 from typing import Literal, final
 
 reveal_type(bool(1))  # revealed: Literal[True]
@@ -129,13 +130,20 @@ class FinalClassWithNoLenOrBool: ...
 
 reveal_type(bool(FinalClassWithNoLenOrBool()))  # revealed: Literal[True]
 
-def f(x: SingleElementTupleSubclass | FinalClassOverridingLenAndNotBool | FinalClassWithNoLenOrBool):
+class EnumWithMembers(enum.Enum):
+    A = 1
+    B = 2
+
+reveal_type(bool(EnumWithMembers.A))  # revealed: Literal[True]
+
+def f(x: SingleElementTupleSubclass | FinalClassOverridingLenAndNotBool | FinalClassWithNoLenOrBool | Literal[EnumWithMembers.A]):
     reveal_type(bool(x))  # revealed: Literal[True]
 ```
 
 ## Falsy values
 
 ```py
+import enum
 from typing import final, Literal
 
 reveal_type(bool(0))  # revealed: Literal[False]
@@ -156,13 +164,23 @@ class FinalClassOverridingLenAndNotBool:
 
 reveal_type(bool(FinalClassOverridingLenAndNotBool()))  # revealed: Literal[False]
 
-def f(x: EmptyTupleSubclass | FinalClassOverridingLenAndNotBool):
+class EnumWithMembersOverridingBool(enum.Enum):
+    A = 1
+    B = 2
+
+    def __bool__(self) -> Literal[False]:
+        return False
+
+reveal_type(bool(EnumWithMembersOverridingBool.A))  # revealed: Literal[False]
+
+def f(x: EmptyTupleSubclass | FinalClassOverridingLenAndNotBool | Literal[EnumWithMembersOverridingBool.A]):
     reveal_type(bool(x))  # revealed: Literal[False]
 ```
 
 ## Ambiguous values
 
 ```py
+import enum
 from typing import Literal
 
 reveal_type(bool([]))  # revealed: bool
@@ -182,6 +200,15 @@ class NonFinalOverridingLenAndNotBool:
 # because a subclass might override `__bool__`,
 # and `__bool__` takes precedence over `__len__`
 reveal_type(bool(NonFinalOverridingLenAndNotBool()))  # revealed: bool
+
+class EnumWithMembersOverridingBool(enum.Enum):
+    A = 1
+    B = 2
+
+    def __bool__(self) -> bool:
+        return False
+
+reveal_type(bool(EnumWithMembersOverridingBool.A))  # revealed: bool
 ```
 
 ## `__bool__` returning `NoReturn`

crates/ty_python_semantic/resources/mdtest/type_properties/truthiness.md

@@ -183,13 +183,11 @@ class CustomLenEnum(Enum):
     def __len__(self):
         return 0
 
-# TODO: these could be `Literal[True]`
+reveal_type(bool(NormalEnum.NO))  # revealed: Literal[True]
-reveal_type(bool(NormalEnum.NO))  # revealed: bool
+reveal_type(bool(NormalEnum.YES))  # revealed: Literal[True]
-reveal_type(bool(NormalEnum.YES))  # revealed: bool
 
-# TODO: these could be `Literal[False]`
+reveal_type(bool(FalsyEnum.NO))  # revealed: Literal[False]
-reveal_type(bool(FalsyEnum.NO))  # revealed: bool
+reveal_type(bool(FalsyEnum.YES))  # revealed: Literal[False]
-reveal_type(bool(FalsyEnum.YES))  # revealed: bool
 
 # All of the following must be `bool`:
 

crates/ty_python_semantic/src/types.rs

@@ -4692,10 +4692,10 @@ impl<'db> Type<'db> {
                 Truthiness::Ambiguous
             }
 
-            Type::EnumLiteral(_) => {
+            Type::EnumLiteral(enum_type) => {
-                // We currently make no attempt to infer the precise truthiness, but it's not impossible to do so.
+                enum_type
-                // Note that custom `__bool__` or `__len__` methods on the class or superclasses affect the outcome.
+                    .enum_class_instance(db)
-                Truthiness::Ambiguous
+                    .try_bool_impl(db, allow_short_circuit, visitor)?
             }
 
             Type::IntLiteral(num) => Truthiness::from(*num != 0),