[red-knot] Decompose bool to Literal[True, False] in unions and intersections (v2)

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

@@ -58,7 +58,22 @@ reveal_type(c >= d)  # revealed: Literal[True]
 #### Results with Ambiguity
 
 ```py
-def _(x: bool, y: int):
+class P:
+    def __lt__(self, other: "P") -> bool:
+        return True
+
+    def __le__(self, other: "P") -> bool:
+        return True
+
+    def __gt__(self, other: "P") -> bool:
+        return True
+
+    def __ge__(self, other: "P") -> bool:
+        return True
+
+class Q(P): ...
+
+def _(x: P, y: Q):
     a = (x,)
     b = (y,)
 

crates/red_knot_python_semantic/resources/mdtest/exception/control_flow.md

@@ -455,9 +455,9 @@ else:
     reveal_type(x)  # revealed: slice
 finally:
     # TODO: should be `Literal[1] | str | bytes | bool | memoryview | float | range | slice`
-    reveal_type(x)  # revealed: bool | float | slice
+    reveal_type(x)  # revealed: bool | slice | float
 
-reveal_type(x)  # revealed: bool | float | slice
+reveal_type(x)  # revealed: bool | slice | float
 ```
 
 ## Nested `try`/`except` blocks
@@ -534,7 +534,7 @@ try:
         reveal_type(x)  # revealed: slice
     finally:
         # TODO: should be `Literal[1] | str | bytes | bool | memoryview | float | range | slice`
-        reveal_type(x)  # revealed: bool | float | slice
+        reveal_type(x)  # revealed: bool | slice | float
         x = 2
         reveal_type(x)  # revealed: Literal[2]
     reveal_type(x)  # revealed: Literal[2]

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

@@ -21,22 +21,22 @@ else:
 if x and not x:
     reveal_type(x)  # revealed: Never
 else:
-    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | None | tuple[()]
+    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | tuple[()] | None
 
 if not (x and not x):
-    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | None | tuple[()]
+    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | tuple[()] | None
 else:
     reveal_type(x)  # revealed: Never
 
 if x or not x:
-    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | None | tuple[()]
+    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | tuple[()] | None
 else:
     reveal_type(x)  # revealed: Never
 
 if not (x or not x):
     reveal_type(x)  # revealed: Never
 else:
-    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | None | tuple[()]
+    reveal_type(x)  # revealed: Literal[0, -1, "", "foo", b"", b"bar"] | bool | tuple[()] | None
 
 if (isinstance(x, int) or isinstance(x, str)) and x:
     reveal_type(x)  # revealed: Literal[-1, True, "foo"]

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_assignable_to.md

@@ -346,4 +346,16 @@ static_assert(is_assignable_to(Never, type[str]))
 static_assert(is_assignable_to(Never, type[Any]))
 ```
 
+### `bool` is assignable to unions that include `bool`
+
+Since we decompose `bool` to `Literal[True, False]` in unions, it would be surprisingly easy to get
+this wrong if we forgot to normalize `bool` to `Literal[True, False]` when it appeared on the
+left-hand side in `Type::is_assignable_to()`.
+
+```py
+from knot_extensions import is_assignable_to, static_assert
+
+static_assert(is_assignable_to(bool, str | bool))
+```
+
 [typing documentation]: https://typing.readthedocs.io/en/latest/spec/concepts.html#the-assignable-to-or-consistent-subtyping-relation

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_equivalent_to.md

@@ -118,4 +118,48 @@ class R: ...
 static_assert(is_equivalent_to(Intersection[tuple[P | Q], R], Intersection[tuple[Q | P], R]))
 ```
 
+## Unions containing tuples containing `bool`
+
+```py
+from knot_extensions import is_equivalent_to, static_assert
+from typing_extensions import Literal
+
+class P: ...
+
+static_assert(is_equivalent_to(tuple[Literal[True, False]] | P, tuple[bool] | P))
+static_assert(is_equivalent_to(P | tuple[bool], P | tuple[Literal[True, False]]))
+```
+
+## Unions and intersections involving `AlwaysTruthy`, `bool` and `AlwaysFalsy`
+
+```py
+from knot_extensions import AlwaysTruthy, AlwaysFalsy, static_assert, is_equivalent_to, Not
+from typing_extensions import Literal
+
+static_assert(is_equivalent_to(AlwaysTruthy | bool, Literal[False] | AlwaysTruthy))
+static_assert(is_equivalent_to(AlwaysFalsy | bool, Literal[True] | AlwaysFalsy))
+static_assert(is_equivalent_to(Not[AlwaysTruthy] | bool, Not[AlwaysTruthy] | Literal[True]))
+static_assert(is_equivalent_to(Not[AlwaysFalsy] | bool, Literal[False] | Not[AlwaysFalsy]))
+```
+
+## Unions and intersections involving `AlwaysTruthy`, `LiteralString` and `AlwaysFalsy`
+
+```py
+from knot_extensions import AlwaysTruthy, AlwaysFalsy, static_assert, is_equivalent_to, Not, Intersection
+from typing_extensions import Literal, LiteralString
+
+# TODO: these should all pass!
+
+# error: [static-assert-error]
+static_assert(is_equivalent_to(AlwaysTruthy | LiteralString, Literal[""] | AlwaysTruthy))
+# error: [static-assert-error]
+static_assert(is_equivalent_to(AlwaysFalsy | LiteralString, Intersection[LiteralString, Not[Literal[""]]] | AlwaysFalsy))
+# error: [static-assert-error]
+static_assert(is_equivalent_to(Not[AlwaysFalsy] | LiteralString, Literal[""] | Not[AlwaysFalsy]))
+# error: [static-assert-error]
+static_assert(
+    is_equivalent_to(Not[AlwaysTruthy] | LiteralString, Not[AlwaysTruthy] | Intersection[LiteralString, Not[Literal[""]]])
+)
+```
+
 [the equivalence relation]: https://typing.readthedocs.io/en/latest/spec/glossary.html#term-equivalent

crates/red_knot_python_semantic/resources/mdtest/type_properties/is_subtype_of.md

@@ -449,5 +449,31 @@ static_assert(not is_subtype_of(Intersection[Unknown, int], int))
 static_assert(not is_subtype_of(tuple[int, int], tuple[int, Unknown]))
 ```
 
+## `bool` is a subtype of `AlwaysTruthy | AlwaysFalsy`
+
+`bool` is equivalent to `Literal[True] | Literal[False]`. `Literal[True]` is a subtype of
+`AlwaysTruthy` and `Literal[False]` is a subtype of `AlwaysFalsy`; it therefore stands to reason
+that `bool` is a subtype of `AlwaysTruthy | AlwaysFalsy`.
+
+```py
+from knot_extensions import AlwaysTruthy, AlwaysFalsy, is_subtype_of, static_assert, Not, is_disjoint_from
+from typing_extensions import Literal
+
+static_assert(is_subtype_of(bool, AlwaysTruthy | AlwaysFalsy))
+
+# the inverse also applies -- TODO: this should pass!
+# See the TODO comments in the `Type::Intersection` branch of `Type::is_disjoint_from()`.
+static_assert(is_disjoint_from(bool, Not[AlwaysTruthy | AlwaysFalsy]))  # error: [static-assert-error]
+
+# `Type::is_subtype_of` delegates many questions of `bool` subtyping to `int`,
+# but set-theoretic types like intersections and unions are still handled differently to `int`
+static_assert(is_subtype_of(Literal[True], Not[Literal[2]]))
+static_assert(is_subtype_of(bool, Not[Literal[2]]))
+static_assert(is_subtype_of(Literal[True], bool | None))
+static_assert(is_subtype_of(bool, bool | None))
+
+static_assert(not is_subtype_of(int, Not[Literal[2]]))
+```
+
 [special case for float and complex]: https://typing.readthedocs.io/en/latest/spec/special-types.html#special-cases-for-float-and-complex
 [typing documentation]: https://typing.readthedocs.io/en/latest/spec/concepts.html#subtype-supertype-and-type-equivalence

crates/red_knot_python_semantic/src/types.rs

@@ -811,6 +811,29 @@ impl<'db> Type<'db> {
         }
     }
 
+    /// Normalize the type `bool` -> `Literal[True, False]`.
+    ///
+    /// Using this method in various type-relational methods
+    /// ensures that the following invariants hold true:
+    ///
+    /// - bool ≡ Literal[True, False]
+    /// - bool | T ≡ Literal[True, False] | T
+    /// - bool <: Literal[True, False]
+    /// - bool | T <: Literal[True, False] | T
+    /// - Literal[True, False] <: bool
+    /// - Literal[True, False] | T <: bool | T
+    #[must_use]
+    pub fn with_normalized_bools(self, db: &'db dyn Db) -> Self {
+        match self {
+            Type::Instance(InstanceType { class }) if class.is_known(db, KnownClass::Bool) => {
+                Type::normalized_bool(db)
+            }
+            // TODO: decompose `LiteralString` into `Literal[""] | TruthyLiteralString`?
+            // We'd need to rename this method... --Alex
+            _ => self,
+        }
+    }
+
     /// Return a normalized version of `self` in which all unions and intersections are sorted
     /// according to a canonical order, no matter how "deeply" a union/intersection may be nested.
     #[must_use]
@@ -881,6 +904,13 @@ impl<'db> Type<'db> {
             (Type::Never, _) => true,
             (_, Type::Never) => false,
 
+            (Type::Instance(InstanceType { class }), _) if class.is_known(db, KnownClass::Bool) => {
+                Type::normalized_bool(db).is_subtype_of(db, target)
+            }
+            (_, Type::Instance(InstanceType { class })) if class.is_known(db, KnownClass::Bool) => {
+                self.is_subtype_of(db, Type::normalized_bool(db))
+            }
+
             (Type::Union(union), _) => union
                 .elements(db)
                 .iter()
@@ -961,7 +991,7 @@ impl<'db> Type<'db> {
                 KnownClass::Str.to_instance(db).is_subtype_of(db, target)
             }
             (Type::BooleanLiteral(_), _) => {
-                KnownClass::Bool.to_instance(db).is_subtype_of(db, target)
+                KnownClass::Int.to_instance(db).is_subtype_of(db, target)
             }
             (Type::IntLiteral(_), _) => KnownClass::Int.to_instance(db).is_subtype_of(db, target),
             (Type::BytesLiteral(_), _) => {
@@ -1093,6 +1123,13 @@ impl<'db> Type<'db> {
                 true
             }
 
+            (Type::Instance(InstanceType { class }), _) if class.is_known(db, KnownClass::Bool) => {
+                Type::normalized_bool(db).is_assignable_to(db, target)
+            }
+            (_, Type::Instance(InstanceType { class })) if class.is_known(db, KnownClass::Bool) => {
+                self.is_assignable_to(db, Type::normalized_bool(db))
+            }
+
             // A union is assignable to a type T iff every element of the union is assignable to T.
             (Type::Union(union), ty) => union
                 .elements(db)
@@ -1183,6 +1220,12 @@ impl<'db> Type<'db> {
                 left.is_equivalent_to(db, right)
             }
             (Type::Tuple(left), Type::Tuple(right)) => left.is_equivalent_to(db, right),
+            (Type::Instance(InstanceType { class }), _) if class.is_known(db, KnownClass::Bool) => {
+                Type::normalized_bool(db).is_equivalent_to(db, other)
+            }
+            (_, Type::Instance(InstanceType { class })) if class.is_known(db, KnownClass::Bool) => {
+                self.is_equivalent_to(db, Type::normalized_bool(db))
+            }
             _ => self == other && self.is_fully_static(db) && other.is_fully_static(db),
         }
     }
@@ -1241,6 +1284,13 @@ impl<'db> Type<'db> {
                 first.is_gradual_equivalent_to(db, second)
             }
 
+            (Type::Instance(InstanceType { class }), _) if class.is_known(db, KnownClass::Bool) => {
+                Type::normalized_bool(db).is_gradual_equivalent_to(db, other)
+            }
+            (_, Type::Instance(InstanceType { class })) if class.is_known(db, KnownClass::Bool) => {
+                self.is_gradual_equivalent_to(db, Type::normalized_bool(db))
+            }
+
             _ => false,
         }
     }
@@ -1255,6 +1305,13 @@ impl<'db> Type<'db> {
 
             (Type::Dynamic(_), _) | (_, Type::Dynamic(_)) => false,
 
+            (Type::Instance(InstanceType { class }), ty)
+            | (ty, Type::Instance(InstanceType { class }))
+                if class.is_known(db, KnownClass::Bool) =>
+            {
+                Type::normalized_bool(db).is_disjoint_from(db, ty)
+            }
+
             (Type::Union(union), other) | (other, Type::Union(union)) => union
                 .elements(db)
                 .iter()
@@ -2371,6 +2428,13 @@ impl<'db> Type<'db> {
         KnownClass::NoneType.to_instance(db)
     }
 
+    /// The type `Literal[True, False]`, which is exactly equivalent to `bool`
+    /// (and which `bool` is eagerly normalized to in several situations)
+    pub fn normalized_bool(db: &'db dyn Db) -> Type<'db> {
+        const LITERAL_BOOLS: [Type; 2] = [Type::BooleanLiteral(false), Type::BooleanLiteral(true)];
+        Type::Union(UnionType::new(db, Box::from(LITERAL_BOOLS)))
+    }
+
     /// Return the type of `tuple(sys.version_info)`.
     ///
     /// This is not exactly the type that `sys.version_info` has at runtime,
@@ -4642,18 +4706,19 @@ pub struct TupleType<'db> {
 }
 
 impl<'db> TupleType<'db> {
-    pub fn from_elements<T: Into<Type<'db>>>(
-        db: &'db dyn Db,
-        types: impl IntoIterator<Item = T>,
-    ) -> Type<'db> {
+    pub fn from_elements<I, T>(db: &'db dyn Db, types: I) -> Type<'db>
+    where
+        I: IntoIterator<Item = T>,
+        T: Into<Type<'db>>,
+    {
         let mut elements = vec![];
 
         for ty in types {
-            let ty = ty.into();
+            let ty: Type<'db> = ty.into();
             if ty.is_never() {
                 return Type::Never;
             }
-            elements.push(ty);
+            elements.push(ty.with_normalized_bools(db));
         }
 
         Type::Tuple(Self::new(db, elements.into_boxed_slice()))