[red-knot] Consolidate all gradual types into single Type variant (#1…

…5386)

Prompted by

> One nit: I think we need to consider `Any` and `Unknown` and `Todo` as
all (gradually) equivalent to each other, and thus `type & Any` and
`type & Unknown` and `type & Todo` as also equivalent. The distinction
between `Any` vs `Unknown` vs `Todo` is entirely about
provenance/debugging, there is no type level distinction. (And I've been
wondering if the `Any` vs `Unknown` distinction is really worth it.)

The thought here is that _most_ places want to treat `Any`, `Unknown`,
and `Todo` identically. So this PR simplifies things by having a single
`Type::Any` variant, and moves the provenance part into a new `AnyType`
type. If you need to treat e.g. `Todo` differently, you still can by
pattern-matching into the `AnyType`. But if you don't, you can just use
`Type::Any(_)`.

(This would also allow us to (more easily) distinguish "unknown via an
unannotated value" from "unknown because of a typing error" should we
want to do that in the future)

---------

Co-authored-by: Alex Waygood <[email protected]>
Co-authored-by: Carl Meyer <[email protected]>

crates/red_knot_python_semantic/src/types/builder.rs

@@ -321,7 +321,7 @@ impl<'db> InnerIntersectionBuilder<'db> {
                     self.add_positive(db, *neg);
                 }
             }
-            ty @ (Type::Any | Type::Unknown | Type::Todo(_)) => {
+            ty @ Type::Dynamic(_) => {
                 // Adding any of these types to the negative side of an intersection
                 // is equivalent to adding it to the positive side. We do this to
                 // simplify the representation.
@@ -434,7 +434,7 @@ mod tests {
     fn build_intersection() {
         let db = setup_db();
         let t0 = Type::IntLiteral(0);
-        let ta = Type::Any;
+        let ta = Type::any();
         let intersection = IntersectionBuilder::new(&db)
             .add_positive(ta)
             .add_negative(t0)
@@ -457,7 +457,7 @@ mod tests {
     #[test]
     fn build_intersection_flatten_positive() {
         let db = setup_db();
-        let ta = Type::Any;
+        let ta = Type::any();
         let t1 = Type::IntLiteral(1);
         let t2 = Type::IntLiteral(2);
         let i0 = IntersectionBuilder::new(&db)
@@ -477,7 +477,7 @@ mod tests {
     #[test]
     fn build_intersection_flatten_negative() {
         let db = setup_db();
-        let ta = Type::Any;
+        let ta = Type::any();
         let t1 = Type::IntLiteral(1);
         let t2 = KnownClass::Int.to_instance(&db);
         // i0 = Any & ~Literal[1]
@@ -503,13 +503,13 @@ mod tests {
         let db = setup_db();
 
         let ty = IntersectionBuilder::new(&db)
-            .add_negative(Type::Any)
+            .add_negative(Type::any())
             .build();
-        assert_eq!(ty, Type::Any);
+        assert_eq!(ty, Type::any());
 
         let ty = IntersectionBuilder::new(&db)
             .add_positive(Type::Never)
-            .add_negative(Type::Any)
+            .add_negative(Type::any())
             .build();
         assert_eq!(ty, Type::Never);
     }
@@ -519,32 +519,32 @@ mod tests {
         let db = setup_db();
 
         let ty = IntersectionBuilder::new(&db)
-            .add_positive(Type::Unknown)
-            .add_positive(Type::Unknown)
+            .add_positive(Type::unknown())
+            .add_positive(Type::unknown())
             .build();
-        assert_eq!(ty, Type::Unknown);
+        assert_eq!(ty, Type::unknown());
 
         let ty = IntersectionBuilder::new(&db)
-            .add_positive(Type::Unknown)
-            .add_negative(Type::Unknown)
+            .add_positive(Type::unknown())
+            .add_negative(Type::unknown())
             .build();
-        assert_eq!(ty, Type::Unknown);
+        assert_eq!(ty, Type::unknown());
 
         let ty = IntersectionBuilder::new(&db)
-            .add_negative(Type::Unknown)
-            .add_negative(Type::Unknown)
+            .add_negative(Type::unknown())
+            .add_negative(Type::unknown())
             .build();
-        assert_eq!(ty, Type::Unknown);
+        assert_eq!(ty, Type::unknown());
 
         let ty = IntersectionBuilder::new(&db)
-            .add_positive(Type::Unknown)
+            .add_positive(Type::unknown())
             .add_positive(Type::IntLiteral(0))
-            .add_negative(Type::Unknown)
+            .add_negative(Type::unknown())
             .build();
         assert_eq!(
             ty,
             IntersectionBuilder::new(&db)
-                .add_positive(Type::Unknown)
+                .add_positive(Type::unknown())
                 .add_positive(Type::IntLiteral(0))
                 .build()
         );
@@ -555,7 +555,7 @@ mod tests {
         let db = setup_db();
         let t0 = Type::IntLiteral(0);
         let t1 = Type::IntLiteral(1);
-        let ta = Type::Any;
+        let ta = Type::any();
         let u0 = UnionType::from_elements(&db, [t0, t1]);
 
         let union = IntersectionBuilder::new(&db)
@@ -958,8 +958,8 @@ mod tests {
         assert_eq!(ty, Type::BooleanLiteral(!bool_value));
     }
 
-    #[test_case(Type::Any)]
-    #[test_case(Type::Unknown)]
+    #[test_case(Type::any())]
+    #[test_case(Type::unknown())]
     #[test_case(todo_type!())]
     fn build_intersection_t_and_negative_t_does_not_simplify(ty: Type) {
         let db = setup_db();

crates/red_knot_python_semantic/src/types/call.rs

@@ -97,7 +97,7 @@ impl<'db> CallOutcome<'db> {
                     match (acc, ty) {
                         (None, None) => None,
                         (None, Some(ty)) => Some(UnionBuilder::new(db).add(ty)),
-                        (Some(builder), ty) => Some(builder.add(ty.unwrap_or(Type::Unknown))),
+                        (Some(builder), ty) => Some(builder.add(ty.unwrap_or(Type::unknown()))),
                     }
                 })
                 .map(UnionBuilder::build),
@@ -206,7 +206,7 @@ impl<'db> CallOutcome<'db> {
             }
             Self::NotCallable { not_callable_ty } => Err(NotCallableError::Type {
                 not_callable_ty: *not_callable_ty,
-                return_ty: Type::Unknown,
+                return_ty: Type::unknown(),
             }),
             Self::PossiblyUnboundDunderCall {
                 called_ty,
@@ -215,7 +215,7 @@ impl<'db> CallOutcome<'db> {
                 callable_ty: *called_ty,
                 return_ty: call_outcome
                     .return_ty(context.db())
-                    .unwrap_or(Type::Unknown),
+                    .unwrap_or(Type::unknown()),
             }),
             Self::Union {
                 outcomes,
@@ -228,7 +228,7 @@ impl<'db> CallOutcome<'db> {
                     let return_ty = match outcome {
                         Self::NotCallable { not_callable_ty } => {
                             not_callable.push(*not_callable_ty);
-                            Type::Unknown
+                            Type::unknown()
                         }
                         Self::RevealType {
                             binding,
@@ -307,7 +307,7 @@ impl<'db> CallOutcome<'db> {
                     }
                 }
 
-                Ok(Type::Unknown)
+                Ok(Type::unknown())
             }
         }
     }

crates/red_knot_python_semantic/src/types/call/bind.rs

@@ -125,10 +125,10 @@ pub(crate) fn bind_call<'db>(
 
     CallBinding {
         callable_ty,
-        return_ty: signature.return_ty.unwrap_or(Type::Unknown),
+        return_ty: signature.return_ty.unwrap_or(Type::unknown()),
         parameter_tys: parameter_tys
             .into_iter()
-            .map(|opt_ty| opt_ty.unwrap_or(Type::Unknown))
+            .map(|opt_ty| opt_ty.unwrap_or(Type::unknown()))
             .collect(),
         errors,
     }

crates/red_knot_python_semantic/src/types/class_base.rs

@@ -1,5 +1,5 @@
 use crate::types::{
-    todo_type, Class, ClassLiteralType, KnownClass, KnownInstanceType, TodoType, Type,
+    todo_type, Class, ClassLiteralType, DynamicType, KnownClass, KnownInstanceType, Type,
 };
 use crate::Db;
 use itertools::Either;
@@ -8,19 +8,25 @@ use itertools::Either;
 ///
 /// This is much more limited than the [`Type`] enum:
 /// all types that would be invalid to have as a class base are
-/// transformed into [`ClassBase::Unknown`]
+/// transformed into [`ClassBase::unknown`]
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq, salsa::Update)]
 pub enum ClassBase<'db> {
-    Any,
-    Unknown,
-    Todo(TodoType),
+    Dynamic(DynamicType),
     Class(Class<'db>),
 }
 
 impl<'db> ClassBase<'db> {
+    pub const fn any() -> Self {
+        Self::Dynamic(DynamicType::Any)
+    }
+
+    pub const fn unknown() -> Self {
+        Self::Dynamic(DynamicType::Unknown)
+    }
+
     pub const fn is_dynamic(self) -> bool {
         match self {
-            ClassBase::Any | ClassBase::Unknown | ClassBase::Todo(_) => true,
+            ClassBase::Dynamic(_) => true,
             ClassBase::Class(_) => false,
         }
     }
@@ -34,9 +40,7 @@ impl<'db> ClassBase<'db> {
         impl std::fmt::Display for Display<'_> {
             fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
                 match self.base {
-                    ClassBase::Any => f.write_str("Any"),
-                    ClassBase::Todo(todo) => todo.fmt(f),
-                    ClassBase::Unknown => f.write_str("Unknown"),
+                    ClassBase::Dynamic(dynamic) => dynamic.fmt(f),
                     ClassBase::Class(class) => write!(f, "<class '{}'>", class.name(self.db)),
                 }
             }
@@ -50,7 +54,7 @@ impl<'db> ClassBase<'db> {
         KnownClass::Object
             .to_class_literal(db)
             .into_class_literal()
-            .map_or(Self::Unknown, |ClassLiteralType { class }| {
+            .map_or(Self::unknown(), |ClassLiteralType { class }| {
                 Self::Class(class)
             })
     }
@@ -60,9 +64,7 @@ impl<'db> ClassBase<'db> {
     /// Return `None` if `ty` is not an acceptable type for a class base.
     pub(super) fn try_from_ty(db: &'db dyn Db, ty: Type<'db>) -> Option<Self> {
         match ty {
-            Type::Any => Some(Self::Any),
-            Type::Unknown => Some(Self::Unknown),
-            Type::Todo(todo) => Some(Self::Todo(todo)),
+            Type::Dynamic(dynamic) => Some(Self::Dynamic(dynamic)),
             Type::ClassLiteral(ClassLiteralType { class }) => Some(Self::Class(class)),
             Type::Union(_) => None, // TODO -- forces consideration of multiple possible MROs?
             Type::Intersection(_) => None, // TODO -- probably incorrect?
@@ -104,8 +106,8 @@ impl<'db> ClassBase<'db> {
                 | KnownInstanceType::Not
                 | KnownInstanceType::Intersection
                 | KnownInstanceType::TypeOf => None,
-                KnownInstanceType::Unknown => Some(Self::Unknown),
-                KnownInstanceType::Any => Some(Self::Any),
+                KnownInstanceType::Unknown => Some(Self::unknown()),
+                KnownInstanceType::Any => Some(Self::any()),
                 // TODO: Classes inheriting from `typing.Type` et al. also have `Generic` in their MRO
                 KnownInstanceType::Dict => {
                     Self::try_from_ty(db, KnownClass::Dict.to_class_literal(db))
@@ -150,7 +152,7 @@ impl<'db> ClassBase<'db> {
     pub(super) fn into_class(self) -> Option<Class<'db>> {
         match self {
             Self::Class(class) => Some(class),
-            _ => None,
+            Self::Dynamic(_) => None,
         }
     }
 
@@ -160,13 +162,7 @@ impl<'db> ClassBase<'db> {
         db: &'db dyn Db,
     ) -> Either<impl Iterator<Item = ClassBase<'db>>, impl Iterator<Item = ClassBase<'db>>> {
         match self {
-            ClassBase::Any => Either::Left([ClassBase::Any, ClassBase::object(db)].into_iter()),
-            ClassBase::Unknown => {
-                Either::Left([ClassBase::Unknown, ClassBase::object(db)].into_iter())
-            }
-            ClassBase::Todo(todo) => {
-                Either::Left([ClassBase::Todo(todo), ClassBase::object(db)].into_iter())
-            }
+            ClassBase::Dynamic(_) => Either::Left([self, ClassBase::object(db)].into_iter()),
             ClassBase::Class(class) => Either::Right(class.iter_mro(db)),
         }
     }
@@ -181,9 +177,7 @@ impl<'db> From<Class<'db>> for ClassBase<'db> {
 impl<'db> From<ClassBase<'db>> for Type<'db> {
     fn from(value: ClassBase<'db>) -> Self {
         match value {
-            ClassBase::Any => Type::Any,
-            ClassBase::Todo(todo) => Type::Todo(todo),
-            ClassBase::Unknown => Type::Unknown,
+            ClassBase::Dynamic(dynamic) => Type::Dynamic(dynamic),
             ClassBase::Class(class) => Type::class_literal(class),
         }
     }

crates/red_knot_python_semantic/src/types/display.rs

@@ -65,9 +65,8 @@ struct DisplayRepresentation<'db> {
 impl Display for DisplayRepresentation<'_> {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         match self.ty {
-            Type::Any => f.write_str("Any"),
+            Type::Dynamic(dynamic) => dynamic.fmt(f),
             Type::Never => f.write_str("Never"),
-            Type::Unknown => f.write_str("Unknown"),
             Type::Instance(InstanceType { class }) => {
                 let representation = match class.known(self.db) {
                     Some(KnownClass::NoneType) => "None",
@@ -76,9 +75,6 @@ impl Display for DisplayRepresentation<'_> {
                 };
                 f.write_str(representation)
             }
-            // `[Type::Todo]`'s display should be explicit that is not a valid display of
-            // any other type
-            Type::Todo(todo) => write!(f, "@Todo{todo}"),
             Type::ModuleLiteral(module) => {
                 write!(f, "<module '{}'>", module.module(self.db).name())
             }
@@ -88,9 +84,7 @@ impl Display for DisplayRepresentation<'_> {
                 // Only show the bare class name here; ClassBase::display would render this as
                 // type[<class 'Foo'>] instead of type[Foo].
                 ClassBase::Class(class) => write!(f, "type[{}]", class.name(self.db)),
-                base @ (ClassBase::Any | ClassBase::Todo(_) | ClassBase::Unknown) => {
-                    write!(f, "type[{}]", base.display(self.db))
-                }
+                ClassBase::Dynamic(dynamic) => write!(f, "type[{dynamic}]"),
             },
             Type::KnownInstance(known_instance) => f.write_str(known_instance.repr(self.db)),
             Type::FunctionLiteral(function) => f.write_str(function.name(self.db)),