Skip lookup on protocols

Author: sharkdp

crates/red_knot_python_semantic/resources/mdtest/annotations/stdlib_typing_aliases.md

@@ -71,7 +71,7 @@ import typing
 class ListSubclass(typing.List): ...
 
 # TODO: should have `Generic`, should not have `Unknown`
-# revealed: tuple[Literal[ListSubclass], Literal[list], Literal[object]]
+# revealed: tuple[Literal[ListSubclass], Literal[list], Literal[MutableSequence], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
 reveal_type(ListSubclass.__mro__)
 
 class DictSubclass(typing.Dict): ...

crates/red_knot_python_semantic/resources/mdtest/generics.md

@@ -39,7 +39,7 @@ class MySecureBox[T](MyBox[T]): ...
 secure_box: MySecureBox[int] = MySecureBox(5)
 reveal_type(secure_box)  # revealed: MySecureBox
 # TODO reveal int
-reveal_type(secure_box.data)  # revealed: Unknown
+reveal_type(secure_box.data)  # revealed: T
 ```
 
 ## Cyclical class definition

crates/red_knot_python_semantic/resources/mdtest/scopes/moduletype_attrs.md

@@ -9,7 +9,7 @@ is unbound.
 ```py
 reveal_type(__name__)  # revealed: str
 reveal_type(__file__)  # revealed: str | None
-reveal_type(__loader__)  # revealed: @Todo(Support for protocols) | None
+reveal_type(__loader__)  # revealed: LoaderProtocol | None
 reveal_type(__package__)  # revealed: str | None
 reveal_type(__doc__)  # revealed: str | None
 

crates/red_knot_python_semantic/resources/mdtest/stubs/class.md

@@ -13,7 +13,9 @@ class Foo[T]: ...
 class Bar(Foo[Bar]): ...
 
 reveal_type(Bar)  # revealed: Literal[Bar]
-reveal_type(Bar.__mro__)  # revealed: tuple[Literal[Bar], Unknown, Literal[object]]
+
+# TODO: Support for generic `Foo`
+reveal_type(Bar.__mro__)  # revealed: tuple[Literal[Bar], Literal[Foo], Literal[object]]
 ```
 
 ## Access to attributes declarated in stubs

crates/red_knot_python_semantic/resources/mdtest/subscript/tuple.md

@@ -119,5 +119,7 @@ class C(Tuple): ...
 
 # Runtime value: `(C, tuple, typing.Generic, object)`
 # TODO: Add `Generic` to the MRO
-reveal_type(C.__mro__)  # revealed: tuple[Literal[C], Literal[tuple], Literal[object]]
+reveal_type(
+    C.__mro__
+)  # revealed: tuple[Literal[C], Literal[tuple], Literal[Sequence], Literal[Reversible], Literal[Collection], Literal[Iterable], Literal[Container], @Todo(protocol), Literal[object]]
 ```

crates/red_knot_python_semantic/src/types.rs

@@ -3181,6 +3181,8 @@ pub enum DynamicType {
     ///
     /// This variant should be created with the `todo_type!` macro.
     Todo(TodoType),
+    /// Temporary type until we support protocols.
+    TodoProtocol,
 }
 
 impl std::fmt::Display for DynamicType {
@@ -3191,6 +3193,7 @@ impl std::fmt::Display for DynamicType {
             // `DynamicType::Todo`'s display should be explicit that is not a valid display of
             // any other type
             DynamicType::Todo(todo) => write!(f, "@Todo{todo}"),
+            DynamicType::TodoProtocol => f.write_str("@Todo(protocol)"),
         }
     }
 }

crates/red_knot_python_semantic/src/types/class.rs

@@ -9,8 +9,8 @@ use crate::{
         Boundness, LookupError, LookupResult, Symbol, SymbolAndQualifiers,
     },
     types::{
-        definition_expression_type, CallArguments, CallError, MetaclassCandidate, TupleType,
-        UnionBuilder, UnionCallError,
+        definition_expression_type, CallArguments, CallError, DynamicType, MetaclassCandidate,
+        TupleType, UnionBuilder, UnionCallError,
     },
     Db, KnownModule, Program,
 };
@@ -339,6 +339,11 @@ impl<'db> Class<'db> {
 
         for superclass in self.iter_mro(db) {
             match superclass {
+                ClassBase::Dynamic(DynamicType::TodoProtocol) => {
+                    // TODO: We currently skip protocols when looking up class members, in order to
+                    // avoid creating many dynamic types in our test suite that would otherwise
+                    // result from looking up attributes on builtin types like `str`, `list`, `tuple`
+                }
                 ClassBase::Dynamic(_) => {
                     // Note: calling `Type::from(superclass).member()` would be incorrect here.
                     // What we'd really want is a `Type::Any.own_class_member()` method,
@@ -407,6 +412,11 @@ impl<'db> Class<'db> {
 
         for superclass in self.iter_mro(db) {
             match superclass {
+                ClassBase::Dynamic(DynamicType::TodoProtocol) => {
+                    // TODO: We currently skip protocols when looking up instance members, in order to
+                    // avoid creating many dynamic types in our test suite that would otherwise
+                    // result from looking up attributes on builtin types like `str`, `list`, `tuple`
+                }
                 ClassBase::Dynamic(_) => {
                     return SymbolAndQualifiers::todo(
                         "instance attribute on class with dynamic base",

crates/red_knot_python_semantic/src/types/class_base.rs

@@ -144,9 +144,7 @@ impl<'db> ClassBase<'db> {
                 KnownInstanceType::Callable => {
                     Self::try_from_type(db, todo_type!("Support for Callable as a base class"))
                 }
-                KnownInstanceType::Protocol => {
-                    Self::try_from_type(db, todo_type!("Support for protocols"))
-                }
+                KnownInstanceType::Protocol => Some(ClassBase::Dynamic(DynamicType::TodoProtocol)),
             },
         }
     }

crates/red_knot_python_semantic/src/types/infer.rs

@@ -4005,6 +4005,8 @@ impl<'db> TypeInferenceBuilder<'db> {
             | (_, unknown @ Type::Dynamic(DynamicType::Unknown), _) => Some(unknown),
             (todo @ Type::Dynamic(DynamicType::Todo(_)), _, _)
             | (_, todo @ Type::Dynamic(DynamicType::Todo(_)), _) => Some(todo),
+            (todo @ Type::Dynamic(DynamicType::TodoProtocol), _, _)
+            | (_, todo @ Type::Dynamic(DynamicType::TodoProtocol), _) => Some(todo),
             (Type::Never, _, _) | (_, Type::Never, _) => Some(Type::Never),
 
             (Type::IntLiteral(n), Type::IntLiteral(m), ast::Operator::Add) => Some(
@@ -5178,6 +5180,9 @@ impl<'db> TypeInferenceBuilder<'db> {
                 value_ty,
                 Type::IntLiteral(i64::from(bool)),
             ),
+            (Type::KnownInstance(KnownInstanceType::Protocol), _) => {
+                Type::Dynamic(DynamicType::TodoProtocol)
+            }
             (value_ty, slice_ty) => {
                 // If the class defines `__getitem__`, return its return type.
                 //
@@ -5283,7 +5288,13 @@ impl<'db> TypeInferenceBuilder<'db> {
                     );
                 }
 
-                Type::unknown()
+                match value_ty {
+                    Type::ClassLiteral(_) => {
+                        // TODO: proper support for generic classes
+                        value_ty
+                    }
+                    _ => Type::unknown(),
+                }
             }
         }
     }
@@ -6146,7 +6157,7 @@ impl<'db> TypeInferenceBuilder<'db> {
             }
             KnownInstanceType::Protocol => {
                 self.infer_type_expression(arguments_slice);
-                todo_type!("Generic protocol")
+                Type::Dynamic(DynamicType::TodoProtocol)
             }
             KnownInstanceType::NoReturn
             | KnownInstanceType::Never

crates/red_knot_python_semantic/src/types/type_ordering.rs

@@ -288,5 +288,8 @@ fn dynamic_elements_ordering(left: DynamicType, right: DynamicType) -> Ordering
 
         #[cfg(not(debug_assertions))]
         (DynamicType::Todo(TodoType), DynamicType::Todo(TodoType)) => Ordering::Equal,
+
+        (DynamicType::TodoProtocol, _) => Ordering::Less,
+        (_, DynamicType::TodoProtocol) => Ordering::Greater,
     }
 }