interfaces, impls, and constrained generics (basics) (#1073)

* interfaces, impls, and constrained generics (basics) * separate type checking into declare vs. type check, removing redundancy * external impls * added impl scopes to handle generics calling generics * cleanup * more cleanup * Update executable_semantics/testdata/interface/external_impl_point_vector.carbon Co-authored-by: josh11b <josh11b@users.noreply.github.com> * Update executable_semantics/testdata/interface/generic_call_generic.carbon Co-authored-by: josh11b <josh11b@users.noreply.github.com> * Update executable_semantics/testdata/interface/tuple_vector_add_scale.carbon Co-authored-by: josh11b <josh11b@users.noreply.github.com> * Update executable_semantics/testdata/interface/vector_point_add_scale.carbon Co-authored-by: josh11b <josh11b@users.noreply.github.com> * change ImplementationDeclaration to ImplDeclaration * remove impl_type_value * split NamedEntity into two * changed GetName to be a free function * adding comments * more edits to respond to review * introduce ImplBinding, remove punning on GenericBinding * new test case and some minor edits * refactor GetMember and GetField to move impl logic to interpreter * remove commennt * change EntityView to ImplBinding in FieldAccess... * move ImplBinding * review response * added example to impl_scope.h * minor edits * Update executable_semantics/interpreter/field_path.h Co-authored-by: Geoff Romer <gromer@google.com> * Update executable_semantics/interpreter/value.cpp Co-authored-by: Geoff Romer <gromer@google.com> * Update executable_semantics/interpreter/interpreter.cpp Co-authored-by: Geoff Romer <gromer@google.com> * Update executable_semantics/ast/expression.h Co-authored-by: Geoff Romer <gromer@google.com> * Update executable_semantics/ast/expression.h Co-authored-by: Geoff Romer <gromer@google.com> * Update executable_semantics/ast/generic_binding.h Co-authored-by: Geoff Romer <gromer@google.com> * more edits from review * review response * Update executable_semantics/ast/static_scope.h Co-authored-by: Geoff Romer <gromer@google.com> * remove ImplType, renamed node_view to value_node Co-authored-by: josh11b <josh11b@users.noreply.github.com> Co-authored-by: Geoff Romer <gromer@google.com>
2026-10-03 22:02:51 +01:00 · 2022-03-02 15:58:45 -05:00
parent 8f6e42d866
commit 7cce1bd124
43 changed files with 1722 additions and 441 deletions
@@ -0,0 +1,83 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef EXECUTABLE_SEMANTICS_AST_IMPL_SCOPE_H_
+#define EXECUTABLE_SEMANTICS_AST_IMPL_SCOPE_H_
+
+#include "executable_semantics/ast/declaration.h"
+
+namespace Carbon {
+
+class Value;
+
+// The `ImplScope` class is responsible for mapping a type and
+// interface to the location of the witness table for the `impl` for
+// that type and interface.  A scope may have parent scopes, whose
+// impls will also be visible in the child scope.
+//
+// There is typically one instance of `ImplScope` class per scope
+// because the impls that are visible for a given type and interface
+// can vary from scope to scope. For example, consider the `bar` and
+// `baz` methods in the following class C and nested class D.
+//
+//     class C(U:! Type, T:! Type)  {
+//       class D(V:! Type where U is Fooable(T)) {
+//         fn bar[me: Self](x: U, y : T) -> T{
+//           return x.foo(y)
+//         }
+//       }
+//       fn baz[me: Self](x: U, y : T) -> T {
+//         return x.foo(y);
+//       }
+//     }
+//
+//  The call to `x.foo` in `bar` is valid because the `U is Fooable(T)`
+//  impl is visible in the body of `bar`. In contrast, the call to
+//  `x.foo` in `baz` is not valid because there is no visible impl for
+//  `U` and `Fooable` in that scope.
+class ImplScope {
+ public:
+  // Associates `iface` and `type` with the `impl` in this scope.
+  void Add(Nonnull<const Value*> iface, Nonnull<const Value*> type,
+           ValueNodeView impl);
+
+  // Make `parent` a parent of this scope.
+  // REQUIRES: `parent` is not already a parent of this scope.
+  void AddParent(Nonnull<const ImplScope*> parent);
+
+  // Returns the associated impl for the given `iface` and `type` in
+  // the ancestor graph of this scope, or reports a compilation error
+  // at `source_loc` there isn't exactly one matching impl.
+  auto Resolve(Nonnull<const Value*> iface, Nonnull<const Value*> type,
+               SourceLocation source_loc) const -> ValueNodeView;
+
+ private:
+  auto TryResolve(Nonnull<const Value*> iface_type, Nonnull<const Value*> type,
+                  SourceLocation source_loc) const
+      -> std::optional<ValueNodeView>;
+  auto ResolveHere(Nonnull<const Value*> iface_type,
+                   Nonnull<const Value*> impl_type,
+                   SourceLocation source_loc) const
+      -> std::optional<ValueNodeView>;
+
+  // The `Impl` struct is a key-value pair where the key is the
+  // combination of a type and an interface, e.g., `List` and `Container`,
+  // and the value is the result of statically resolving to the `impl`
+  // for `List` as `Container`, which is an `ValueNodeView`. The generality
+  // of `ValueNodeView` is needed (not just `ImplDeclaration`) because
+  // inside a generic, we need to map, e.g., from `T` and `Container` to the
+  // witness table that is passed into the generic.
+  struct Impl {
+    Nonnull<const Value*> interface;
+    Nonnull<const Value*> type;
+    ValueNodeView impl;
+  };
+
+  std::vector<Impl> impls_;
+  std::vector<Nonnull<const ImplScope*>> parent_scopes_;
+};
+
+}  // namespace Carbon
+
+#endif  // EXECUTABLE_SEMANTICS_AST_IMPL_SCOPE_H_