Associated constants can be used in member function signatures (#5089)

This required allowing incomplete facet types where previously
completeness was required. Once we support named constraints, we will
need a way to consistently go from an interface to a facet type witness
index without requiring the interface to be complete in these cases.

---------

Co-authored-by: Josh L <[email protected]>

Author: josh11b

toolchain/check/convert.cpp

@@ -1148,7 +1148,10 @@ auto Convert(Context& context, SemIR::LocId loc_id, SemIR::InstId expr_id,
     return SemIR::ErrorInst::SingletonInstId;
   }
 
-  // We can only perform initialization for complete, non-abstract types.
+  // We can only perform initialization for complete, non-abstract types. Note
+  // that `RequireConcreteType` returns true for facet types, since their
+  // representation is fixed. This allows us to support using the `Self` of an
+  // interface inside its definition.
   if (!RequireConcreteType(
           context, target.type_id, loc_id,
           [&] {

toolchain/check/handle_interface.cpp

@@ -154,6 +154,9 @@ auto HandleParseNode(Context& context,
   interface_info.definition_id = interface_decl_id;
   interface_info.scope_id = context.name_scopes().Add(
       interface_decl_id, SemIR::NameId::None, interface_info.parent_scope_id);
+  context.name_scopes()
+      .Get(interface_info.scope_id)
+      .set_is_interface_definition();
 
   auto self_specific_id =
       context.generics().GetSelfSpecific(interface_info.generic_id);

toolchain/check/impl_lookup.cpp

@@ -165,28 +165,17 @@ static auto FindAndDiagnoseImplLookupCycle(
 static auto GetInterfacesFromConstantId(
     Context& context, SemIR::ConstantId query_facet_type_const_id,
     bool& has_other_requirements)
-    -> llvm::SmallVector<SemIR::CompleteFacetType::RequiredInterface> {
-  // The `query_facet_type_const_id` is a constant value for some facet type. We
-  // do this long chain of steps to go from that constant value to the
-  // `FacetTypeId` found on the `FacetType` instruction of this constant value,
-  // and finally to the `CompleteFacetType`.
+    -> llvm::SmallVector<SemIR::SpecificInterface> {
   auto facet_type_inst_id =
       context.constant_values().GetInstId(query_facet_type_const_id);
   auto facet_type_inst =
       context.insts().GetAs<SemIR::FacetType>(facet_type_inst_id);
-  auto facet_type_id = facet_type_inst.facet_type_id;
-  auto complete_facet_type_id =
-      context.complete_facet_types().TryGetId(facet_type_id);
-  // The facet type will already be completed before coming here. If we're
-  // converting from a concrete type to a facet type, the conversion step
-  // requires everything to be complete before doing impl lookup.
-  CARBON_CHECK(complete_facet_type_id.has_value());
-  const auto& complete_facet_type =
-      context.complete_facet_types().Get(complete_facet_type_id);
-
-  has_other_requirements =
-      context.facet_types().Get(facet_type_id).other_requirements;
-  return complete_facet_type.required_interfaces;
+  const auto& facet_type_info =
+      context.facet_types().Get(facet_type_inst.facet_type_id);
+  has_other_requirements = facet_type_info.other_requirements;
+  // TODO: Once we add support for named constraints, we will need to change
+  // this to return the same interfaces as in the complete facet type.
+  return facet_type_info.impls_constraints;
 }
 
 static auto GetWitnessIdForImpl(
@@ -257,23 +246,20 @@ static auto GetWitnessIdForImpl(
       context.insts()
           .GetAs<SemIR::FacetType>(deduced_constraint_id)
           .facet_type_id;
-  const auto& deduced_constraint_complete_facet_type =
-      context.complete_facet_types().Get(
-          context.complete_facet_types().TryGetId(
-              deduced_constraint_facet_type_id));
-  CARBON_CHECK(deduced_constraint_complete_facet_type.num_to_impl == 1);
-
-  if (context.facet_types()
-          .Get(deduced_constraint_facet_type_id)
-          .other_requirements) {
+  const auto& deduced_constraint_facet_type_info =
+      context.facet_types().Get(deduced_constraint_facet_type_id);
+  CARBON_CHECK(deduced_constraint_facet_type_info.impls_constraints.size() ==
+               1);
+
+  if (deduced_constraint_facet_type_info.other_requirements) {
     // TODO: Remove this when other requirements goes away.
     return SemIR::InstId::None;
   }
 
   // The specifics in the queried interface must match the deduced specifics in
   // the impl's constraint facet type.
   auto impl_interface_specific_id =
-      deduced_constraint_complete_facet_type.required_interfaces[0].specific_id;
+      deduced_constraint_facet_type_info.impls_constraints[0].specific_id;
   auto query_interface_specific_id = interface.specific_id;
   if (impl_interface_specific_id != query_interface_specific_id) {
     return SemIR::InstId::None;

toolchain/check/import_ref.cpp

@@ -2314,6 +2314,7 @@ static auto AddInterfaceDefinition(ImportContext& context,
       new_interface.first_owning_decl_id, SemIR::NameId::None,
       new_interface.parent_scope_id);
   auto& new_scope = context.local_name_scopes().Get(new_interface.scope_id);
+  new_scope.set_is_interface_definition();
   const auto& import_scope =
       context.import_name_scopes().Get(import_interface.scope_id);
 

toolchain/check/member_access.cpp

@@ -568,10 +568,6 @@ auto PerformCompoundMemberAccess(Context& context, SemIR::LocId loc_id,
     auto interface_type = GetInterfaceFromFacetType(context, interface_type_id);
     // An associated entity is always associated with a single interface.
     CARBON_CHECK(interface_type);
-    const auto& interface =
-        context.interfaces().Get(interface_type->interface_id);
-    auto assoc_entities =
-        context.inst_blocks().Get(interface.associated_entities_id);
     auto value_inst_id = context.constant_values().GetConstantInstId(member_id);
     // TODO: According to
     // https://docs.carbon-lang.dev/docs/design/expressions/member_access.html#member-resolution
@@ -584,7 +580,7 @@ auto PerformCompoundMemberAccess(Context& context, SemIR::LocId loc_id,
     }
     auto assoc_entity =
         context.insts().GetAs<SemIR::AssociatedEntity>(value_inst_id);
-    auto decl_id = assoc_entities[assoc_entity.index.index];
+    auto decl_id = assoc_entity.decl_id;
     LoadImportRef(context, decl_id);
     auto decl_value_id = context.constant_values().GetConstantInstId(decl_id);
     auto decl_type_id = context.insts().Get(decl_value_id).type_id();

toolchain/check/name_lookup.cpp

@@ -8,6 +8,7 @@
 #include "toolchain/check/import.h"
 #include "toolchain/check/import_cpp.h"
 #include "toolchain/check/import_ref.h"
+#include "toolchain/check/member_access.h"
 #include "toolchain/check/type_completion.h"
 #include "toolchain/diagnostics/format_providers.h"
 #include "toolchain/sem_ir/name_scope.h"
@@ -101,6 +102,27 @@ auto LookupUnqualifiedName(Context& context, Parse::NodeId node_id,
                                             .specific_id = specific_id},
                                 /*required=*/false);
         non_lexical_result.scope_result.is_found()) {
+      // In an interface definition, replace associated entity `M` with
+      // `Self.M` (where the `Self` is the `Self` of the interface).
+      const auto& scope = context.name_scopes().Get(lookup_scope_id);
+      if (scope.is_interface_definition()) {
+        SemIR::InstId target_inst_id =
+            non_lexical_result.scope_result.target_inst_id();
+        if (context.types().Is<SemIR::AssociatedEntityType>(
+                context.insts().Get(target_inst_id).type_id())) {
+          auto interface_decl =
+              context.insts().GetAs<SemIR::InterfaceDecl>(scope.inst_id());
+          const auto& interface =
+              context.interfaces().Get(interface_decl.interface_id);
+          // TODO: Refactor the code so that we can call the "no instance
+          // binding" case from `PerformCompoundMemberAccess` as a separate
+          // function (`GetAssociatedValue`).
+          SemIR::InstId result_inst_id = PerformCompoundMemberAccess(
+              context, node_id, interface.self_param_id, target_inst_id);
+          non_lexical_result.scope_result = SemIR::ScopeLookupResult::MakeFound(
+              result_inst_id, non_lexical_result.scope_result.access_kind());
+        }
+      }
       return non_lexical_result;
     }
   }

toolchain/check/testdata/builtin_conversions/min_prelude/convert_facet_value_to_narrowed_facet_type.carbon

@@ -78,7 +78,6 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %BitAnd.assoc_type: type = assoc_entity_type %BitAnd.type [concrete]
 // CHECK:STDOUT:   %assoc0: %BitAnd.assoc_type = assoc_entity element0, imports.%Core.import_ref.a93 [concrete]
 // CHECK:STDOUT:   %Op.type.27a: type = fn_type @Op.1 [concrete]
-// CHECK:STDOUT:   %Op.ab9: %Op.type.27a = struct_value () [concrete]
 // CHECK:STDOUT:   %Self.as_type: type = facet_access_type %Self.25f [symbolic]
 // CHECK:STDOUT:   %T.8b3: type = bind_symbolic_name T, 0 [symbolic]
 // CHECK:STDOUT:   %T.patt.e01: type = symbolic_binding_pattern T, 0 [symbolic]
@@ -115,7 +114,7 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import_ref.ad0 = import_ref Core//prelude, inst100 [no loc], unloaded
 // CHECK:STDOUT:   %Core.import_ref.08d: %BitAnd.assoc_type = import_ref Core//prelude, loc18_41, loaded [concrete = constants.%assoc0]
-// CHECK:STDOUT:   %Core.Op: %Op.type.27a = import_ref Core//prelude, Op, loaded [concrete = constants.%Op.ab9]
+// CHECK:STDOUT:   %Core.Op = import_ref Core//prelude, Op, unloaded
 // CHECK:STDOUT:   %Core.import_ref.040: %BitAnd.type = import_ref Core//prelude, inst100 [no loc], loaded [symbolic = constants.%Self.25f]
 // CHECK:STDOUT:   %Core.import_ref.51c: <witness> = import_ref Core//prelude, loc21_36, loaded [symbolic = @impl.%impl_witness (constants.%impl_witness.b81)]
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.1: type = import_ref Core//prelude, loc21_14, loaded [symbolic = @impl.%T (constants.%T.8b3)]
@@ -345,7 +344,6 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %BitAnd.assoc_type: type = assoc_entity_type %BitAnd.type [concrete]
 // CHECK:STDOUT:   %assoc0: %BitAnd.assoc_type = assoc_entity element0, imports.%Core.import_ref.a93 [concrete]
 // CHECK:STDOUT:   %Op.type.27a: type = fn_type @Op.1 [concrete]
-// CHECK:STDOUT:   %Op.ab9: %Op.type.27a = struct_value () [concrete]
 // CHECK:STDOUT:   %Self.as_type: type = facet_access_type %Self.25f [symbolic]
 // CHECK:STDOUT:   %T: type = bind_symbolic_name T, 0 [symbolic]
 // CHECK:STDOUT:   %T.patt: type = symbolic_binding_pattern T, 0 [symbolic]
@@ -395,7 +393,7 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import_ref.ad0 = import_ref Core//prelude, inst100 [no loc], unloaded
 // CHECK:STDOUT:   %Core.import_ref.08d: %BitAnd.assoc_type = import_ref Core//prelude, loc18_41, loaded [concrete = constants.%assoc0]
-// CHECK:STDOUT:   %Core.Op: %Op.type.27a = import_ref Core//prelude, Op, loaded [concrete = constants.%Op.ab9]
+// CHECK:STDOUT:   %Core.Op = import_ref Core//prelude, Op, unloaded
 // CHECK:STDOUT:   %Core.import_ref.040: %BitAnd.type = import_ref Core//prelude, inst100 [no loc], loaded [symbolic = constants.%Self.25f]
 // CHECK:STDOUT:   %Core.import_ref.51c: <witness> = import_ref Core//prelude, loc21_36, loaded [symbolic = @impl.%impl_witness (constants.%impl_witness.b81)]
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.1: type = import_ref Core//prelude, loc21_14, loaded [symbolic = @impl.%T (constants.%T)]
@@ -659,7 +657,6 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %BitAnd.assoc_type: type = assoc_entity_type %BitAnd.type [concrete]
 // CHECK:STDOUT:   %assoc0.a63: %BitAnd.assoc_type = assoc_entity element0, imports.%Core.import_ref.a93 [concrete]
 // CHECK:STDOUT:   %Op.type.27a: type = fn_type @Op.1 [concrete]
-// CHECK:STDOUT:   %Op.ab9: %Op.type.27a = struct_value () [concrete]
 // CHECK:STDOUT:   %Self.as_type.19f: type = facet_access_type %Self.25f [symbolic]
 // CHECK:STDOUT:   %T: type = bind_symbolic_name T, 0 [symbolic]
 // CHECK:STDOUT:   %T.patt: type = symbolic_binding_pattern T, 0 [symbolic]
@@ -704,13 +701,13 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %Convert.42e: %Convert.type.275 = struct_value () [symbolic]
 // CHECK:STDOUT:   %Self.as_type.40a: type = facet_access_type %Self.519 [symbolic]
 // CHECK:STDOUT:   %ImplicitAs.assoc_type.837: type = assoc_entity_type %ImplicitAs.type.d62 [symbolic]
-// CHECK:STDOUT:   %assoc0.43db8b.1: %ImplicitAs.assoc_type.837 = assoc_entity element0, imports.%Core.import_ref.207961.1 [symbolic]
+// CHECK:STDOUT:   %assoc0.02f: %ImplicitAs.assoc_type.837 = assoc_entity element0, imports.%Core.import_ref.1c7 [symbolic]
 // CHECK:STDOUT:   %ImplicitAs.type.dbb: type = facet_type <@ImplicitAs, @ImplicitAs(%facet_type.6ff)> [concrete]
 // CHECK:STDOUT:   %Convert.type.bd1: type = fn_type @Convert, @ImplicitAs(%facet_type.6ff) [concrete]
 // CHECK:STDOUT:   %Convert.af7: %Convert.type.bd1 = struct_value () [concrete]
 // CHECK:STDOUT:   %ImplicitAs.assoc_type.f1b: type = assoc_entity_type %ImplicitAs.type.dbb [concrete]
-// CHECK:STDOUT:   %assoc0.976: %ImplicitAs.assoc_type.f1b = assoc_entity element0, imports.%Core.import_ref.207961.1 [concrete]
-// CHECK:STDOUT:   %assoc0.43db8b.2: %ImplicitAs.assoc_type.837 = assoc_entity element0, imports.%Core.import_ref.207961.2 [symbolic]
+// CHECK:STDOUT:   %assoc0.15b: %ImplicitAs.assoc_type.f1b = assoc_entity element0, imports.%Core.import_ref.1c7 [concrete]
+// CHECK:STDOUT:   %assoc0.43d: %ImplicitAs.assoc_type.837 = assoc_entity element0, imports.%Core.import_ref.207 [symbolic]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: imports {
@@ -721,7 +718,7 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:   %Core.import_ref.ad0 = import_ref Core//prelude, inst100 [no loc], unloaded
 // CHECK:STDOUT:   %Core.import_ref.08d: %BitAnd.assoc_type = import_ref Core//prelude, loc18_41, loaded [concrete = constants.%assoc0.a63]
-// CHECK:STDOUT:   %Core.Op: %Op.type.27a = import_ref Core//prelude, Op, loaded [concrete = constants.%Op.ab9]
+// CHECK:STDOUT:   %Core.Op = import_ref Core//prelude, Op, unloaded
 // CHECK:STDOUT:   %Core.import_ref.040: %BitAnd.type = import_ref Core//prelude, inst100 [no loc], loaded [symbolic = constants.%Self.25f]
 // CHECK:STDOUT:   %Core.import_ref.51c: <witness> = import_ref Core//prelude, loc21_36, loaded [symbolic = @impl.f92.%impl_witness (constants.%impl_witness.b81)]
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.1: type = import_ref Core//prelude, loc21_14, loaded [symbolic = @impl.f92.%T (constants.%T)]
@@ -731,11 +728,11 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.2: type = import_ref Core//prelude, loc21_14, loaded [symbolic = @impl.f92.%T (constants.%T)]
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.3: type = import_ref Core//prelude, loc13_22, loaded [symbolic = @ImplicitAs.%Dest (constants.%Dest)]
 // CHECK:STDOUT:   %Core.import_ref.ff5 = import_ref Core//prelude, inst65 [no loc], unloaded
-// CHECK:STDOUT:   %Core.import_ref.630: @ImplicitAs.%ImplicitAs.assoc_type (%ImplicitAs.assoc_type.837) = import_ref Core//prelude, loc14_35, loaded [symbolic = @ImplicitAs.%assoc0 (constants.%assoc0.43db8b.2)]
-// CHECK:STDOUT:   %Core.Convert: @ImplicitAs.%Convert.type (%Convert.type.275) = import_ref Core//prelude, Convert, loaded [symbolic = @ImplicitAs.%Convert (constants.%Convert.42e)]
+// CHECK:STDOUT:   %Core.import_ref.630: @ImplicitAs.%ImplicitAs.assoc_type (%ImplicitAs.assoc_type.837) = import_ref Core//prelude, loc14_35, loaded [symbolic = @ImplicitAs.%assoc0 (constants.%assoc0.43d)]
+// CHECK:STDOUT:   %Core.Convert = import_ref Core//prelude, Convert, unloaded
 // CHECK:STDOUT:   %Core.import_ref.5ab3ec.4: type = import_ref Core//prelude, loc13_22, loaded [symbolic = @ImplicitAs.%Dest (constants.%Dest)]
 // CHECK:STDOUT:   %Core.import_ref.ce1: @ImplicitAs.%ImplicitAs.type (%ImplicitAs.type.d62) = import_ref Core//prelude, inst65 [no loc], loaded [symbolic = @ImplicitAs.%Self (constants.%Self.519)]
-// CHECK:STDOUT:   %Core.import_ref.207961.1 = import_ref Core//prelude, loc14_35, unloaded
+// CHECK:STDOUT:   %Core.import_ref.1c7: @ImplicitAs.%Convert.type (%Convert.type.275) = import_ref Core//prelude, loc14_35, loaded [symbolic = @ImplicitAs.%Convert (constants.%Convert.42e)]
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: file {
@@ -855,7 +852,7 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %Convert.type: type = fn_type @Convert, @ImplicitAs(%Dest) [symbolic = %Convert.type (constants.%Convert.type.275)]
 // CHECK:STDOUT:   %Convert: @ImplicitAs.%Convert.type (%Convert.type.275) = struct_value () [symbolic = %Convert (constants.%Convert.42e)]
 // CHECK:STDOUT:   %ImplicitAs.assoc_type: type = assoc_entity_type @ImplicitAs.%ImplicitAs.type (%ImplicitAs.type.d62) [symbolic = %ImplicitAs.assoc_type (constants.%ImplicitAs.assoc_type.837)]
-// CHECK:STDOUT:   %assoc0: @ImplicitAs.%ImplicitAs.assoc_type (%ImplicitAs.assoc_type.837) = assoc_entity element0, imports.%Core.import_ref.207961.1 [symbolic = %assoc0 (constants.%assoc0.43db8b.1)]
+// CHECK:STDOUT:   %assoc0: @ImplicitAs.%ImplicitAs.assoc_type (%ImplicitAs.assoc_type.837) = assoc_entity element0, imports.%Core.import_ref.1c7 [symbolic = %assoc0 (constants.%assoc0.02f)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   interface {
 // CHECK:STDOUT:   !members:
@@ -1050,7 +1047,7 @@ fn HandleTameAnimal2[W:! Animal & Tame](w: W) {
 // CHECK:STDOUT:   %Convert.type => constants.%Convert.type.bd1
 // CHECK:STDOUT:   %Convert => constants.%Convert.af7
 // CHECK:STDOUT:   %ImplicitAs.assoc_type => constants.%ImplicitAs.assoc_type.f1b
-// CHECK:STDOUT:   %assoc0 => constants.%assoc0.976
+// CHECK:STDOUT:   %assoc0 => constants.%assoc0.15b
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- toolchain/testing/min_prelude/facet_types.carbon