Allow incomplete types in associated constants (#6657)

Reference: #1084, [Example of declaring interfaces with cyclic
references](https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/generics/details.md#example-of-declaring-interfaces-with-cyclic-references).
Part of #6411: "Associated constants shouldn't have to be complete".

toolchain/check/handle_binding_pattern.cpp

@@ -366,13 +366,6 @@ auto HandleParseNode(Context& context,
     // add a proper diagnostic.
     context.TODO(node_id, "_ used as associated constant name");
   }
-  cast_type_id = AsCompleteType(context, cast_type_id, type_node, [&] {
-    CARBON_DIAGNOSTIC(IncompleteTypeInAssociatedConstantDecl, Error,
-                      "associated constant has incomplete type {0}",
-                      SemIR::TypeId);
-    return context.emitter().Build(
-        type_node, IncompleteTypeInAssociatedConstantDecl, cast_type_id);
-  });
 
   SemIR::AssociatedConstantDecl assoc_const_decl = {
       .type_id = cast_type_id,

toolchain/check/testdata/facet/facet_assoc_const.carbon

@@ -471,76 +471,39 @@ interface N {
 
 fn F(T:! N where .Y1 = () and .Y2 = .Y1 and .Y2 = .Self.Y1) { }
 
-// --- fail_todo_cycle_through_self_reference.carbon
+// --- fail_cycle_through_self_reference.carbon
 library "[[@TEST_NAME]]";
 
 interface Z {
   let T:! type;
-  // TODO: This should not be an error.
-  //
-  // CHECK:STDERR: fail_todo_cycle_through_self_reference.carbon:[[@LINE+7]]:11: error: associated constant has incomplete type `Z` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let U:! Z;
-  // CHECK:STDERR:           ^
-  // CHECK:STDERR: fail_todo_cycle_through_self_reference.carbon:[[@LINE-7]]:1: note: interface is currently being defined [InterfaceIncompleteWithinDefinition]
-  // CHECK:STDERR: interface Z {
-  // CHECK:STDERR: ^~~~~~~~~~~~~
-  // CHECK:STDERR:
   let U:! Z;
 }
 
-// TODO: Should be diagnosed as a cycle.
+// CHECK:STDERR: fail_cycle_through_self_reference.carbon:[[@LINE+4]]:10: error: found cycle in facet type constraint for `.(Z.T)` [FacetTypeConstraintCycle]
+// CHECK:STDERR: fn F(A:! Z where .T = .U.T and .U = .Self) {}
+// CHECK:STDERR:          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+// CHECK:STDERR:
 fn F(A:! Z where .T = .U.T and .U = .Self) {}
 
-// --- fail_todo_reference_same_constant_in_different_self.carbon
+// --- reference_same_constant_in_different_self.carbon
 library "[[@TEST_NAME]]";
 
 interface Z {
   let T:! type;
-  // TODO: This should not be an error.
-  //
-  // CHECK:STDERR: fail_todo_reference_same_constant_in_different_self.carbon:[[@LINE+7]]:11: error: associated constant has incomplete type `Z` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let U:! Z;
-  // CHECK:STDERR:           ^
-  // CHECK:STDERR: fail_todo_reference_same_constant_in_different_self.carbon:[[@LINE-7]]:1: note: interface is currently being defined [InterfaceIncompleteWithinDefinition]
-  // CHECK:STDERR: interface Z {
-  // CHECK:STDERR: ^~~~~~~~~~~~~
-  // CHECK:STDERR:
   let U:! Z;
 }
 
-// TODO: Should not be diagnosed as a cycle, once the incorrect failure above is
-// fixed.
 fn F(A:! Z where .T = (), B:! Z where .T = .U.T and .U = A) {}
 
-// --- fail_todo_non_cycle_with_self_reference.carbon
+// --- non_cycle_with_self_reference.carbon
 library "[[@TEST_NAME]]";
 
 interface Z {
-  // TODO: This should not be an error.
-  //
-  // CHECK:STDERR: fail_todo_non_cycle_with_self_reference.carbon:[[@LINE+7]]:11: error: associated constant has incomplete type `Z` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let T:! Z;
-  // CHECK:STDERR:           ^
-  // CHECK:STDERR: fail_todo_non_cycle_with_self_reference.carbon:[[@LINE-6]]:1: note: interface is currently being defined [InterfaceIncompleteWithinDefinition]
-  // CHECK:STDERR: interface Z {
-  // CHECK:STDERR: ^~~~~~~~~~~~~
-  // CHECK:STDERR:
-  let T:! Z;
+  let T:! type;
   let U:! type;
-  // TODO: This should not be an error.
-  //
-  // CHECK:STDERR: fail_todo_non_cycle_with_self_reference.carbon:[[@LINE+7]]:11: error: associated constant has incomplete type `Z` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let V:! Z;
-  // CHECK:STDERR:           ^
-  // CHECK:STDERR: fail_todo_non_cycle_with_self_reference.carbon:[[@LINE-17]]:1: note: interface is currently being defined [InterfaceIncompleteWithinDefinition]
-  // CHECK:STDERR: interface Z {
-  // CHECK:STDERR: ^~~~~~~~~~~~~
-  // CHECK:STDERR:
   let V:! Z;
 }
 
-// TODO: Should not be diagnosed as a cycle, once the incorrect failure above is
-// fixed.
 fn F(A:! Z where .T = .V.U and .V = .Self and .U = ()) -> A.T {
   return ();
 }

toolchain/check/testdata/facet/validate_rewrite_constraints.carbon

@@ -698,25 +698,16 @@ fn G(U:! I where .X1 = {} and .X2 = (), T:! I where .X1 = U.X2 and .X2 = {}) {
   F(U, T);
 }
 
-// --- fail_todo_value_through_self_value.carbon
+// --- value_through_self_value.carbon
 library "[[@TEST_NAME]]";
 
 interface I {
-  // TODO: This should not be diagnosed.
-  //
-  // CHECK:STDERR: fail_todo_value_through_self_value.carbon:[[@LINE+7]]:12: error: associated constant has incomplete type `I` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let X1:! I;
-  // CHECK:STDERR:            ^
-  // CHECK:STDERR: fail_todo_value_through_self_value.carbon:[[@LINE-6]]:1: note: interface is currently being defined [InterfaceIncompleteWithinDefinition]
-  // CHECK:STDERR: interface I {
-  // CHECK:STDERR: ^~~~~~~~~~~~~
-  // CHECK:STDERR:
   let X1:! I;
   let X2:! type;
   let X3:! type;
 }
 
-fn F(T:! I where .X1 = .Self and .X2 = .X1.X3 and .X3 = ());
+fn F(T:! I where .X1 = .Self and .X2 = .X1.X3 and .X3 = ()) {}
 
 fn G(T:! I where .X1 = .Self and .X2 = () and .X3 = ()) {
   F(T);

toolchain/check/testdata/impl/assoc_const_self.carbon

@@ -106,7 +106,6 @@ fn CallF() {
 // CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %Self.ab9: %I.type = symbolic_binding Self, 0 [symbolic]
 // CHECK:STDOUT:   %Self.binding.as_type.d31: type = symbolic_binding_type Self, 0, %Self.ab9 [symbolic]
-// CHECK:STDOUT:   %require_complete.4df: <witness> = require_complete_type %Self.binding.as_type.d31 [symbolic]
 // CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
 // CHECK:STDOUT:   %assoc0.8a1: %I.assoc_type = assoc_entity element0, @I.%V [concrete]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
@@ -114,12 +113,10 @@ fn CallF() {
 // CHECK:STDOUT:   %.Self: %I.type = symbolic_binding .Self [symbolic_self]
 // CHECK:STDOUT:   %.Self.binding.as_type: type = symbolic_binding_type .Self, %.Self [symbolic_self]
 // CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self, @I [symbolic_self]
-// CHECK:STDOUT:   %require_complete.716: <witness> = require_complete_type %.Self.binding.as_type [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %.Self.binding.as_type = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
 // CHECK:STDOUT:   %I_where.type.ec3: type = facet_type <@I where %impl.elem0 = %empty_struct> [concrete]
 // CHECK:STDOUT:   %I.impl_witness.df7: <witness> = impl_witness @empty_struct_type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %I.facet.47f: %I.type = facet_value %empty_struct_type, (%I.impl_witness.df7) [concrete]
-// CHECK:STDOUT:   %complete_type.357: <witness> = complete_type_witness %empty_struct_type [concrete]
 // CHECK:STDOUT:   %int_32: Core.IntLiteral = int_value 32 [concrete]
 // CHECK:STDOUT:   %Int.type: type = generic_class_type @Int [concrete]
 // CHECK:STDOUT:   %Int.generic: %Int.type = struct_value () [concrete]
@@ -128,8 +125,6 @@ fn CallF() {
 // CHECK:STDOUT:   %I_where.type.b52: type = facet_type <@I where %impl.elem0 = %int_0.5c6> [concrete]
 // CHECK:STDOUT:   %I.impl_witness.550: <witness> = impl_witness @i32.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %I.facet.608: %I.type = facet_value %i32, (%I.impl_witness.550) [concrete]
-// CHECK:STDOUT:   %i32.builtin: type = int_type signed, %int_32 [concrete]
-// CHECK:STDOUT:   %complete_type.f8a: <witness> = complete_type_witness %i32.builtin [concrete]
 // CHECK:STDOUT:   %ImplicitAs.type.cc7: type = generic_interface_type @ImplicitAs [concrete]
 // CHECK:STDOUT:   %ImplicitAs.generic: %ImplicitAs.type.cc7 = struct_value () [concrete]
 // CHECK:STDOUT:   %ImplicitAs.type.e8c: type = facet_type <@ImplicitAs, @ImplicitAs(%i32)> [concrete]
@@ -221,7 +216,6 @@ fn CallF() {
 // CHECK:STDOUT: generic assoc_const @V(@I.%Self: %I.type) {
 // CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = %Self (constants.%Self.ab9)]
 // CHECK:STDOUT:   %Self.binding.as_type: type = symbolic_binding_type Self, 0, %Self [symbolic = %Self.binding.as_type (constants.%Self.binding.as_type.d31)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %Self.binding.as_type [symbolic = %require_complete (constants.%require_complete.4df)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const V:! @V.%Self.binding.as_type (%Self.binding.as_type.d31);
 // CHECK:STDOUT: }
@@ -254,25 +248,21 @@ fn CallF() {
 // CHECK:STDOUT: specific @V(constants.%Self.ab9) {
 // CHECK:STDOUT:   %Self => constants.%Self.ab9
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%Self.binding.as_type.d31
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.4df
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%.Self) {
 // CHECK:STDOUT:   %Self => constants.%.Self
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%.Self.binding.as_type
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.716
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%I.facet.47f) {
 // CHECK:STDOUT:   %Self => constants.%I.facet.47f
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%empty_struct_type
-// CHECK:STDOUT:   %require_complete => constants.%complete_type.357
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%I.facet.608) {
 // CHECK:STDOUT:   %Self => constants.%I.facet.608
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%i32
-// CHECK:STDOUT:   %require_complete => constants.%complete_type.f8a
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_assoc_const_mismatch.carbon
@@ -281,7 +271,6 @@ fn CallF() {
 // CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %Self.ab9: %I.type = symbolic_binding Self, 0 [symbolic]
 // CHECK:STDOUT:   %Self.binding.as_type.d31: type = symbolic_binding_type Self, 0, %Self.ab9 [symbolic]
-// CHECK:STDOUT:   %require_complete.4df: <witness> = require_complete_type %Self.binding.as_type.d31 [symbolic]
 // CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
 // CHECK:STDOUT:   %assoc0.8a1: %I.assoc_type = assoc_entity element0, @I.%V [concrete]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
@@ -289,13 +278,11 @@ fn CallF() {
 // CHECK:STDOUT:   %.Self: %I.type = symbolic_binding .Self [symbolic_self]
 // CHECK:STDOUT:   %.Self.binding.as_type: type = symbolic_binding_type .Self, %.Self [symbolic_self]
 // CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self, @I [symbolic_self]
-// CHECK:STDOUT:   %require_complete.716: <witness> = require_complete_type %.Self.binding.as_type [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %.Self.binding.as_type = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
 // CHECK:STDOUT:   %int_0: Core.IntLiteral = int_value 0 [concrete]
 // CHECK:STDOUT:   %I_where.type: type = facet_type <@I where %impl.elem0 = %int_0> [concrete]
 // CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @empty_struct_type.as.I.impl.%I.impl_witness_table [concrete]
 // CHECK:STDOUT:   %I.facet: %I.type = facet_value %empty_struct_type, (%I.impl_witness) [concrete]
-// CHECK:STDOUT:   %complete_type: <witness> = complete_type_witness %empty_struct_type [concrete]
 // CHECK:STDOUT:   %ImplicitAs.type.cc7: type = generic_interface_type @ImplicitAs [concrete]
 // CHECK:STDOUT:   %ImplicitAs.generic: %ImplicitAs.type.cc7 = struct_value () [concrete]
 // CHECK:STDOUT: }
@@ -351,7 +338,6 @@ fn CallF() {
 // CHECK:STDOUT: generic assoc_const @V(@I.%Self: %I.type) {
 // CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = %Self (constants.%Self.ab9)]
 // CHECK:STDOUT:   %Self.binding.as_type: type = symbolic_binding_type Self, 0, %Self [symbolic = %Self.binding.as_type (constants.%Self.binding.as_type.d31)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %Self.binding.as_type [symbolic = %require_complete (constants.%require_complete.4df)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const V:! @V.%Self.binding.as_type (%Self.binding.as_type.d31);
 // CHECK:STDOUT: }
@@ -369,19 +355,16 @@ fn CallF() {
 // CHECK:STDOUT: specific @V(constants.%Self.ab9) {
 // CHECK:STDOUT:   %Self => constants.%Self.ab9
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%Self.binding.as_type.d31
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.4df
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%.Self) {
 // CHECK:STDOUT:   %Self => constants.%.Self
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%.Self.binding.as_type
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.716
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%I.facet) {
 // CHECK:STDOUT:   %Self => constants.%I.facet
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%empty_struct_type
-// CHECK:STDOUT:   %require_complete => constants.%complete_type
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_assoc_const_not_constant_after_conversion.carbon
@@ -390,7 +373,6 @@ fn CallF() {
 // CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %Self.ab9: %I.type = symbolic_binding Self, 0 [symbolic]
 // CHECK:STDOUT:   %Self.binding.as_type.d31: type = symbolic_binding_type Self, 0, %Self.ab9 [symbolic]
-// CHECK:STDOUT:   %require_complete.4df: <witness> = require_complete_type %Self.binding.as_type.d31 [symbolic]
 // CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
 // CHECK:STDOUT:   %assoc0.8a1: %I.assoc_type = assoc_entity element0, @I.%V [concrete]
 // CHECK:STDOUT:   %C: type = class_type @C [concrete]
@@ -414,7 +396,6 @@ fn CallF() {
 // CHECK:STDOUT:   %.Self: %I.type = symbolic_binding .Self [symbolic_self]
 // CHECK:STDOUT:   %.Self.binding.as_type: type = symbolic_binding_type .Self, %.Self [symbolic_self]
 // CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self, @I [symbolic_self]
-// CHECK:STDOUT:   %require_complete.716: <witness> = require_complete_type %.Self.binding.as_type [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %.Self.binding.as_type = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
 // CHECK:STDOUT:   %I_where.type: type = facet_type <@I where %impl.elem0 = %empty_tuple> [concrete]
 // CHECK:STDOUT:   %I.impl_witness: <witness> = impl_witness @C.as.I.impl.%I.impl_witness_table [concrete]
@@ -485,7 +466,6 @@ fn CallF() {
 // CHECK:STDOUT: generic assoc_const @V(@I.%Self: %I.type) {
 // CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = %Self (constants.%Self.ab9)]
 // CHECK:STDOUT:   %Self.binding.as_type: type = symbolic_binding_type Self, 0, %Self [symbolic = %Self.binding.as_type (constants.%Self.binding.as_type.d31)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %Self.binding.as_type [symbolic = %require_complete (constants.%require_complete.4df)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const V:! @V.%Self.binding.as_type (%Self.binding.as_type.d31);
 // CHECK:STDOUT: }
@@ -552,19 +532,16 @@ fn CallF() {
 // CHECK:STDOUT: specific @V(constants.%Self.ab9) {
 // CHECK:STDOUT:   %Self => constants.%Self.ab9
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%Self.binding.as_type.d31
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.4df
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%.Self) {
 // CHECK:STDOUT:   %Self => constants.%.Self
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%.Self.binding.as_type
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.716
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%I.facet) {
 // CHECK:STDOUT:   %Self => constants.%I.facet
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%C
-// CHECK:STDOUT:   %require_complete => constants.%complete_type
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_monomorphization_failure.carbon
@@ -583,7 +560,6 @@ fn CallF() {
 // CHECK:STDOUT:   %Self.cad: %I.type.68b = symbolic_binding Self, 1 [symbolic]
 // CHECK:STDOUT:   %Self.binding.as_type.6f3: type = symbolic_binding_type Self, 1, %Self.cad [symbolic]
 // CHECK:STDOUT:   %array_type: type = array_type %N, %Self.binding.as_type.6f3 [symbolic]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %array_type [symbolic]
 // CHECK:STDOUT:   %I.assoc_type.223: type = assoc_entity_type @I, @I(%N) [symbolic]
 // CHECK:STDOUT:   %assoc0.e69: %I.assoc_type.223 = assoc_entity element0, @I.%V [symbolic]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
@@ -698,7 +674,6 @@ fn CallF() {
 // CHECK:STDOUT:   %Self: @V.%I.type (%I.type.68b) = symbolic_binding Self, 1 [symbolic = %Self (constants.%Self.cad)]
 // CHECK:STDOUT:   %Self.binding.as_type: type = symbolic_binding_type Self, 1, %Self [symbolic = %Self.binding.as_type (constants.%Self.binding.as_type.6f3)]
 // CHECK:STDOUT:   %array_type: type = array_type %N, %Self.binding.as_type [symbolic = %array_type (constants.%array_type)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %array_type [symbolic = %require_complete (constants.%require_complete)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const V:! @V.%array_type (%array_type);
 // CHECK:STDOUT: }
@@ -718,7 +693,6 @@ fn CallF() {
 // CHECK:STDOUT:   %Self => constants.%Self.cad
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%Self.binding.as_type.6f3
 // CHECK:STDOUT:   %array_type => constants.%array_type
-// CHECK:STDOUT:   %require_complete => constants.%require_complete
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @I(constants.%int_-1) {
@@ -737,7 +711,6 @@ fn CallF() {
 // CHECK:STDOUT:   %Self => constants.%.Self.6e0
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%.Self.binding.as_type
 // CHECK:STDOUT:   %array_type => <error>
-// CHECK:STDOUT:   %require_complete => <error>
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_todo_constrained_fn.carbon
@@ -746,7 +719,6 @@ fn CallF() {
 // CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
 // CHECK:STDOUT:   %Self.ab9: %I.type = symbolic_binding Self, 0 [symbolic]
 // CHECK:STDOUT:   %Self.binding.as_type.d31: type = symbolic_binding_type Self, 0, %Self.ab9 [symbolic]
-// CHECK:STDOUT:   %require_complete.4df: <witness> = require_complete_type %Self.binding.as_type.d31 [symbolic]
 // CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
 // CHECK:STDOUT:   %assoc0.8a1: %I.assoc_type = assoc_entity element0, @I.%V [concrete]
 // CHECK:STDOUT:   %type: type = facet_type <type> [concrete]
@@ -759,7 +731,6 @@ fn CallF() {
 // CHECK:STDOUT:   %.Self.binding.as_type: type = symbolic_binding_type .Self, %.Self.1dc [symbolic_self]
 // CHECK:STDOUT:   %ImplicitAs.type.d65: type = facet_type <@ImplicitAs, @ImplicitAs(%.Self.binding.as_type)> [symbolic_self]
 // CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self.1dc, @I [symbolic_self]
-// CHECK:STDOUT:   %require_complete.716: <witness> = require_complete_type %.Self.binding.as_type [symbolic_self]
 // CHECK:STDOUT:   %impl.elem0: %.Self.binding.as_type = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
 // CHECK:STDOUT:   %I_where.type: type = facet_type <@I where %impl.elem0 = %empty_struct and TODO> [concrete]
 // CHECK:STDOUT:   %T: %I_where.type = symbolic_binding T, 0 [symbolic]
@@ -839,7 +810,6 @@ fn CallF() {
 // CHECK:STDOUT: generic assoc_const @V(@I.%Self: %I.type) {
 // CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = %Self (constants.%Self.ab9)]
 // CHECK:STDOUT:   %Self.binding.as_type: type = symbolic_binding_type Self, 0, %Self [symbolic = %Self.binding.as_type (constants.%Self.binding.as_type.d31)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %Self.binding.as_type [symbolic = %require_complete (constants.%require_complete.4df)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const V:! @V.%Self.binding.as_type (%Self.binding.as_type.d31);
 // CHECK:STDOUT: }
@@ -860,13 +830,11 @@ fn CallF() {
 // CHECK:STDOUT: specific @V(constants.%Self.ab9) {
 // CHECK:STDOUT:   %Self => constants.%Self.ab9
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%Self.binding.as_type.d31
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.4df
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @V(constants.%.Self.1dc) {
 // CHECK:STDOUT:   %Self => constants.%.Self.1dc
 // CHECK:STDOUT:   %Self.binding.as_type => constants.%.Self.binding.as_type
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.716
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @F(constants.%T) {

toolchain/check/testdata/impl/import_interface_assoc_const.carbon

@@ -218,7 +218,7 @@ impl CD as IF where .F = 0 {
 // CHECK:STDOUT:   %NonType.type: type = facet_type <@NonType> [concrete]
 // CHECK:STDOUT:   %Self.13f: %NonType.type = symbolic_binding Self, 0 [symbolic]
 // CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
-// CHECK:STDOUT:   %struct_type.a.225: type = struct_type {.a: %empty_struct_type} [concrete]
+// CHECK:STDOUT:   %struct_type.a: type = struct_type {.a: %empty_struct_type} [concrete]
 // CHECK:STDOUT:   %NonType.assoc_type: type = assoc_entity_type @NonType [concrete]
 // CHECK:STDOUT:   %assoc0.b16: %NonType.assoc_type = assoc_entity element0, @NonType.%Y [concrete]
 // CHECK:STDOUT: }
@@ -272,7 +272,7 @@ impl CD as IF where .F = 0 {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @NonType {
 // CHECK:STDOUT:   %Self: %NonType.type = symbolic_binding Self, 0 [symbolic = constants.%Self.13f]
-// CHECK:STDOUT:   %Y: %struct_type.a.225 = assoc_const_decl @Y [concrete] {
+// CHECK:STDOUT:   %Y: %struct_type.a = assoc_const_decl @Y [concrete] {
 // CHECK:STDOUT:     %assoc0: %NonType.assoc_type = assoc_entity element0, @NonType.%Y [concrete = constants.%assoc0.b16]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
@@ -301,7 +301,7 @@ impl CD as IF where .F = 0 {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: generic assoc_const @Y(@NonType.%Self: %NonType.type) {
-// CHECK:STDOUT:   assoc_const Y:! %struct_type.a.225;
+// CHECK:STDOUT:   assoc_const Y:! %struct_type.a;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @T(constants.%Self.ab9) {}

toolchain/check/testdata/interface/incomplete.carbon

@@ -12,20 +12,51 @@
 // TIP: To dump output, run:
 // TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/interface/incomplete.carbon
 
-// --- fail_incomplete_type.carbon
+// --- incomplete_type.carbon
 library "[[@TEST_NAME]]";
 
 class C;
 
 interface I {
-  // CHECK:STDERR: fail_incomplete_type.carbon:[[@LINE+7]]:11: error: associated constant has incomplete type `C` [IncompleteTypeInAssociatedConstantDecl]
-  // CHECK:STDERR:   let T:! C;
-  // CHECK:STDERR:           ^
-  // CHECK:STDERR: fail_incomplete_type.carbon:[[@LINE-6]]:1: note: class was forward declared here [ClassForwardDeclaredHere]
+  let T:! C;
+}
+
+// --- fail_incomplete_type_impl.carbon
+library "[[@TEST_NAME]]";
+
+class C;
+
+interface I {
+  let T:! C;
+}
+
+// CHECK:STDERR: fail_incomplete_type_impl.carbon:[[@LINE+7]]:26: error: invalid use of incomplete type `C` [IncompleteTypeInConversion]
+// CHECK:STDERR: impl {} as I where .T = ({} as C) {}
+// CHECK:STDERR:                          ^~~~~~~
+// CHECK:STDERR: fail_incomplete_type_impl.carbon:[[@LINE-9]]:1: note: class was forward declared here [ClassForwardDeclaredHere]
+// CHECK:STDERR: class C;
+// CHECK:STDERR: ^~~~~~~~
+// CHECK:STDERR:
+impl {} as I where .T = ({} as C) {}
+
+// --- fail_incomplete_type_usage.carbon
+library "[[@TEST_NAME]]";
+
+class C;
+
+interface I {
+  let T:! C;
+}
+
+fn F[U:! I](a: U) {
+  // CHECK:STDERR: fail_incomplete_type_usage.carbon:[[@LINE+7]]:3: error: invalid use of incomplete type `C` [IncompleteTypeInConversion]
+  // CHECK:STDERR:   a.T;
+  // CHECK:STDERR:   ^~~
+  // CHECK:STDERR: fail_incomplete_type_usage.carbon:[[@LINE-10]]:1: note: class was forward declared here [ClassForwardDeclaredHere]
   // CHECK:STDERR: class C;
   // CHECK:STDERR: ^~~~~~~~
   // CHECK:STDERR:
-  let T:! C;
+  a.T;
 }
 
 // --- fail_incomplete_extend_constraint.carbon
@@ -72,7 +103,7 @@ interface A(T:! type) {
   extend require impls A({});
 }
 
-// CHECK:STDOUT: --- fail_incomplete_type.carbon
+// CHECK:STDOUT: --- incomplete_type.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
 // CHECK:STDOUT:   %C: type = class_type @C [concrete]
@@ -93,7 +124,7 @@ interface A(T:! type) {
 // CHECK:STDOUT:
 // CHECK:STDOUT: interface @I {
 // CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = constants.%Self]
-// CHECK:STDOUT:   %T: <error> = assoc_const_decl @T [concrete] {
+// CHECK:STDOUT:   %T: %C = assoc_const_decl @T [concrete] {
 // CHECK:STDOUT:     %assoc0: %I.assoc_type = assoc_entity element0, @I.%T [concrete = constants.%assoc0]
 // CHECK:STDOUT:   }
 // CHECK:STDOUT:
@@ -107,13 +138,184 @@ interface A(T:! type) {
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: generic assoc_const @T(@I.%Self: %I.type) {
-// CHECK:STDOUT:   assoc_const T:! <error>;
+// CHECK:STDOUT:   assoc_const T:! %C;
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: class @C;
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @T(constants.%Self) {}
 // CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_incomplete_type_impl.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %C: type = class_type @C [concrete]
+// CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
+// CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic]
+// CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
+// CHECK:STDOUT:   %assoc0: %I.assoc_type = assoc_entity element0, @I.%T [concrete]
+// CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
+// CHECK:STDOUT:   %empty_struct: %empty_struct_type = struct_value () [concrete]
+// CHECK:STDOUT:   %.Self: %I.type = symbolic_binding .Self [symbolic_self]
+// CHECK:STDOUT:   %.Self.binding.as_type: type = symbolic_binding_type .Self, %.Self [symbolic_self]
+// CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self, @I [symbolic_self]
+// CHECK:STDOUT:   %impl.elem0: %C = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [concrete] {
+// CHECK:STDOUT:     .C = %C.decl
+// CHECK:STDOUT:     .I = %I.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %C.decl: type = class_decl @C [concrete = constants.%C] {} {}
+// CHECK:STDOUT:   %I.decl: type = interface_decl @I [concrete = constants.%I.type] {} {}
+// CHECK:STDOUT:   impl_decl @empty_struct_type.as.<error>.impl [concrete] {} {
+// CHECK:STDOUT:     %.loc16_7.1: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:     %.loc16_7.2: type = converted %.loc16_7.1, constants.%empty_struct_type [concrete = constants.%empty_struct_type]
+// CHECK:STDOUT:     %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
+// CHECK:STDOUT:     %.Self: %I.type = symbolic_binding .Self [symbolic_self = constants.%.Self]
+// CHECK:STDOUT:     %.Self.ref: %I.type = name_ref .Self, %.Self [symbolic_self = constants.%.Self]
+// CHECK:STDOUT:     %.Self.as_type: type = facet_access_type %.Self.ref [symbolic_self = constants.%.Self.binding.as_type]
+// CHECK:STDOUT:     %.loc16_20: type = converted %.Self.ref, %.Self.as_type [symbolic_self = constants.%.Self.binding.as_type]
+// CHECK:STDOUT:     %T.ref: %I.assoc_type = name_ref T, @T.%assoc0 [concrete = constants.%assoc0]
+// CHECK:STDOUT:     %impl.elem0: %C = impl_witness_access constants.%I.lookup_impl_witness, element0 [symbolic_self = constants.%impl.elem0]
+// CHECK:STDOUT:     %.loc16_27: %empty_struct_type = struct_literal () [concrete = constants.%empty_struct]
+// CHECK:STDOUT:     %C.ref: type = name_ref C, file.%C.decl [concrete = constants.%C]
+// CHECK:STDOUT:     %.loc16_14: type = where_expr %.Self [concrete = <error>] {
+// CHECK:STDOUT:       requirement_base_facet_type constants.%I.type
+// CHECK:STDOUT:       requirement_rewrite %impl.elem0, <error>
+// CHECK:STDOUT:     }
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: interface @I {
+// CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = constants.%Self]
+// CHECK:STDOUT:   %T: %C = assoc_const_decl @T [concrete] {
+// CHECK:STDOUT:     %assoc0: %I.assoc_type = assoc_entity element0, @I.%T [concrete = constants.%assoc0]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = %Self
+// CHECK:STDOUT:   .C = <poisoned>
+// CHECK:STDOUT:   .T = @T.%assoc0
+// CHECK:STDOUT:   witness = (%T)
+// CHECK:STDOUT:
+// CHECK:STDOUT: !requires:
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic assoc_const @T(@I.%Self: %I.type) {
+// CHECK:STDOUT:   assoc_const T:! %C;
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: impl @empty_struct_type.as.<error>.impl: %.loc16_7.2 as %.loc16_14 {
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   witness = <error>
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: class @C;
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @T(constants.%Self) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @T(constants.%.Self) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_incomplete_type_usage.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %C: type = class_type @C [concrete]
+// CHECK:STDOUT:   %I.type: type = facet_type <@I> [concrete]
+// CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic]
+// CHECK:STDOUT:   %I.assoc_type: type = assoc_entity_type @I [concrete]
+// CHECK:STDOUT:   %assoc0: %I.assoc_type = assoc_entity element0, @I.%T [concrete]
+// CHECK:STDOUT:   %type: type = facet_type <type> [concrete]
+// CHECK:STDOUT:   %.Self: %type = symbolic_binding .Self [symbolic_self]
+// CHECK:STDOUT:   %U: %I.type = symbolic_binding U, 0 [symbolic]
+// CHECK:STDOUT:   %pattern_type.9d9: type = pattern_type %I.type [concrete]
+// CHECK:STDOUT:   %U.binding.as_type: type = symbolic_binding_type U, 0, %U [symbolic]
+// CHECK:STDOUT:   %pattern_type.422: type = pattern_type %U.binding.as_type [symbolic]
+// CHECK:STDOUT:   %F.type: type = fn_type @F [concrete]
+// CHECK:STDOUT:   %F: %F.type = struct_value () [concrete]
+// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %U.binding.as_type [symbolic]
+// CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %U, @I [symbolic]
+// CHECK:STDOUT:   %impl.elem0: %C = impl_witness_access %I.lookup_impl_witness, element0 [symbolic]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [concrete] {
+// CHECK:STDOUT:     .C = %C.decl
+// CHECK:STDOUT:     .I = %I.decl
+// CHECK:STDOUT:     .F = %F.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %C.decl: type = class_decl @C [concrete = constants.%C] {} {}
+// CHECK:STDOUT:   %I.decl: type = interface_decl @I [concrete = constants.%I.type] {} {}
+// CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [concrete = constants.%F] {
+// CHECK:STDOUT:     %U.patt: %pattern_type.9d9 = symbolic_binding_pattern U, 0 [concrete]
+// CHECK:STDOUT:     %a.patt: @F.%pattern_type (%pattern_type.422) = value_binding_pattern a [concrete]
+// CHECK:STDOUT:     %a.param_patt: @F.%pattern_type (%pattern_type.422) = value_param_pattern %a.patt, call_param0 [concrete]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %.loc9_10: type = splice_block %I.ref [concrete = constants.%I.type] {
+// CHECK:STDOUT:       %.Self: %type = symbolic_binding .Self [symbolic_self = constants.%.Self]
+// CHECK:STDOUT:       %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
+// CHECK:STDOUT:     }
+// CHECK:STDOUT:     %U.loc9_6.2: %I.type = symbolic_binding U, 0 [symbolic = %U.loc9_6.1 (constants.%U)]
+// CHECK:STDOUT:     %a.param: @F.%U.binding.as_type (%U.binding.as_type) = value_param call_param0
+// CHECK:STDOUT:     %.loc9_16.1: type = splice_block %.loc9_16.2 [symbolic = %U.binding.as_type (constants.%U.binding.as_type)] {
+// CHECK:STDOUT:       %U.ref: %I.type = name_ref U, %U.loc9_6.2 [symbolic = %U.loc9_6.1 (constants.%U)]
+// CHECK:STDOUT:       %U.as_type: type = facet_access_type %U.ref [symbolic = %U.binding.as_type (constants.%U.binding.as_type)]
+// CHECK:STDOUT:       %.loc9_16.2: type = converted %U.ref, %U.as_type [symbolic = %U.binding.as_type (constants.%U.binding.as_type)]
+// CHECK:STDOUT:     }
+// CHECK:STDOUT:     %a: @F.%U.binding.as_type (%U.binding.as_type) = value_binding a, %a.param
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: interface @I {
+// CHECK:STDOUT:   %Self: %I.type = symbolic_binding Self, 0 [symbolic = constants.%Self]
+// CHECK:STDOUT:   %T: %C = assoc_const_decl @T [concrete] {
+// CHECK:STDOUT:     %assoc0: %I.assoc_type = assoc_entity element0, @I.%T [concrete = constants.%assoc0]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = %Self
+// CHECK:STDOUT:   .C = <poisoned>
+// CHECK:STDOUT:   .T = @T.%assoc0
+// CHECK:STDOUT:   witness = (%T)
+// CHECK:STDOUT:
+// CHECK:STDOUT: !requires:
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic assoc_const @T(@I.%Self: %I.type) {
+// CHECK:STDOUT:   assoc_const T:! %C;
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: class @C;
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic fn @F(%U.loc9_6.2: %I.type) {
+// CHECK:STDOUT:   %U.loc9_6.1: %I.type = symbolic_binding U, 0 [symbolic = %U.loc9_6.1 (constants.%U)]
+// CHECK:STDOUT:   %U.binding.as_type: type = symbolic_binding_type U, 0, %U.loc9_6.1 [symbolic = %U.binding.as_type (constants.%U.binding.as_type)]
+// CHECK:STDOUT:   %pattern_type: type = pattern_type %U.binding.as_type [symbolic = %pattern_type (constants.%pattern_type.422)]
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %U.binding.as_type [symbolic = %require_complete (constants.%require_complete)]
+// CHECK:STDOUT:   %I.lookup_impl_witness: <witness> = lookup_impl_witness %U.loc9_6.1, @I [symbolic = %I.lookup_impl_witness (constants.%I.lookup_impl_witness)]
+// CHECK:STDOUT:   %impl.elem0.loc17_4.2: %C = impl_witness_access %I.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc17_4.2 (constants.%impl.elem0)]
+// CHECK:STDOUT:
+// CHECK:STDOUT:   fn(%a.param: @F.%U.binding.as_type (%U.binding.as_type)) {
+// CHECK:STDOUT:   !entry:
+// CHECK:STDOUT:     %a.ref: @F.%U.binding.as_type (%U.binding.as_type) = name_ref a, %a
+// CHECK:STDOUT:     %T.ref: %I.assoc_type = name_ref T, @T.%assoc0 [concrete = constants.%assoc0]
+// CHECK:STDOUT:     %impl.elem0.loc17_4.1: %C = impl_witness_access constants.%I.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc17_4.2 (constants.%impl.elem0)]
+// CHECK:STDOUT:     return
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @T(constants.%Self) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @F(constants.%U) {
+// CHECK:STDOUT:   %U.loc9_6.1 => constants.%U
+// CHECK:STDOUT:   %U.binding.as_type => constants.%U.binding.as_type
+// CHECK:STDOUT:   %pattern_type => constants.%pattern_type.422
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @T(constants.%U) {}
+// CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_incomplete_extend_constraint.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {

toolchain/check/testdata/interface/member_lookup.carbon

@@ -64,7 +64,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT:   %Interface.type.442: type = facet_type <@Interface, @Interface(%T.67d)> [symbolic]
 // CHECK:STDOUT:   %Self.ade: %Interface.type.442 = symbolic_binding Self, 1 [symbolic]
 // CHECK:STDOUT:   %ptr.e8f: type = ptr_type %T.67d [symbolic]
-// CHECK:STDOUT:   %require_complete.ef1: <witness> = require_complete_type %ptr.e8f [symbolic]
 // CHECK:STDOUT:   %Interface.assoc_type.5a2: type = assoc_entity_type @Interface, @Interface(%T.67d) [symbolic]
 // CHECK:STDOUT:   %assoc0.624: %Interface.assoc_type.5a2 = assoc_entity element0, @Interface.%X [symbolic]
 // CHECK:STDOUT:   %I.682: %Interface.type.442 = symbolic_binding I, 1 [symbolic]
@@ -73,6 +72,7 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT:   %pattern_type.4f4: type = pattern_type %ptr.e8f [symbolic]
 // CHECK:STDOUT:   %AccessGeneric.type: type = fn_type @AccessGeneric [concrete]
 // CHECK:STDOUT:   %AccessGeneric: %AccessGeneric.type = struct_value () [concrete]
+// CHECK:STDOUT:   %require_complete.ef1: <witness> = require_complete_type %ptr.e8f [symbolic]
 // CHECK:STDOUT:   %require_complete.46e: <witness> = require_complete_type %Interface.type.442 [symbolic]
 // CHECK:STDOUT:   %I.binding.as_type.24f: type = symbolic_binding_type I, 1, %I.682 [symbolic]
 // CHECK:STDOUT:   %Interface.lookup_impl_witness.9f1: <witness> = lookup_impl_witness %I.682, @Interface, @Interface(%T.67d) [symbolic]
@@ -106,7 +106,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT:   %assoc0.2ec: %Interface.assoc_type.77f = assoc_entity element0, @Interface.%X [concrete]
 // CHECK:STDOUT:   %I.binding.as_type.78a: type = symbolic_binding_type I, 0, %I.50d [symbolic]
 // CHECK:STDOUT:   %Interface.lookup_impl_witness.4be: <witness> = lookup_impl_witness %I.50d, @Interface, @Interface(%i32) [symbolic]
-// CHECK:STDOUT:   %complete_type.3d0: <witness> = complete_type_witness %ptr.235 [concrete]
 // CHECK:STDOUT:   %impl.elem0.322: %ptr.235 = impl_witness_access %Interface.lookup_impl_witness.4be, element0 [symbolic]
 // CHECK:STDOUT:   %Copy.impl_witness.843: <witness> = impl_witness imports.%Copy.impl_witness_table.c3a, @ptr.as.Copy.impl(%i32) [concrete]
 // CHECK:STDOUT:   %ptr.as.Copy.impl.Op.type.c3c: type = fn_type @ptr.as.Copy.impl.Op, @ptr.as.Copy.impl(%i32) [concrete]
@@ -216,7 +215,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: generic assoc_const @X(@Interface.%T.loc4_21.2: type, @Interface.%Self.loc4_31.1: @Interface.%Interface.type (%Interface.type.442)) {
 // CHECK:STDOUT:   %T: type = symbolic_binding T, 0 [symbolic = %T (constants.%T.67d)]
 // CHECK:STDOUT:   %ptr: type = ptr_type %T [symbolic = %ptr (constants.%ptr.e8f)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %ptr [symbolic = %require_complete (constants.%require_complete.ef1)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const X:! @X.%ptr (%ptr.e8f);
 // CHECK:STDOUT: }
@@ -304,7 +302,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: specific @X(constants.%T.67d, constants.%Self.ade) {
 // CHECK:STDOUT:   %T => constants.%T.67d
 // CHECK:STDOUT:   %ptr => constants.%ptr.e8f
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.ef1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @AccessGeneric(constants.%T.67d, constants.%I.682) {
@@ -320,7 +317,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: specific @X(constants.%T.67d, constants.%I.682) {
 // CHECK:STDOUT:   %T => constants.%T.67d
 // CHECK:STDOUT:   %ptr => constants.%ptr.e8f
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.ef1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @Interface(constants.%i32) {
@@ -340,7 +336,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: specific @X(constants.%i32, constants.%I.50d) {
 // CHECK:STDOUT:   %T => constants.%i32
 // CHECK:STDOUT:   %ptr => constants.%ptr.235
-// CHECK:STDOUT:   %require_complete => constants.%complete_type.3d0
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: --- fail_no_member.carbon
@@ -355,7 +350,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT:   %Interface.type.442: type = facet_type <@Interface, @Interface(%T)> [symbolic]
 // CHECK:STDOUT:   %Self.ade: %Interface.type.442 = symbolic_binding Self, 1 [symbolic]
 // CHECK:STDOUT:   %ptr: type = ptr_type %T [symbolic]
-// CHECK:STDOUT:   %require_complete.ef1: <witness> = require_complete_type %ptr [symbolic]
 // CHECK:STDOUT:   %Interface.assoc_type.5a2: type = assoc_entity_type @Interface, @Interface(%T) [symbolic]
 // CHECK:STDOUT:   %assoc0.624: %Interface.assoc_type.5a2 = assoc_entity element0, @Interface.%X [symbolic]
 // CHECK:STDOUT:   %I.682: %Interface.type.442 = symbolic_binding I, 1 [symbolic]
@@ -477,7 +471,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: generic assoc_const @X(@Interface.%T.loc4_21.2: type, @Interface.%Self.loc4_31.1: @Interface.%Interface.type (%Interface.type.442)) {
 // CHECK:STDOUT:   %T: type = symbolic_binding T, 0 [symbolic = %T (constants.%T)]
 // CHECK:STDOUT:   %ptr: type = ptr_type %T [symbolic = %ptr (constants.%ptr)]
-// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type %ptr [symbolic = %require_complete (constants.%require_complete.ef1)]
 // CHECK:STDOUT:
 // CHECK:STDOUT:   assoc_const X:! @X.%ptr (%ptr);
 // CHECK:STDOUT: }
@@ -534,7 +527,6 @@ fn AccessMissingConcrete(I:! Interface(i32)) -> i32 {
 // CHECK:STDOUT: specific @X(constants.%T, constants.%Self.ade) {
 // CHECK:STDOUT:   %T => constants.%T
 // CHECK:STDOUT:   %ptr => constants.%ptr
-// CHECK:STDOUT:   %require_complete => constants.%require_complete.ef1
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: specific @AccessMissingGeneric(constants.%T, constants.%I.682) {

toolchain/diagnostics/diagnostic_kind.def

@@ -435,7 +435,6 @@ CARBON_DIAGNOSTIC_KIND(NameUseBeforeDecl)
 CARBON_DIAGNOSTIC_KIND(NameUseBeforeDeclNote)
 CARBON_DIAGNOSTIC_KIND(RepeatedConst)
 CARBON_DIAGNOSTIC_KIND(IncompleteTypeInAdaptDecl)
-CARBON_DIAGNOSTIC_KIND(IncompleteTypeInAssociatedConstantDecl)
 CARBON_DIAGNOSTIC_KIND(IncompleteTypeInBaseDecl)
 CARBON_DIAGNOSTIC_KIND(IncompleteTypeInBindingDecl)
 CARBON_DIAGNOSTIC_KIND(IncompleteTypeInConversion)