diff --git a/toolchain/check/testdata/impl/use_assoc_const.carbon b/toolchain/check/testdata/impl/use_assoc_const.carbon
index c4a88a3cdaee..a8a02fb33a48 100644
--- a/toolchain/check/testdata/impl/use_assoc_const.carbon
+++ b/toolchain/check/testdata/impl/use_assoc_const.carbon
@@ -268,6 +268,31 @@ impl () as I where .N = 2 {
   fn F[self: Self]() -> array(bool, 2) { return (true, false); }
 }
 
+// --- fail_todo_symbolic_associated_type_in_concrete_context.carbon
+
+interface Z {
+  let X:! type;
+}
+
+class C(T:! type) {}
+class D {}
+
+impl forall [T:! type] T as Z where .X = C(T) {}
+
+fn F() {
+  // TODO: `D.(Z.X)` is `C(D)`, but is incorrecty treated only as the symbolic
+  // `C(T)` here which fails to convert.
+
+  // CHECK:STDERR: fail_todo_symbolic_associated_type_in_concrete_context.carbon:[[@LINE+7]]:20: error: cannot implicitly convert value of type `C(D)` to `C(T)` [ImplicitAsConversionFailure]
+  // CHECK:STDERR:   let a: D.(Z.X) = {} as C(D);
+  // CHECK:STDERR:                    ^~~~~~~~~~
+  // CHECK:STDERR: fail_todo_symbolic_associated_type_in_concrete_context.carbon:[[@LINE+4]]:20: note: type `C(D)` does not implement interface `Core.ImplicitAs(C(T))` [MissingImplInMemberAccessNote]
+  // CHECK:STDERR:   let a: D.(Z.X) = {} as C(D);
+  // CHECK:STDERR:                    ^~~~~~~~~~
+  // CHECK:STDERR:
+  let a: D.(Z.X) = {} as C(D);
+}
+
 // CHECK:STDOUT: --- associated_type_in_method_signature.carbon
 // CHECK:STDOUT:
 // CHECK:STDOUT: constants {
@@ -3304,3 +3329,210 @@ impl () as I where .N = 2 {
 // CHECK:STDOUT:   %array_type.loc5_38.1 => constants.%array_type.c9b
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
+// CHECK:STDOUT: --- fail_todo_symbolic_associated_type_in_concrete_context.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %Z.type: type = facet_type <@Z> [concrete]
+// CHECK:STDOUT:   %Self.6e6: %Z.type = bind_symbolic_name Self, 0 [symbolic]
+// CHECK:STDOUT:   %Z.assoc_type: type = assoc_entity_type %Z.type [concrete]
+// CHECK:STDOUT:   %assoc0.e86: %Z.assoc_type = assoc_entity element0, @Z.%X [concrete]
+// CHECK:STDOUT:   %T: type = bind_symbolic_name T, 0 [symbolic]
+// CHECK:STDOUT:   %T.patt: type = symbolic_binding_pattern T, 0 [symbolic]
+// CHECK:STDOUT:   %C.type: type = generic_class_type @C [concrete]
+// CHECK:STDOUT:   %C.generic: %C.type = struct_value () [concrete]
+// CHECK:STDOUT:   %C.f2e: type = class_type @C, @C(%T) [symbolic]
+// CHECK:STDOUT:   %empty_struct_type: type = struct_type {} [concrete]
+// CHECK:STDOUT:   %complete_type.357: <witness> = complete_type_witness %empty_struct_type [concrete]
+// CHECK:STDOUT:   %D: type = class_type @D [concrete]
+// CHECK:STDOUT:   %.Self: %Z.type = bind_symbolic_name .Self [symbolic_self]
+// CHECK:STDOUT:   %.Self.as_type: type = facet_access_type %.Self [symbolic_self]
+// CHECK:STDOUT:   %.Self.as_wit.iface0: <witness> = facet_access_witness %.Self, element0 [symbolic_self]
+// CHECK:STDOUT:   %Z.facet.bf2: %Z.type = facet_value %.Self.as_type, (%.Self.as_wit.iface0) [symbolic_self]
+// CHECK:STDOUT:   %impl.elem0: type = impl_witness_access %.Self.as_wit.iface0, element0 [symbolic_self]
+// CHECK:STDOUT:   %Z_where.type.b30: type = facet_type <@Z where %impl.elem0 = %C.f2e> [symbolic]
+// CHECK:STDOUT:   %require_complete.f02: <witness> = require_complete_type %Z_where.type.b30 [symbolic]
+// CHECK:STDOUT:   %impl_witness.00e: <witness> = impl_witness (%C.f2e), @impl(%T) [symbolic]
+// CHECK:STDOUT:   %F.type: type = fn_type @F [concrete]
+// CHECK:STDOUT:   %F: %F.type = struct_value () [concrete]
+// CHECK:STDOUT:   %C.131: type = class_type @C, @C(%D) [concrete]
+// CHECK:STDOUT:   %Z_where.type.116: type = facet_type <@Z where %impl.elem0 = %C.131> [concrete]
+// CHECK:STDOUT:   %complete_type.fc8: <witness> = complete_type_witness %Z_where.type.116 [concrete]
+// CHECK:STDOUT:   %impl_witness.b6f: <witness> = impl_witness (%C.f2e), @impl(%D) [concrete]
+// CHECK:STDOUT:   %Z.facet.94c: %Z.type = facet_value %D, (%impl_witness.b6f) [concrete]
+// CHECK:STDOUT:   %C.val: %C.131 = struct_value () [concrete]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: imports {
+// CHECK:STDOUT:   %Core: <namespace> = namespace file.%Core.import, [concrete] {
+// CHECK:STDOUT:     .ImplicitAs = %Core.ImplicitAs
+// CHECK:STDOUT:     import Core//prelude
+// CHECK:STDOUT:     import Core//prelude/...
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [concrete] {
+// CHECK:STDOUT:     .Core = imports.%Core
+// CHECK:STDOUT:     .Z = %Z.decl
+// CHECK:STDOUT:     .C = %C.decl
+// CHECK:STDOUT:     .D = %D.decl
+// CHECK:STDOUT:     .F = %F.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Core.import = import Core
+// CHECK:STDOUT:   %Z.decl: type = interface_decl @Z [concrete = constants.%Z.type] {} {}
+// CHECK:STDOUT:   %C.decl: %C.type = class_decl @C [concrete = constants.%C.generic] {
+// CHECK:STDOUT:     %T.patt.loc6_9.1: type = symbolic_binding_pattern T, 0 [symbolic = %T.patt.loc6_9.2 (constants.%T.patt)]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %T.loc6_9.1: type = bind_symbolic_name T, 0 [symbolic = %T.loc6_9.2 (constants.%T)]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %D.decl: type = class_decl @D [concrete = constants.%D] {} {}
+// CHECK:STDOUT:   impl_decl @impl [concrete] {
+// CHECK:STDOUT:     %T.patt.loc9_14.1: type = symbolic_binding_pattern T, 0 [symbolic = %T.patt.loc9_14.2 (constants.%T.patt)]
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %T.ref.loc9_24: type = name_ref T, %T.loc9_14.1 [symbolic = %T.loc9_14.2 (constants.%T)]
+// CHECK:STDOUT:     %Z.ref: type = name_ref Z, file.%Z.decl [concrete = constants.%Z.type]
+// CHECK:STDOUT:     %.Self: %Z.type = bind_symbolic_name .Self [symbolic_self = constants.%.Self]
+// CHECK:STDOUT:     %.Self.ref: %Z.type = name_ref .Self, %.Self [symbolic_self = constants.%.Self]
+// CHECK:STDOUT:     %X.ref: %Z.assoc_type = name_ref X, @X.%assoc0 [concrete = constants.%assoc0.e86]
+// CHECK:STDOUT:     %.Self.as_type: type = facet_access_type %.Self.ref [symbolic_self = constants.%.Self.as_type]
+// CHECK:STDOUT:     %.loc9_37: type = converted %.Self.ref, %.Self.as_type [symbolic_self = constants.%.Self.as_type]
+// CHECK:STDOUT:     %.Self.as_wit.iface0: <witness> = facet_access_witness %.Self.ref, element0 [symbolic_self = constants.%.Self.as_wit.iface0]
+// CHECK:STDOUT:     %impl.elem0: type = impl_witness_access %.Self.as_wit.iface0, element0 [symbolic_self = constants.%impl.elem0]
+// CHECK:STDOUT:     %C.ref: %C.type = name_ref C, file.%C.decl [concrete = constants.%C.generic]
+// CHECK:STDOUT:     %T.ref.loc9_44: type = name_ref T, %T.loc9_14.1 [symbolic = %T.loc9_14.2 (constants.%T)]
+// CHECK:STDOUT:     %C.loc9_45.1: type = class_type @C, @C(constants.%T) [symbolic = %C.loc9_45.2 (constants.%C.f2e)]
+// CHECK:STDOUT:     %.loc9_31: type = where_expr %.Self [symbolic = %Z_where.type (constants.%Z_where.type.b30)] {
+// CHECK:STDOUT:       requirement_rewrite %impl.elem0, %C.loc9_45.1
+// CHECK:STDOUT:     }
+// CHECK:STDOUT:     %T.loc9_14.1: type = bind_symbolic_name T, 0 [symbolic = %T.loc9_14.2 (constants.%T)]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %impl_witness: <witness> = impl_witness (constants.%C.f2e), @impl(constants.%T) [symbolic = @impl.%impl_witness (constants.%impl_witness.00e)]
+// CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [concrete = constants.%F] {} {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: interface @Z {
+// CHECK:STDOUT:   %Self: %Z.type = bind_symbolic_name Self, 0 [symbolic = constants.%Self.6e6]
+// CHECK:STDOUT:   %X: type = assoc_const_decl @X [concrete] {
+// CHECK:STDOUT:     %assoc0: %Z.assoc_type = assoc_entity element0, @Z.%X [concrete = constants.%assoc0.e86]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = %Self
+// CHECK:STDOUT:   .X = @X.%assoc0
+// CHECK:STDOUT:   witness = (%X)
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic assoc_const @X(@Z.%Self: %Z.type) {
+// CHECK:STDOUT:   assoc_const X:! type;
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic impl @impl(%T.loc9_14.1: type) {
+// CHECK:STDOUT:   %T.loc9_14.2: type = bind_symbolic_name T, 0 [symbolic = %T.loc9_14.2 (constants.%T)]
+// CHECK:STDOUT:   %T.patt.loc9_14.2: type = symbolic_binding_pattern T, 0 [symbolic = %T.patt.loc9_14.2 (constants.%T.patt)]
+// CHECK:STDOUT:   %C.loc9_45.2: type = class_type @C, @C(%T.loc9_14.2) [symbolic = %C.loc9_45.2 (constants.%C.f2e)]
+// CHECK:STDOUT:   %Z_where.type: type = facet_type <@Z where constants.%impl.elem0 = %C.loc9_45.2 (constants.%C.f2e)> [symbolic = %Z_where.type (constants.%Z_where.type.b30)]
+// CHECK:STDOUT:   %require_complete: <witness> = require_complete_type @impl.%Z_where.type (%Z_where.type.b30) [symbolic = %require_complete (constants.%require_complete.f02)]
+// CHECK:STDOUT:   %impl_witness: <witness> = impl_witness (constants.%C.f2e), @impl(%T.loc9_14.2) [symbolic = %impl_witness (constants.%impl_witness.00e)]
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT:
+// CHECK:STDOUT:   impl: %T.ref.loc9_24 as %.loc9_31 {
+// CHECK:STDOUT:   !members:
+// CHECK:STDOUT:     witness = file.%impl_witness
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: generic class @C(%T.loc6_9.1: type) {
+// CHECK:STDOUT:   %T.loc6_9.2: type = bind_symbolic_name T, 0 [symbolic = %T.loc6_9.2 (constants.%T)]
+// CHECK:STDOUT:   %T.patt.loc6_9.2: type = symbolic_binding_pattern T, 0 [symbolic = %T.patt.loc6_9.2 (constants.%T.patt)]
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT:
+// CHECK:STDOUT:   class {
+// CHECK:STDOUT:     %complete_type: <witness> = complete_type_witness %empty_struct_type [concrete = constants.%complete_type.357]
+// CHECK:STDOUT:     complete_type_witness = %complete_type
+// CHECK:STDOUT:
+// CHECK:STDOUT:   !members:
+// CHECK:STDOUT:     .Self = constants.%C.f2e
+// CHECK:STDOUT:   }
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: class @D {
+// CHECK:STDOUT:   %complete_type: <witness> = complete_type_witness %empty_struct_type [concrete = constants.%complete_type.357]
+// CHECK:STDOUT:   complete_type_witness = %complete_type
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = constants.%D
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @F() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   name_binding_decl {
+// CHECK:STDOUT:     %a.patt: %C.f2e = binding_pattern a
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc22_21.1: %empty_struct_type = struct_literal ()
+// CHECK:STDOUT:   %C.ref: %C.type = name_ref C, file.%C.decl [concrete = constants.%C.generic]
+// CHECK:STDOUT:   %D.ref.loc22_28: type = name_ref D, file.%D.decl [concrete = constants.%D]
+// CHECK:STDOUT:   %C: type = class_type @C, @C(constants.%D) [concrete = constants.%C.131]
+// CHECK:STDOUT:   %.loc22_21.2: ref %C.131 = temporary_storage
+// CHECK:STDOUT:   %.loc22_21.3: init %C.131 = class_init (), %.loc22_21.2 [concrete = constants.%C.val]
+// CHECK:STDOUT:   %.loc22_21.4: ref %C.131 = temporary %.loc22_21.2, %.loc22_21.3
+// CHECK:STDOUT:   %.loc22_23.1: ref %C.131 = converted %.loc22_21.1, %.loc22_21.4
+// CHECK:STDOUT:   %.loc22_11.1: type = splice_block %impl.elem0 [symbolic = constants.%C.f2e] {
+// CHECK:STDOUT:     %D.ref.loc22_10: type = name_ref D, file.%D.decl [concrete = constants.%D]
+// CHECK:STDOUT:     %Z.ref: type = name_ref Z, file.%Z.decl [concrete = constants.%Z.type]
+// CHECK:STDOUT:     %X.ref: %Z.assoc_type = name_ref X, @X.%assoc0 [concrete = constants.%assoc0.e86]
+// CHECK:STDOUT:     %Z.facet: %Z.type = facet_value constants.%D, (constants.%impl_witness.b6f) [concrete = constants.%Z.facet.94c]
+// CHECK:STDOUT:     %.loc22_11.2: %Z.type = converted %D.ref.loc22_10, %Z.facet [concrete = constants.%Z.facet.94c]
+// CHECK:STDOUT:     %as_wit.iface0: <witness> = facet_access_witness %.loc22_11.2, element0 [concrete = constants.%impl_witness.b6f]
+// CHECK:STDOUT:     %impl.elem0: type = impl_witness_access %as_wit.iface0, element0 [symbolic = constants.%C.f2e]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %.loc22_23.2: %C.f2e = converted %.loc22_23.1, <error> [concrete = <error>]
+// CHECK:STDOUT:   %a: %C.f2e = bind_name a, <error>
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @X(constants.%Self.6e6) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @C(constants.%T) {
+// CHECK:STDOUT:   %T.loc6_9.2 => constants.%T
+// CHECK:STDOUT:   %T.patt.loc6_9.2 => constants.%T
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @X(constants.%Z.facet.bf2) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @impl(constants.%T) {
+// CHECK:STDOUT:   %T.loc9_14.2 => constants.%T
+// CHECK:STDOUT:   %T.patt.loc9_14.2 => constants.%T
+// CHECK:STDOUT:   %C.loc9_45.2 => constants.%C.f2e
+// CHECK:STDOUT:   %Z_where.type => constants.%Z_where.type.b30
+// CHECK:STDOUT:   %require_complete => constants.%require_complete.f02
+// CHECK:STDOUT:   %impl_witness => constants.%impl_witness.00e
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @C(@impl.%T.loc9_14.2) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @impl(%T.loc9_14.2) {}
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @impl(constants.%D) {
+// CHECK:STDOUT:   %T.loc9_14.2 => constants.%D
+// CHECK:STDOUT:   %T.patt.loc9_14.2 => constants.%D
+// CHECK:STDOUT:   %C.loc9_45.2 => constants.%C.131
+// CHECK:STDOUT:   %Z_where.type => constants.%Z_where.type.116
+// CHECK:STDOUT:   %require_complete => constants.%complete_type.fc8
+// CHECK:STDOUT:   %impl_witness => constants.%impl_witness.b6f
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @C(constants.%D) {
+// CHECK:STDOUT:   %T.loc6_9.2 => constants.%D
+// CHECK:STDOUT:   %T.patt.loc6_9.2 => constants.%D
+// CHECK:STDOUT:
+// CHECK:STDOUT: !definition:
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: specific @X(constants.%Z.facet.94c) {}
+// CHECK:STDOUT: