Don't treat dependent types as having a copy value representation. (#6055)

Add `Dependent` value and initializing representations for types whose
representations are unknown because they are dependent. When generating
SemIR in such cases, use a worst-case initializing representation that
both provides a destination address and also propagates a potential
result value.

Use this to fix incorrect lowering and lowering crashes for specific
functions involving generic types that don't use a copy value
representation.

In lowering, be careful to distinguish between whether the initializing
representation for the generic return type uses a return slot (which
affects whether the SemIR declaration and call have one) and whether the
initializing representation for the specific return type uses a return
slot (which affects whether the LLVM IR declaration and call have one).

toolchain/check/testdata/class/generic/base_is_generic.carbon

@@ -974,12 +974,13 @@ fn H() {
 // CHECK:STDOUT:   %X.G: @X.G.%X.G.type (%X.G.type.56f312.1) = struct_value () [symbolic = %X.G (constants.%X.G.b504c4.1)]
 // CHECK:STDOUT:   %X.G.specific_fn.loc5_24.2: <specific function> = specific_function %X.G, @X.G(%U) [symbolic = %X.G.specific_fn.loc5_24.2 (constants.%X.G.specific_fn.169)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn() -> @X.G.%U (%U) {
+// CHECK:STDOUT:   fn() -> %return.param: @X.G.%U (%U) {
 // CHECK:STDOUT:   !entry:
-// CHECK:STDOUT:     %.loc5: @X.G.%X.G.type (%X.G.type.56f312.1) = specific_constant @X.%X.G.decl, @X(constants.%U) [symbolic = %X.G (constants.%X.G.b504c4.1)]
-// CHECK:STDOUT:     %G.ref: @X.G.%X.G.type (%X.G.type.56f312.1) = name_ref G, %.loc5 [symbolic = %X.G (constants.%X.G.b504c4.1)]
+// CHECK:STDOUT:     %.loc5_24: @X.G.%X.G.type (%X.G.type.56f312.1) = specific_constant @X.%X.G.decl, @X(constants.%U) [symbolic = %X.G (constants.%X.G.b504c4.1)]
+// CHECK:STDOUT:     %G.ref: @X.G.%X.G.type (%X.G.type.56f312.1) = name_ref G, %.loc5_24 [symbolic = %X.G (constants.%X.G.b504c4.1)]
 // CHECK:STDOUT:     %X.G.specific_fn.loc5_24.1: <specific function> = specific_function %G.ref, @X.G(constants.%U) [symbolic = %X.G.specific_fn.loc5_24.2 (constants.%X.G.specific_fn.169)]
-// CHECK:STDOUT:     %X.G.call: init @X.G.%U (%U) = call %X.G.specific_fn.loc5_24.1()
+// CHECK:STDOUT:     %.loc5_10: ref @X.G.%U (%U) = splice_block %return {}
+// CHECK:STDOUT:     %X.G.call: init @X.G.%U (%U) = call %X.G.specific_fn.loc5_24.1() to %.loc5_10
 // CHECK:STDOUT:     return %X.G.call to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -1174,7 +1175,7 @@ fn H() {
 // CHECK:STDOUT:   %Main.import_ref.b8a: @X.%X.G.type (%X.G.type.56f312.1) = import_ref Main//extend_generic_symbolic_base, loc5_15, loaded [symbolic = @X.%X.G (constants.%X.G.b504c4.1)]
 // CHECK:STDOUT:   %Main.import_ref.5ab3ec.2: type = import_ref Main//extend_generic_symbolic_base, loc8_9, loaded [symbolic = @C.%T (constants.%T)]
 // CHECK:STDOUT:   %Main.import_ref.93f: <witness> = import_ref Main//extend_generic_symbolic_base, loc10_1, loaded [symbolic = @C.%complete_type (constants.%complete_type.768)]
-// CHECK:STDOUT:   %Main.import_ref.4c0 = import_ref Main//extend_generic_symbolic_base, inst117 [no loc], unloaded
+// CHECK:STDOUT:   %Main.import_ref.4c0 = import_ref Main//extend_generic_symbolic_base, inst118 [no loc], unloaded
 // CHECK:STDOUT:   %Main.import_ref.65d = import_ref Main//extend_generic_symbolic_base, loc9_20, unloaded
 // CHECK:STDOUT:   %Main.import_ref.561eb2.2: type = import_ref Main//extend_generic_symbolic_base, loc9_19, loaded [symbolic = @C.%X (constants.%X.75b6d8.2)]
 // CHECK:STDOUT:   %Main.import_ref.5ab3ec.3: type = import_ref Main//extend_generic_symbolic_base, loc4_14, loaded [symbolic = @X.%U (constants.%U)]

toolchain/check/testdata/class/generic/basic.carbon

@@ -272,7 +272,7 @@ class Declaration(T:! type);
 // CHECK:STDOUT:   %impl.elem0.loc11_16.2: @Class.GetValue.%.loc11_16.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc11_16.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc11_16.2: <specific function> = specific_impl_function %impl.elem0.loc11_16.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc11_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: @Class.GetValue.%Class (%Class)) -> @Class.GetValue.%T.as_type.loc10_32.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%self.param: @Class.GetValue.%Class (%Class)) -> %return.param: @Class.GetValue.%T.as_type.loc10_32.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %self.ref: @Class.GetValue.%Class (%Class) = name_ref self, %self
 // CHECK:STDOUT:     %k.ref: @Class.GetValue.%Class.elem (%Class.elem) = name_ref k, @Class.%.loc14_8 [concrete = @Class.%.loc14_8]
@@ -282,7 +282,8 @@ class Declaration(T:! type);
 // CHECK:STDOUT:     %bound_method.loc11_16.1: <bound method> = bound_method %.loc11_16.2, %impl.elem0.loc11_16.1
 // CHECK:STDOUT:     %specific_impl_fn.loc11_16.1: <specific function> = specific_impl_function %impl.elem0.loc11_16.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc11_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc11_16.2: <bound method> = bound_method %.loc11_16.2, %specific_impl_fn.loc11_16.1
-// CHECK:STDOUT:     %.loc11_16.3: init @Class.GetValue.%T.as_type.loc10_32.1 (%T.as_type) = call %bound_method.loc11_16.2(%.loc11_16.2)
+// CHECK:STDOUT:     %.loc10_29: ref @Class.GetValue.%T.as_type.loc10_32.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc11_16.3: init @Class.GetValue.%T.as_type.loc10_32.1 (%T.as_type) = call %bound_method.loc11_16.2(%.loc11_16.2) to %.loc10_29
 // CHECK:STDOUT:     return %.loc11_16.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/field.carbon

@@ -310,7 +310,7 @@ fn H(U:! Core.Copy, c: Class(U)) -> U {
 // CHECK:STDOUT:   %impl.elem0.loc14_11.2: @G.%.loc14_11.4 (%.c500ab.1) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc14_11.2 (constants.%impl.elem0.792e99.1)]
 // CHECK:STDOUT:   %specific_impl_fn.loc14_11.2: <specific function> = specific_impl_function %impl.elem0.loc14_11.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc14_11.2 (constants.%specific_impl_fn.547931.1)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%c.param: @G.%Class.loc13_31.1 (%Class.a5ccb5.1)) -> @G.%T.as_type.loc13_31.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%c.param: @G.%Class.loc13_31.1 (%Class.a5ccb5.1)) -> %return.param: @G.%T.as_type.loc13_31.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %c.ref: @G.%Class.loc13_31.1 (%Class.a5ccb5.1) = name_ref c, %c
 // CHECK:STDOUT:     %x.ref: @G.%Class.elem (%Class.elem.14abad.1) = name_ref x, @Class.%.loc6 [concrete = @Class.%.loc6]
@@ -320,7 +320,8 @@ fn H(U:! Core.Copy, c: Class(U)) -> U {
 // CHECK:STDOUT:     %bound_method.loc14_11.1: <bound method> = bound_method %.loc14_11.2, %impl.elem0.loc14_11.1
 // CHECK:STDOUT:     %specific_impl_fn.loc14_11.1: <specific function> = specific_impl_function %impl.elem0.loc14_11.1, @Copy.Op(constants.%Copy.facet.021101.1) [symbolic = %specific_impl_fn.loc14_11.2 (constants.%specific_impl_fn.547931.1)]
 // CHECK:STDOUT:     %bound_method.loc14_11.2: <bound method> = bound_method %.loc14_11.2, %specific_impl_fn.loc14_11.1
-// CHECK:STDOUT:     %.loc14_11.3: init @G.%T.as_type.loc13_31.1 (%T.as_type) = call %bound_method.loc14_11.2(%.loc14_11.2)
+// CHECK:STDOUT:     %.loc13_34: ref @G.%T.as_type.loc13_31.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc14_11.3: init @G.%T.as_type.loc13_31.1 (%T.as_type) = call %bound_method.loc14_11.2(%.loc14_11.2) to %.loc13_34
 // CHECK:STDOUT:     return %.loc14_11.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -342,7 +343,7 @@ fn H(U:! Core.Copy, c: Class(U)) -> U {
 // CHECK:STDOUT:   %impl.elem0.loc18_11.2: @H.%.loc18_11.4 (%.c500ab.2) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc18_11.2 (constants.%impl.elem0.792e99.2)]
 // CHECK:STDOUT:   %specific_impl_fn.loc18_11.2: <specific function> = specific_impl_function %impl.elem0.loc18_11.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc18_11.2 (constants.%specific_impl_fn.547931.2)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%c.param: @H.%Class.loc17_31.1 (%Class.a5ccb5.2)) -> @H.%U.as_type.loc17_31.1 (%U.as_type.870) {
+// CHECK:STDOUT:   fn(%c.param: @H.%Class.loc17_31.1 (%Class.a5ccb5.2)) -> %return.param: @H.%U.as_type.loc17_31.1 (%U.as_type.870) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %c.ref: @H.%Class.loc17_31.1 (%Class.a5ccb5.2) = name_ref c, %c
 // CHECK:STDOUT:     %x.ref: @H.%Class.elem (%Class.elem.14abad.2) = name_ref x, @Class.%.loc6 [concrete = @Class.%.loc6]
@@ -352,7 +353,8 @@ fn H(U:! Core.Copy, c: Class(U)) -> U {
 // CHECK:STDOUT:     %bound_method.loc18_11.1: <bound method> = bound_method %.loc18_11.2, %impl.elem0.loc18_11.1
 // CHECK:STDOUT:     %specific_impl_fn.loc18_11.1: <specific function> = specific_impl_function %impl.elem0.loc18_11.1, @Copy.Op(constants.%Copy.facet.021101.2) [symbolic = %specific_impl_fn.loc18_11.2 (constants.%specific_impl_fn.547931.2)]
 // CHECK:STDOUT:     %bound_method.loc18_11.2: <bound method> = bound_method %.loc18_11.2, %specific_impl_fn.loc18_11.1
-// CHECK:STDOUT:     %.loc18_11.3: init @H.%U.as_type.loc17_31.1 (%U.as_type.870) = call %bound_method.loc18_11.2(%.loc18_11.2)
+// CHECK:STDOUT:     %.loc17_34: ref @H.%U.as_type.loc17_31.1 (%U.as_type.870) = splice_block %return {}
+// CHECK:STDOUT:     %.loc18_11.3: init @H.%U.as_type.loc17_31.1 (%U.as_type.870) = call %bound_method.loc18_11.2(%.loc18_11.2) to %.loc17_34
 // CHECK:STDOUT:     return %.loc18_11.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/init.carbon

@@ -195,7 +195,7 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:   %ptr: type = ptr_type %Class.loc10_17.2 [symbolic = %ptr (constants.%ptr.e19)]
 // CHECK:STDOUT:   %require_complete.loc10_3: <witness> = require_complete_type %ptr [symbolic = %require_complete.loc10_3 (constants.%require_complete.3cb)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type)) -> @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%x.param: @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type)) -> %return.param: @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     name_binding_decl {
 // CHECK:STDOUT:       %v.patt: @InitFromStructGeneric.%pattern_type.loc10 (%pattern_type.0a3) = binding_pattern v [concrete]
@@ -208,8 +208,8 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc10_27.1: <bound method> = bound_method %x.ref, %impl.elem0.loc10_27.1
 // CHECK:STDOUT:     %specific_impl_fn.loc10_27.1: <specific function> = specific_impl_function %impl.elem0.loc10_27.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc10_27.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc10_27.2: <bound method> = bound_method %x.ref, %specific_impl_fn.loc10_27.1
-// CHECK:STDOUT:     %.loc10_27.1: init @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = call %bound_method.loc10_27.2(%x.ref)
 // CHECK:STDOUT:     %.loc10_28.2: ref @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = class_element_access %v.var, element0
+// CHECK:STDOUT:     %.loc10_27.1: init @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = call %bound_method.loc10_27.2(%x.ref) to %.loc10_28.2
 // CHECK:STDOUT:     %.loc10_28.3: init @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = initialize_from %.loc10_27.1 to %.loc10_28.2
 // CHECK:STDOUT:     %.loc10_28.4: init @InitFromStructGeneric.%Class.loc10_17.2 (%Class.a5c) = class_init (%.loc10_28.3), %v.var
 // CHECK:STDOUT:     %.loc10_3.1: init @InitFromStructGeneric.%Class.loc10_17.2 (%Class.a5c) = converted %.loc10_28.1, %.loc10_28.4
@@ -230,7 +230,8 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc11_11.1: <bound method> = bound_method %.loc11_11.2, %impl.elem0.loc11
 // CHECK:STDOUT:     %specific_impl_fn.loc11: <specific function> = specific_impl_function %impl.elem0.loc11, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc10_27.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc11_11.2: <bound method> = bound_method %.loc11_11.2, %specific_impl_fn.loc11
-// CHECK:STDOUT:     %.loc11_11.3: init @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = call %bound_method.loc11_11.2(%.loc11_11.2)
+// CHECK:STDOUT:     %.loc9_47: ref @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc11_11.3: init @InitFromStructGeneric.%T.as_type.loc9_44.1 (%T.as_type) = call %bound_method.loc11_11.2(%.loc11_11.2) to %.loc9_47
 // CHECK:STDOUT:     %impl.elem0.loc10_3: @InitFromStructGeneric.%.loc10_3.2 (%.4f0) = impl_witness_access constants.%Destroy.impl_witness.a5d, element0 [symbolic = %Class.as.Destroy.impl.Op (constants.%Class.as.Destroy.impl.Op.d2f)]
 // CHECK:STDOUT:     %bound_method.loc10_3.1: <bound method> = bound_method %v.var, %impl.elem0.loc10_3
 // CHECK:STDOUT:     %specific_fn: <specific function> = specific_function %impl.elem0.loc10_3, @Class.as.Destroy.impl.Op(constants.%T.as_type) [symbolic = %Class.as.Destroy.impl.Op.specific_fn (constants.%Class.as.Destroy.impl.Op.specific_fn.8ad)]
@@ -407,7 +408,7 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:   %impl.elem0.loc10_26.2: @InitFromAdaptedGeneric.%.loc10_26.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc10_26.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc10_26.2: <specific function> = specific_impl_function %impl.elem0.loc10_26.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc10_26.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type)) -> @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%x.param: @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type)) -> %return.param: @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %x.ref: @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) = name_ref x, %x
 // CHECK:STDOUT:     %Adapt.ref: %Adapt.type = name_ref Adapt, file.%Adapt.decl [concrete = constants.%Adapt.generic]
@@ -426,7 +427,8 @@ fn InitFromAdaptedSpecific(x: i32) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc10_26.1: <bound method> = bound_method %.loc10_26.2, %impl.elem0.loc10_26.1
 // CHECK:STDOUT:     %specific_impl_fn.loc10_26.1: <specific function> = specific_impl_function %impl.elem0.loc10_26.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc10_26.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc10_26.2: <bound method> = bound_method %.loc10_26.2, %specific_impl_fn.loc10_26.1
-// CHECK:STDOUT:     %.loc10_26.3: init @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) = call %bound_method.loc10_26.2(%.loc10_26.2)
+// CHECK:STDOUT:     %.loc9_48: ref @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc10_26.3: init @InitFromAdaptedGeneric.%T.as_type.loc9_45.1 (%T.as_type) = call %bound_method.loc10_26.2(%.loc10_26.2) to %.loc9_48
 // CHECK:STDOUT:     return %.loc10_26.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/member_access.carbon

@@ -193,7 +193,7 @@ fn StaticMemberFunctionCall(T:! type) -> Class(T) {
 // CHECK:STDOUT:   %impl.elem0.loc9_16.2: @Class.Get.%.loc9_16.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc9_16.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc9_16.2: <specific function> = specific_impl_function %impl.elem0.loc9_16.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc9_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: @Class.Get.%Class (%Class.2c5)) -> @Class.Get.%T.as_type.loc7_27.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%self.param: @Class.Get.%Class (%Class.2c5)) -> %return.param: @Class.Get.%T.as_type.loc7_27.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %self.ref: @Class.Get.%Class (%Class.2c5) = name_ref self, %self
 // CHECK:STDOUT:     %x.ref: @Class.Get.%Class.elem (%Class.elem.3a8) = name_ref x, @Class.%.loc5_8 [concrete = @Class.%.loc5_8]
@@ -203,7 +203,8 @@ fn StaticMemberFunctionCall(T:! type) -> Class(T) {
 // CHECK:STDOUT:     %bound_method.loc9_16.1: <bound method> = bound_method %.loc9_16.2, %impl.elem0.loc9_16.1
 // CHECK:STDOUT:     %specific_impl_fn.loc9_16.1: <specific function> = specific_impl_function %impl.elem0.loc9_16.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc9_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc9_16.2: <bound method> = bound_method %.loc9_16.2, %specific_impl_fn.loc9_16.1
-// CHECK:STDOUT:     %.loc9_16.3: init @Class.Get.%T.as_type.loc7_27.1 (%T.as_type) = call %bound_method.loc9_16.2(%.loc9_16.2)
+// CHECK:STDOUT:     <elided>
+// CHECK:STDOUT:     %.loc9_16.3: init @Class.Get.%T.as_type.loc7_27.1 (%T.as_type) = call %bound_method.loc9_16.2(%.loc9_16.2) to %.loc7_24
 // CHECK:STDOUT:     return %.loc9_16.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/member_inline.carbon

@@ -220,14 +220,15 @@ class C(T:! Core.Copy) {
 // CHECK:STDOUT:   %impl.elem0.loc7_12.2: @Class.F.%.loc7_12.2 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc7_12.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc7_12.2: <specific function> = specific_impl_function %impl.elem0.loc7_12.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc7_12.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%n.param: @Class.F.%T.as_type.loc6_11.1 (%T.as_type)) -> @Class.F.%T.as_type.loc6_11.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%n.param: @Class.F.%T.as_type.loc6_11.1 (%T.as_type)) -> %return.param: @Class.F.%T.as_type.loc6_11.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %n.ref: @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = name_ref n, %n
 // CHECK:STDOUT:     %impl.elem0.loc7_12.1: @Class.F.%.loc7_12.2 (%.c50) = impl_witness_access constants.%Copy.lookup_impl_witness.e15, element0 [symbolic = %impl.elem0.loc7_12.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:     %bound_method.loc7_12.1: <bound method> = bound_method %n.ref, %impl.elem0.loc7_12.1
 // CHECK:STDOUT:     %specific_impl_fn.loc7_12.1: <specific function> = specific_impl_function %impl.elem0.loc7_12.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc7_12.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc7_12.2: <bound method> = bound_method %n.ref, %specific_impl_fn.loc7_12.1
-// CHECK:STDOUT:     %.loc7_12.1: init @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = call %bound_method.loc7_12.2(%n.ref)
+// CHECK:STDOUT:     %.loc6_14: ref @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc7_12.1: init @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = call %bound_method.loc7_12.2(%n.ref) to %.loc6_14
 // CHECK:STDOUT:     return %.loc7_12.1 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -249,7 +250,7 @@ class C(T:! Core.Copy) {
 // CHECK:STDOUT:   %impl.elem0.loc11_16.2: @Class.G.%.loc11_16.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc11_16.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc11_16.2: <specific function> = specific_impl_function %impl.elem0.loc11_16.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc11_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: @Class.G.%Class (%Class)) -> @Class.G.%T.as_type.loc10_25.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%self.param: @Class.G.%Class (%Class)) -> %return.param: @Class.G.%T.as_type.loc10_25.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %self.ref: @Class.G.%Class (%Class) = name_ref self, %self
 // CHECK:STDOUT:     %n.ref: @Class.G.%Class.elem (%Class.elem) = name_ref n, @Class.%.loc14_8 [concrete = @Class.%.loc14_8]
@@ -259,7 +260,8 @@ class C(T:! Core.Copy) {
 // CHECK:STDOUT:     %bound_method.loc11_16.1: <bound method> = bound_method %.loc11_16.2, %impl.elem0.loc11_16.1
 // CHECK:STDOUT:     %specific_impl_fn.loc11_16.1: <specific function> = specific_impl_function %impl.elem0.loc11_16.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc11_16.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc11_16.2: <bound method> = bound_method %.loc11_16.2, %specific_impl_fn.loc11_16.1
-// CHECK:STDOUT:     %.loc11_16.3: init @Class.G.%T.as_type.loc10_25.1 (%T.as_type) = call %bound_method.loc11_16.2(%.loc11_16.2)
+// CHECK:STDOUT:     %.loc10_22: ref @Class.G.%T.as_type.loc10_25.1 (%T.as_type) = splice_block %return {}
+// CHECK:STDOUT:     %.loc11_16.3: init @Class.G.%T.as_type.loc10_25.1 (%T.as_type) = call %bound_method.loc11_16.2(%.loc11_16.2) to %.loc10_22
 // CHECK:STDOUT:     return %.loc11_16.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/member_lookup.carbon

@@ -113,7 +113,7 @@ fn AccessMissingConcrete(x: Derived(i32)) -> i32 {
 // CHECK:STDOUT:   %impl.elem0.loc15_11.2: @AccessDerived.%.loc15_11.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc15_11.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc15_11.2: <specific function> = specific_impl_function %impl.elem0.loc15_11.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc15_11.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: @AccessDerived.%Derived.loc13_45.1 (%Derived.3ba)) -> @AccessDerived.%T.as_type.loc13_45.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%x.param: @AccessDerived.%Derived.loc13_45.1 (%Derived.3ba)) -> %return.param: @AccessDerived.%T.as_type.loc13_45.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %x.ref: @AccessDerived.%Derived.loc13_45.1 (%Derived.3ba) = name_ref x, %x
 // CHECK:STDOUT:     %d.ref: @AccessDerived.%Derived.elem (%Derived.elem.1c7) = name_ref d, @Derived.%.loc10 [concrete = @Derived.%.loc10]
@@ -123,7 +123,8 @@ fn AccessMissingConcrete(x: Derived(i32)) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc15_11.1: <bound method> = bound_method %.loc15_11.2, %impl.elem0.loc15_11.1
 // CHECK:STDOUT:     %specific_impl_fn.loc15_11.1: <specific function> = specific_impl_function %impl.elem0.loc15_11.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc15_11.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc15_11.2: <bound method> = bound_method %.loc15_11.2, %specific_impl_fn.loc15_11.1
-// CHECK:STDOUT:     %.loc15_11.3: init @AccessDerived.%T.as_type.loc13_45.1 (%T.as_type) = call %bound_method.loc15_11.2(%.loc15_11.2)
+// CHECK:STDOUT:     <elided>
+// CHECK:STDOUT:     %.loc15_11.3: init @AccessDerived.%T.as_type.loc13_45.1 (%T.as_type) = call %bound_method.loc15_11.2(%.loc15_11.2) to %.loc13_48
 // CHECK:STDOUT:     return %.loc15_11.3 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -143,7 +144,7 @@ fn AccessMissingConcrete(x: Derived(i32)) -> i32 {
 // CHECK:STDOUT:   %impl.elem0.loc21_11.2: @AccessBase.%.loc21_11.6 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc21_11.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc21_11.2: <specific function> = specific_impl_function %impl.elem0.loc21_11.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc21_11.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%x.param: @AccessBase.%Derived.loc19_42.1 (%Derived.3ba)) -> @AccessBase.%T.as_type.loc19_42.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%x.param: @AccessBase.%Derived.loc19_42.1 (%Derived.3ba)) -> %return.param: @AccessBase.%T.as_type.loc19_42.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %x.ref: @AccessBase.%Derived.loc19_42.1 (%Derived.3ba) = name_ref x, %x
 // CHECK:STDOUT:     %b.ref: @AccessBase.%Base.elem (%Base.elem.58f) = name_ref b, @Base.%.loc5 [concrete = @Base.%.loc5]
@@ -155,7 +156,8 @@ fn AccessMissingConcrete(x: Derived(i32)) -> i32 {
 // CHECK:STDOUT:     %bound_method.loc21_11.1: <bound method> = bound_method %.loc21_11.4, %impl.elem0.loc21_11.1
 // CHECK:STDOUT:     %specific_impl_fn.loc21_11.1: <specific function> = specific_impl_function %impl.elem0.loc21_11.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc21_11.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc21_11.2: <bound method> = bound_method %.loc21_11.4, %specific_impl_fn.loc21_11.1
-// CHECK:STDOUT:     %.loc21_11.5: init @AccessBase.%T.as_type.loc19_42.1 (%T.as_type) = call %bound_method.loc21_11.2(%.loc21_11.4)
+// CHECK:STDOUT:     <elided>
+// CHECK:STDOUT:     %.loc21_11.5: init @AccessBase.%T.as_type.loc19_42.1 (%T.as_type) = call %bound_method.loc21_11.2(%.loc21_11.4) to %.loc19_45
 // CHECK:STDOUT:     return %.loc21_11.5 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/member_out_of_line.carbon

@@ -336,14 +336,15 @@ fn Generic(T:! ()).WrongType() {}
 // CHECK:STDOUT:   %impl.elem0.loc12_10.2: @Class.F.%.loc12_10.2 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc12_10.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc12_10.2: <specific function> = specific_impl_function %impl.elem0.loc12_10.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc12_10.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%n.param.loc11: @Class.F.%T.as_type.loc6_11.1 (%T.as_type)) -> @Class.F.%T.as_type.loc6_11.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%n.param.loc11: @Class.F.%T.as_type.loc6_11.1 (%T.as_type)) -> %return.param.loc11: @Class.F.%T.as_type.loc6_11.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %n.ref: @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = name_ref n, %n.loc11
 // CHECK:STDOUT:     %impl.elem0.loc12_10.1: @Class.F.%.loc12_10.2 (%.c50) = impl_witness_access constants.%Copy.lookup_impl_witness.e15, element0 [symbolic = %impl.elem0.loc12_10.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:     %bound_method.loc12_10.1: <bound method> = bound_method %n.ref, %impl.elem0.loc12_10.1
 // CHECK:STDOUT:     %specific_impl_fn.loc12_10.1: <specific function> = specific_impl_function %impl.elem0.loc12_10.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc12_10.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc12_10.2: <bound method> = bound_method %n.ref, %specific_impl_fn.loc12_10.1
-// CHECK:STDOUT:     %.loc12_10.1: init @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = call %bound_method.loc12_10.2(%n.ref)
+// CHECK:STDOUT:     %.loc11_33: ref @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = splice_block %return.loc11 {}
+// CHECK:STDOUT:     %.loc12_10.1: init @Class.F.%T.as_type.loc6_11.1 (%T.as_type) = call %bound_method.loc12_10.2(%n.ref) to %.loc11_33
 // CHECK:STDOUT:     return %.loc12_10.1 to %return.loc11
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }
@@ -365,7 +366,7 @@ fn Generic(T:! ()).WrongType() {}
 // CHECK:STDOUT:   %impl.elem0.loc16_14.2: @Class.G.%.loc16_14.4 (%.c50) = impl_witness_access %Copy.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc16_14.2 (constants.%impl.elem0.792)]
 // CHECK:STDOUT:   %specific_impl_fn.loc16_14.2: <specific function> = specific_impl_function %impl.elem0.loc16_14.2, @Copy.Op(%Copy.facet) [symbolic = %specific_impl_fn.loc16_14.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param.loc15: @Class.G.%Class (%Class)) -> @Class.G.%T.as_type.loc7_25.1 (%T.as_type) {
+// CHECK:STDOUT:   fn(%self.param.loc15: @Class.G.%Class (%Class)) -> %return.param.loc15: @Class.G.%T.as_type.loc7_25.1 (%T.as_type) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %self.ref: @Class.G.%Class (%Class) = name_ref self, %self.loc15
 // CHECK:STDOUT:     %n.ref: @Class.G.%Class.elem (%Class.elem) = name_ref n, @Class.%.loc8_8 [concrete = @Class.%.loc8_8]
@@ -375,7 +376,8 @@ fn Generic(T:! ()).WrongType() {}
 // CHECK:STDOUT:     %bound_method.loc16_14.1: <bound method> = bound_method %.loc16_14.2, %impl.elem0.loc16_14.1
 // CHECK:STDOUT:     %specific_impl_fn.loc16_14.1: <specific function> = specific_impl_function %impl.elem0.loc16_14.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc16_14.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc16_14.2: <bound method> = bound_method %.loc16_14.2, %specific_impl_fn.loc16_14.1
-// CHECK:STDOUT:     %.loc16_14.3: init @Class.G.%T.as_type.loc7_25.1 (%T.as_type) = call %bound_method.loc16_14.2(%.loc16_14.2)
+// CHECK:STDOUT:     %.loc15_41: ref @Class.G.%T.as_type.loc7_25.1 (%T.as_type) = splice_block %return.loc15 {}
+// CHECK:STDOUT:     %.loc16_14.3: init @Class.G.%T.as_type.loc7_25.1 (%T.as_type) = call %bound_method.loc16_14.2(%.loc16_14.2) to %.loc15_41
 // CHECK:STDOUT:     return %.loc16_14.3 to %return.loc15
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }

toolchain/check/testdata/class/generic/member_type.carbon

@@ -368,8 +368,8 @@ fn Test() -> i32 {
 // CHECK:STDOUT:     %bound_method.loc9_38.1: <bound method> = bound_method %n.ref, %impl.elem0.loc9_38.1
 // CHECK:STDOUT:     %specific_impl_fn.loc9_38.1: <specific function> = specific_impl_function %impl.elem0.loc9_38.1, @Copy.Op(constants.%Copy.facet.021) [symbolic = %specific_impl_fn.loc9_38.2 (constants.%specific_impl_fn.547)]
 // CHECK:STDOUT:     %bound_method.loc9_38.2: <bound method> = bound_method %n.ref, %specific_impl_fn.loc9_38.1
-// CHECK:STDOUT:     %.loc9_38.1: init @Outer.F.%T.as_type.loc9_11.1 (%T.as_type) = call %bound_method.loc9_38.2(%n.ref)
 // CHECK:STDOUT:     %.loc9_39.2: ref @Outer.F.%T.as_type.loc9_11.1 (%T.as_type) = class_element_access %return, element0
+// CHECK:STDOUT:     %.loc9_38.1: init @Outer.F.%T.as_type.loc9_11.1 (%T.as_type) = call %bound_method.loc9_38.2(%n.ref) to %.loc9_39.2
 // CHECK:STDOUT:     %.loc9_39.3: init @Outer.F.%T.as_type.loc9_11.1 (%T.as_type) = initialize_from %.loc9_38.1 to %.loc9_39.2
 // CHECK:STDOUT:     %.loc9_39.4: init @Outer.F.%Inner (%Inner.6ee) = class_init (%.loc9_39.3), %return
 // CHECK:STDOUT:     %.loc9_40: init @Outer.F.%Inner (%Inner.6ee) = converted %.loc9_39.1, %.loc9_39.4
@@ -944,7 +944,7 @@ fn Test() -> i32 {
 // CHECK:STDOUT:   %pattern_type.loc6_10: type = pattern_type %Self.as_type.loc6_16.1 [symbolic = %pattern_type.loc6_10 (constants.%pattern_type.120)]
 // CHECK:STDOUT:   %pattern_type.loc6_24: type = pattern_type %T [symbolic = %pattern_type.loc6_24 (constants.%pattern_type.7dc)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: @Inner.F.%Self.as_type.loc6_16.1 (%Self.as_type.bd3)) -> @Inner.F.%T (%T);
+// CHECK:STDOUT:   fn(%self.param: @Inner.F.%Self.as_type.loc6_16.1 (%Self.as_type.bd3)) -> %return.param: @Inner.F.%T (%T);
 // CHECK:STDOUT: }
 // CHECK:STDOUT:
 // CHECK:STDOUT: generic fn @C.as.Inner.impl.F(@Outer.%T.loc4_13.2: type) {
@@ -967,7 +967,7 @@ fn Test() -> i32 {
 // CHECK:STDOUT:   %impl.elem0.loc11_41.2: @C.as.Inner.impl.F.%.loc11_41 (%.4e7) = impl_witness_access %Inner.lookup_impl_witness, element0 [symbolic = %impl.elem0.loc11_41.2 (constants.%impl.elem0)]
 // CHECK:STDOUT:   %specific_impl_fn.loc11_41.2: <specific function> = specific_impl_function %impl.elem0.loc11_41.2, @Inner.F(%T, %Inner.facet) [symbolic = %specific_impl_fn.loc11_41.2 (constants.%specific_impl_fn)]
 // CHECK:STDOUT:
-// CHECK:STDOUT:   fn(%self.param: @C.as.Inner.impl.F.%C (%C.390)) -> @C.as.Inner.impl.F.%T (%T) {
+// CHECK:STDOUT:   fn(%self.param: @C.as.Inner.impl.F.%C (%C.390)) -> %return.param: @C.as.Inner.impl.F.%T (%T) {
 // CHECK:STDOUT:   !entry:
 // CHECK:STDOUT:     %self.ref: @C.as.Inner.impl.F.%C (%C.390) = name_ref self, %self
 // CHECK:STDOUT:     %.loc11_43: type = specific_constant @Outer.%Inner.decl, @Outer(constants.%T) [symbolic = %Inner.type (constants.%Inner.type.d07)]
@@ -978,7 +978,8 @@ fn Test() -> i32 {
 // CHECK:STDOUT:     %bound_method.loc11_41: <bound method> = bound_method %self.ref, %impl.elem0.loc11_41.1
 // CHECK:STDOUT:     %specific_impl_fn.loc11_41.1: <specific function> = specific_impl_function %impl.elem0.loc11_41.1, @Inner.F(constants.%T, constants.%Inner.facet.949) [symbolic = %specific_impl_fn.loc11_41.2 (constants.%specific_impl_fn)]
 // CHECK:STDOUT:     %bound_method.loc11_52: <bound method> = bound_method %self.ref, %specific_impl_fn.loc11_41.1
-// CHECK:STDOUT:     %.loc11_52: init @C.as.Inner.impl.F.%T (%T) = call %bound_method.loc11_52(%self.ref)
+// CHECK:STDOUT:     %.loc11_23: ref @C.as.Inner.impl.F.%T (%T) = splice_block %return {}
+// CHECK:STDOUT:     %.loc11_52: init @C.as.Inner.impl.F.%T (%T) = call %bound_method.loc11_52(%self.ref) to %.loc11_23
 // CHECK:STDOUT:     return %.loc11_52 to %return
 // CHECK:STDOUT:   }
 // CHECK:STDOUT: }