Add a test where a FacetType is deduced as another FacetType (#4917)

toolchain/check/testdata/builtin_conversions/no_prelude/convert_interface.carbon

@@ -0,0 +1,97 @@
+// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+// Exceptions. See /LICENSE for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+// AUTOUPDATE
+// TIP: To test this file alone, run:
+// TIP:   bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/builtin_conversions/no_prelude/convert_interface.carbon
+// TIP: To dump output, run:
+// TIP:   bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/builtin_conversions/no_prelude/convert_interface.carbon
+
+interface Eats {}
+interface Animal {}
+
+// TODO: This may be rejected in the future.
+// https://github.com/carbon-language/carbon-lang/issues/4853
+impl Animal as Eats {}
+
+fn F(e: Eats) {}
+fn G() { F(Animal); }
+
+// CHECK:STDOUT: --- convert_interface.carbon
+// CHECK:STDOUT:
+// CHECK:STDOUT: constants {
+// CHECK:STDOUT:   %Eats.type: type = facet_type <@Eats> [template]
+// CHECK:STDOUT:   %Self.1b5: %Eats.type = bind_symbolic_name Self, 0 [symbolic]
+// CHECK:STDOUT:   %Animal.type: type = facet_type <@Animal> [template]
+// CHECK:STDOUT:   %Self.fd4: %Animal.type = bind_symbolic_name Self, 0 [symbolic]
+// CHECK:STDOUT:   %empty_tuple.type: type = tuple_type () [template]
+// CHECK:STDOUT:   %impl_witness: <witness> = impl_witness () [template]
+// CHECK:STDOUT:   %F.type: type = fn_type @F [template]
+// CHECK:STDOUT:   %F: %F.type = struct_value () [template]
+// CHECK:STDOUT:   %G.type: type = fn_type @G [template]
+// CHECK:STDOUT:   %G: %G.type = struct_value () [template]
+// CHECK:STDOUT:   %Eats.facet: %Eats.type = facet_value %Animal.type, %impl_witness [template]
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: file {
+// CHECK:STDOUT:   package: <namespace> = namespace [template] {
+// CHECK:STDOUT:     .Eats = %Eats.decl
+// CHECK:STDOUT:     .Animal = %Animal.decl
+// CHECK:STDOUT:     .F = %F.decl
+// CHECK:STDOUT:     .G = %G.decl
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %Eats.decl: type = interface_decl @Eats [template = constants.%Eats.type] {} {}
+// CHECK:STDOUT:   %Animal.decl: type = interface_decl @Animal [template = constants.%Animal.type] {} {}
+// CHECK:STDOUT:   impl_decl @impl [template] {} {
+// CHECK:STDOUT:     %Animal.ref: type = name_ref Animal, file.%Animal.decl [template = constants.%Animal.type]
+// CHECK:STDOUT:     %Eats.ref: type = name_ref Eats, file.%Eats.decl [template = constants.%Eats.type]
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %impl_witness: <witness> = impl_witness () [template = constants.%impl_witness]
+// CHECK:STDOUT:   %F.decl: %F.type = fn_decl @F [template = constants.%F] {
+// CHECK:STDOUT:     %e.patt: %Eats.type = binding_pattern e
+// CHECK:STDOUT:     %e.param_patt: %Eats.type = value_param_pattern %e.patt, runtime_param0
+// CHECK:STDOUT:   } {
+// CHECK:STDOUT:     %e.param: %Eats.type = value_param runtime_param0
+// CHECK:STDOUT:     %Eats.ref: type = name_ref Eats, file.%Eats.decl [template = constants.%Eats.type]
+// CHECK:STDOUT:     %e: %Eats.type = bind_name e, %e.param
+// CHECK:STDOUT:   }
+// CHECK:STDOUT:   %G.decl: %G.type = fn_decl @G [template = constants.%G] {} {}
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: interface @Eats {
+// CHECK:STDOUT:   %Self: %Eats.type = bind_symbolic_name Self, 0 [symbolic = constants.%Self.1b5]
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = %Self
+// CHECK:STDOUT:   witness = ()
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: interface @Animal {
+// CHECK:STDOUT:   %Self: %Animal.type = bind_symbolic_name Self, 0 [symbolic = constants.%Self.fd4]
+// CHECK:STDOUT:
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   .Self = %Self
+// CHECK:STDOUT:   witness = ()
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: impl @impl: %Animal.ref as %Eats.ref {
+// CHECK:STDOUT: !members:
+// CHECK:STDOUT:   witness = file.%impl_witness
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @F(%e.param_patt: %Eats.type) {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT:
+// CHECK:STDOUT: fn @G() {
+// CHECK:STDOUT: !entry:
+// CHECK:STDOUT:   %F.ref: %F.type = name_ref F, file.%F.decl [template = constants.%F]
+// CHECK:STDOUT:   %Animal.ref: type = name_ref Animal, file.%Animal.decl [template = constants.%Animal.type]
+// CHECK:STDOUT:   %Eats.facet: %Eats.type = facet_value %Animal.ref, constants.%impl_witness [template = constants.%Eats.facet]
+// CHECK:STDOUT:   %.loc19: %Eats.type = converted %Animal.ref, %Eats.facet [template = constants.%Eats.facet]
+// CHECK:STDOUT:   %F.call: init %empty_tuple.type = call %F.ref(%.loc19)
+// CHECK:STDOUT:   return
+// CHECK:STDOUT: }
+// CHECK:STDOUT: