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carbon-lang/toolchain/check/testdata/impl/lookup/fail_todo_undefined_impl.carbon
T
Jon Ross-PerkinsandDana Jansens 5e3bb523f8 Add builtin functions for destroy, with special requirements in facet types (#6035) 
This is in support of a goal of changing the blanket `destroy` impl to
use (roughly):

```
private fn CanAggregateDestroy() -> type = "type.can_aggregate_destroy";

// Handles aggregate type destruction.
impl forall [AggregateDestroyT:! CanAggregateDestroy()] AggregateDestroyT as Destroy {
  fn Op[addr self: Self*]() = "type.aggregate_destroy";
}
```

That isn't done here because there's still other issues that migrating
raises. What this *does* do is add the builtin functions, and in
particular, support to `FacetTypeInfo` to make `CanAggregateDestroy`
work.

The "special requirement" approach in `FacetTypeInfo` allows us to
support restricting a blanket impl under the current approach of impls.
Maybe we'll find a cleaner approach that can work in the future, but
this fits into the current model by propagating similar to other
requirements. I'm using an enum mask because we have a number of similar
things to add (e.g. copy, move) but I'm not sure we need a full vector.

A few alternatives considered were:

- Supporting syntax more like `where .Self impls
TypeCanAggregateDestroy(.Self, SupportedInterface,
UnsupportedInterface)`. I think it'd be a little cleaner, but requires
better compile-time evaluation in order to assess the type of the call.
Right now it's expected to be a `FacetType` too early to make this work,
and I was concerned about pouring too much more time down this route.
- Providing an actual interface, in particular doing name lookup back
into `Core.` for an interface. This would've added name lookup overhead,
and the question of whether an `impl` exists.
- Generating an interface. This avoids the name lookup, but would still
raise the question of whether an `impl` should also be generated. Work
I've previously done generating interfaces for class destruction also
feels complex to both write and understand (an unfortunate issue).
- Still modeling as an `ImplsConstraint`, for example by defining a
special `InterfaceId::CanAggregateDestroy = -2` similar to what we do on
other ids. I was hesitant because of how this expands the number of
modes of `InterfaceId`, and things for consuming code to watch out for,
for what feels like a relatively niche set of use-cases that are only
interface-like.

---------

Co-authored-by: Dana Jansens <danakj@orodu.net>
2025-09-15 17:03:43 +00:00

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// 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
//
// INCLUDE-FILE: toolchain/testing/testdata/min_prelude/none.carbon
// TODO: Add ranges and switch to "--dump-sem-ir-ranges=only".
// EXTRA-ARGS: --dump-sem-ir-ranges=if-present
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/impl/lookup/fail_todo_undefined_impl.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/impl/lookup/fail_todo_undefined_impl.carbon
interface I {
fn F();
}
class C {
// This doesn't match `impl C as I` below under proposal #3763.
extend impl as I;
}
fn F() {
// CHECK:STDERR: fail_todo_undefined_impl.carbon:[[@LINE+4]]:3: error: accessing member from impl before it has a defined value [ImplAccessMemberBeforeSet]
// CHECK:STDERR: C.F();
// CHECK:STDERR: ^~~
// CHECK:STDERR:
C.F();
}
// TODO: This should be written `impl C.(Self as I)` or `impl C.(as I)`, once
// that is supported.
impl C as I {
fn F() {}
}
fn G() {
// CHECK:STDERR: fail_todo_undefined_impl.carbon:[[@LINE+8]]:3: error: accessing member from impl before it has a defined value [ImplAccessMemberBeforeSet]
// CHECK:STDERR: C.F();
// CHECK:STDERR: ^~~
// CHECK:STDERR:
// CHECK:STDERR: fail_todo_undefined_impl.carbon:[[@LINE-22]]:3: error: impl declared but not defined [ImplMissingDefinition]
// CHECK:STDERR: extend impl as I;
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~
// CHECK:STDERR:
C.F();
}
// CHECK:STDOUT: --- fail_todo_undefined_impl.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %I.type: type = facet_type <@I> [concrete]
// CHECK:STDOUT: %Self: %I.type = bind_symbolic_name Self, 0 [symbolic]
// CHECK:STDOUT: %I.F.type: type = fn_type @I.F [concrete]
// CHECK:STDOUT: %I.F: %I.F.type = struct_value () [concrete]
// CHECK:STDOUT: %I.assoc_type: type = assoc_entity_type @I [concrete]
// CHECK:STDOUT: %assoc0: %I.assoc_type = assoc_entity element0, @I.%I.F.decl [concrete]
// CHECK:STDOUT: %C: type = class_type @C [concrete]
// CHECK:STDOUT: %I.impl_witness.874: <witness> = impl_witness @C.%I.impl_witness_table [concrete]
// CHECK:STDOUT: %empty_struct_type: type = struct_type {} [concrete]
// CHECK:STDOUT: %complete_type: <witness> = complete_type_witness %empty_struct_type [concrete]
// CHECK:STDOUT: %F.type: type = fn_type @F [concrete]
// CHECK:STDOUT: %F: %F.type = struct_value () [concrete]
// CHECK:STDOUT: %I.facet.2cf: %I.type = facet_value %C, (%I.impl_witness.874) [concrete]
// CHECK:STDOUT: %.4d6: type = fn_type_with_self_type %I.F.type, %I.facet.2cf [concrete]
// CHECK:STDOUT: %I.impl_witness.686: <witness> = impl_witness file.%I.impl_witness_table [concrete]
// CHECK:STDOUT: %C.as.I.impl.F.type: type = fn_type @C.as.I.impl.F [concrete]
// CHECK:STDOUT: %C.as.I.impl.F: %C.as.I.impl.F.type = struct_value () [concrete]
// CHECK:STDOUT: %I.facet.137: %I.type = facet_value %C, (%I.impl_witness.686) [concrete]
// CHECK:STDOUT: %G.type: type = fn_type @G [concrete]
// CHECK:STDOUT: %G: %G.type = struct_value () [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: package: <namespace> = namespace [concrete] {
// CHECK:STDOUT: .I = %I.decl
// CHECK:STDOUT: .C = %C.decl
// CHECK:STDOUT: .F = %F.decl
// CHECK:STDOUT: .G = %G.decl
// CHECK:STDOUT: }
// CHECK:STDOUT: %I.decl: type = interface_decl @I [concrete = constants.%I.type] {} {}
// CHECK:STDOUT: %C.decl: type = class_decl @C [concrete = constants.%C] {} {}
// CHECK:STDOUT: %F.decl: %F.type = fn_decl @F [concrete = constants.%F] {} {}
// CHECK:STDOUT: impl_decl @C.as.I.impl.7de [concrete] {} {
// CHECK:STDOUT: %C.ref: type = name_ref C, file.%C.decl [concrete = constants.%C]
// CHECK:STDOUT: %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
// CHECK:STDOUT: }
// CHECK:STDOUT: %I.impl_witness_table = impl_witness_table (@C.as.I.impl.7de.%C.as.I.impl.F.decl), @C.as.I.impl.7de [concrete]
// CHECK:STDOUT: %I.impl_witness: <witness> = impl_witness %I.impl_witness_table [concrete = constants.%I.impl_witness.686]
// CHECK:STDOUT: %G.decl: %G.type = fn_decl @G [concrete = constants.%G] {} {}
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: interface @I {
// CHECK:STDOUT: %Self: %I.type = bind_symbolic_name Self, 0 [symbolic = constants.%Self]
// CHECK:STDOUT: %I.F.decl: %I.F.type = fn_decl @I.F [concrete = constants.%I.F] {} {}
// CHECK:STDOUT: %assoc0: %I.assoc_type = assoc_entity element0, %I.F.decl [concrete = constants.%assoc0]
// CHECK:STDOUT:
// CHECK:STDOUT: !members:
// CHECK:STDOUT: .Self = %Self
// CHECK:STDOUT: .F = %assoc0
// CHECK:STDOUT: witness = (%I.F.decl)
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: impl @C.as.I.impl.bd0: %Self.ref as %I.ref;
// CHECK:STDOUT:
// CHECK:STDOUT: impl @C.as.I.impl.7de: %C.ref as %I.ref {
// CHECK:STDOUT: %C.as.I.impl.F.decl: %C.as.I.impl.F.type = fn_decl @C.as.I.impl.F [concrete = constants.%C.as.I.impl.F] {} {}
// CHECK:STDOUT:
// CHECK:STDOUT: !members:
// CHECK:STDOUT: .F = %C.as.I.impl.F.decl
// CHECK:STDOUT: witness = file.%I.impl_witness
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: class @C {
// CHECK:STDOUT: impl_decl @C.as.I.impl.bd0 [concrete] {} {
// CHECK:STDOUT: %Self.ref: type = name_ref Self, constants.%C [concrete = constants.%C]
// CHECK:STDOUT: %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
// CHECK:STDOUT: }
// CHECK:STDOUT: %I.impl_witness_table = impl_witness_table (), @C.as.I.impl.bd0 [concrete]
// CHECK:STDOUT: %I.impl_witness: <witness> = impl_witness %I.impl_witness_table [concrete = constants.%I.impl_witness.874]
// CHECK:STDOUT: %complete_type: <witness> = complete_type_witness constants.%empty_struct_type [concrete = constants.%complete_type]
// CHECK:STDOUT: complete_type_witness = %complete_type
// CHECK:STDOUT:
// CHECK:STDOUT: !members:
// CHECK:STDOUT: .Self = constants.%C
// CHECK:STDOUT: .I = <poisoned>
// CHECK:STDOUT: .F = <poisoned>
// CHECK:STDOUT: extend @C.as.I.impl.bd0.%I.ref
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: generic fn @I.F(@I.%Self: %I.type) {
// CHECK:STDOUT: fn();
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @F() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %C.ref: type = name_ref C, file.%C.decl [concrete = constants.%C]
// CHECK:STDOUT: %F.ref: %I.assoc_type = name_ref F, @I.%assoc0 [concrete = constants.%assoc0]
// CHECK:STDOUT: %impl.elem0: %.4d6 = impl_witness_access constants.%I.impl_witness.874, element0 [concrete = <error>]
// CHECK:STDOUT: return
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @C.as.I.impl.F() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: return
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: fn @G() {
// CHECK:STDOUT: !entry:
// CHECK:STDOUT: %C.ref: type = name_ref C, file.%C.decl [concrete = constants.%C]
// CHECK:STDOUT: %F.ref: %I.assoc_type = name_ref F, @I.%assoc0 [concrete = constants.%assoc0]
// CHECK:STDOUT: %impl.elem0: %.4d6 = impl_witness_access constants.%I.impl_witness.874, element0 [concrete = <error>]
// CHECK:STDOUT: return
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: specific @I.F(constants.%Self) {}
// CHECK:STDOUT:
// CHECK:STDOUT: specific @I.F(constants.%I.facet.137) {}
// CHECK:STDOUT:
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