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carbon-lang/toolchain/check/testdata/where_expr/designator.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/convert.carbon
//
// AUTOUPDATE
// TIP: To test this file alone, run:
// TIP: bazel test //toolchain/testing:file_test --test_arg=--file_tests=toolchain/check/testdata/where_expr/designator.carbon
// TIP: To dump output, run:
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/check/testdata/where_expr/designator.carbon
// --- success.carbon
library "[[@TEST_NAME]]";
interface I {
let Member:! type;
}
//@dump-sem-ir-begin
fn PeriodSelf(T:! I where .Self == ());
fn PeriodMember(U:! I where .Member == ());
fn TypeSelfImpls(V:! type where .Self impls I);
//@dump-sem-ir-end
// --- fail_wrong_member.carbon
library "[[@TEST_NAME]]";
interface J {
let Member:! type;
}
// CHECK:STDERR: fail_wrong_member.carbon:[[@LINE+4]]:31: error: member name `Mismatch` not found in `J` [MemberNameNotFoundInInstScope]
// CHECK:STDERR: fn PeriodMismatch(W:! J where .Mismatch = {});
// CHECK:STDERR: ^~~~~~~~~
// CHECK:STDERR:
fn PeriodMismatch(W:! J where .Mismatch = {});
// --- fail_designator_matches_var.carbon
library "[[@TEST_NAME]]";
fn Foo() -> () {
var x: ();
// CHECK:STDERR: fail_designator_matches_var.carbon:[[@LINE+5]]:10: error: name `.Self` not found [NameNotFound]
// CHECK:STDERR: return .x;
// CHECK:STDERR: ^~
// CHECK:STDERR: fail_designator_matches_var.carbon: note: designator may only be used when `.Self` is in scope [NoPeriodSelfForDesignator]
// CHECK:STDERR:
return .x;
}
// --- fail_unknown_designator.carbon
library "[[@TEST_NAME]]";
fn Bar() -> () {
// CHECK:STDERR: fail_unknown_designator.carbon:[[@LINE+5]]:10: error: name `.Self` not found [NameNotFound]
// CHECK:STDERR: return .undef;
// CHECK:STDERR: ^~~~~~
// CHECK:STDERR: fail_unknown_designator.carbon: note: designator may only be used when `.Self` is in scope [NoPeriodSelfForDesignator]
// CHECK:STDERR:
return .undef;
}
// --- fail_dot_self_method_return_value.carbon
library "[[@TEST_NAME]]";
class C {
// CHECK:STDERR: fail_dot_self_method_return_value.carbon:[[@LINE+4]]:27: error: name `.Self` not found [NameNotFound]
// CHECK:STDERR: fn F() -> Self { return .Self; }
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
fn F() -> Self { return .Self; }
}
// --- fail_dot_self_method_return_type.carbon
library "[[@TEST_NAME]]";
class D {
// CHECK:STDERR: fail_dot_self_method_return_type.carbon:[[@LINE+4]]:13: error: name `.Self` not found [NameNotFound]
// CHECK:STDERR: fn G() -> .Self { return Self; }
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
fn G() -> .Self { return Self; }
}
// --- todo_fail_impls_constraint_does_not_constrain_self.carbon
library "[[@TEST_NAME]]";
interface I {}
// TODO: Diagnose that the `where` on `T` does not refer to `.Self` at all.
// See https://docs.carbon-lang.dev/docs/design/generics/details.html#constraints-must-use-a-designator
fn F(U:! type, T:! type where U impls I) {}
// --- todo_fail_equality_constraint_does_not_constrain_self.carbon
library "[[@TEST_NAME]]";
interface I {
let X:! type;
}
// TODO: Diagnose that the `where` on `T` does not refer to `.Self` at all.
// See https://docs.carbon-lang.dev/docs/design/generics/details.html#constraints-must-use-a-designator
fn F(U:! I, T:! type where U.X == ()) {}
// --- todo_fail_combined_constraint_does_not_constrain_self.carbon
library "[[@TEST_NAME]]";
interface I {
let X:! type;
}
// TODO: Diagnose that the `where` on `T` does not refer to `.Self` at all.
// See https://docs.carbon-lang.dev/docs/design/generics/details.html#constraints-must-use-a-designator
fn F(U:! I, T:! type where U impls I and U.X == ()) {}
// --- impls_constraint_does_constrain_self.carbon
library "[[@TEST_NAME]]";
interface I(T:! type) {}
class C(T:! type);
fn F(T:! type where C(.Self) impls I(())) {}
fn G(T:! type where C(()) impls I(.Self)) {}
// CHECK:STDOUT: --- success.carbon
// CHECK:STDOUT:
// CHECK:STDOUT: constants {
// CHECK:STDOUT: %I.type: type = facet_type <@I> [concrete]
// CHECK:STDOUT: %I.assoc_type: type = assoc_entity_type @I [concrete]
// CHECK:STDOUT: %assoc0: %I.assoc_type = assoc_entity element0, @I.%Member [concrete]
// CHECK:STDOUT: %.Self.364: %I.type = bind_symbolic_name .Self [symbolic_self]
// CHECK:STDOUT: %empty_tuple.type: type = tuple_type () [concrete]
// CHECK:STDOUT: %I_where.type: type = facet_type <@I where TODO> [concrete]
// CHECK:STDOUT: %T: %I_where.type = bind_symbolic_name T, 0 [symbolic]
// CHECK:STDOUT: %pattern_type.917: type = pattern_type %I_where.type [concrete]
// CHECK:STDOUT: %PeriodSelf.type: type = fn_type @PeriodSelf [concrete]
// CHECK:STDOUT: %PeriodSelf: %PeriodSelf.type = struct_value () [concrete]
// CHECK:STDOUT: %.Self.as_type: type = facet_access_type %.Self.364 [symbolic_self]
// CHECK:STDOUT: %I.lookup_impl_witness: <witness> = lookup_impl_witness %.Self.364, @I [symbolic_self]
// CHECK:STDOUT: %impl.elem0: type = impl_witness_access %I.lookup_impl_witness, element0 [symbolic_self]
// CHECK:STDOUT: %U: %I_where.type = bind_symbolic_name U, 0 [symbolic]
// CHECK:STDOUT: %PeriodMember.type: type = fn_type @PeriodMember [concrete]
// CHECK:STDOUT: %PeriodMember: %PeriodMember.type = struct_value () [concrete]
// CHECK:STDOUT: %.Self.644: type = bind_symbolic_name .Self [symbolic_self]
// CHECK:STDOUT: %type_where: type = facet_type <type where .Self impls @I> [concrete]
// CHECK:STDOUT: %V: %type_where = bind_symbolic_name V, 0 [symbolic]
// CHECK:STDOUT: %pattern_type.09a: type = pattern_type %type_where [concrete]
// CHECK:STDOUT: %TypeSelfImpls.type: type = fn_type @TypeSelfImpls [concrete]
// CHECK:STDOUT: %TypeSelfImpls: %TypeSelfImpls.type = struct_value () [concrete]
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: imports {
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: file {
// CHECK:STDOUT: %PeriodSelf.decl: %PeriodSelf.type = fn_decl @PeriodSelf [concrete = constants.%PeriodSelf] {
// CHECK:STDOUT: %T.patt: %pattern_type.917 = symbolic_binding_pattern T, 0 [concrete]
// CHECK:STDOUT: } {
// CHECK:STDOUT: %.loc9_21.1: type = splice_block %.loc9_21.2 [concrete = constants.%I_where.type] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %.Self.ref: %I.type = name_ref .Self, %.Self.2 [symbolic_self = constants.%.Self.364]
// CHECK:STDOUT: %.loc9_37: %empty_tuple.type = tuple_literal ()
// CHECK:STDOUT: %.loc9_21.2: type = where_expr %.Self.2 [concrete = constants.%I_where.type] {
// CHECK:STDOUT: requirement_base_facet_type constants.%I.type
// CHECK:STDOUT: requirement_equivalent %.Self.ref, %.loc9_37
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT: %T.loc9_15.2: %I_where.type = bind_symbolic_name T, 0 [symbolic = %T.loc9_15.1 (constants.%T)]
// CHECK:STDOUT: }
// CHECK:STDOUT: %PeriodMember.decl: %PeriodMember.type = fn_decl @PeriodMember [concrete = constants.%PeriodMember] {
// CHECK:STDOUT: %U.patt: %pattern_type.917 = symbolic_binding_pattern U, 0 [concrete]
// CHECK:STDOUT: } {
// CHECK:STDOUT: %.loc11_23.1: type = splice_block %.loc11_23.2 [concrete = constants.%I_where.type] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %.Self.ref: %I.type = name_ref .Self, %.Self.2 [symbolic_self = constants.%.Self.364]
// CHECK:STDOUT: %Member.ref: %I.assoc_type = name_ref Member, @Member.%assoc0 [concrete = constants.%assoc0]
// CHECK:STDOUT: %.Self.as_type: type = facet_access_type %.Self.ref [symbolic_self = constants.%.Self.as_type]
// CHECK:STDOUT: %.loc11_29: type = converted %.Self.ref, %.Self.as_type [symbolic_self = constants.%.Self.as_type]
// CHECK:STDOUT: %impl.elem0: type = impl_witness_access constants.%I.lookup_impl_witness, element0 [symbolic_self = constants.%impl.elem0]
// CHECK:STDOUT: %.loc11_41: %empty_tuple.type = tuple_literal ()
// CHECK:STDOUT: %.loc11_23.2: type = where_expr %.Self.2 [concrete = constants.%I_where.type] {
// CHECK:STDOUT: requirement_base_facet_type constants.%I.type
// CHECK:STDOUT: requirement_equivalent %impl.elem0, %.loc11_41
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT: %U.loc11_17.2: %I_where.type = bind_symbolic_name U, 0 [symbolic = %U.loc11_17.1 (constants.%U)]
// CHECK:STDOUT: }
// CHECK:STDOUT: %TypeSelfImpls.decl: %TypeSelfImpls.type = fn_decl @TypeSelfImpls [concrete = constants.%TypeSelfImpls] {
// CHECK:STDOUT: %V.patt: %pattern_type.09a = symbolic_binding_pattern V, 0 [concrete]
// CHECK:STDOUT: } {
// CHECK:STDOUT: %.loc13_27.1: type = splice_block %.loc13_27.2 [concrete = constants.%type_where] {
// CHECK:STDOUT: <elided>
// CHECK:STDOUT: %.Self.ref: type = name_ref .Self, %.Self.2 [symbolic_self = constants.%.Self.644]
// CHECK:STDOUT: %I.ref: type = name_ref I, file.%I.decl [concrete = constants.%I.type]
// CHECK:STDOUT: %.loc13_27.2: type = where_expr %.Self.2 [concrete = constants.%type_where] {
// CHECK:STDOUT: requirement_base_facet_type type
// CHECK:STDOUT: requirement_impls %.Self.ref, %I.ref
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT: %V.loc13_18.2: %type_where = bind_symbolic_name V, 0 [symbolic = %V.loc13_18.1 (constants.%V)]
// CHECK:STDOUT: }
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: generic fn @PeriodSelf(%T.loc9_15.2: %I_where.type) {
// CHECK:STDOUT: %T.loc9_15.1: %I_where.type = bind_symbolic_name T, 0 [symbolic = %T.loc9_15.1 (constants.%T)]
// CHECK:STDOUT:
// CHECK:STDOUT: fn();
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: generic fn @PeriodMember(%U.loc11_17.2: %I_where.type) {
// CHECK:STDOUT: %U.loc11_17.1: %I_where.type = bind_symbolic_name U, 0 [symbolic = %U.loc11_17.1 (constants.%U)]
// CHECK:STDOUT:
// CHECK:STDOUT: fn();
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: generic fn @TypeSelfImpls(%V.loc13_18.2: %type_where) {
// CHECK:STDOUT: %V.loc13_18.1: %type_where = bind_symbolic_name V, 0 [symbolic = %V.loc13_18.1 (constants.%V)]
// CHECK:STDOUT:
// CHECK:STDOUT: fn();
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: specific @PeriodSelf(constants.%T) {
// CHECK:STDOUT: %T.loc9_15.1 => constants.%T
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: specific @PeriodMember(constants.%U) {
// CHECK:STDOUT: %U.loc11_17.1 => constants.%U
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: specific @TypeSelfImpls(constants.%V) {
// CHECK:STDOUT: %V.loc13_18.1 => constants.%V
// CHECK:STDOUT: }
// CHECK:STDOUT:
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