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Add builtin functions for destroy, with special requirements in facet types (#6035)

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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>
This commit is contained in:
Jon Ross-Perkins
2025-09-15 17:03:43 +00:00
committed by GitHub
co-authored by Dana Jansens
parent 3ec0bcb4fd
commit 5e3bb523f8
401 changed files with 20575 additions and 20097 deletions
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toolchain/lower/testdata/function/generic/call_impl_function.carbon
Vendored
+3 -3
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@@ -54,11 +54,11 @@ fn G() {
// CHECK:STDOUT:
// CHECK:STDOUT: define void @_CG.Main() !dbg !9 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %CallGenericMethod.call = call i32 @_CCallGenericMethod.Main.acc47153a1124d08(i32 10), !dbg !10
// CHECK:STDOUT: %CallGenericMethod.call = call i32 @_CCallGenericMethod.Main.dc54e41cb8a9bf68(i32 10), !dbg !10
// CHECK:STDOUT: ret void, !dbg !11
// CHECK:STDOUT: }
// CHECK:STDOUT:
// CHECK:STDOUT: define linkonce_odr i32 @_CCallGenericMethod.Main.acc47153a1124d08(i32 %x) !dbg !12 {
// CHECK:STDOUT: define linkonce_odr i32 @_CCallGenericMethod.Main.dc54e41cb8a9bf68(i32 %x) !dbg !12 {
// CHECK:STDOUT: entry:
// CHECK:STDOUT: %.loc36_15 = call i32 @"_CF.ImplsSomeInterface.Main:SomeInterface.Main"(i32 %x), !dbg !13
// CHECK:STDOUT: ret i32 %.loc36_15, !dbg !14
@@ -79,6 +79,6 @@ fn G() {
// CHECK:STDOUT: !9 = distinct !DISubprogram(name: "G", linkageName: "_CG.Main", scope: null, file: !3, line: 39, type: !5, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !10 = !DILocation(line: 40, column: 3, scope: !9)
// CHECK:STDOUT: !11 = !DILocation(line: 39, column: 1, scope: !9)
// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "CallGenericMethod", linkageName: "_CCallGenericMethod.Main.acc47153a1124d08", scope: null, file: !3, line: 35, type: !5, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !12 = distinct !DISubprogram(name: "CallGenericMethod", linkageName: "_CCallGenericMethod.Main.dc54e41cb8a9bf68", scope: null, file: !3, line: 35, type: !5, spFlags: DISPFlagDefinition, unit: !2)
// CHECK:STDOUT: !13 = !DILocation(line: 36, column: 10, scope: !12)
// CHECK:STDOUT: !14 = !DILocation(line: 36, column: 3, scope: !12)