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Auto merge of #116447 - oli-obk:gen_fn, r=compiler-errors

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Implement `gen` blocks in the 2024 edition

Coroutines tracking issue https://github.com/rust-lang/rust/issues/43122
`gen` block tracking issue https://github.com/rust-lang/rust/issues/117078

This PR implements `gen` blocks that implement `Iterator`. Most of the logic with `async` blocks is shared, and thus I renamed various types that were referring to `async` specifically.

An example usage of `gen` blocks is

```rust
fn foo() -> impl Iterator<Item = i32> {
    gen {
        yield 42;
        for i in 5..18 {
            if i.is_even() { continue }
            yield i * 2;
        }
    }
}
```

The limitations (to be resolved) of the implementation are listed in the tracking issue
This commit is contained in:
bors 2023-10-29 00:03:52 +00:00
commit 2cad938a81
75 changed files with 1096 additions and 148 deletions
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13
compiler/rustc_ty_utils/src/instance.rs
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@ -258,6 +258,19 @@ fn resolve_associated_item<'tcx>(
debug_assert!(tcx.defaultness(trait_item_id).has_value());
Some(Instance::new(trait_item_id, rcvr_args))
}
} else if Some(trait_ref.def_id) == lang_items.iterator_trait() {
let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
bug!()
};
if Some(trait_item_id) == tcx.lang_items().next_fn() {
// `Iterator::next` is generated by the compiler.
Some(Instance { def: ty::InstanceDef::Item(coroutine_def_id), args })
} else {
// All other methods are default methods of the `Iterator` trait.
// (this assumes that `ImplSource::Builtin` is only used for methods on `Iterator`)
debug_assert!(tcx.defaultness(trait_item_id).has_value());
Some(Instance::new(trait_item_id, rcvr_args))
}
} else if Some(trait_ref.def_id) == lang_items.gen_trait() {
let ty::Coroutine(coroutine_def_id, args, _) = *rcvr_args.type_at(0).kind() else {
bug!()