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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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143
compiler/rustc_mir_transform/src/coroutine.rs
View file

@ -224,7 +224,7 @@ struct SuspensionPoint<'tcx> {
struct TransformVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
is_async_kind: bool,
coroutine_kind: hir::CoroutineKind,
state_adt_ref: AdtDef<'tcx>,
state_args: GenericArgsRef<'tcx>,
@ -249,6 +249,47 @@ struct TransformVisitor<'tcx> {
}
impl<'tcx> TransformVisitor<'tcx> {
fn insert_none_ret_block(&self, body: &mut Body<'tcx>) -> BasicBlock {
let block = BasicBlock::new(body.basic_blocks.len());
let source_info = SourceInfo::outermost(body.span);
let (kind, idx) = self.coroutine_state_adt_and_variant_idx(true);
assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
let statements = vec![Statement {
kind: StatementKind::Assign(Box::new((
Place::return_place(),
Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
))),
source_info,
}];
body.basic_blocks_mut().push(BasicBlockData {
statements,
terminator: Some(Terminator { source_info, kind: TerminatorKind::Return }),
is_cleanup: false,
});
block
}
fn coroutine_state_adt_and_variant_idx(
&self,
is_return: bool,
) -> (AggregateKind<'tcx>, VariantIdx) {
let idx = VariantIdx::new(match (is_return, self.coroutine_kind) {
(true, hir::CoroutineKind::Coroutine) => 1, // CoroutineState::Complete
(false, hir::CoroutineKind::Coroutine) => 0, // CoroutineState::Yielded
(true, hir::CoroutineKind::Async(_)) => 0, // Poll::Ready
(false, hir::CoroutineKind::Async(_)) => 1, // Poll::Pending
(true, hir::CoroutineKind::Gen(_)) => 0, // Option::None
(false, hir::CoroutineKind::Gen(_)) => 1, // Option::Some
});
let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
(kind, idx)
}
// Make a `CoroutineState` or `Poll` variant assignment.
//
// `core::ops::CoroutineState` only has single element tuple variants,
@ -261,31 +302,44 @@ impl<'tcx> TransformVisitor<'tcx> {
is_return: bool,
statements: &mut Vec<Statement<'tcx>>,
) {
let idx = VariantIdx::new(match (is_return, self.is_async_kind) {
(true, false) => 1, // CoroutineState::Complete
(false, false) => 0, // CoroutineState::Yielded
(true, true) => 0, // Poll::Ready
(false, true) => 1, // Poll::Pending
});
let (kind, idx) = self.coroutine_state_adt_and_variant_idx(is_return);
let kind = AggregateKind::Adt(self.state_adt_ref.did(), idx, self.state_args, None, None);
match self.coroutine_kind {
// `Poll::Pending`
CoroutineKind::Async(_) => {
if !is_return {
assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
// `Poll::Pending`
if self.is_async_kind && idx == VariantIdx::new(1) {
assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
// FIXME(swatinem): assert that `val` is indeed unit?
statements.push(Statement {
kind: StatementKind::Assign(Box::new((
Place::return_place(),
Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
))),
source_info,
});
return;
}
}
// `Option::None`
CoroutineKind::Gen(_) => {
if is_return {
assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 0);
// FIXME(swatinem): assert that `val` is indeed unit?
statements.push(Statement {
kind: StatementKind::Assign(Box::new((
Place::return_place(),
Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
))),
source_info,
});
return;
statements.push(Statement {
kind: StatementKind::Assign(Box::new((
Place::return_place(),
Rvalue::Aggregate(Box::new(kind), IndexVec::new()),
))),
source_info,
});
return;
}
}
CoroutineKind::Coroutine => {}
}
// else: `Poll::Ready(x)`, `CoroutineState::Yielded(x)` or `CoroutineState::Complete(x)`
// else: `Poll::Ready(x)`, `CoroutineState::Yielded(x)`, `CoroutineState::Complete(x)`, or `Option::Some(x)`
assert_eq!(self.state_adt_ref.variant(idx).fields.len(), 1);
statements.push(Statement {
@ -1263,10 +1317,13 @@ fn create_coroutine_resume_function<'tcx>(
}
if can_return {
cases.insert(
1,
(RETURNED, insert_panic_block(tcx, body, ResumedAfterReturn(coroutine_kind))),
);
let block = match coroutine_kind {
CoroutineKind::Async(_) | CoroutineKind::Coroutine => {
insert_panic_block(tcx, body, ResumedAfterReturn(coroutine_kind))
}
CoroutineKind::Gen(_) => transform.insert_none_ret_block(body),
};
cases.insert(1, (RETURNED, block));
}
insert_switch(body, cases, &transform, TerminatorKind::Unreachable);
@ -1439,18 +1496,28 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
};
let is_async_kind = matches!(body.coroutine_kind(), Some(CoroutineKind::Async(_)));
let (state_adt_ref, state_args) = if is_async_kind {
// Compute Poll<return_ty>
let poll_did = tcx.require_lang_item(LangItem::Poll, None);
let poll_adt_ref = tcx.adt_def(poll_did);
let poll_args = tcx.mk_args(&[body.return_ty().into()]);
(poll_adt_ref, poll_args)
} else {
// Compute CoroutineState<yield_ty, return_ty>
let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);
let state_adt_ref = tcx.adt_def(state_did);
let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
(state_adt_ref, state_args)
let (state_adt_ref, state_args) = match body.coroutine_kind().unwrap() {
CoroutineKind::Async(_) => {
// Compute Poll<return_ty>
let poll_did = tcx.require_lang_item(LangItem::Poll, None);
let poll_adt_ref = tcx.adt_def(poll_did);
let poll_args = tcx.mk_args(&[body.return_ty().into()]);
(poll_adt_ref, poll_args)
}
CoroutineKind::Gen(_) => {
// Compute Option<yield_ty>
let option_did = tcx.require_lang_item(LangItem::Option, None);
let option_adt_ref = tcx.adt_def(option_did);
let option_args = tcx.mk_args(&[body.yield_ty().unwrap().into()]);
(option_adt_ref, option_args)
}
CoroutineKind::Coroutine => {
// Compute CoroutineState<yield_ty, return_ty>
let state_did = tcx.require_lang_item(LangItem::CoroutineState, None);
let state_adt_ref = tcx.adt_def(state_did);
let state_args = tcx.mk_args(&[yield_ty.into(), body.return_ty().into()]);
(state_adt_ref, state_args)
}
};
let ret_ty = Ty::new_adt(tcx, state_adt_ref, state_args);
@ -1518,7 +1585,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
// or Poll::Ready(x) and Poll::Pending respectively depending on `is_async_kind`.
let mut transform = TransformVisitor {
tcx,
is_async_kind,
coroutine_kind: body.coroutine_kind().unwrap(),
state_adt_ref,
state_args,
remap,