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Auto merge of rust-lang#118457 - eholk:genfn, r=compiler-errors
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Add support for `gen fn`

This builds on rust-lang#116447 to add support for `gen fn` functions. For the most part we follow the same approach as desugaring `async fn`, but replacing `Future` with `Iterator` and `async {}` with `gen {}` for the body.

The version implemented here uses the return type of a `gen fn` as the yield type. For example:

```rust
gen fn count_to_three() -> i32 {
    yield 1;
    yield 2;
    yield 3;
}
```

In the future, I think we should experiment with a syntax like `gen fn count_to_three() yield i32 { ... }`, but that can go in another PR.

cc `@oli-obk` `@compiler-errors`
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@bors
bors committed Dec 5, 2023
2 parents ec94480 + 2c8dbd9 commit 56278a6
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Showing 36 changed files with 417 additions and 234 deletions.
55 changes: 28 additions & 27 deletions compiler/rustc_ast/src/ast.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1311,7 +1311,7 @@ pub struct Closure {
pub binder: ClosureBinder,
pub capture_clause: CaptureBy,
pub constness: Const,
pub asyncness: Async,
pub coro_kind: Option<CoroutineKind>,
pub movability: Movability,
pub fn_decl: P<FnDecl>,
pub body: P<Expr>,
Expand Down Expand Up @@ -2406,28 +2406,34 @@ pub enum Unsafe {
No,
}

/// Describes what kind of coroutine markers, if any, a function has.
///
/// Coroutine markers are things that cause the function to generate a coroutine, such as `async`,
/// which makes the function return `impl Future`, or `gen`, which makes the function return `impl
/// Iterator`.
#[derive(Copy, Clone, Encodable, Decodable, Debug)]
pub enum Async {
Yes { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
No,
pub enum CoroutineKind {
/// `async`, which evaluates to `impl Future`
Async { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
/// `gen`, which evaluates to `impl Iterator`
Gen { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
}

#[derive(Copy, Clone, Encodable, Decodable, Debug)]
pub enum Gen {
Yes { span: Span, closure_id: NodeId, return_impl_trait_id: NodeId },
No,
}

impl Async {
impl CoroutineKind {
pub fn is_async(self) -> bool {
matches!(self, Async::Yes { .. })
matches!(self, CoroutineKind::Async { .. })
}

pub fn is_gen(self) -> bool {
matches!(self, CoroutineKind::Gen { .. })
}

/// In this case this is an `async` return, the `NodeId` for the generated `impl Trait` item.
pub fn opt_return_id(self) -> Option<(NodeId, Span)> {
/// In this case this is an `async` or `gen` return, the `NodeId` for the generated `impl Trait`
/// item.
pub fn return_id(self) -> (NodeId, Span) {
match self {
Async::Yes { return_impl_trait_id, span, .. } => Some((return_impl_trait_id, span)),
Async::No => None,
CoroutineKind::Async { return_impl_trait_id, span, .. }
| CoroutineKind::Gen { return_impl_trait_id, span, .. } => (return_impl_trait_id, span),
}
}
}
Expand Down Expand Up @@ -2831,8 +2837,8 @@ impl Extern {
pub struct FnHeader {
/// The `unsafe` keyword, if any
pub unsafety: Unsafe,
/// The `async` keyword, if any
pub asyncness: Async,
/// Whether this is `async`, `gen`, or nothing.
pub coro_kind: Option<CoroutineKind>,
/// The `const` keyword, if any
pub constness: Const,
/// The `extern` keyword and corresponding ABI string, if any
Expand All @@ -2842,22 +2848,17 @@ pub struct FnHeader {
impl FnHeader {
/// Does this function header have any qualifiers or is it empty?
pub fn has_qualifiers(&self) -> bool {
let Self { unsafety, asyncness, constness, ext } = self;
let Self { unsafety, coro_kind, constness, ext } = self;
matches!(unsafety, Unsafe::Yes(_))
|| asyncness.is_async()
|| coro_kind.is_some()
|| matches!(constness, Const::Yes(_))
|| !matches!(ext, Extern::None)
}
}

impl Default for FnHeader {
fn default() -> FnHeader {
FnHeader {
unsafety: Unsafe::No,
asyncness: Async::No,
constness: Const::No,
ext: Extern::None,
}
FnHeader { unsafety: Unsafe::No, coro_kind: None, constness: Const::No, ext: Extern::None }
}
}

Expand Down Expand Up @@ -3177,7 +3178,7 @@ mod size_asserts {
static_assert_size!(Block, 32);
static_assert_size!(Expr, 72);
static_assert_size!(ExprKind, 40);
static_assert_size!(Fn, 152);
static_assert_size!(Fn, 160);
static_assert_size!(ForeignItem, 96);
static_assert_size!(ForeignItemKind, 24);
static_assert_size!(GenericArg, 24);
Expand Down
21 changes: 11 additions & 10 deletions compiler/rustc_ast/src/mut_visit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -121,8 +121,8 @@ pub trait MutVisitor: Sized {
noop_visit_fn_decl(d, self);
}

fn visit_asyncness(&mut self, a: &mut Async) {
noop_visit_asyncness(a, self);
fn visit_coro_kind(&mut self, a: &mut CoroutineKind) {
noop_visit_coro_kind(a, self);
}

fn visit_closure_binder(&mut self, b: &mut ClosureBinder) {
Expand Down Expand Up @@ -871,13 +871,14 @@ pub fn noop_visit_closure_binder<T: MutVisitor>(binder: &mut ClosureBinder, vis:
}
}

pub fn noop_visit_asyncness<T: MutVisitor>(asyncness: &mut Async, vis: &mut T) {
match asyncness {
Async::Yes { span: _, closure_id, return_impl_trait_id } => {
pub fn noop_visit_coro_kind<T: MutVisitor>(coro_kind: &mut CoroutineKind, vis: &mut T) {
match coro_kind {
CoroutineKind::Async { span, closure_id, return_impl_trait_id }
| CoroutineKind::Gen { span, closure_id, return_impl_trait_id } => {
vis.visit_span(span);
vis.visit_id(closure_id);
vis.visit_id(return_impl_trait_id);
}
Async::No => {}
}
}

Expand Down Expand Up @@ -1170,9 +1171,9 @@ fn visit_const_item<T: MutVisitor>(
}

pub fn noop_visit_fn_header<T: MutVisitor>(header: &mut FnHeader, vis: &mut T) {
let FnHeader { unsafety, asyncness, constness, ext: _ } = header;
let FnHeader { unsafety, coro_kind, constness, ext: _ } = header;
visit_constness(constness, vis);
vis.visit_asyncness(asyncness);
coro_kind.as_mut().map(|coro_kind| vis.visit_coro_kind(coro_kind));
visit_unsafety(unsafety, vis);
}

Expand Down Expand Up @@ -1406,7 +1407,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
binder,
capture_clause,
constness,
asyncness,
coro_kind,
movability: _,
fn_decl,
body,
Expand All @@ -1415,7 +1416,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
}) => {
vis.visit_closure_binder(binder);
visit_constness(constness, vis);
vis.visit_asyncness(asyncness);
coro_kind.as_mut().map(|coro_kind| vis.visit_coro_kind(coro_kind));
vis.visit_capture_by(capture_clause);
vis.visit_fn_decl(fn_decl);
vis.visit_expr(body);
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_ast/src/visit.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -861,7 +861,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
ExprKind::Closure(box Closure {
binder,
capture_clause,
asyncness: _,
coro_kind: _,
constness: _,
movability: _,
fn_decl,
Expand Down
56 changes: 28 additions & 28 deletions compiler/rustc_ast_lowering/src/expr.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -195,39 +195,39 @@ impl<'hir> LoweringContext<'_, 'hir> {
binder,
capture_clause,
constness,
asyncness,
coro_kind,
movability,
fn_decl,
body,
fn_decl_span,
fn_arg_span,
}) => {
if let Async::Yes { closure_id, .. } = asyncness {
self.lower_expr_async_closure(
binder,
*capture_clause,
e.id,
hir_id,
*closure_id,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
)
} else {
self.lower_expr_closure(
binder,
*capture_clause,
e.id,
*constness,
*movability,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
)
}
}
}) => match coro_kind {
Some(
CoroutineKind::Async { closure_id, .. }
| CoroutineKind::Gen { closure_id, .. },
) => self.lower_expr_async_closure(
binder,
*capture_clause,
e.id,
hir_id,
*closure_id,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
),
None => self.lower_expr_closure(
binder,
*capture_clause,
e.id,
*constness,
*movability,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
),
},
ExprKind::Block(blk, opt_label) => {
let opt_label = self.lower_label(*opt_label);
hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
Expand Down
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