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Rollup merge of rust-lang#126754 - compiler-errors:use-rustfmt, r=cal…
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…ebcartwright

Implement `use<>` formatting in rustfmt

This PR implements formatting for precise-capturing `use<>` syntax as proposed in rust-lang#126753.

The syntax is implemented as-if the `use<>` bound were a trait bound but with the `use` keyword as its path segment identifier.

I opted to develop this in the rust-lang/rust tree since I'm not certain when the next rustfmt subtree sync is going to be, and I'd rather not block landing nightly support for `use<>` on something I have no control over. If ``@rust-lang/rustfmt`` would rather I move this PR over to that repository, then I would at least like to know when the next rustfmt->rust subtree sync is going to be, since stabilizing `precise_capturing` without formatting will be disruptive.

This implementation is otherwise rather straightforward.

Tracking:

- rust-lang#123432
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matthiaskrgr authored Jun 24, 2024
2 parents ad0531a + a426d6f commit b24e3df
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Showing 5 changed files with 105 additions and 9 deletions.
15 changes: 14 additions & 1 deletion src/tools/rustfmt/src/overflow.rs
Original file line number Diff line number Diff line change
Expand Up @@ -83,6 +83,7 @@ pub(crate) enum OverflowableItem<'a> {
TuplePatField(&'a TuplePatField<'a>),
Ty(&'a ast::Ty),
Pat(&'a ast::Pat),
PreciseCapturingArg(&'a ast::PreciseCapturingArg),
}

impl<'a> Rewrite for OverflowableItem<'a> {
Expand Down Expand Up @@ -123,6 +124,7 @@ impl<'a> OverflowableItem<'a> {
OverflowableItem::TuplePatField(pat) => f(*pat),
OverflowableItem::Ty(ty) => f(*ty),
OverflowableItem::Pat(pat) => f(*pat),
OverflowableItem::PreciseCapturingArg(arg) => f(*arg),
}
}

Expand All @@ -137,6 +139,9 @@ impl<'a> OverflowableItem<'a> {
matches!(meta_item.kind, ast::MetaItemKind::Word)
}
},
// FIXME: Why don't we consider `SegmentParam` to be simple?
// FIXME: If we also fix `SegmentParam`, then we should apply the same
// heuristic to `PreciseCapturingArg`.
_ => false,
}
}
Expand Down Expand Up @@ -244,7 +249,15 @@ macro_rules! impl_into_overflowable_item_for_rustfmt_types {
}
}

impl_into_overflowable_item_for_ast_node!(Expr, GenericParam, NestedMetaItem, FieldDef, Ty, Pat);
impl_into_overflowable_item_for_ast_node!(
Expr,
GenericParam,
NestedMetaItem,
FieldDef,
Ty,
Pat,
PreciseCapturingArg
);
impl_into_overflowable_item_for_rustfmt_types!([MacroArg], [SegmentParam, TuplePatField]);

pub(crate) fn into_overflowable_list<'a, T>(
Expand Down
9 changes: 9 additions & 0 deletions src/tools/rustfmt/src/spanned.rs
Original file line number Diff line number Diff line change
Expand Up @@ -203,3 +203,12 @@ impl Spanned for ast::NestedMetaItem {
self.span()
}
}

impl Spanned for ast::PreciseCapturingArg {
fn span(&self) -> Span {
match self {
ast::PreciseCapturingArg::Lifetime(lt) => lt.ident.span,
ast::PreciseCapturingArg::Arg(path, _) => path.span,
}
}
}
26 changes: 18 additions & 8 deletions src/tools/rustfmt/src/types.rs
Original file line number Diff line number Diff line change
Expand Up @@ -177,6 +177,17 @@ impl<'a> Rewrite for SegmentParam<'a> {
}
}

impl Rewrite for ast::PreciseCapturingArg {
fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
match self {
ast::PreciseCapturingArg::Lifetime(lt) => lt.rewrite(context, shape),
ast::PreciseCapturingArg::Arg(p, _) => {
rewrite_path(context, PathContext::Type, &None, p, shape)
}
}
}
}

impl Rewrite for ast::AssocItemConstraint {
fn rewrite(&self, context: &RewriteContext<'_>, shape: Shape) -> Option<String> {
use ast::AssocItemConstraintKind::{Bound, Equality};
Expand Down Expand Up @@ -564,9 +575,10 @@ impl Rewrite for ast::GenericBound {
.map(|s| format!("{constness}{asyncness}{polarity}{s}"))
.map(|s| if has_paren { format!("({})", s) } else { s })
}
ast::GenericBound::Use(ref args, span) => {
overflow::rewrite_with_angle_brackets(context, "use", args.iter(), shape, span)
}
ast::GenericBound::Outlives(ref lifetime) => lifetime.rewrite(context, shape),
// FIXME(precise_capturing): Should implement formatting before stabilization.
ast::GenericBound::Use(..) => None,
}
}
}
Expand Down Expand Up @@ -933,9 +945,7 @@ fn rewrite_bare_fn(
fn is_generic_bounds_in_order(generic_bounds: &[ast::GenericBound]) -> bool {
let is_trait = |b: &ast::GenericBound| match b {
ast::GenericBound::Outlives(..) => false,
ast::GenericBound::Trait(..) => true,
// FIXME(precise_capturing): This ordering fn should be reworked.
ast::GenericBound::Use(..) => false,
ast::GenericBound::Trait(..) | ast::GenericBound::Use(..) => true,
};
let is_lifetime = |b: &ast::GenericBound| !is_trait(b);
let last_trait_index = generic_bounds.iter().rposition(is_trait);
Expand Down Expand Up @@ -969,9 +979,8 @@ fn join_bounds_inner(
let generic_bounds_in_order = is_generic_bounds_in_order(items);
let is_bound_extendable = |s: &str, b: &ast::GenericBound| match b {
ast::GenericBound::Outlives(..) => true,
ast::GenericBound::Trait(..) => last_line_extendable(s),
// FIXME(precise_capturing): This ordering fn should be reworked.
ast::GenericBound::Use(..) => true,
// We treat `use<>` like a trait bound here.
ast::GenericBound::Trait(..) | ast::GenericBound::Use(..) => last_line_extendable(s),
};

// Whether a GenericBound item is a PathSegment segment that includes internal array
Expand All @@ -993,6 +1002,7 @@ fn join_bounds_inner(
}
}
}
ast::GenericBound::Use(args, _) => args.len() > 1,
_ => false,
};

Expand Down
9 changes: 9 additions & 0 deletions src/tools/rustfmt/tests/source/precise-capturing.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
fn hello() -> impl
use<'a> + Sized {}

fn all_three() -> impl Sized + use<'a> + 'a;

fn pathological() -> impl use<'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a,
'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a,
'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a,
'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a, 'a> + Sized {}
55 changes: 55 additions & 0 deletions src/tools/rustfmt/tests/target/precise-capturing.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,55 @@
fn hello() -> impl use<'a> + Sized {}

fn all_three() -> impl Sized + use<'a> + 'a;

fn pathological() -> impl use<
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
'a,
> + Sized {
}

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