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Rollup merge of #127092 - compiler-errors:rtn-dots-redux, r=estebank
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Change return-type-notation to use `(..)`

Aligns the syntax with the current wording of [RFC 3654](rust-lang/rfcs#3654). Also implements rustfmt support (along with making a match exhaustive).

Tracking:
* #109417
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matthiaskrgr authored Jul 3, 2024
2 parents 2b90614 + 99365a5 commit 33e9f25
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Showing 51 changed files with 248 additions and 179 deletions.
5 changes: 4 additions & 1 deletion compiler/rustc_ast/src/ast.rs
Original file line number Diff line number Diff line change
Expand Up @@ -176,6 +176,8 @@ pub enum GenericArgs {
AngleBracketed(AngleBracketedArgs),
/// The `(A, B)` and `C` in `Foo(A, B) -> C`.
Parenthesized(ParenthesizedArgs),
/// `(..)` in return type notation
ParenthesizedElided(Span),
}

impl GenericArgs {
Expand All @@ -187,6 +189,7 @@ impl GenericArgs {
match self {
AngleBracketed(data) => data.span,
Parenthesized(data) => data.span,
ParenthesizedElided(span) => *span,
}
}
}
Expand Down Expand Up @@ -2051,7 +2054,7 @@ impl UintTy {
/// * the `A: Bound` in `Trait<A: Bound>`
/// * the `RetTy` in `Trait(ArgTy, ArgTy) -> RetTy`
/// * the `C = { Ct }` in `Trait<C = { Ct }>` (feature `associated_const_equality`)
/// * the `f(): Bound` in `Trait<f(): Bound>` (feature `return_type_notation`)
/// * the `f(..): Bound` in `Trait<f(..): Bound>` (feature `return_type_notation`)
#[derive(Clone, Encodable, Decodable, Debug)]
pub struct AssocItemConstraint {
pub id: NodeId,
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_ast/src/mut_visit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -582,6 +582,7 @@ fn noop_visit_generic_args<T: MutVisitor>(generic_args: &mut GenericArgs, vis: &
match generic_args {
GenericArgs::AngleBracketed(data) => vis.visit_angle_bracketed_parameter_data(data),
GenericArgs::Parenthesized(data) => vis.visit_parenthesized_parameter_data(data),
GenericArgs::ParenthesizedElided(span) => vis.visit_span(span),
}
}

Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_ast/src/util/classify.rs
Original file line number Diff line number Diff line change
Expand Up @@ -311,6 +311,6 @@ fn path_return_type(path: &ast::Path) -> Option<&ast::Ty> {
ast::FnRetTy::Default(_) => None,
ast::FnRetTy::Ty(ret) => Some(ret),
},
ast::GenericArgs::AngleBracketed(_) => None,
ast::GenericArgs::AngleBracketed(_) | ast::GenericArgs::ParenthesizedElided(_) => None,
}
}
1 change: 1 addition & 0 deletions compiler/rustc_ast/src/visit.rs
Original file line number Diff line number Diff line change
Expand Up @@ -609,6 +609,7 @@ where
walk_list!(visitor, visit_ty, inputs);
try_visit!(visitor.visit_fn_ret_ty(output));
}
GenericArgs::ParenthesizedElided(_span) => {}
}
V::Result::output()
}
Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_ast_lowering/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -36,10 +36,15 @@ ast_lowering_bad_return_type_notation_inputs =
argument types not allowed with return type notation
.suggestion = remove the input types
ast_lowering_bad_return_type_notation_needs_dots = return type notation arguments must be elided with `..`
.suggestion = add `..`
ast_lowering_bad_return_type_notation_output =
return type not allowed with return type notation
.suggestion = remove the return type
ast_lowering_bad_return_type_notation_position = return type notation not allowed in this position yet
ast_lowering_base_expression_double_dot =
base expression required after `..`
.suggestion = add a base expression here
Expand Down
11 changes: 11 additions & 0 deletions compiler/rustc_ast_lowering/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -393,6 +393,17 @@ pub enum BadReturnTypeNotation {
#[suggestion(code = "", applicability = "maybe-incorrect")]
span: Span,
},
#[diag(ast_lowering_bad_return_type_notation_needs_dots)]
NeedsDots {
#[primary_span]
#[suggestion(code = "(..)", applicability = "maybe-incorrect")]
span: Span,
},
#[diag(ast_lowering_bad_return_type_notation_position)]
Position {
#[primary_span]
span: Span,
},
}

#[derive(Diagnostic)]
Expand Down
25 changes: 10 additions & 15 deletions compiler/rustc_ast_lowering/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -985,20 +985,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
self.lower_angle_bracketed_parameter_data(data, ParamMode::Explicit, itctx).0
}
GenericArgs::Parenthesized(data) => {
if data.inputs.is_empty() && matches!(data.output, FnRetTy::Default(..)) {
let parenthesized = if self.tcx.features().return_type_notation {
hir::GenericArgsParentheses::ReturnTypeNotation
} else {
self.emit_bad_parenthesized_trait_in_assoc_ty(data);
hir::GenericArgsParentheses::No
};
GenericArgsCtor {
args: Default::default(),
constraints: &[],
parenthesized,
span: data.inputs_span,
}
} else if let Some(first_char) = constraint.ident.as_str().chars().next()
if let Some(first_char) = constraint.ident.as_str().chars().next()
&& first_char.is_ascii_lowercase()
{
let mut err = if !data.inputs.is_empty() {
Expand All @@ -1010,7 +997,9 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
span: data.inputs_span.shrink_to_hi().to(ty.span),
})
} else {
unreachable!("inputs are empty and return type is not provided")
self.dcx().create_err(errors::BadReturnTypeNotation::NeedsDots {
span: data.inputs_span,
})
};
if !self.tcx.features().return_type_notation
&& self.tcx.sess.is_nightly_build()
Expand Down Expand Up @@ -1040,6 +1029,12 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
.0
}
}
GenericArgs::ParenthesizedElided(span) => GenericArgsCtor {
args: Default::default(),
constraints: &[],
parenthesized: hir::GenericArgsParentheses::ReturnTypeNotation,
span: *span,
},
};
gen_args_ctor.into_generic_args(self)
} else {
Expand Down
15 changes: 14 additions & 1 deletion compiler/rustc_ast_lowering/src/path.rs
Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
use crate::ImplTraitPosition;

use super::errors::{
AsyncBoundNotOnTrait, AsyncBoundOnlyForFnTraits, GenericTypeWithParentheses, UseAngleBrackets,
AsyncBoundNotOnTrait, AsyncBoundOnlyForFnTraits, BadReturnTypeNotation,
GenericTypeWithParentheses, UseAngleBrackets,
};
use super::ResolverAstLoweringExt;
use super::{GenericArgsCtor, LifetimeRes, ParenthesizedGenericArgs};
Expand Down Expand Up @@ -271,6 +272,18 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
)
}
},
GenericArgs::ParenthesizedElided(span) => {
self.dcx().emit_err(BadReturnTypeNotation::Position { span: *span });
(
GenericArgsCtor {
args: Default::default(),
constraints: &[],
parenthesized: hir::GenericArgsParentheses::ReturnTypeNotation,
span: *span,
},
false,
)
}
}
} else {
(
Expand Down
7 changes: 5 additions & 2 deletions compiler/rustc_ast_passes/src/ast_validation.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1312,6 +1312,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
self.with_impl_trait(None, |this| this.visit_ty(ty));
}
}
GenericArgs::ParenthesizedElided(_span) => {}
}
}

Expand Down Expand Up @@ -1468,7 +1469,7 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
span: args.span,
});
}
None => {}
Some(ast::GenericArgs::ParenthesizedElided(_)) | None => {}
}
}
}
Expand Down Expand Up @@ -1716,7 +1717,9 @@ fn deny_equality_constraints(
// Add `<Bar = RhsTy>` to `Foo`.
match &mut assoc_path.segments[len].args {
Some(args) => match args.deref_mut() {
GenericArgs::Parenthesized(_) => continue,
GenericArgs::Parenthesized(_) | GenericArgs::ParenthesizedElided(..) => {
continue;
}
GenericArgs::AngleBracketed(args) => {
args.args.push(arg);
}
Expand Down
24 changes: 2 additions & 22 deletions compiler/rustc_ast_passes/src/feature_gate.rs
Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
use rustc_ast as ast;
use rustc_ast::visit::{self, AssocCtxt, FnCtxt, FnKind, Visitor};
use rustc_ast::{attr, AssocItemConstraint, AssocItemConstraintKind, NodeId};
use rustc_ast::{attr, NodeId};
use rustc_ast::{token, PatKind};
use rustc_feature::{AttributeGate, BuiltinAttribute, Features, GateIssue, BUILTIN_ATTRIBUTE_MAP};
use rustc_session::parse::{feature_err, feature_err_issue, feature_warn};
Expand Down Expand Up @@ -445,23 +445,6 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
visit::walk_fn(self, fn_kind)
}

fn visit_assoc_item_constraint(&mut self, constraint: &'a AssocItemConstraint) {
if let AssocItemConstraintKind::Bound { .. } = constraint.kind
&& let Some(ast::GenericArgs::Parenthesized(args)) = constraint.gen_args.as_ref()
&& args.inputs.is_empty()
&& let ast::FnRetTy::Default(..) = args.output
{
gate!(
&self,
return_type_notation,
constraint.span,
"return type notation is experimental"
);
}

visit::walk_assoc_item_constraint(self, constraint)
}

fn visit_assoc_item(&mut self, i: &'a ast::AssocItem, ctxt: AssocCtxt) {
let is_fn = match &i.kind {
ast::AssocItemKind::Fn(_) => true,
Expand Down Expand Up @@ -566,6 +549,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
unsafe_extern_blocks,
"`unsafe extern {}` blocks and `safe` keyword are experimental"
);
gate_all!(return_type_notation, "return type notation is experimental");

if !visitor.features.never_patterns {
if let Some(spans) = spans.get(&sym::never_patterns) {
Expand Down Expand Up @@ -611,10 +595,6 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {

gate_all_legacy_dont_use!(box_patterns, "box pattern syntax is experimental");
gate_all_legacy_dont_use!(trait_alias, "trait aliases are experimental");
// Despite being a new feature, `where T: Trait<Assoc(): Sized>`, which is RTN syntax now,
// used to be gated under associated_type_bounds, which are right above, so RTN needs to
// be too.
gate_all_legacy_dont_use!(return_type_notation, "return type notation is experimental");
gate_all_legacy_dont_use!(decl_macro, "`macro` is experimental");
gate_all_legacy_dont_use!(try_blocks, "`try` blocks are unstable");
gate_all_legacy_dont_use!(auto_traits, "`auto` traits are unstable");
Expand Down
5 changes: 5 additions & 0 deletions compiler/rustc_ast_pretty/src/pprust/state.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1060,6 +1060,11 @@ impl<'a> PrintState<'a> for State<'a> {
self.word(")");
self.print_fn_ret_ty(&data.output);
}
ast::GenericArgs::ParenthesizedElided(_) => {
self.word("(");
self.word("..");
self.word(")");
}
}
}
}
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_hir/src/hir.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2414,7 +2414,7 @@ pub enum ImplItemKind<'hir> {
/// * the `A: Bound` in `Trait<A: Bound>`
/// * the `RetTy` in `Trait(ArgTy, ArgTy) -> RetTy`
/// * the `C = { Ct }` in `Trait<C = { Ct }>` (feature `associated_const_equality`)
/// * the `f(): Bound` in `Trait<f(): Bound>` (feature `return_type_notation`)
/// * the `f(..): Bound` in `Trait<f(..): Bound>` (feature `return_type_notation`)
#[derive(Debug, Clone, Copy, HashStable_Generic)]
pub struct AssocItemConstraint<'hir> {
pub hir_id: HirId,
Expand Down
4 changes: 0 additions & 4 deletions compiler/rustc_parse/messages.ftl
Original file line number Diff line number Diff line change
Expand Up @@ -45,10 +45,6 @@ parse_bad_assoc_type_bounds = bounds on associated types do not belong here
parse_bad_item_kind = {$descr} is not supported in {$ctx}
.help = consider moving the {$descr} out to a nearby module scope
parse_bad_return_type_notation_dotdot =
return type notation uses `()` instead of `(..)` for elided arguments
.suggestion = remove the `..`
parse_bad_return_type_notation_output =
return type not allowed with return type notation
.suggestion = remove the return type
Expand Down
8 changes: 0 additions & 8 deletions compiler/rustc_parse/src/errors.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2567,14 +2567,6 @@ pub(crate) struct BadReturnTypeNotationOutput {
pub span: Span,
}

#[derive(Diagnostic)]
#[diag(parse_bad_return_type_notation_dotdot)]
pub(crate) struct BadReturnTypeNotationDotDot {
#[primary_span]
#[suggestion(code = "", applicability = "maybe-incorrect")]
pub span: Span,
}

#[derive(Diagnostic)]
#[diag(parse_bad_assoc_type_bounds)]
pub(crate) struct BadAssocTypeBounds {
Expand Down
27 changes: 6 additions & 21 deletions compiler/rustc_parse/src/parser/path.rs
Original file line number Diff line number Diff line change
Expand Up @@ -353,32 +353,25 @@ impl<'a> Parser<'a> {
})?;
let span = lo.to(self.prev_token.span);
AngleBracketedArgs { args, span }.into()
} else if self.may_recover()
&& self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
} else if self.token.kind == token::OpenDelim(Delimiter::Parenthesis)
// FIXME(return_type_notation): Could also recover `...` here.
&& self.look_ahead(1, |tok| tok.kind == token::DotDot)
{
self.bump();
self.dcx()
.emit_err(errors::BadReturnTypeNotationDotDot { span: self.token.span });
self.bump();
self.bump(); // (
self.bump(); // ..
self.expect(&token::CloseDelim(Delimiter::Parenthesis))?;
let span = lo.to(self.prev_token.span);

self.psess.gated_spans.gate(sym::return_type_notation, span);

if self.eat_noexpect(&token::RArrow) {
let lo = self.prev_token.span;
let ty = self.parse_ty()?;
self.dcx()
.emit_err(errors::BadReturnTypeNotationOutput { span: lo.to(ty.span) });
}

ParenthesizedArgs {
span,
inputs: ThinVec::new(),
inputs_span: span,
output: ast::FnRetTy::Default(self.prev_token.span.shrink_to_hi()),
}
.into()
P(ast::GenericArgs::ParenthesizedElided(span))
} else {
// `(T, U) -> R`

Expand Down Expand Up @@ -733,14 +726,6 @@ impl<'a> Parser<'a> {

let span = lo.to(self.prev_token.span);

if let AssocItemConstraintKind::Bound { .. } = kind
&& let Some(ast::GenericArgs::Parenthesized(args)) = &gen_args
&& args.inputs.is_empty()
&& let ast::FnRetTy::Default(..) = args.output
{
self.psess.gated_spans.gate(sym::return_type_notation, span);
}

let constraint =
AssocItemConstraint { id: ast::DUMMY_NODE_ID, ident, gen_args, kind, span };
Ok(Some(AngleBracketedArg::Constraint(constraint)))
Expand Down
2 changes: 1 addition & 1 deletion compiler/rustc_passes/src/hir_stats.rs
Original file line number Diff line number Diff line change
Expand Up @@ -695,7 +695,7 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> {
fn visit_generic_args(&mut self, g: &'v ast::GenericArgs) {
record_variants!(
(self, g, g, Id::None, ast, GenericArgs, GenericArgs),
[AngleBracketed, Parenthesized]
[AngleBracketed, Parenthesized, ParenthesizedElided]
);
ast_visit::walk_generic_args(self, g)
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_resolve/src/late.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1221,6 +1221,7 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
}
}
}
GenericArgs::ParenthesizedElided(_) => {}
}
}
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_resolve/src/lib.rs
Original file line number Diff line number Diff line change
Expand Up @@ -350,6 +350,7 @@ impl<'a> From<&'a ast::PathSegment> for Segment {
(args.span, found_lifetimes)
}
GenericArgs::Parenthesized(args) => (args.span, true),
GenericArgs::ParenthesizedElided(span) => (*span, true),
}
} else {
(DUMMY_SP, false)
Expand Down
2 changes: 1 addition & 1 deletion src/librustdoc/clean/types.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2557,7 +2557,7 @@ pub(crate) struct ProcMacro {
/// * the `A: Bound` in `Trait<A: Bound>`
/// * the `RetTy` in `Trait(ArgTy, ArgTy) -> RetTy`
/// * the `C = { Ct }` in `Trait<C = { Ct }>` (feature `associated_const_equality`)
/// * the `f(): Bound` in `Trait<f(): Bound>` (feature `return_type_notation`)
/// * the `f(..): Bound` in `Trait<f(..): Bound>` (feature `return_type_notation`)
#[derive(Clone, PartialEq, Eq, Debug, Hash)]
pub(crate) struct AssocItemConstraint {
pub(crate) assoc: PathSegment,
Expand Down
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