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Rollup merge of #41077 - petrochenkov:boundparen, r=nikomatsakis

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syntax: Support parentheses around trait bounds

An implementation for https://github.com/rust-lang/rust/issues/39318#issuecomment-290956826

r? @nikomatsakis
This commit is contained in:
Corey Farwell 2017-04-22 09:02:56 -04:00 committed by GitHub
commit 5e1351b17b
6 changed files with 139 additions and 39 deletions
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5
src/doc/grammar.md
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@ -781,10 +781,11 @@ never_type : "!" ;
### Type parameter bounds
```antlr
bound-list := bound | bound '+' bound-list '+' ?
bound := ty_bound | lt_bound
lt_bound := lifetime
ty_bound := [?] [ for<lt_param_defs> ] simple_path
bound-list := bound | bound '+' bound-list '+' ?
ty_bound := ty_bound_noparen | (ty_bound_noparen)
ty_bound_noparen := [?] [ for<lt_param_defs> ] simple_path
```
### Self types

101
src/libsyntax/parse/parser.rs
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@ -152,6 +152,7 @@ fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
enum PrevTokenKind {
DocComment,
Comma,
Plus,
Interpolated,
Eof,
Other,
@ -1061,6 +1062,7 @@ impl<'a> Parser<'a> {
self.prev_token_kind = match self.token {
token::DocComment(..) => PrevTokenKind::DocComment,
token::Comma => PrevTokenKind::Comma,
token::BinOp(token::Plus) => PrevTokenKind::Plus,
token::Interpolated(..) => PrevTokenKind::Interpolated,
token::Eof => PrevTokenKind::Eof,
_ => PrevTokenKind::Other,
@ -1354,20 +1356,26 @@ impl<'a> Parser<'a> {
break;
}
}
let trailing_plus = self.prev_token_kind == PrevTokenKind::Plus;
self.expect(&token::CloseDelim(token::Paren))?;
if ts.len() == 1 && !last_comma {
let ty = ts.into_iter().nth(0).unwrap().unwrap();
let maybe_bounds = allow_plus && self.token == token::BinOp(token::Plus);
match ty.node {
// Accept `(Trait1) + Trait2 + 'a` for backward compatibility (#39318).
TyKind::Path(None, ref path)
if allow_plus && self.token == token::BinOp(token::Plus) => {
self.bump(); // `+`
let pt = PolyTraitRef::new(Vec::new(), path.clone(), lo.to(self.prev_span));
let mut bounds = vec![TraitTyParamBound(pt, TraitBoundModifier::None)];
bounds.append(&mut self.parse_ty_param_bounds()?);
TyKind::TraitObject(bounds)
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
self.parse_remaining_bounds(Vec::new(), path.clone(), lo, true)?
}
TyKind::TraitObject(ref bounds)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
let path = match bounds[0] {
TraitTyParamBound(ref pt, ..) => pt.trait_ref.path.clone(),
_ => self.bug("unexpected lifetime bound"),
};
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
@ -1418,11 +1426,8 @@ impl<'a> Parser<'a> {
// Just a type path or bound list (trait object type) starting with a trait.
// `Type`
// `Trait1 + Trait2 + 'a`
if allow_plus && self.eat(&token::BinOp(token::Plus)) {
let poly_trait = PolyTraitRef::new(Vec::new(), path, lo.to(self.prev_span));
let mut bounds = vec![TraitTyParamBound(poly_trait, TraitBoundModifier::None)];
bounds.append(&mut self.parse_ty_param_bounds()?);
TyKind::TraitObject(bounds)
if allow_plus && self.check(&token::BinOp(token::Plus)) {
self.parse_remaining_bounds(Vec::new(), path, lo, true)?
} else {
TyKind::Path(None, path)
}
@ -1440,12 +1445,8 @@ impl<'a> Parser<'a> {
self.parse_ty_bare_fn(lifetime_defs)?
} else {
let path = self.parse_path(PathStyle::Type)?;
let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
let mut bounds = vec![TraitTyParamBound(poly_trait, TraitBoundModifier::None)];
if allow_plus && self.eat(&token::BinOp(token::Plus)) {
bounds.append(&mut self.parse_ty_param_bounds()?)
}
TyKind::TraitObject(bounds)
let parse_plus = allow_plus && self.check(&token::BinOp(token::Plus));
self.parse_remaining_bounds(lifetime_defs, path, lo, parse_plus)?
}
} else if self.eat_keyword(keywords::Impl) {
// FIXME: figure out priority of `+` in `impl Trait1 + Trait2` (#34511).
@ -1468,6 +1469,17 @@ impl<'a> Parser<'a> {
Ok(P(ty))
}
fn parse_remaining_bounds(&mut self, lifetime_defs: Vec<LifetimeDef>, path: ast::Path,
lo: Span, parse_plus: bool) -> PResult<'a, TyKind> {
let poly_trait_ref = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
let mut bounds = vec![TraitTyParamBound(poly_trait_ref, TraitBoundModifier::None)];
if parse_plus {
self.bump(); // `+`
bounds.append(&mut self.parse_ty_param_bounds()?);
}
Ok(TyKind::TraitObject(bounds))
}
fn maybe_recover_from_bad_type_plus(&mut self, allow_plus: bool, ty: &Ty) -> PResult<'a, ()> {
// Do not add `+` to expected tokens.
if !allow_plus || self.token != token::BinOp(token::Plus) {
@ -4070,28 +4082,43 @@ impl<'a> Parser<'a> {
// Parse bounds of a type parameter `BOUND + BOUND + BOUND`, possibly with trailing `+`.
// BOUND = TY_BOUND | LT_BOUND
// LT_BOUND = LIFETIME (e.g. `'a`)
// TY_BOUND = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g. `?for<'a: 'b> m::Trait<'a>`)
// TY_BOUND = TY_BOUND_NOPAREN | (TY_BOUND_NOPAREN)
// TY_BOUND_NOPAREN = [?] [for<LT_PARAM_DEFS>] SIMPLE_PATH (e.g. `?for<'a: 'b> m::Trait<'a>`)
fn parse_ty_param_bounds_common(&mut self, allow_plus: bool) -> PResult<'a, TyParamBounds> {
let mut bounds = Vec::new();
loop {
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.check_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(RegionTyParamBound(self.expect_lifetime()));
} else if self.check_keyword(keywords::For) || self.check_path() {
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
let is_bound_start = self.check_path() || self.check_lifetime() ||
self.check(&token::Question) ||
self.check_keyword(keywords::For) ||
self.check(&token::OpenDelim(token::Paren));
if is_bound_start {
let has_parens = self.eat(&token::OpenDelim(token::Paren));
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.token.is_lifetime() {
if let Some(question_span) = question {
self.span_err(question_span,
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(RegionTyParamBound(self.expect_lifetime()));
} else {
TraitBoundModifier::None
};
bounds.push(TraitTyParamBound(poly_trait, modifier));
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
let poly_trait = PolyTraitRef::new(lifetime_defs, path, lo.to(self.prev_span));
let modifier = if question.is_some() {
TraitBoundModifier::Maybe
} else {
TraitBoundModifier::None
};
bounds.push(TraitTyParamBound(poly_trait, modifier));
}
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
if let Some(&RegionTyParamBound(..)) = bounds.last() {
self.span_err(self.prev_span,
"parenthesized lifetime bounds are not supported");
}
}
} else {
break
}

13
src/test/parse-fail/bound-single-question-mark.rs Normal file
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@ -0,0 +1,13 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -Z parse-only
fn f<T: ?>() {} //~ ERROR expected identifier, found `>`

20
src/test/parse-fail/trait-object-bad-parens.rs Normal file
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@ -0,0 +1,20 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -Z parse-only -Z continue-parse-after-error
fn main() {
let _: Box<((Copy)) + Copy>;
//~^ ERROR expected a path on the left-hand side of `+`, not `((Copy))`
let _: Box<(Copy + Copy) + Copy>;
//~^ ERROR expected a path on the left-hand side of `+`, not `( Copy + Copy)`
let _: Box<(Copy +) + Copy>;
//~^ ERROR expected a path on the left-hand side of `+`, not `( Copy)`
}

18
src/test/parse-fail/trait-object-lifetime-parens.rs Normal file
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@ -0,0 +1,18 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -Z parse-only -Z continue-parse-after-error
fn f<T: Copy + ('a)>() {} //~ ERROR parenthesized lifetime bounds are not supported
fn main() {
let _: Box<Copy + ('a)>; //~ ERROR parenthesized lifetime bounds are not supported
let _: Box<('a) + Copy>; //~ ERROR expected type, found `'a`
}

21
src/test/parse-fail/trait-object-trait-parens.rs Normal file
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@ -0,0 +1,21 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// compile-flags: -Z parse-only
fn f<T: (Copy) + (?Sized) + (for<'a> Trait<'a>)>() {}
fn main() {
let _: Box<(Copy) + (?Sized) + (for<'a> Trait<'a>)>;
let _: Box<(?Sized) + (for<'a> Trait<'a>) + (Copy)>;
let _: Box<(for<'a> Trait<'a>) + (Copy) + (?Sized)>;
}
FAIL //~ ERROR