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syntax: Support parentheses around trait bounds

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This commit is contained in:
Vadim Petrochenkov
2017-04-05 01:12:53 +03:00
parent 5695c3e943
commit e038f58105
4 changed files with 84 additions and 4 deletions
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29
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 +1356,29 @@ 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) => {
// `(TY_BOUND_NOPAREN) + BOUND + ...`.
TyKind::Path(None, ref path) if maybe_bounds => {
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)
}
TyKind::TraitObject(ref bounds)
if maybe_bounds && bounds.len() == 1 && !trailing_plus => {
self.bump(); // `+`
let mut bounds = bounds.clone();
bounds.append(&mut self.parse_ty_param_bounds()?);
TyKind::TraitObject(bounds)
}
// `(TYPE)`
_ => TyKind::Paren(P(ty))
}
} else {
@@ -4070,10 +4081,12 @@ 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 has_parens = self.eat(&token::OpenDelim(token::Paren));
let question = if self.eat(&token::Question) { Some(self.prev_span) } else { None };
if self.check_lifetime() {
if let Some(question_span) = question {
@@ -4081,6 +4094,11 @@ impl<'a> Parser<'a> {
"`?` may only modify trait bounds, not lifetime bounds");
}
bounds.push(RegionTyParamBound(self.expect_lifetime()));
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
self.span_err(self.prev_span,
"parenthesized lifetime bounds are not supported");
}
} else if self.check_keyword(keywords::For) || self.check_path() {
let lo = self.span;
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
@@ -4092,6 +4110,9 @@ impl<'a> Parser<'a> {
TraitBoundModifier::None
};
bounds.push(TraitTyParamBound(poly_trait, modifier));
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
}
} else {
break
}