bjoernager/rust
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Implement .. syntax for RangeFull as expression

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Allows the expression `..` (without either endpoint) in general, can be
used in slicing syntax `&expr[..]` where we previously wrote `&expr[]`.

The old syntax &expr[] is not yet removed or warned for.
This commit is contained in:
Ulrik Sverdrup 2015-02-04 23:23:12 +01:00
parent 3b2ed14906
commit 75239142a8
6 changed files with 28 additions and 23 deletions
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33
src/libsyntax/parse/parser.rs
View file

@ -2524,16 +2524,7 @@ impl<'a> Parser<'a> {
let bracket_pos = self.span.lo;
self.bump();
let mut found_dotdot = false;
if self.token == token::DotDot &&
self.look_ahead(1, |t| t == &token::CloseDelim(token::Bracket)) {
// Using expr[..], which is a mistake, should be expr[]
self.bump();
self.bump();
found_dotdot = true;
}
if found_dotdot || self.eat(&token::CloseDelim(token::Bracket)) {
if self.eat(&token::CloseDelim(token::Bracket)) {
// No expression, expand to a RangeFull
// FIXME(#20516) It would be better to use a lang item or
// something for RangeFull.
@ -2557,7 +2548,11 @@ impl<'a> Parser<'a> {
let range = ExprStruct(path, vec![], None);
let ix = self.mk_expr(bracket_pos, hi, range);
let index = self.mk_index(e, ix);
e = self.mk_expr(lo, hi, index)
e = self.mk_expr(lo, hi, index);
// Enable after snapshot.
// self.span_warn(e.span, "deprecated slicing syntax: `[]`");
// self.span_note(e.span,
// "use `&expr[..]` to construct a slice of the whole of expr");
} else {
let ix = self.parse_expr();
hi = self.span.hi;
@ -2566,11 +2561,6 @@ impl<'a> Parser<'a> {
e = self.mk_expr(lo, hi, index)
}
if found_dotdot {
self.span_err(e.span, "incorrect slicing expression: `[..]`");
self.span_note(e.span,
"use `&expr[]` to construct a slice of the whole of expr");
}
}
_ => return e
}
@ -2931,9 +2921,14 @@ impl<'a> Parser<'a> {
// with the postfix-form 'expr..'
let lo = self.span.lo;
self.bump();
let rhs = self.parse_binops();
let hi = rhs.span.hi;
let ex = self.mk_range(None, Some(rhs));
let opt_end = if self.is_at_start_of_range_notation_rhs() {
let end = self.parse_binops();
Some(end)
} else {
None
};
let hi = self.span.hi;
let ex = self.mk_range(None, opt_end);
self.mk_expr(lo, hi, ex)
}
_ => {