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Auto merge of #21278 - thchittenden:issue-21033-struct-var-pattern-fix, r=alexcrichton

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Closes #21033. The new strategy for parsing a field pattern is to look 1 token ahead and if it's a colon, parse as "fieldname: pat", otherwise parse the shorthand form "(box) (ref) (mut) fieldname)". The previous strategy was to parse "(ref) (mut) fieldname" then if we encounter a colon, throw an error if either "ref" or "mut" were encountered.
This commit is contained in:
bors 2015-01-19 19:40:51 +00:00
commit 4032b85aec
3 changed files with 87 additions and 26 deletions
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59
src/libsyntax/parse/parser.rs
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@ -3255,39 +3255,48 @@ impl<'a> Parser<'a> {
break;
}
let bind_type = if self.eat_keyword(keywords::Mut) {
BindByValue(MutMutable)
} else if self.eat_keyword(keywords::Ref) {
BindByRef(self.parse_mutability())
} else {
BindByValue(MutImmutable)
};
let fieldname = self.parse_ident();
let (subpat, is_shorthand) = if self.check(&token::Colon) {
match bind_type {
BindByRef(..) | BindByValue(MutMutable) => {
let token_str = self.this_token_to_string();
self.fatal(&format!("unexpected `{}`",
token_str)[])
}
_ => {}
}
// Check if a colon exists one ahead. This means we're parsing a fieldname.
let (subpat, fieldname, is_shorthand) = if self.look_ahead(1, |t| t == &token::Colon) {
// Parsing a pattern of the form "fieldname: pat"
let fieldname = self.parse_ident();
self.bump();
let pat = self.parse_pat();
hi = pat.span.hi;
(pat, false)
(pat, fieldname, false)
} else {
// Parsing a pattern of the form "(box) (ref) (mut) fieldname"
let is_box = self.eat_keyword(keywords::Box);
let boxed_span_lo = self.span.lo;
let is_ref = self.eat_keyword(keywords::Ref);
let is_mut = self.eat_keyword(keywords::Mut);
let fieldname = self.parse_ident();
hi = self.last_span.hi;
let fieldpath = codemap::Spanned{span:self.last_span, node: fieldname};
(P(ast::Pat {
let bind_type = match (is_ref, is_mut) {
(true, true) => BindByRef(MutMutable),
(true, false) => BindByRef(MutImmutable),
(false, true) => BindByValue(MutMutable),
(false, false) => BindByValue(MutImmutable),
};
let fieldpath = codemap::Spanned{span:self.last_span, node:fieldname};
let fieldpat = P(ast::Pat{
id: ast::DUMMY_NODE_ID,
node: PatIdent(bind_type, fieldpath, None),
span: self.last_span
}), true)
span: mk_sp(boxed_span_lo, hi),
});
let subpat = if is_box {
P(ast::Pat{
id: ast::DUMMY_NODE_ID,
node: PatBox(fieldpat),
span: mk_sp(lo, hi),
})
} else {
fieldpat
};
(subpat, fieldname, true)
};
fields.push(codemap::Spanned { span: mk_sp(lo, hi),
node: ast::FieldPat { ident: fieldname,
pat: subpat,