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Some cleanup to maybe_parse_struct_expr

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This commit is contained in:
Vadim Petrochenkov 2019-04-18 23:58:57 +03:00 • committed by Esteban Küber
parent 4c4ca60edd
commit aa393b0cde
4 changed files with 26 additions and 54 deletions
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31
src/libsyntax/parse/parser.rs
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@ -2910,27 +2910,22 @@ impl<'a> Parser<'a> {
path: &ast::Path,
attrs: &ThinVec<Attribute>,
) -> Option<PResult<'a, P<Expr>>> {
// We don't want to assume it's a struct when encountering `{ <ident>: <ident> }` because
// it could be type ascription, like in `{ ident: u32 }`.
let isnt_ascription = self.look_ahead(1, |t| t.is_ident()) &&
self.look_ahead(2, |t| *t == token::Colon) && (
(self.look_ahead(3, |t| t.is_ident()) &&
self.look_ahead(4, |t| *t == token::Comma)) ||
self.look_ahead(3, |t| t.is_lit()) ||
self.look_ahead(3, |t| *t == token::BinOp(token::Minus)) &&
self.look_ahead(4, |t| t.is_lit())
);
let could_be_struct = self.look_ahead(1, |t| t.is_ident()) && (
self.look_ahead(2, |t| *t == token::Colon) && isnt_ascription
|| self.look_ahead(2, |t| *t == token::Comma)
// We could also check for `token::CloseDelim(token::Brace)`, but that would
// have false positives in the case of `if x == y { z } { a }`.
let struct_allowed = !self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
let certainly_not_a_block = || self.look_ahead(1, |t| t.is_ident()) && (
// `{ ident, ` cannot start a block
self.look_ahead(2, |t| t == &token::Comma) ||
self.look_ahead(2, |t| t == &token::Colon) && (
// `{ ident: token, ` cannot start a block
self.look_ahead(4, |t| t == &token::Comma) ||
// `{ ident: ` cannot start a block unless it's a type ascription `ident: Type`
self.look_ahead(3, |t| !t.can_begin_type())
)
);
let bad_struct = self.restrictions.contains(Restrictions::NO_STRUCT_LITERAL);
if !bad_struct || could_be_struct {
if struct_allowed || certainly_not_a_block() {
// This is a struct literal, but we don't can't accept them here
let expr = self.parse_struct_expr(lo, path.clone(), attrs.clone());
if let (Ok(expr), true) = (&expr, bad_struct) {
if let (Ok(expr), false) = (&expr, struct_allowed) {
let mut err = self.diagnostic().struct_span_err(
expr.span,
"struct literals are not allowed here",