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parser: Remove outdated checks for empty braced struct expressions (S {}) #34691

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merged 1 commit into from
Jul 8, 2016
Merged

parser: Remove outdated checks for empty braced struct expressions (S {}) #34691

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83 changes: 11 additions & 72 deletions src/libsyntax/parse/parser.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -495,64 +495,6 @@ impl<'a> Parser<'a> {
}
}

/// Check for erroneous `ident { }`; if matches, signal error and
/// recover (without consuming any expected input token). Returns
/// true if and only if input was consumed for recovery.
pub fn check_for_erroneous_unit_struct_expecting(&mut self,
expected: &[token::Token])
-> bool {
if self.token == token::OpenDelim(token::Brace)
&& expected.iter().all(|t| *t != token::OpenDelim(token::Brace))
&& self.look_ahead(1, |t| *t == token::CloseDelim(token::Brace)) {
// matched; signal non-fatal error and recover.
let span = self.span;
self.span_err(span, "unit-like struct construction is written with no trailing `{ }`");
self.eat(&token::OpenDelim(token::Brace));
self.eat(&token::CloseDelim(token::Brace));
true
} else {
false
}
}

/// Commit to parsing a complete expression `e` expected to be
/// followed by some token from the set edible + inedible. Recover
/// from anticipated input errors, discarding erroneous characters.
pub fn commit_expr(&mut self, e: &Expr, edible: &[token::Token],
inedible: &[token::Token]) -> PResult<'a, ()> {
debug!("commit_expr {:?}", e);
if let ExprKind::Path(..) = e.node {
// might be unit-struct construction; check for recoverableinput error.
let expected = edible.iter()
.cloned()
.chain(inedible.iter().cloned())
.collect::<Vec<_>>();
self.check_for_erroneous_unit_struct_expecting(&expected[..]);
}
self.expect_one_of(edible, inedible)
}

pub fn commit_expr_expecting(&mut self, e: &Expr, edible: token::Token) -> PResult<'a, ()> {
self.commit_expr(e, &[edible], &[])
}

/// Commit to parsing a complete statement `s`, which expects to be
/// followed by some token from the set edible + inedible. Check
/// for recoverable input errors, discarding erroneous characters.
pub fn commit_stmt(&mut self, edible: &[token::Token],
inedible: &[token::Token]) -> PResult<'a, ()> {
if self.last_token
.as_ref()
.map_or(false, |t| t.is_ident() || t.is_path()) {
let expected = edible.iter()
.cloned()
.chain(inedible.iter().cloned())
.collect::<Vec<_>>();
self.check_for_erroneous_unit_struct_expecting(&expected);
}
self.expect_one_of(edible, inedible)
}

/// returns the span of expr, if it was not interpolated or the span of the interpolated token
fn interpolated_or_expr_span(&self,
expr: PResult<'a, P<Expr>>)
Expand Down Expand Up @@ -1247,7 +1189,7 @@ impl<'a> Parser<'a> {
let default = if self.check(&token::Eq) {
self.bump();
let expr = self.parse_expr()?;
self.commit_expr_expecting(&expr, token::Semi)?;
self.expect(&token::Semi)?;
Some(expr)
} else {
self.expect(&token::Semi)?;
Expand Down Expand Up @@ -2195,8 +2137,7 @@ impl<'a> Parser<'a> {
let mut trailing_comma = false;
while self.token != token::CloseDelim(token::Paren) {
es.push(self.parse_expr()?);
self.commit_expr(&es.last().unwrap(), &[],
&[token::Comma, token::CloseDelim(token::Paren)])?;
self.expect_one_of(&[], &[token::Comma, token::CloseDelim(token::Paren)])?;
if self.check(&token::Comma) {
trailing_comma = true;

Expand Down Expand Up @@ -2407,9 +2348,8 @@ impl<'a> Parser<'a> {
}
}

match self.commit_expr(&fields.last().unwrap().expr,
&[token::Comma],
&[token::CloseDelim(token::Brace)]) {
match self.expect_one_of(&[token::Comma],
&[token::CloseDelim(token::Brace)]) {
Ok(()) => {}
Err(mut e) => {
e.emit();
Expand Down Expand Up @@ -2662,7 +2602,7 @@ impl<'a> Parser<'a> {
self.bump();
let ix = self.parse_expr()?;
hi = self.span.hi;
self.commit_expr_expecting(&ix, token::CloseDelim(token::Bracket))?;
self.expect(&token::CloseDelim(token::Bracket))?;
let index = self.mk_index(e, ix);
e = self.mk_expr(lo, hi, index, ThinVec::new())
}
Expand Down Expand Up @@ -3329,8 +3269,7 @@ impl<'a> Parser<'a> {
let lo = self.last_span.lo;
let discriminant = self.parse_expr_res(Restrictions::RESTRICTION_NO_STRUCT_LITERAL,
None)?;
if let Err(mut e) = self.commit_expr_expecting(&discriminant,
token::OpenDelim(token::Brace)) {
if let Err(mut e) = self.expect(&token::OpenDelim(token::Brace)) {
if self.token == token::Token::Semi {
e.span_note(match_span, "did you mean to remove this `match` keyword?");
}
Expand Down Expand Up @@ -3376,7 +3315,7 @@ impl<'a> Parser<'a> {
&& self.token != token::CloseDelim(token::Brace);

if require_comma {
self.commit_expr(&expr, &[token::Comma], &[token::CloseDelim(token::Brace)])?;
self.expect_one_of(&[token::Comma], &[token::CloseDelim(token::Brace)])?;
} else {
self.eat(&token::Comma);
}
Expand Down Expand Up @@ -4118,7 +4057,7 @@ impl<'a> Parser<'a> {
_ => { // all other kinds of statements:
let mut hi = span.hi;
if classify::stmt_ends_with_semi(&node) {
self.commit_stmt(&[token::Semi], &[])?;
self.expect(&token::Semi)?;
hi = self.last_span.hi;
}

Expand Down Expand Up @@ -4196,7 +4135,7 @@ impl<'a> Parser<'a> {
if classify::expr_requires_semi_to_be_stmt(&e) {
// Just check for errors and recover; do not eat semicolon yet.
if let Err(mut e) =
self.commit_stmt(&[], &[token::Semi, token::CloseDelim(token::Brace)])
self.expect_one_of(&[], &[token::Semi, token::CloseDelim(token::Brace)])
{
e.emit();
self.recover_stmt();
Expand Down Expand Up @@ -4863,7 +4802,7 @@ impl<'a> Parser<'a> {
let typ = self.parse_ty_sum()?;
self.expect(&token::Eq)?;
let expr = self.parse_expr()?;
self.commit_expr_expecting(&expr, token::Semi)?;
self.expect(&token::Semi)?;
(name, ast::ImplItemKind::Const(typ, expr))
} else {
let (name, inner_attrs, node) = self.parse_impl_method(&vis)?;
Expand Down Expand Up @@ -5287,7 +5226,7 @@ impl<'a> Parser<'a> {
let ty = self.parse_ty_sum()?;
self.expect(&token::Eq)?;
let e = self.parse_expr()?;
self.commit_expr_expecting(&e, token::Semi)?;
self.expect(&token::Semi)?;
let item = match m {
Some(m) => ItemKind::Static(ty, m, e),
None => ItemKind::Const(ty, e),
Expand Down