bjoernager/rust
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Handle incorrect placement of parentheses in trait bounds more gracefully

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Fix #84772.
This commit is contained in:
Esteban Küber 2021-05-03 23:48:56 -07:00
parent 8a9fa3682d
commit 6b64202d5e
3 changed files with 130 additions and 3 deletions
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39
compiler/rustc_parse/src/parser/ty.rs
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@ -470,7 +470,7 @@ impl<'a> Parser<'a> {
/// Is a `dyn B0 + ... + Bn` type allowed here?
fn is_explicit_dyn_type(&mut self) -> bool {
self.check_keyword(kw::Dyn)
&& (self.token.uninterpolated_span().rust_2018()
&& (!self.token.uninterpolated_span().rust_2015()
|| self.look_ahead(1, |t| {
t.can_begin_bound() && !can_continue_type_after_non_fn_ident(t)
}))
@ -539,7 +539,21 @@ impl<'a> Parser<'a> {
) -> PResult<'a, GenericBounds> {
let mut bounds = Vec::new();
let mut negative_bounds = Vec::new();
while self.can_begin_bound() {
while self.can_begin_bound() || self.token.is_keyword(kw::Dyn) {
if self.token.is_keyword(kw::Dyn) {
// Account for `&dyn Trait + dyn Other`.
self.struct_span_err(self.token.span, "invalid `dyn` keyword")
.help("`dyn` is only needed at the start of a trait `+`-separated list")
.span_suggestion(
self.token.span,
"remove this keyword",
String::new(),
Applicability::MachineApplicable,
)
.emit();
self.bump();
}
match self.parse_generic_bound()? {
Ok(bound) => bounds.push(bound),
Err(neg_sp) => negative_bounds.push(neg_sp),
@ -721,7 +735,26 @@ impl<'a> Parser<'a> {
let lifetime_defs = self.parse_late_bound_lifetime_defs()?;
let path = self.parse_path(PathStyle::Type)?;
if has_parens {
self.expect(&token::CloseDelim(token::Paren))?;
if self.token.is_like_plus() {
// Someone has written something like `&dyn (Trait + Other)`. The correct code
// would be `&(dyn Trait + Other)`, but we don't have access to the appropriate
// span to suggest that. When written as `&dyn Trait + Other`, an appropriate
// suggestion is given.
let bounds = vec![];
self.parse_remaining_bounds(bounds, true)?;
self.expect(&token::CloseDelim(token::Paren))?;
let sp = vec![lo, self.prev_token.span];
let sugg: Vec<_> = sp.iter().map(|sp| (*sp, String::new())).collect();
self.struct_span_err(sp, "incorrect braces around trait bounds")
.multipart_suggestion(
"remove the parentheses",
sugg,
Applicability::MachineApplicable,
)
.emit();
} else {
self.expect(&token::CloseDelim(token::Paren))?;
}
}
let modifier = modifiers.to_trait_bound_modifier();