bjoernager/rust
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Suggest correct location for lifetime parameters in use

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This commit is contained in:
Esteban Küber 2019-01-12 19:25:03 -08:00
parent db740313e0
commit 28ea03e114
7 changed files with 82 additions and 47 deletions
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52
src/libsyntax/parse/parser.rs
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@ -5330,23 +5330,28 @@ impl<'a> Parser<'a> {
/// Parses (possibly empty) list of lifetime and type arguments and associated type bindings,
/// possibly including trailing comma.
fn parse_generic_args(&mut self)
-> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
fn parse_generic_args(&mut self) -> PResult<'a, (Vec<GenericArg>, Vec<TypeBinding>)> {
let mut args = Vec::new();
let mut bindings = Vec::new();
let mut seen_type = false;
let mut seen_binding = false;
let mut first_type_or_binding_span: Option<Span> = None;
let mut bad_lifetime_pos = vec![];
let mut last_comma_span = None;
let mut suggestions = vec![];
loop {
if self.check_lifetime() && self.look_ahead(1, |t| !t.is_like_plus()) {
// Parse lifetime argument.
args.push(GenericArg::Lifetime(self.expect_lifetime()));
if seen_type || seen_binding {
self.struct_span_err(
self.prev_span,
"lifetime parameters must be declared prior to type parameters"
)
.span_label(self.prev_span, "must be declared prior to type parameters")
.emit();
let remove_sp = last_comma_span.unwrap_or(self.prev_span).to(self.prev_span);
bad_lifetime_pos.push(self.prev_span);
if let Ok(snippet) = self.sess.source_map().span_to_snippet(self.prev_span) {
suggestions.push((remove_sp, String::new()));
suggestions.push((
first_type_or_binding_span.unwrap().shrink_to_lo(),
format!("{}, ", snippet)));
}
}
} else if self.check_ident() && self.look_ahead(1, |t| t == &token::Eq) {
// Parse associated type binding.
@ -5354,13 +5359,17 @@ impl<'a> Parser<'a> {
let ident = self.parse_ident()?;
self.bump();
let ty = self.parse_ty()?;
let span = lo.to(self.prev_span);
bindings.push(TypeBinding {
id: ast::DUMMY_NODE_ID,
ident,
ty,
span: lo.to(self.prev_span),
span,
});
seen_binding = true;
if first_type_or_binding_span.is_none() {
first_type_or_binding_span = Some(span);
}
} else if self.check_type() {
// Parse type argument.
let ty_param = self.parse_ty()?;
@ -5375,6 +5384,9 @@ impl<'a> Parser<'a> {
)
.emit();
}
if first_type_or_binding_span.is_none() {
first_type_or_binding_span = Some(ty_param.span);
}
args.push(GenericArg::Type(ty_param));
seen_type = true;
} else {
@ -5383,8 +5395,30 @@ impl<'a> Parser<'a> {
if !self.eat(&token::Comma) {
break
} else {
last_comma_span = Some(self.prev_span);
}
}
if !bad_lifetime_pos.is_empty() {
let mut err = self.struct_span_err(
bad_lifetime_pos.clone(),
"lifetime parameters must be declared prior to type parameters"
);
for sp in &bad_lifetime_pos {
err.span_label(*sp, "must be declared prior to type parameters");
}
if !suggestions.is_empty() {
err.multipart_suggestion_with_applicability(
&format!(
"move the lifetime parameter{} prior to the first type parameter",
if bad_lifetime_pos.len() > 1 { "s" } else { "" },
),
suggestions,
Applicability::MachineApplicable,
);
}
err.emit();
}
Ok((args, bindings))
}