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Auto merge of #87071 - inquisitivecrystal:inclusive-range, r=estebank

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Add diagnostics for mistyped inclusive range

Inclusive ranges are correctly typed as `..=`. However, it's quite easy to think of it as being like `==`, and type `..==` instead. This PR adds helpful diagnostics for this case.

Resolves #86395 (there are some other cases there, but I think those should probably have separate issues).

r? `@estebank`
This commit is contained in:
bors 2021-07-18 05:58:16 +00:00
commit 3ab6b60337
4 changed files with 62 additions and 7 deletions
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39
compiler/rustc_parse/src/parser/pat.rs
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@ -797,15 +797,48 @@ impl<'a> Parser<'a> {
// Parsing e.g. `X..`.
if let RangeEnd::Included(_) = re.node {
// FIXME(Centril): Consider semantic errors instead in `ast_validation`.
// Possibly also do this for `X..=` in *expression* contexts.
self.error_inclusive_range_with_no_end(re.span);
self.inclusive_range_with_incorrect_end(re.span);
}
None
};
Ok(PatKind::Range(Some(begin), end, re))
}
pub(super) fn error_inclusive_range_with_no_end(&self, span: Span) {
pub(super) fn inclusive_range_with_incorrect_end(&mut self, span: Span) {
let tok = &self.token;
// If the user typed "..==" instead of "..=", we want to give them
// a specific error message telling them to use "..=".
// Otherwise, we assume that they meant to type a half open exclusive
// range and give them an error telling them to do that instead.
if matches!(tok.kind, token::Eq) && tok.span.lo() == span.hi() {
let span_with_eq = span.to(tok.span);
// Ensure the user doesn't receive unhelpful unexpected token errors
self.bump();
if self.is_pat_range_end_start(0) {
let _ = self.parse_pat_range_end();
}
self.error_inclusive_range_with_extra_equals(span_with_eq);
} else {
self.error_inclusive_range_with_no_end(span);
}
}
fn error_inclusive_range_with_extra_equals(&self, span: Span) {
self.struct_span_err(span, "unexpected `=` after inclusive range")
.span_suggestion_short(
span,
"use `..=` instead",
"..=".to_string(),
Applicability::MaybeIncorrect,
)
.note("inclusive ranges end with a single equals sign (`..=`)")
.emit();
}
fn error_inclusive_range_with_no_end(&self, span: Span) {
struct_span_err!(self.sess.span_diagnostic, span, E0586, "inclusive range with no end")
.span_suggestion_short(
span,