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Account for existing _ field pattern when suggesting ..

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Follow up to #80017.
This commit is contained in:
Esteban Küber 2021-01-26 16:53:56 -08:00
parent 7907345e58
commit a398994cb2
2 changed files with 17 additions and 9 deletions
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22
compiler/rustc_typeck/src/check/pat.rs
View File

@ -1041,12 +1041,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
vec![(left, "(".to_string()), (right.shrink_to_hi(), ")".to_string())],
Applicability::MachineApplicable,
);
} else if fields.len() > subpats.len() {
let after_fields_span = if pat_span == DUMMY_SP {
pat_span
} else {
pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi()
};
} else if fields.len() > subpats.len() && pat_span != DUMMY_SP {
let after_fields_span = pat_span.with_hi(pat_span.hi() - BytePos(1)).shrink_to_hi();
let all_fields_span = match subpats {
[] => after_fields_span,
[field] => field.span,
@ -1055,7 +1051,19 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// Check if all the fields in the pattern are wildcards.
let all_wildcards = subpats.iter().all(|pat| matches!(pat.kind, PatKind::Wild));
let first_tail_wildcard =
subpats.iter().enumerate().fold(None, |acc, (pos, pat)| match (acc, &pat.kind) {
(None, PatKind::Wild) => Some(pos),
(Some(_), PatKind::Wild) => acc,
_ => None,
});
let tail_span = match first_tail_wildcard {
None => after_fields_span,
Some(0) => subpats[0].span.to(after_fields_span),
Some(pos) => subpats[pos - 1].span.shrink_to_hi().to(after_fields_span),
};
// FIXME: heuristic-based suggestion to check current types for where to add `_`.
let mut wildcard_sugg = vec!["_"; fields.len() - subpats.len()].join(", ");
if !subpats.is_empty() {
wildcard_sugg = String::from(", ") + &wildcard_sugg;
@ -1080,7 +1088,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
);
} else {
err.span_suggestion_verbose(
after_fields_span,
tail_span,
"use `..` to ignore the rest of the fields",
String::from(", .."),
Applicability::MaybeIncorrect,

4
src/test/ui/pattern/pat-tuple-underfield.stderr
View File

@ -122,8 +122,8 @@ LL | Point4( a , _ , _, _) => {}
| ^^^^^^
help: use `..` to ignore the rest of the fields
|
LL | Point4( a , _ , ..) => {}
| ^^^^
LL | Point4( a, ..) => {}
| ^^^^
error: aborting due to 8 previous errors