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Auto merge of #76612 - estebank:pat-missing-fields-suggestion, r=davidtwco

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Provide suggestion for missing fields in patterns
This commit is contained in:
bors 2020-09-15 00:17:13 +00:00
commit 255ceeb5ff
7 changed files with 96 additions and 38 deletions
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58
compiler/rustc_typeck/src/check/pat.rs
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@ -1150,7 +1150,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
if no_accessible_unmentioned_fields {
unmentioned_err = Some(self.error_no_accessible_fields(pat, &fields));
} else {
unmentioned_err = Some(self.error_unmentioned_fields(pat, &unmentioned_fields));
unmentioned_err =
Some(self.error_unmentioned_fields(pat, &unmentioned_fields, &fields));
}
}
match (inexistent_fields_err, unmentioned_err) {
@ -1405,6 +1406,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
&self,
pat: &Pat<'_>,
unmentioned_fields: &[(&ty::FieldDef, Ident)],
fields: &'tcx [hir::FieldPat<'tcx>],
) -> DiagnosticBuilder<'tcx> {
let field_names = if unmentioned_fields.len() == 1 {
format!("field `{}`", unmentioned_fields[0].1)
@ -1424,14 +1426,52 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
field_names
);
err.span_label(pat.span, format!("missing {}", field_names));
if self.tcx.sess.teach(&err.get_code().unwrap()) {
err.note(
"This error indicates that a pattern for a struct fails to specify a \
sub-pattern for every one of the struct's fields. Ensure that each field \
from the struct's definition is mentioned in the pattern, or use `..` to \
ignore unwanted fields.",
);
}
let len = unmentioned_fields.len();
let (prefix, postfix, sp) = match fields {
[] => match &pat.kind {
PatKind::Struct(path, [], false) => {
(" { ", " }", path.span().shrink_to_hi().until(pat.span.shrink_to_hi()))
}
_ => return err,
},
[.., field] => (
match pat.kind {
PatKind::Struct(_, [_, ..], _) => ", ",
_ => "",
},
"",
field.span.shrink_to_hi(),
),
};
err.span_suggestion(
sp,
&format!(
"include the missing field{} in the pattern",
if len == 1 { "" } else { "s" },
),
format!(
"{}{}{}",
prefix,
unmentioned_fields
.iter()
.map(|(_, name)| name.to_string())
.collect::<Vec<_>>()
.join(", "),
postfix,
),
Applicability::MachineApplicable,
);
err.span_suggestion(
sp,
&format!(
"if you don't care about {} missing field{}, you can explicitely ignore {}",
if len == 1 { "this" } else { "these" },
if len == 1 { "" } else { "s" },
if len == 1 { "it" } else { "them" },
),
format!("{}..{}", prefix, postfix),
Applicability::MachineApplicable,
);
err
}