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Rollup merge of #94739 - estebank:suggest-let-else, r=oli-obk

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Suggest `if let`/`let_else` for refutable pat in `let`

r? `````@oli-obk`````
This commit is contained in:
Matthias Krüger 2022-03-09 23:14:11 +01:00 • committed by GitHub
commit ec09e70ee1
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GPG key ID: 4AEE18F83AFDEB23
15 changed files with 162 additions and 58 deletions
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86
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -7,7 +7,8 @@ use super::{PatCtxt, PatternError};
use rustc_arena::TypedArena;
use rustc_ast::Mutability;
use rustc_errors::{
error_code, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder, ErrorGuaranteed,
error_code, pluralize, struct_span_err, Applicability, Diagnostic, DiagnosticBuilder,
ErrorGuaranteed,
};
use rustc_hir as hir;
use rustc_hir::def::*;
@ -20,7 +21,7 @@ use rustc_session::lint::builtin::{
};
use rustc_session::Session;
use rustc_span::source_map::Spanned;
use rustc_span::{DesugaringKind, ExpnKind, MultiSpan, Span};
use rustc_span::{BytePos, DesugaringKind, ExpnKind, MultiSpan, Span};
crate fn check_match(tcx: TyCtxt<'_>, def_id: DefId) {
let body_id = match def_id.as_local() {
@ -241,6 +242,9 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
}
let joined_patterns = joined_uncovered_patterns(&cx, &witnesses);
let mut bindings = vec![];
let mut err = struct_span_err!(
self.tcx.sess,
pat.span,
@ -257,6 +261,16 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
false
}
_ => {
pat.walk(&mut |pat: &hir::Pat<'_>| {
match pat.kind {
hir::PatKind::Binding(_, _, ident, _) => {
bindings.push(ident);
}
_ => {}
}
true
});
err.span_label(pat.span, pattern_not_covered_label(&witnesses, &joined_patterns));
true
}
@ -267,13 +281,71 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
"`let` bindings require an \"irrefutable pattern\", like a `struct` or \
an `enum` with only one variant",
);
if let Ok(snippet) = self.tcx.sess.source_map().span_to_snippet(span) {
err.span_suggestion(
span,
"you might want to use `if let` to ignore the variant that isn't matched",
format!("if {} {{ /* */ }}", &snippet[..snippet.len() - 1]),
if self.tcx.sess.source_map().span_to_snippet(span).is_ok() {
let semi_span = span.shrink_to_hi().with_lo(span.hi() - BytePos(1));
let start_span = span.shrink_to_lo();
let end_span = semi_span.shrink_to_lo();
err.multipart_suggestion(
&format!(
"you might want to use `if let` to ignore the variant{} that {} matched",
pluralize!(witnesses.len()),
match witnesses.len() {
1 => "isn't",
_ => "aren't",
},
),
vec![
match &bindings[..] {
[] => (start_span, "if ".to_string()),
[binding] => (start_span, format!("let {} = if ", binding)),
bindings => (
start_span,
format!(
"let ({}) = if ",
bindings
.iter()
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ")
),
),
},
match &bindings[..] {
[] => (semi_span, " { todo!() }".to_string()),
[binding] => {
(end_span, format!(" {{ {} }} else {{ todo!() }}", binding))
}
bindings => (
end_span,
format!(
" {{ ({}) }} else {{ todo!() }}",
bindings
.iter()
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ")
),
),
},
],
Applicability::HasPlaceholders,
);
if !bindings.is_empty() && cx.tcx.sess.is_nightly_build() {
err.span_suggestion_verbose(
semi_span.shrink_to_lo(),
&format!(
"alternatively, on nightly, you might want to use \
`#![feature(let_else)]` to handle the variant{} that {} matched",
pluralize!(witnesses.len()),
match witnesses.len() {
1 => "isn't",
_ => "aren't",
},
),
" else { todo!() }".to_string(),
Applicability::HasPlaceholders,
);
}
}
err.note(
"for more information, visit \