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Auto merge of #115270 - sebastiantoh:issue-105479, r=Nadrieril

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Add note on non-exhaustiveness when matching on str and nested non-exhaustive enums

Fixes https://github.com/rust-lang/rust/issues/105479

r? `@Nadrieril`
This commit is contained in:
bors 2023-09-03 19:31:47 +00:00
commit 21305f4d5f
11 changed files with 119 additions and 41 deletions
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27
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -720,32 +720,31 @@ fn non_exhaustive_match<'p, 'tcx>(
};
};
let is_variant_list_non_exhaustive = matches!(scrut_ty.kind(),
ty::Adt(def, _) if def.is_variant_list_non_exhaustive() && !def.did().is_local());
adt_defined_here(cx, &mut err, scrut_ty, &witnesses);
err.note(format!(
"the matched value is of type `{}`{}",
scrut_ty,
if is_variant_list_non_exhaustive { ", which is marked as non-exhaustive" } else { "" }
));
err.note(format!("the matched value is of type `{}`", scrut_ty));
if !is_empty_match && witnesses.len() == 1 {
let mut non_exhaustive_tys = FxHashSet::default();
collect_non_exhaustive_tys(&witnesses[0], &mut non_exhaustive_tys);
for ty in non_exhaustive_tys {
if ty == cx.tcx.types.usize || ty == cx.tcx.types.isize {
if ty.is_ptr_sized_integral() {
err.note(format!(
"`{ty}` does not have a fixed maximum value, so a wildcard `_` is necessary to match \
exhaustively",
));
exhaustively",
));
if cx.tcx.sess.is_nightly_build() {
err.help(format!(
"add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
enable precise `{ty}` matching",
));
"add `#![feature(precise_pointer_size_matching)]` to the crate attributes to \
enable precise `{ty}` matching",
));
}
} else if ty == cx.tcx.types.str_ {
err.note(format!(
"`&str` cannot be matched exhaustively, so a wildcard `_` is necessary",
));
} else if cx.is_foreign_non_exhaustive_enum(ty) {
err.note(format!("`{ty}` is marked as non-exhaustive, so a wildcard `_` is necessary to match exhaustively"));
}
}
}

49
compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
View file

@ -618,10 +618,15 @@ impl<'p, 'tcx> Usefulness<'p, 'tcx> {
let new_witnesses = if let Constructor::Missing { .. } = ctor {
// We got the special `Missing` constructor, so each of the missing constructors
// gives a new pattern that is not caught by the match. We list those patterns.
let new_patterns = if pcx.is_non_exhaustive {
// Here we don't want the user to try to list all variants, we want them to add
// a wildcard, so we only suggest that.
vec![DeconstructedPat::wildcard(pcx.ty, pcx.span)]
if pcx.is_non_exhaustive {
witnesses
.into_iter()
// Here we don't want the user to try to list all variants, we want them to add
// a wildcard, so we only suggest that.
.map(|witness| {
witness.apply_constructor(pcx, &Constructor::NonExhaustive)
})
.collect()
} else {
let mut split_wildcard = SplitWildcard::new(pcx);
split_wildcard.split(pcx, matrix.heads().map(DeconstructedPat::ctor));
@ -633,7 +638,7 @@ impl<'p, 'tcx> Usefulness<'p, 'tcx> {
// constructor, that matches everything that can be built with
// it. For example, if `ctor` is a `Constructor::Variant` for
// `Option::Some`, we get the pattern `Some(_)`.
let mut new: Vec<DeconstructedPat<'_, '_>> = split_wildcard
let mut new_patterns: Vec<DeconstructedPat<'_, '_>> = split_wildcard
.iter_missing(pcx)
.filter_map(|missing_ctor| {
// Check if this variant is marked `doc(hidden)`
@ -648,27 +653,25 @@ impl<'p, 'tcx> Usefulness<'p, 'tcx> {
.collect();
if hide_variant_show_wild {
new.push(DeconstructedPat::wildcard(pcx.ty, pcx.span));
new_patterns.push(DeconstructedPat::wildcard(pcx.ty, pcx.span));
}
new
};
witnesses
.into_iter()
.flat_map(|witness| {
new_patterns.iter().map(move |pat| {
Witness(
witness
.0
.iter()
.chain(once(pat))
.map(DeconstructedPat::clone_and_forget_reachability)
.collect(),
)
witnesses
.into_iter()
.flat_map(|witness| {
new_patterns.iter().map(move |pat| {
Witness(
witness
.0
.iter()
.chain(once(pat))
.map(DeconstructedPat::clone_and_forget_reachability)
.collect(),
)
})
})
})
.collect()
.collect()
}
} else {
witnesses
.into_iter()