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Tweak how we record missing constructors

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This is slower but also not a performance-sensitive path.
This commit is contained in:
Nadrieril 2024-02-06 01:14:12 +01:00
parent 1280928a99
commit 924d6cd1a6
1 changed files with 16 additions and 21 deletions
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37
compiler/rustc_pattern_analysis/src/usefulness.rs
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@ -1319,7 +1319,7 @@ fn push_pattern(&mut self, pat: WitnessPat<Cx>) {
fn apply_constructor(
&mut self,
pcx: &PlaceCtxt<'_, Cx>,
missing_ctors: &[Constructor<Cx>],
mut missing_ctors: &[Constructor<Cx>],
ctor: &Constructor<Cx>,
report_individual_missing_ctors: bool,
) {
@ -1329,32 +1329,27 @@ fn apply_constructor(
if matches!(ctor, Constructor::Missing) {
// We got the special `Missing` constructor that stands for the constructors not present
// in the match.
if missing_ctors.is_empty() {
// Nothing to report.
*self = Self::empty();
} else if !report_individual_missing_ctors {
if !missing_ctors.is_empty() && !report_individual_missing_ctors {
// Report `_` as missing.
let pat = pcx.wild_from_ctor(Constructor::Wildcard);
self.push_pattern(pat);
missing_ctors = &[Constructor::Wildcard];
} else if missing_ctors.iter().any(|c| c.is_non_exhaustive()) {
// We need to report a `_` anyway, so listing other constructors would be redundant.
// `NonExhaustive` is displayed as `_` just like `Wildcard`, but it will be picked
// up by diagnostics to add a note about why `_` is required here.
let pat = pcx.wild_from_ctor(Constructor::NonExhaustive);
self.push_pattern(pat);
} else {
// For each missing constructor `c`, we add a `c(_, _, _)` witness appropriately
// filled with wildcards.
let mut ret = Self::empty();
for ctor in missing_ctors {
let pat = pcx.wild_from_ctor(ctor.clone());
// Clone `self` and add `c(_, _, _)` to each of its witnesses.
let mut wit_matrix = self.clone();
wit_matrix.push_pattern(pat);
ret.extend(wit_matrix);
}
*self = ret;
missing_ctors = &[Constructor::NonExhaustive];
}
// For each missing constructor `c`, we add a `c(_, _, _)` witness appropriately
// filled with wildcards.
let mut ret = Self::empty();
for ctor in missing_ctors {
let pat = pcx.wild_from_ctor(ctor.clone());
// Clone `self` and add `c(_, _, _)` to each of its witnesses.
let mut wit_matrix = self.clone();
wit_matrix.push_pattern(pat);
ret.extend(wit_matrix);
}
*self = ret;
} else {
// Any other constructor we unspecialize as expected.
for witness in self.0.iter_mut() {