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use true recursion

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This commit is contained in:
ouz-a 2022-06-24 14:16:48 +03:00
parent 90abfe9ce2
commit 661d488bfd
1 changed files with 19 additions and 14 deletions
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33
compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
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@ -364,8 +364,8 @@ impl<'a, 'p, 'tcx> fmt::Debug for PatCtxt<'a, 'p, 'tcx> {
/// A row of a matrix. Rows of len 1 are very common, which is why `SmallVec[_; 2]`
/// works well.
#[derive(Clone)]
struct PatStack<'p, 'tcx> {
pats: SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]>,
pub(crate) struct PatStack<'p, 'tcx> {
pub(crate) pats: SmallVec<[&'p DeconstructedPat<'p, 'tcx>; 2]>,
}
impl<'p, 'tcx> PatStack<'p, 'tcx> {
@ -403,6 +403,21 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
})
}
// Recursively expand all patterns into their subpatterns and push each `PatStack` to matrix.
fn expand_and_extend<'a>(&'a self, matrix: &mut Matrix<'p, 'tcx>) {
if !self.is_empty() && self.head().is_or_pat() {
for pat in self.head().iter_fields() {
let mut new_patstack = PatStack::from_pattern(pat);
new_patstack.pats.extend_from_slice(&self.pats[1..]);
if !new_patstack.is_empty() && new_patstack.head().is_or_pat() {
new_patstack.expand_and_extend(matrix);
} else if !new_patstack.is_empty() {
matrix.push(new_patstack);
}
}
}
}
/// This computes `S(self.head().ctor(), self)`. See top of the file for explanations.
///
/// Structure patterns with a partial wild pattern (Foo { a: 42, .. }) have their missing
@ -436,7 +451,7 @@ impl<'p, 'tcx> fmt::Debug for PatStack<'p, 'tcx> {
/// A 2D matrix.
#[derive(Clone)]
pub(super) struct Matrix<'p, 'tcx> {
patterns: Vec<PatStack<'p, 'tcx>>,
pub patterns: Vec<PatStack<'p, 'tcx>>,
}
impl<'p, 'tcx> Matrix<'p, 'tcx> {
@ -453,17 +468,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
/// expands it.
fn push(&mut self, row: PatStack<'p, 'tcx>) {
if !row.is_empty() && row.head().is_or_pat() {
let pats = row.expand_or_pat();
let mut no_inner_or = true;
for pat in pats {
if !pat.is_empty() && pat.head().is_or_pat() {
self.patterns.extend(pat.expand_or_pat());
no_inner_or = false;
}
}
if no_inner_or {
self.patterns.extend(row.expand_or_pat());
}
row.expand_and_extend(self);
} else {
self.patterns.push(row);
}