Skip to content

Skip match usefulness analysis for bare bindings and wildcards [-0.18% avg] #48

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Draft
xmakro wants to merge 1 commit into
base: perf/base-0713
Choose a base branch
from
Draft

Skip match usefulness analysis for bare bindings and wildcards [-0.18% avg] #48

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
12 changes: 12 additions & 0 deletions compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -674,6 +674,18 @@ impl<'p, 'tcx> MatchVisitor<'p, 'tcx> {
) {
let pattern_ty = pat.ty;

// Fast path: a bare binding or wildcard — the shape of almost every
// `let` statement and function parameter — is irrefutable for any
// type, so don't lower the pattern or run the usefulness engine on
// it. Anything nested (`x @ sub`, destructuring, constants) still
// runs the full analysis. The only per-pattern check from the full
// path that can apply to a bare binding is the binding-named-same-
// as-variant error, so run that directly.
if matches!(pat.kind, PatKind::Binding { subpattern: None, .. } | PatKind::Wild) {
check_for_bindings_named_same_as_variants(self, pat, Irrefutable);
return;
}

let Ok((cx, report)) = self.analyze_binding(pat, Irrefutable, scrut) else { return };
let witnesses = report.non_exhaustiveness_witnesses;
if witnesses.is_empty() {
Expand Down
Loading