bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Suppress irrefutable let patterns lint for prefixes in match guards

Browse source 
In match guards, irrefutable prefixes might use the bindings created
by the match pattern. Ideally, we check for this, but we can do the
next best thing and just not lint for irrefutable prefixes in match
guards.
This commit is contained in:
est31 2022-10-14 01:46:24 +02:00
parent 4891d57f7a
commit eab41a136a
3 changed files with 36 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

18
compiler/rustc_mir_build/src/thir/pattern/check_match.rs
View file

@ -370,8 +370,12 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
// Check if the let source is while, for there is no alternative place to put a prefix,
// and we shouldn't lint.
// For let guards inside a match, prefixes might use bindings of the match pattern,
// so can't always be moved out.
// FIXME: Add checking whether the bindings are actually used in the prefix,
// and lint if they are not.
let let_source = let_source_parent(self.tcx, top, None);
if !matches!(let_source, LetSource::WhileLet) {
if !matches!(let_source, LetSource::WhileLet | LetSource::IfLetGuard) {
// Emit the lint
let prefix = &chain_refutabilities[..until];
lint_affix(prefix, "leading", "outside of the construct");
@ -1151,10 +1155,14 @@ fn let_source_parent(tcx: TyCtxt<'_>, parent: HirId, pat_id: Option<HirId>) -> L
let parent_parent = hir.get_parent_node(parent);
let parent_parent_node = hir.get(parent_parent);
if let hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(_), span, .. }) =
parent_parent_node
{
return LetSource::LetElse(*span);
match parent_parent_node {
hir::Node::Stmt(hir::Stmt { kind: hir::StmtKind::Local(_), span, .. }) => {
return LetSource::LetElse(*span);
}
hir::Node::Arm(hir::Arm { guard: Some(hir::Guard::If(_)), .. }) => {
return LetSource::IfLetGuard;
}
_ => {}
}
let parent_parent_parent = hir.get_parent_node(parent_parent);