diff options
3 files changed, 36 insertions, 19 deletions
diff --git a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs index ec709a1db51..5984c800d83 100644 --- a/compiler/rustc_mir_build/src/thir/pattern/check_match.rs +++ b/compiler/rustc_mir_build/src/thir/pattern/check_match.rs @@ -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); diff --git a/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.disallowed.stderr b/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.disallowed.stderr index 2570c36b810..be4a5231558 100644 --- a/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.disallowed.stderr +++ b/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.disallowed.stderr @@ -75,26 +75,26 @@ LL | if let first = &opt && let None = Some(1) {} = note: this pattern will always match = help: consider moving it outside of the construct -error: irrefutable `let` patterns +error: irrefutable `if let` guard patterns --> $DIR/irrefutable-lets.rs:44:28 | LL | Some(ref first) if let second = first && let _third = second && let v = 4 + 4 => {}, | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | - = note: these patterns will always match, so the `let` is useless - = help: consider removing `let` + = note: these patterns will always match, so the guard is useless + = help: consider removing the guard and adding a `let` inside the match arm -error: leading irrefutable pattern in let chain - --> $DIR/irrefutable-lets.rs:50:28 +error: trailing irrefutable patterns in let chain + --> $DIR/irrefutable-lets.rs:59:16 | -LL | Some(ref first) if let Range { start: local_start, end: _ } = first - | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +LL | && let v = local_end && let w = v => {}, + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | - = note: this pattern will always match - = help: consider moving it outside of the construct + = note: these patterns will always match + = help: consider moving them into the body error: irrefutable `while let` patterns - --> $DIR/irrefutable-lets.rs:59:11 + --> $DIR/irrefutable-lets.rs:68:11 | LL | while let first = &opt && let (a, b) = (1, 2) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -103,7 +103,7 @@ LL | while let first = &opt && let (a, b) = (1, 2) {} = help: consider instead using a `loop { ... }` with a `let` inside it error: trailing irrefutable patterns in let chain - --> $DIR/irrefutable-lets.rs:62:40 + --> $DIR/irrefutable-lets.rs:71:40 | LL | while let Some(ref first) = opt && let second = first && let _third = second {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ diff --git a/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.rs b/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.rs index 3d1626e8ffb..9afb6853b36 100644 --- a/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.rs +++ b/src/test/ui/rfc-2497-if-let-chains/irrefutable-lets.rs @@ -42,18 +42,27 @@ fn main() { match opt { Some(ref first) if let second = first && let _third = second && let v = 4 + 4 => {}, - //[disallowed]~^ ERROR irrefutable `let` patterns + //[disallowed]~^ ERROR irrefutable `if let` guard patterns _ => {} } + // No error about leading irrefutable patterns: the expr on the rhs might + // use the bindings created by the match. match opt { Some(ref first) if let Range { start: local_start, end: _ } = first - //[disallowed]~^ ERROR leading irrefutable pattern in let chain && let None = local_start => {}, _ => {} } - // No error, despite the prefix being irrefutable + match opt { + Some(ref first) if let Range { start: Some(_), end: local_end } = first + && let v = local_end && let w = v => {}, + //[disallowed]~^ ERROR trailing irrefutable patterns in let chain + _ => {} + } + + // No error, despite the prefix being irrefutable: moving out could change the behaviour, + // due to possible side effects of the operation. while let first = &opt && let Some(ref second) = first && let None = second.start {} while let first = &opt && let (a, b) = (1, 2) {} |