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Auto merge of rust-lang#10955 - Centri3:redundant_matches_guard, r=Al…
…exendoo,blyxyas new lint [`redundant_guards`] Closes rust-lang#7825, maybe somebody else can get the ranges lint in the comments? changelog: New lint [`redundant_guards`]
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,190 @@ | ||
| use clippy_utils::diagnostics::span_lint_and_then; | ||
| use clippy_utils::path_to_local; | ||
| use clippy_utils::source::snippet_with_applicability; | ||
| use clippy_utils::visitors::{for_each_expr, is_local_used}; | ||
| use rustc_errors::Applicability; | ||
| use rustc_hir::def::{DefKind, Res}; | ||
| use rustc_hir::{Arm, BinOpKind, Expr, ExprKind, Guard, MatchSource, Node, Pat, PatKind}; | ||
| use rustc_lint::LateContext; | ||
| use rustc_span::Span; | ||
| use std::ops::ControlFlow; | ||
|
|
||
| use super::REDUNDANT_GUARDS; | ||
|
|
||
| pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, arms: &'tcx [Arm<'tcx>]) { | ||
| for outer_arm in arms { | ||
| let Some(guard) = outer_arm.guard else { | ||
| continue; | ||
| }; | ||
|
|
||
| // `Some(x) if matches!(x, y)` | ||
| if let Guard::If(if_expr) = guard | ||
| && let ExprKind::Match( | ||
| scrutinee, | ||
| [ | ||
| arm, | ||
| Arm { | ||
| pat: Pat { | ||
| kind: PatKind::Wild, | ||
| .. | ||
| }, | ||
| .. | ||
| }, | ||
| ], | ||
| MatchSource::Normal, | ||
| ) = if_expr.kind | ||
| { | ||
| emit_redundant_guards( | ||
| cx, | ||
| outer_arm, | ||
| if_expr.span, | ||
| scrutinee, | ||
| arm.pat.span, | ||
| arm.guard, | ||
| ); | ||
| } | ||
| // `Some(x) if let Some(2) = x` | ||
| else if let Guard::IfLet(let_expr) = guard { | ||
| emit_redundant_guards( | ||
| cx, | ||
| outer_arm, | ||
| let_expr.span, | ||
| let_expr.init, | ||
| let_expr.pat.span, | ||
| None, | ||
| ); | ||
| } | ||
| // `Some(x) if x == Some(2)` | ||
| else if let Guard::If(if_expr) = guard | ||
| && let ExprKind::Binary(bin_op, local, pat) = if_expr.kind | ||
| && matches!(bin_op.node, BinOpKind::Eq) | ||
| && expr_can_be_pat(cx, pat) | ||
| // Ensure they have the same type. If they don't, we'd need deref coercion which isn't | ||
| // possible (currently) in a pattern. In some cases, you can use something like | ||
| // `as_deref` or similar but in general, we shouldn't lint this as it'd create an | ||
| // extraordinary amount of FPs. | ||
| // | ||
| // This isn't necessary in the other two checks, as they must be a pattern already. | ||
| && cx.typeck_results().expr_ty(local) == cx.typeck_results().expr_ty(pat) | ||
| { | ||
| emit_redundant_guards( | ||
| cx, | ||
| outer_arm, | ||
| if_expr.span, | ||
| local, | ||
| pat.span, | ||
| None, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
|
|
||
| fn get_pat_binding<'tcx>(cx: &LateContext<'tcx>, guard_expr: &Expr<'_>, outer_arm: &Arm<'tcx>) -> Option<(Span, bool)> { | ||
| if let Some(local) = path_to_local(guard_expr) && !is_local_used(cx, outer_arm.body, local) { | ||
| let mut span = None; | ||
| let mut multiple_bindings = false; | ||
| // `each_binding` gives the `HirId` of the `Pat` itself, not the binding | ||
| outer_arm.pat.walk(|pat| { | ||
| if let PatKind::Binding(_, hir_id, _, _) = pat.kind | ||
| && hir_id == local | ||
| && span.replace(pat.span).is_some() | ||
| { | ||
| multiple_bindings = true; | ||
| return false; | ||
| } | ||
|
|
||
| true | ||
| }); | ||
|
|
||
| // Ignore bindings from or patterns, like `First(x) | Second(x, _) | Third(x, _, _)` | ||
| if !multiple_bindings { | ||
| return span.map(|span| { | ||
| ( | ||
| span, | ||
| !matches!(cx.tcx.hir().get_parent(local), Node::PatField(_)), | ||
| ) | ||
| }); | ||
| } | ||
| } | ||
|
|
||
| None | ||
| } | ||
|
|
||
| fn emit_redundant_guards<'tcx>( | ||
| cx: &LateContext<'tcx>, | ||
| outer_arm: &Arm<'tcx>, | ||
| guard_span: Span, | ||
| local: &Expr<'_>, | ||
| pat_span: Span, | ||
| inner_guard: Option<Guard<'_>>, | ||
| ) { | ||
| let mut app = Applicability::MaybeIncorrect; | ||
| let Some((pat_binding, can_use_shorthand)) = get_pat_binding(cx, local, outer_arm) else { | ||
| return; | ||
| }; | ||
|
|
||
| span_lint_and_then( | ||
| cx, | ||
| REDUNDANT_GUARDS, | ||
| guard_span.source_callsite(), | ||
| "redundant guard", | ||
| |diag| { | ||
| let binding_replacement = snippet_with_applicability(cx, pat_span, "<binding_repl>", &mut app); | ||
| diag.multipart_suggestion_verbose( | ||
| "try", | ||
| vec![ | ||
| if can_use_shorthand { | ||
| (pat_binding, binding_replacement.into_owned()) | ||
| } else { | ||
| (pat_binding.shrink_to_hi(), format!(": {binding_replacement}")) | ||
| }, | ||
| ( | ||
| guard_span.source_callsite().with_lo(outer_arm.pat.span.hi()), | ||
| inner_guard.map_or_else(String::new, |guard| { | ||
| let (prefix, span) = match guard { | ||
| Guard::If(e) => ("if", e.span), | ||
| Guard::IfLet(l) => ("if let", l.span), | ||
| }; | ||
|
|
||
| format!( | ||
| " {prefix} {}", | ||
| snippet_with_applicability(cx, span, "<guard>", &mut app), | ||
| ) | ||
| }), | ||
| ), | ||
| ], | ||
| app, | ||
| ); | ||
| }, | ||
| ); | ||
| } | ||
|
|
||
| /// Checks if the given `Expr` can also be represented as a `Pat`. | ||
| fn expr_can_be_pat(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { | ||
| for_each_expr(expr, |expr| { | ||
| if match expr.kind { | ||
| ExprKind::ConstBlock(..) => cx.tcx.features().inline_const_pat, | ||
| ExprKind::Call(c, ..) if let ExprKind::Path(qpath) = c.kind => { | ||
| // Allow ctors | ||
| matches!(cx.qpath_res(&qpath, c.hir_id), Res::Def(DefKind::Ctor(..), ..)) | ||
| }, | ||
| ExprKind::Path(qpath) => { | ||
| matches!( | ||
| cx.qpath_res(&qpath, expr.hir_id), | ||
| Res::Def(DefKind::Struct | DefKind::Enum | DefKind::Ctor(..), ..), | ||
| ) | ||
| }, | ||
| ExprKind::AddrOf(..) | ||
| | ExprKind::Array(..) | ||
| | ExprKind::Tup(..) | ||
| | ExprKind::Struct(..) | ||
| | ExprKind::Lit(..) => true, | ||
| _ => false, | ||
| } { | ||
| return ControlFlow::Continue(()); | ||
| } | ||
|
|
||
| ControlFlow::Break(()) | ||
| }) | ||
| .is_none() | ||
| } |
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