| //! Lint on unnecessary double comparisons. Some examples: |
| |
| use rustc_errors::Applicability; |
| use rustc_hir::{BinOpKind, Expr, ExprKind}; |
| use rustc_lint::{LateContext, LateLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| use rustc_span::source_map::Span; |
| |
| use crate::utils::{snippet_with_applicability, span_lint_and_sugg, SpanlessEq}; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for double comparisons that could be simplified to a single expression. |
| /// |
| /// |
| /// **Why is this bad?** Readability. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let x = 1; |
| /// # let y = 2; |
| /// if x == y || x < y {} |
| /// ``` |
| /// |
| /// Could be written as: |
| /// |
| /// ```rust |
| /// # let x = 1; |
| /// # let y = 2; |
| /// if x <= y {} |
| /// ``` |
| pub DOUBLE_COMPARISONS, |
| complexity, |
| "unnecessary double comparisons that can be simplified" |
| } |
| |
| declare_lint_pass!(DoubleComparisons => [DOUBLE_COMPARISONS]); |
| |
| impl<'tcx> DoubleComparisons { |
| #[allow(clippy::similar_names)] |
| fn check_binop(cx: &LateContext<'tcx>, op: BinOpKind, lhs: &'tcx Expr<'_>, rhs: &'tcx Expr<'_>, span: Span) { |
| let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (&lhs.kind, &rhs.kind) { |
| (ExprKind::Binary(lb, llhs, lrhs), ExprKind::Binary(rb, rlhs, rrhs)) => { |
| (lb.node, llhs, lrhs, rb.node, rlhs, rrhs) |
| }, |
| _ => return, |
| }; |
| let mut spanless_eq = SpanlessEq::new(cx).ignore_fn(); |
| if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) { |
| return; |
| } |
| macro_rules! lint_double_comparison { |
| ($op:tt) => {{ |
| let mut applicability = Applicability::MachineApplicable; |
| let lhs_str = snippet_with_applicability(cx, llhs.span, "", &mut applicability); |
| let rhs_str = snippet_with_applicability(cx, lrhs.span, "", &mut applicability); |
| let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str); |
| span_lint_and_sugg( |
| cx, |
| DOUBLE_COMPARISONS, |
| span, |
| "This binary expression can be simplified", |
| "try", |
| sugg, |
| applicability, |
| ); |
| }}; |
| } |
| #[rustfmt::skip] |
| match (op, lkind, rkind) { |
| (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Lt) | (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Eq) => { |
| lint_double_comparison!(<=) |
| }, |
| (BinOpKind::Or, BinOpKind::Eq, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Eq) => { |
| lint_double_comparison!(>=) |
| }, |
| (BinOpKind::Or, BinOpKind::Lt, BinOpKind::Gt) | (BinOpKind::Or, BinOpKind::Gt, BinOpKind::Lt) => { |
| lint_double_comparison!(!=) |
| }, |
| (BinOpKind::And, BinOpKind::Le, BinOpKind::Ge) | (BinOpKind::And, BinOpKind::Ge, BinOpKind::Le) => { |
| lint_double_comparison!(==) |
| }, |
| _ => (), |
| }; |
| } |
| } |
| |
| impl<'tcx> LateLintPass<'tcx> for DoubleComparisons { |
| fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { |
| if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = expr.kind { |
| Self::check_binop(cx, kind.node, lhs, rhs, expr.span); |
| } |
| } |
| } |