| //! lint on blocks unnecessarily using >= with a + 1 or - 1 |
| |
| use rustc_ast::ast::{BinOpKind, Expr, ExprKind, Lit, LitKind}; |
| use rustc_errors::Applicability; |
| use rustc_lint::{EarlyContext, EarlyLintPass}; |
| use rustc_session::{declare_lint_pass, declare_tool_lint}; |
| |
| use crate::utils::{snippet_opt, span_lint_and_sugg}; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for usage of `x >= y + 1` or `x - 1 >= y` (and `<=`) in a block |
| /// |
| /// **Why is this bad?** Readability -- better to use `> y` instead of `>= y + 1`. |
| /// |
| /// **Known problems:** None. |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # let x = 1; |
| /// # let y = 1; |
| /// if x >= y + 1 {} |
| /// ``` |
| /// |
| /// Could be written as: |
| /// |
| /// ```rust |
| /// # let x = 1; |
| /// # let y = 1; |
| /// if x > y {} |
| /// ``` |
| pub INT_PLUS_ONE, |
| complexity, |
| "instead of using `x >= y + 1`, use `x > y`" |
| } |
| |
| declare_lint_pass!(IntPlusOne => [INT_PLUS_ONE]); |
| |
| // cases: |
| // BinOpKind::Ge |
| // x >= y + 1 |
| // x - 1 >= y |
| // |
| // BinOpKind::Le |
| // x + 1 <= y |
| // x <= y - 1 |
| |
| #[derive(Copy, Clone)] |
| enum Side { |
| LHS, |
| RHS, |
| } |
| |
| impl IntPlusOne { |
| #[allow(clippy::cast_sign_loss)] |
| fn check_lit(lit: &Lit, target_value: i128) -> bool { |
| if let LitKind::Int(value, ..) = lit.kind { |
| return value == (target_value as u128); |
| } |
| false |
| } |
| |
| fn check_binop(cx: &EarlyContext<'_>, binop: BinOpKind, lhs: &Expr, rhs: &Expr) -> Option<String> { |
| match (binop, &lhs.kind, &rhs.kind) { |
| // case where `x - 1 >= ...` or `-1 + x >= ...` |
| (BinOpKind::Ge, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) => { |
| match (lhskind.node, &lhslhs.kind, &lhsrhs.kind) { |
| // `-1 + x` |
| (BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => { |
| Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::LHS) |
| }, |
| // `x - 1` |
| (BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::LHS) |
| }, |
| _ => None, |
| } |
| }, |
| // case where `... >= y + 1` or `... >= 1 + y` |
| (BinOpKind::Ge, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) |
| if rhskind.node == BinOpKind::Add => |
| { |
| match (&rhslhs.kind, &rhsrhs.kind) { |
| // `y + 1` and `1 + y` |
| (&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::RHS) |
| }, |
| (_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::RHS) |
| }, |
| _ => None, |
| } |
| } |
| // case where `x + 1 <= ...` or `1 + x <= ...` |
| (BinOpKind::Le, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) |
| if lhskind.node == BinOpKind::Add => |
| { |
| match (&lhslhs.kind, &lhsrhs.kind) { |
| // `1 + x` and `x + 1` |
| (&ExprKind::Lit(ref lit), _) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, lhsrhs, rhs, Side::LHS) |
| }, |
| (_, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, lhslhs, rhs, Side::LHS) |
| }, |
| _ => None, |
| } |
| } |
| // case where `... >= y - 1` or `... >= -1 + y` |
| (BinOpKind::Le, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) => { |
| match (rhskind.node, &rhslhs.kind, &rhsrhs.kind) { |
| // `-1 + y` |
| (BinOpKind::Add, &ExprKind::Lit(ref lit), _) if Self::check_lit(lit, -1) => { |
| Self::generate_recommendation(cx, binop, rhsrhs, lhs, Side::RHS) |
| }, |
| // `y - 1` |
| (BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) if Self::check_lit(lit, 1) => { |
| Self::generate_recommendation(cx, binop, rhslhs, lhs, Side::RHS) |
| }, |
| _ => None, |
| } |
| }, |
| _ => None, |
| } |
| } |
| |
| fn generate_recommendation( |
| cx: &EarlyContext<'_>, |
| binop: BinOpKind, |
| node: &Expr, |
| other_side: &Expr, |
| side: Side, |
| ) -> Option<String> { |
| let binop_string = match binop { |
| BinOpKind::Ge => ">", |
| BinOpKind::Le => "<", |
| _ => return None, |
| }; |
| if let Some(snippet) = snippet_opt(cx, node.span) { |
| if let Some(other_side_snippet) = snippet_opt(cx, other_side.span) { |
| let rec = match side { |
| Side::LHS => Some(format!("{} {} {}", snippet, binop_string, other_side_snippet)), |
| Side::RHS => Some(format!("{} {} {}", other_side_snippet, binop_string, snippet)), |
| }; |
| return rec; |
| } |
| } |
| None |
| } |
| |
| fn emit_warning(cx: &EarlyContext<'_>, block: &Expr, recommendation: String) { |
| span_lint_and_sugg( |
| cx, |
| INT_PLUS_ONE, |
| block.span, |
| "Unnecessary `>= y + 1` or `x - 1 >=`", |
| "change it to", |
| recommendation, |
| Applicability::MachineApplicable, // snippet |
| ); |
| } |
| } |
| |
| impl EarlyLintPass for IntPlusOne { |
| fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) { |
| if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = item.kind { |
| if let Some(ref rec) = Self::check_binop(cx, kind.node, lhs, rhs) { |
| Self::emit_warning(cx, item, rec.clone()); |
| } |
| } |
| } |
| } |