rust/clippy_lints/src/double_comparison.rs

97 lines
3.4 KiB
Rust

//! Lint on unnecessary double comparisons. Some examples:
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::eq_expr_value;
use clippy_utils::source::snippet_with_applicability;
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;
declare_clippy_lint! {
/// ### What it does
/// Checks for double comparisons that could be simplified to a single expression.
///
///
/// ### Why is this bad?
/// Readability.
///
/// ### 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 {}
/// ```
#[clippy::version = "pre 1.29.0"]
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,
};
if !(eq_expr_value(cx, llhs, rlhs) && eq_expr_value(cx, 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, lhs, rhs) = expr.kind {
Self::check_binop(cx, kind.node, lhs, rhs, expr.span);
}
}
}