86 lines
2.6 KiB
Rust
86 lines
2.6 KiB
Rust
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//! Lint on unnecessary double comparisons. Some examples:
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use rustc::hir::*;
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use rustc::lint::*;
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use syntax::codemap::Span;
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use utils::{snippet, span_lint_and_sugg, SpanlessEq};
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/// **What it does:** Checks for double comparions that could be simpified to a single expression.
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///
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///
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/// **Why is this bad?** Readability.
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///
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/// **Known problems:** None.
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///
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/// **Example:**
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/// ```rust
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/// x == y || x < y
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/// ```
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///
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/// Could be written as:
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///
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/// ```rust
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/// x <= y
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/// ```
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declare_lint! {
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pub DOUBLE_COMPARISONS,
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Deny,
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"unnecessary double comparisons that can be simplified"
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}
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pub struct DoubleComparisonPass;
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impl LintPass for DoubleComparisonPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(DOUBLE_COMPARISONS)
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}
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}
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impl<'a, 'tcx> DoubleComparisonPass {
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fn check_binop(
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&self,
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cx: &LateContext<'a, 'tcx>,
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op: BinOp_,
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lhs: &'tcx Expr,
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rhs: &'tcx Expr,
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span: Span,
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) {
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let (lkind, llhs, lrhs, rkind, rlhs, rrhs) = match (lhs.node.clone(), rhs.node.clone()) {
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(ExprBinary(lb, llhs, lrhs), ExprBinary(rb, rlhs, rrhs)) => {
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(lb.node, llhs, lrhs, rb.node, rlhs, rrhs)
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}
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_ => return,
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};
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let spanless_eq = SpanlessEq::new(cx).ignore_fn();
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if !(spanless_eq.eq_expr(&llhs, &rlhs) && spanless_eq.eq_expr(&lrhs, &rrhs)) {
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return;
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}
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macro_rules! lint_double_comparison {
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($op:tt) => {{
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let lhs_str = snippet(cx, llhs.span, "");
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let rhs_str = snippet(cx, lrhs.span, "");
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let sugg = format!("{} {} {}", lhs_str, stringify!($op), rhs_str);
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span_lint_and_sugg(cx, DOUBLE_COMPARISONS, span,
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"This binary expression can be simplified",
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"try", sugg);
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}}
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}
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match (op, lkind, rkind) {
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(BiOr, BiEq, BiLt) | (BiOr, BiLt, BiEq) => lint_double_comparison!(<=),
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(BiOr, BiEq, BiGt) | (BiOr, BiGt, BiEq) => lint_double_comparison!(>=),
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(BiOr, BiLt, BiGt) | (BiOr, BiGt, BiLt) => lint_double_comparison!(!=),
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(BiAnd, BiLe, BiGe) | (BiAnd, BiGe, BiLe) => lint_double_comparison!(==),
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_ => (),
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};
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DoubleComparisonPass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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if let ExprBinary(ref kind, ref lhs, ref rhs) = expr.node {
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self.check_binop(cx, kind.node, lhs, rhs, expr.span);
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}
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}
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}
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