163 lines
7.4 KiB
Rust
163 lines
7.4 KiB
Rust
use rustc::hir::*;
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use rustc::lint::*;
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use utils::{in_macro, implements_trait, is_copy, multispan_sugg, snippet, span_lint, span_lint_and_then, SpanlessEq};
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/// **What it does:** Checks for equal operands to comparison, logical and
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/// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
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/// `||`, `&`, `|`, `^`, `-` and `/`).
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///
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/// **Why is this bad?** This is usually just a typo or a copy and paste error.
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///
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/// **Known problems:** False negatives: We had some false positives regarding
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/// calls (notably [racer](https://github.com/phildawes/racer) had one instance
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/// of `x.pop() && x.pop()`), so we removed matching any function or method
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/// calls. We may introduce a whitelist of known pure functions in the future.
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///
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/// **Example:**
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/// ```rust
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/// x + 1 == x + 1
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/// ```
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declare_clippy_lint! {
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pub EQ_OP,
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correctness,
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"equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)"
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}
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/// **What it does:** Checks for arguments to `==` which have their address
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/// taken to satisfy a bound
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/// and suggests to dereference the other argument instead
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///
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/// **Why is this bad?** It is more idiomatic to dereference the other argument.
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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
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/// ```
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declare_clippy_lint! {
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pub OP_REF,
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style,
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"taking a reference to satisfy the type constraints on `==`"
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}
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#[derive(Copy, Clone)]
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pub struct EqOp;
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impl LintPass for EqOp {
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fn get_lints(&self) -> LintArray {
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lint_array!(EQ_OP, OP_REF)
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}
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}
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EqOp {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if let ExprBinary(ref op, ref left, ref right) = e.node {
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if is_valid_operator(op) && SpanlessEq::new(cx).ignore_fn().eq_expr(left, right) && !in_macro(e.span) {
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span_lint(
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cx,
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EQ_OP,
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e.span,
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&format!("equal expressions as operands to `{}`", op.node.as_str()),
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);
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return;
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}
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let (trait_id, requires_ref) = match op.node {
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BiAdd => (cx.tcx.lang_items().add_trait(), false),
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BiSub => (cx.tcx.lang_items().sub_trait(), false),
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BiMul => (cx.tcx.lang_items().mul_trait(), false),
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BiDiv => (cx.tcx.lang_items().div_trait(), false),
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BiRem => (cx.tcx.lang_items().rem_trait(), false),
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// don't lint short circuiting ops
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BiAnd | BiOr => return,
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BiBitXor => (cx.tcx.lang_items().bitxor_trait(), false),
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BiBitAnd => (cx.tcx.lang_items().bitand_trait(), false),
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BiBitOr => (cx.tcx.lang_items().bitor_trait(), false),
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BiShl => (cx.tcx.lang_items().shl_trait(), false),
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BiShr => (cx.tcx.lang_items().shr_trait(), false),
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BiNe | BiEq => (cx.tcx.lang_items().eq_trait(), true),
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BiLt | BiLe | BiGe | BiGt => (cx.tcx.lang_items().ord_trait(), true),
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};
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if let Some(trait_id) = trait_id {
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#[allow(match_same_arms)]
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match (&left.node, &right.node) {
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// do not suggest to dereference literals
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(&ExprLit(..), _) | (_, &ExprLit(..)) => {},
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// &foo == &bar
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(&ExprAddrOf(_, ref l), &ExprAddrOf(_, ref r)) => {
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let lty = cx.tables.expr_ty(l);
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let rty = cx.tables.expr_ty(r);
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let lcpy = is_copy(cx, lty);
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let rcpy = is_copy(cx, rty);
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// either operator autorefs or both args are copyable
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if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty]) {
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span_lint_and_then(
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cx,
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OP_REF,
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e.span,
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"needlessly taken reference of both operands",
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|db| {
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let lsnip = snippet(cx, l.span, "...").to_string();
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let rsnip = snippet(cx, r.span, "...").to_string();
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multispan_sugg(
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db,
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"use the values directly".to_string(),
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vec![(left.span, lsnip), (right.span, rsnip)],
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);
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},
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)
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} else if lcpy && !rcpy && implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
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span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
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let lsnip = snippet(cx, l.span, "...").to_string();
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db.span_suggestion(left.span, "use the left value directly", lsnip);
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})
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} else if !lcpy && rcpy && implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
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span_lint_and_then(
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cx,
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OP_REF,
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e.span,
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"needlessly taken reference of right operand",
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|db| {
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let rsnip = snippet(cx, r.span, "...").to_string();
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db.span_suggestion(right.span, "use the right value directly", rsnip);
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},
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)
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}
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},
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// &foo == bar
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(&ExprAddrOf(_, ref l), _) => {
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let lty = cx.tables.expr_ty(l);
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let lcpy = is_copy(cx, lty);
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if (requires_ref || lcpy) && implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
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span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
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let lsnip = snippet(cx, l.span, "...").to_string();
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db.span_suggestion(left.span, "use the left value directly", lsnip);
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})
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}
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},
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// foo == &bar
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(_, &ExprAddrOf(_, ref r)) => {
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let rty = cx.tables.expr_ty(r);
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let rcpy = is_copy(cx, rty);
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if (requires_ref || rcpy) && implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
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span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |db| {
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let rsnip = snippet(cx, r.span, "...").to_string();
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db.span_suggestion(right.span, "use the right value directly", rsnip);
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})
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}
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},
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_ => {},
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}
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}
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}
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}
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}
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fn is_valid_operator(op: &BinOp) -> bool {
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match op.node {
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BiSub | BiDiv | BiEq | BiLt | BiLe | BiGt | BiGe | BiNe | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr => true,
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_ => false,
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}
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}
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