use rustc::hir::*;
use rustc::lint::*;
-use utils::{SpanlessEq, span_lint};
+use utils::{SpanlessEq, span_lint, span_lint_and_then, multispan_sugg, snippet, implements_trait, is_copy};
-/// **What it does:** This lint checks for equal operands to comparison, logical and bitwise,
-/// difference and division binary operators (`==`, `>`, etc., `&&`, `||`, `&`, `|`, `^`, `-` and
-/// `/`).
+/// **What it does:** Checks for equal operands to comparison, logical and
+/// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
+/// `||`, `&`, `|`, `^`, `-` and `/`).
///
/// **Why is this bad?** This is usually just a typo or a copy and paste error.
///
-/// **Known problems:** False negatives: We had some false positives regarding calls (notably
-/// [racer](https://github.com/phildawes/racer) had one instance of `x.pop() && x.pop()`), so we
-/// removed matching any function or method calls. We may introduce a whitelist of known pure
-/// functions in the future.
+/// **Known problems:** False negatives: We had some false positives regarding
+/// calls (notably [racer](https://github.com/phildawes/racer) had one instance
+/// of `x.pop() && x.pop()`), so we removed matching any function or method
+/// calls. We may introduce a whitelist of known pure functions in the future.
///
/// **Example:**
/// ```rust
"equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)"
}
+/// **What it does:** Checks for arguments to `==` which have their address taken to satisfy a bound
+/// and suggests to dereference the other argument instead
+///
+/// **Why is this bad?** It is more idiomatic to dereference the other argument.
+///
+/// **Known problems:** None
+///
+/// **Example:**
+/// ```rust
+/// &x == y
+/// ```
+declare_lint! {
+ pub OP_REF,
+ Warn,
+ "taking a reference to satisfy the type constraints on `==`"
+}
+
#[derive(Copy,Clone)]
pub struct EqOp;
impl LintPass for EqOp {
fn get_lints(&self) -> LintArray {
- lint_array!(EQ_OP)
+ lint_array!(EQ_OP, OP_REF)
}
}
-impl LateLintPass for EqOp {
- fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EqOp {
+ fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
if let ExprBinary(ref op, ref left, ref right) = e.node {
if is_valid_operator(op) && SpanlessEq::new(cx).ignore_fn().eq_expr(left, right) {
span_lint(cx,
EQ_OP,
e.span,
&format!("equal expressions as operands to `{}`", op.node.as_str()));
+ return;
+ }
+ let (trait_id, requires_ref) = match op.node {
+ BiAdd => (cx.tcx.lang_items.add_trait(), false),
+ BiSub => (cx.tcx.lang_items.sub_trait(), false),
+ BiMul => (cx.tcx.lang_items.mul_trait(), false),
+ BiDiv => (cx.tcx.lang_items.div_trait(), false),
+ BiRem => (cx.tcx.lang_items.rem_trait(), false),
+ // don't lint short circuiting ops
+ BiAnd | BiOr => return,
+ BiBitXor => (cx.tcx.lang_items.bitxor_trait(), false),
+ BiBitAnd => (cx.tcx.lang_items.bitand_trait(), false),
+ BiBitOr => (cx.tcx.lang_items.bitor_trait(), false),
+ BiShl => (cx.tcx.lang_items.shl_trait(), false),
+ BiShr => (cx.tcx.lang_items.shr_trait(), false),
+ BiNe | BiEq => (cx.tcx.lang_items.eq_trait(), true),
+ BiLt | BiLe | BiGe | BiGt => (cx.tcx.lang_items.ord_trait(), true),
+ };
+ if let Some(trait_id) = trait_id {
+ #[allow(match_same_arms)]
+ match (&left.node, &right.node) {
+ // do not suggest to dereference literals
+ (&ExprLit(..), _) |
+ (_, &ExprLit(..)) => {},
+ // &foo == &bar
+ (&ExprAddrOf(_, ref l), &ExprAddrOf(_, ref r)) => {
+ let lty = cx.tables.expr_ty(l);
+ let rty = cx.tables.expr_ty(r);
+ let lcpy = is_copy(cx, lty);
+ let rcpy = is_copy(cx, rty);
+ // either operator autorefs or both args are copyable
+ if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty]) {
+ span_lint_and_then(cx,
+ OP_REF,
+ e.span,
+ "needlessly taken reference of both operands",
+ |db| {
+ let lsnip = snippet(cx, l.span, "...").to_string();
+ let rsnip = snippet(cx, r.span, "...").to_string();
+ multispan_sugg(db,
+ "use the values directly".to_string(),
+ vec![(left.span, lsnip),
+ (right.span, rsnip)]);
+ })
+ } else if lcpy && !rcpy &&
+ implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
+ span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
+ let lsnip = snippet(cx, l.span, "...").to_string();
+ db.span_suggestion(left.span, "use the left value directly", lsnip);
+ })
+ } else if !lcpy && rcpy &&
+ implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
+ span_lint_and_then(cx,
+ OP_REF,
+ e.span,
+ "needlessly taken reference of right operand",
+ |db| {
+ let rsnip = snippet(cx, r.span, "...").to_string();
+ db.span_suggestion(right.span, "use the right value directly", rsnip);
+ })
+ }
+ },
+ // &foo == bar
+ (&ExprAddrOf(_, ref l), _) => {
+ let lty = cx.tables.expr_ty(l);
+ let lcpy = is_copy(cx, lty);
+ if (requires_ref || lcpy) &&
+ implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right)]) {
+ span_lint_and_then(cx, OP_REF, e.span, "needlessly taken reference of left operand", |db| {
+ let lsnip = snippet(cx, l.span, "...").to_string();
+ db.span_suggestion(left.span, "use the left value directly", lsnip);
+ })
+ }
+ },
+ // foo == &bar
+ (_, &ExprAddrOf(_, ref r)) => {
+ let rty = cx.tables.expr_ty(r);
+ let rcpy = is_copy(cx, rty);
+ if (requires_ref || rcpy) &&
+ implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty]) {
+ span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |db| {
+ let rsnip = snippet(cx, r.span, "...").to_string();
+ db.span_suggestion(right.span, "use the right value directly", rsnip);
+ })
+ }
+ },
+ _ => {},
+ }
}
}
}
fn is_valid_operator(op: &BinOp) -> bool {
match op.node {
- BiSub |
- BiDiv |
- BiEq |
- BiLt |
- BiLe |
- BiGt |
- BiGe |
- BiNe |
- BiAnd |
- BiOr |
- BiBitXor |
- BiBitAnd |
- BiBitOr => true,
+ BiSub | BiDiv | BiEq | BiLt | BiLe | BiGt | BiGe | BiNe | BiAnd | BiOr | BiBitXor | BiBitAnd | BiBitOr => true,
_ => false,
}
}