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use rustc::lint::*;
use rustc_front::hir::*;
use rustc_front::util as ast_util;
use utils::{is_exp_equal, span_lint};
/// **What it does:** This lint checks for equal operands to comparisons and bitwise binary operators (`&`, `|` and `^`). It is `Warn` by default.
///
/// **Why is this bad?** This is usually just a typo.
///
/// **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:** `x + 1 == x + 1`
declare_lint! {
pub EQ_OP,
Warn,
"equal operands on both sides of a comparison or bitwise combination (e.g. `x == x`)"
}
#[derive(Copy,Clone)]
pub struct EqOp;
impl LintPass for EqOp {
fn get_lints(&self) -> LintArray {
lint_array!(EQ_OP)
}
}
impl LateLintPass for EqOp {
fn check_expr(&mut self, cx: &LateContext, e: &Expr) {
if let ExprBinary(ref op, ref left, ref right) = e.node {
if is_cmp_or_bit(op) && is_exp_equal(cx, left, right) {
span_lint(cx,
EQ_OP,
e.span,
&format!("equal expressions as operands to {}", ast_util::binop_to_string(op.node)));
}
}
}
}
fn is_cmp_or_bit(op: &BinOp) -> bool {
match op.node {
BiEq |
BiLt |
BiLe |
BiGt |
BiGe |
BiNe |
BiAnd |
BiOr |
BiBitXor |
BiBitAnd |
BiBitOr => true,
_ => false,
}
}