206 lines
9.3 KiB
Rust
206 lines
9.3 KiB
Rust
use crate::utils::{implements_trait, is_copy, multispan_sugg, snippet, span_lint, span_lint_and_then, SpanlessEq};
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_lint_pass, declare_tool_lint};
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use rustc_errors::Applicability;
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declare_clippy_lint! {
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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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/// # let x = 1;
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/// if x + 1 == x + 1 {}
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/// ```
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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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declare_clippy_lint! {
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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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/// ```ignore
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/// &x == y
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/// ```
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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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declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for EqOp {
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#[allow(clippy::similar_names, clippy::too_many_lines)]
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
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if let ExprKind::Binary(op, ref left, ref right) = e.node {
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if e.span.from_expansion() {
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return;
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}
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if is_valid_operator(op) && SpanlessEq::new(cx).ignore_fn().eq_expr(left, right) {
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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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BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
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BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
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BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
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BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
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BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
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// don't lint short circuiting ops
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BinOpKind::And | BinOpKind::Or => return,
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BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
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BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
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BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
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BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
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BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
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BinOpKind::Ne | BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
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BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ge | BinOpKind::Gt => {
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(cx.tcx.lang_items().ord_trait(), true)
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},
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};
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if let Some(trait_id) = trait_id {
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#[allow(clippy::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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(&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
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// &foo == &bar
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(&ExprKind::AddrOf(_, ref l), &ExprKind::AddrOf(_, 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.into()]) {
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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
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&& !rcpy
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&& implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right).into()])
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{
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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(
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left.span,
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"use the left value directly",
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lsnip,
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Applicability::MachineApplicable, // snippet
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);
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})
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} else if !lcpy
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&& rcpy
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&& implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty.into()])
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{
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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(
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right.span,
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"use the right value directly",
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rsnip,
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Applicability::MachineApplicable, // snippet
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);
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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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(&ExprKind::AddrOf(_, 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)
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&& implements_trait(cx, lty, trait_id, &[cx.tables.expr_ty(right).into()])
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{
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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(
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left.span,
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"use the left value directly",
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lsnip,
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Applicability::MachineApplicable, // snippet
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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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(_, &ExprKind::AddrOf(_, 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)
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&& implements_trait(cx, cx.tables.expr_ty(left), trait_id, &[rty.into()])
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{
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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(
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right.span,
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"use the right value directly",
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rsnip,
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Applicability::MachineApplicable, // snippet
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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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}
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fn is_valid_operator(op: BinOp) -> bool {
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match op.node {
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BinOpKind::Sub
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| BinOpKind::Div
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| BinOpKind::Eq
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| BinOpKind::Lt
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| BinOpKind::Le
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| BinOpKind::Gt
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| BinOpKind::Ge
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| BinOpKind::Ne
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| BinOpKind::And
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| BinOpKind::Or
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| BinOpKind::BitXor
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| BinOpKind::BitAnd
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| BinOpKind::BitOr => true,
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_ => false,
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}
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}
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