rust/clippy_lints/src/suspicious_trait_impl.rs

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use rustc::lint::*;
use rustc::hir;
use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
use syntax::ast;
use utils::{get_trait_def_id, span_lint};
/// **What it does:** Lints for suspicious operations in impls of arithmetic operators, e.g.
/// subtracting elements in an Add impl.
///
/// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// impl Add for Foo {
/// type Output = Foo;
///
/// fn add(self, other: Foo) -> Foo {
/// Foo(self.0 - other.0)
/// }
/// }
/// ```
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declare_clippy_lint! {
pub SUSPICIOUS_ARITHMETIC_IMPL,
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correctness,
"suspicious use of operators in impl of arithmetic trait"
}
/// **What it does:** Lints for suspicious operations in impls of OpAssign, e.g.
/// subtracting elements in an AddAssign impl.
///
/// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
///
/// **Known problems:** None.
///
/// **Example:**
/// ```rust
/// impl AddAssign for Foo {
/// fn add_assign(&mut self, other: Foo) {
/// *self = *self - other;
/// }
/// }
/// ```
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declare_clippy_lint! {
pub SUSPICIOUS_OP_ASSIGN_IMPL,
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correctness,
"suspicious use of operators in impl of OpAssign trait"
}
#[derive(Copy, Clone)]
pub struct SuspiciousImpl;
impl LintPass for SuspiciousImpl {
fn get_lints(&self) -> LintArray {
lint_array![SUSPICIOUS_ARITHMETIC_IMPL, SUSPICIOUS_OP_ASSIGN_IMPL]
}
}
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for SuspiciousImpl {
fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
use rustc::hir::BinOp_::*;
if let hir::ExprBinary(binop, _, _) = expr.node {
match binop.node {
BiEq | BiLt | BiLe | BiNe | BiGe | BiGt => return,
_ => {},
}
// Check if the binary expression is part of another bi/unary expression
// as a child node
let mut parent_expr = cx.tcx.hir.get_parent_node(expr.id);
while parent_expr != ast::CRATE_NODE_ID {
if let hir::map::Node::NodeExpr(e) = cx.tcx.hir.get(parent_expr) {
match e.node {
hir::ExprBinary(..)
| hir::ExprUnary(hir::UnOp::UnNot, _)
| hir::ExprUnary(hir::UnOp::UnNeg, _) => return,
_ => {},
}
}
parent_expr = cx.tcx.hir.get_parent_node(parent_expr);
}
// as a parent node
let mut visitor = BinaryExprVisitor {
in_binary_expr: false,
};
walk_expr(&mut visitor, expr);
if visitor.in_binary_expr {
return;
}
if let Some(impl_trait) = check_binop(
cx,
expr,
&binop.node,
&["Add", "Sub", "Mul", "Div"],
&[BiAdd, BiSub, BiMul, BiDiv],
) {
span_lint(
cx,
SUSPICIOUS_ARITHMETIC_IMPL,
binop.span,
&format!(
r#"Suspicious use of binary operator in `{}` impl"#,
impl_trait
),
);
}
if let Some(impl_trait) = check_binop(
cx,
expr,
&binop.node,
&[
"AddAssign",
"SubAssign",
"MulAssign",
"DivAssign",
"BitAndAssign",
"BitOrAssign",
"BitXorAssign",
"RemAssign",
"ShlAssign",
"ShrAssign",
],
&[
BiAdd, BiSub, BiMul, BiDiv, BiBitAnd, BiBitOr, BiBitXor, BiRem, BiShl, BiShr
],
) {
span_lint(
cx,
SUSPICIOUS_OP_ASSIGN_IMPL,
binop.span,
&format!(
r#"Suspicious use of binary operator in `{}` impl"#,
impl_trait
),
);
}
}
}
}
fn check_binop<'a>(
cx: &LateContext,
expr: &hir::Expr,
binop: &hir::BinOp_,
traits: &[&'a str],
expected_ops: &[hir::BinOp_],
) -> Option<&'a str> {
let mut trait_ids = vec![];
let [krate, module] = ::utils::paths::OPS_MODULE;
for t in traits {
let path = [krate, module, t];
if let Some(trait_id) = get_trait_def_id(cx, &path) {
trait_ids.push(trait_id);
} else {
return None;
}
}
// Get the actually implemented trait
let parent_fn = cx.tcx.hir.get_parent(expr.id);
let parent_impl = cx.tcx.hir.get_parent(parent_fn);
if_chain! {
if parent_impl != ast::CRATE_NODE_ID;
if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
if let hir::Item_::ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) = item.node;
if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
if *binop != expected_ops[idx];
then{
return Some(traits[idx])
}
}
None
}
struct BinaryExprVisitor {
in_binary_expr: bool,
}
impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
match expr.node {
hir::ExprBinary(..)
| hir::ExprUnary(hir::UnOp::UnNot, _)
| hir::ExprUnary(hir::UnOp::UnNeg, _) => {
self.in_binary_expr = true
},
_ => {},
}
walk_expr(self, expr);
}
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::None
}
}