1 use clippy_utils::diagnostics::span_lint_and_then;
2 use clippy_utils::source::snippet_opt;
3 use clippy_utils::ty::implements_trait;
4 use clippy_utils::{binop_traits, sugg};
5 use clippy_utils::{eq_expr_value, trait_ref_of_method};
6 use if_chain::if_chain;
7 use rustc_errors::Applicability;
9 use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_middle::hir::map::Map;
12 use rustc_session::{declare_lint_pass, declare_tool_lint};
14 declare_clippy_lint! {
16 /// Checks for `a = a op b` or `a = b commutative_op a`
19 /// ### Why is this bad?
20 /// These can be written as the shorter `a op= b`.
22 /// ### Known problems
23 /// While forbidden by the spec, `OpAssign` traits may have
24 /// implementations that differ from the regular `Op` impl.
37 #[clippy::version = "pre 1.29.0"]
38 pub ASSIGN_OP_PATTERN,
40 "assigning the result of an operation on a variable to that same variable"
43 declare_clippy_lint! {
45 /// Checks for `a op= a op b` or `a op= b op a` patterns.
47 /// ### Why is this bad?
48 /// Most likely these are bugs where one meant to write `a
51 /// ### Known problems
52 /// Clippy cannot know for sure if `a op= a op b` should have
53 /// been `a = a op a op b` or `a = a op b`/`a op= b`. Therefore, it suggests both.
54 /// If `a op= a op b` is really the correct behaviour it should be
55 /// written as `a = a op a op b` as it's less confusing.
64 #[clippy::version = "pre 1.29.0"]
65 pub MISREFACTORED_ASSIGN_OP,
67 "having a variable on both sides of an assign op"
70 declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
72 impl<'tcx> LateLintPass<'tcx> for AssignOps {
73 #[allow(clippy::too_many_lines)]
74 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
76 hir::ExprKind::AssignOp(op, lhs, rhs) => {
77 if let hir::ExprKind::Binary(binop, l, r) = &rhs.kind {
78 if op.node != binop.node {
82 if eq_expr_value(cx, lhs, l) {
83 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, r);
85 // lhs op= l commutative_op r
86 if is_commutative(op.node) && eq_expr_value(cx, lhs, r) {
87 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, l);
91 hir::ExprKind::Assign(assignee, e, _) => {
92 if let hir::ExprKind::Binary(op, l, r) = &e.kind {
93 let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
94 let ty = cx.typeck_results().expr_ty(assignee);
95 let rty = cx.typeck_results().expr_ty(rhs);
97 if let Some((_, lang_item)) = binop_traits(op.node);
98 if let Ok(trait_id) = cx.tcx.lang_items().require(lang_item);
99 let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
100 if trait_ref_of_method(cx, parent_fn)
101 .map_or(true, |t| t.path.res.def_id() != trait_id);
102 if implements_trait(cx, ty, trait_id, &[rty.into()]);
108 "manual implementation of an assign operation",
110 if let (Some(snip_a), Some(snip_r)) =
111 (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
113 diag.span_suggestion(
116 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
117 Applicability::MachineApplicable,
126 let mut visitor = ExprVisitor {
132 walk_expr(&mut visitor, e);
134 if visitor.counter == 1 {
136 if eq_expr_value(cx, assignee, l) {
139 // a = b commutative_op a
140 // Limited to primitive type as these ops are know to be commutative
141 if eq_expr_value(cx, assignee, r) && cx.typeck_results().expr_ty(assignee).is_primitive_ty() {
144 | hir::BinOpKind::Mul
145 | hir::BinOpKind::And
147 | hir::BinOpKind::BitXor
148 | hir::BinOpKind::BitAnd
149 | hir::BinOpKind::BitOr => {
163 fn lint_misrefactored_assign_op(
164 cx: &LateContext<'_>,
165 expr: &hir::Expr<'_>,
168 assignee: &hir::Expr<'_>,
169 rhs_other: &hir::Expr<'_>,
173 MISREFACTORED_ASSIGN_OP,
175 "variable appears on both sides of an assignment operation",
177 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span)) {
178 let a = &sugg::Sugg::hir(cx, assignee, "..");
179 let r = &sugg::Sugg::hir(cx, rhs, "..");
180 let long = format!("{} = {}", snip_a, sugg::make_binop(op.node.into(), a, r));
181 diag.span_suggestion(
184 "did you mean `{} = {} {} {}` or `{}`? Consider replacing it with",
191 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
192 Applicability::MaybeIncorrect,
194 diag.span_suggestion(
198 Applicability::MaybeIncorrect, // snippet
206 fn is_commutative(op: hir::BinOpKind) -> bool {
207 use rustc_hir::BinOpKind::{
208 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
211 Add | Mul | And | Or | BitXor | BitAnd | BitOr | Eq | Ne => true,
212 Sub | Div | Rem | Shl | Shr | Lt | Le | Ge | Gt => false,
216 struct ExprVisitor<'a, 'tcx> {
217 assignee: &'a hir::Expr<'a>,
219 cx: &'a LateContext<'tcx>,
222 impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
223 type Map = Map<'tcx>;
225 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
226 if eq_expr_value(self.cx, self.assignee, expr) {
230 walk_expr(self, expr);
232 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
233 NestedVisitorMap::None