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 pub ASSIGN_OP_PATTERN,
39 "assigning the result of an operation on a variable to that same variable"
42 declare_clippy_lint! {
44 /// Checks for `a op= a op b` or `a op= b op a` patterns.
46 /// ### Why is this bad?
47 /// Most likely these are bugs where one meant to write `a
50 /// ### Known problems
51 /// Clippy cannot know for sure if `a op= a op b` should have
52 /// been `a = a op a op b` or `a = a op b`/`a op= b`. Therefore, it suggests both.
53 /// If `a op= a op b` is really the correct behaviour it should be
54 /// written as `a = a op a op b` as it's less confusing.
63 pub MISREFACTORED_ASSIGN_OP,
65 "having a variable on both sides of an assign op"
68 declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
70 impl<'tcx> LateLintPass<'tcx> for AssignOps {
71 #[allow(clippy::too_many_lines)]
72 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
74 hir::ExprKind::AssignOp(op, lhs, rhs) => {
75 if let hir::ExprKind::Binary(binop, l, r) = &rhs.kind {
76 if op.node != binop.node {
80 if eq_expr_value(cx, lhs, l) {
81 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, r);
83 // lhs op= l commutative_op r
84 if is_commutative(op.node) && eq_expr_value(cx, lhs, r) {
85 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, l);
89 hir::ExprKind::Assign(assignee, e, _) => {
90 if let hir::ExprKind::Binary(op, l, r) = &e.kind {
91 let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
92 let ty = cx.typeck_results().expr_ty(assignee);
93 let rty = cx.typeck_results().expr_ty(rhs);
95 if let Some((_, lang_item)) = binop_traits(op.node);
96 if let Ok(trait_id) = cx.tcx.lang_items().require(lang_item);
97 let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
98 if trait_ref_of_method(cx, parent_fn)
99 .map_or(true, |t| t.path.res.def_id() != trait_id);
100 if implements_trait(cx, ty, trait_id, &[rty.into()]);
106 "manual implementation of an assign operation",
108 if let (Some(snip_a), Some(snip_r)) =
109 (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
111 diag.span_suggestion(
114 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
115 Applicability::MachineApplicable,
124 let mut visitor = ExprVisitor {
130 walk_expr(&mut visitor, e);
132 if visitor.counter == 1 {
134 if eq_expr_value(cx, assignee, l) {
137 // a = b commutative_op a
138 // Limited to primitive type as these ops are know to be commutative
139 if eq_expr_value(cx, assignee, r) && cx.typeck_results().expr_ty(assignee).is_primitive_ty() {
142 | hir::BinOpKind::Mul
143 | hir::BinOpKind::And
145 | hir::BinOpKind::BitXor
146 | hir::BinOpKind::BitAnd
147 | hir::BinOpKind::BitOr => {
161 fn lint_misrefactored_assign_op(
162 cx: &LateContext<'_>,
163 expr: &hir::Expr<'_>,
166 assignee: &hir::Expr<'_>,
167 rhs_other: &hir::Expr<'_>,
171 MISREFACTORED_ASSIGN_OP,
173 "variable appears on both sides of an assignment operation",
175 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span)) {
176 let a = &sugg::Sugg::hir(cx, assignee, "..");
177 let r = &sugg::Sugg::hir(cx, rhs, "..");
178 let long = format!("{} = {}", snip_a, sugg::make_binop(op.node.into(), a, r));
179 diag.span_suggestion(
182 "did you mean `{} = {} {} {}` or `{}`? Consider replacing it with",
189 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
190 Applicability::MaybeIncorrect,
192 diag.span_suggestion(
196 Applicability::MaybeIncorrect, // snippet
204 fn is_commutative(op: hir::BinOpKind) -> bool {
205 use rustc_hir::BinOpKind::{
206 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
209 Add | Mul | And | Or | BitXor | BitAnd | BitOr | Eq | Ne => true,
210 Sub | Div | Rem | Shl | Shr | Lt | Le | Ge | Gt => false,
214 struct ExprVisitor<'a, 'tcx> {
215 assignee: &'a hir::Expr<'a>,
217 cx: &'a LateContext<'tcx>,
220 impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
221 type Map = Map<'tcx>;
223 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
224 if eq_expr_value(self.cx, self.assignee, expr) {
228 walk_expr(self, expr);
230 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
231 NestedVisitorMap::None