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, Visitor};
10 use rustc_lint::{LateContext, LateLintPass};
11 use rustc_session::{declare_lint_pass, declare_tool_lint};
13 declare_clippy_lint! {
15 /// Checks for `a = a op b` or `a = b commutative_op a`
18 /// ### Why is this bad?
19 /// These can be written as the shorter `a op= b`.
21 /// ### Known problems
22 /// While forbidden by the spec, `OpAssign` traits may have
23 /// implementations that differ from the regular `Op` impl.
42 #[clippy::version = "pre 1.29.0"]
43 pub ASSIGN_OP_PATTERN,
45 "assigning the result of an operation on a variable to that same variable"
48 declare_clippy_lint! {
50 /// Checks for `a op= a op b` or `a op= b op a` patterns.
52 /// ### Why is this bad?
53 /// Most likely these are bugs where one meant to write `a
56 /// ### Known problems
57 /// Clippy cannot know for sure if `a op= a op b` should have
58 /// been `a = a op a op b` or `a = a op b`/`a op= b`. Therefore, it suggests both.
59 /// If `a op= a op b` is really the correct behavior it should be
60 /// written as `a = a op a op b` as it's less confusing.
69 #[clippy::version = "pre 1.29.0"]
70 pub MISREFACTORED_ASSIGN_OP,
72 "having a variable on both sides of an assign op"
75 declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
77 impl<'tcx> LateLintPass<'tcx> for AssignOps {
78 #[allow(clippy::too_many_lines)]
79 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
81 hir::ExprKind::AssignOp(op, lhs, rhs) => {
82 if let hir::ExprKind::Binary(binop, l, r) = &rhs.kind {
83 if op.node != binop.node {
87 if eq_expr_value(cx, lhs, l) {
88 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, r);
90 // lhs op= l commutative_op r
91 if is_commutative(op.node) && eq_expr_value(cx, lhs, r) {
92 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, l);
96 hir::ExprKind::Assign(assignee, e, _) => {
97 if let hir::ExprKind::Binary(op, l, r) = &e.kind {
98 let lint = |assignee: &hir::Expr<'_>, rhs: &hir::Expr<'_>| {
99 let ty = cx.typeck_results().expr_ty(assignee);
100 let rty = cx.typeck_results().expr_ty(rhs);
102 if let Some((_, lang_item)) = binop_traits(op.node);
103 if let Ok(trait_id) = cx.tcx.lang_items().require(lang_item);
104 let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
105 if trait_ref_of_method(cx, parent_fn)
106 .map_or(true, |t| t.path.res.def_id() != trait_id);
107 if implements_trait(cx, ty, trait_id, &[rty.into()]);
113 "manual implementation of an assign operation",
115 if let (Some(snip_a), Some(snip_r)) =
116 (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
118 diag.span_suggestion(
121 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
122 Applicability::MachineApplicable,
131 let mut visitor = ExprVisitor {
137 walk_expr(&mut visitor, e);
139 if visitor.counter == 1 {
141 if eq_expr_value(cx, assignee, l) {
144 // a = b commutative_op a
145 // Limited to primitive type as these ops are know to be commutative
146 if eq_expr_value(cx, assignee, r) && cx.typeck_results().expr_ty(assignee).is_primitive_ty() {
149 | hir::BinOpKind::Mul
150 | hir::BinOpKind::And
152 | hir::BinOpKind::BitXor
153 | hir::BinOpKind::BitAnd
154 | hir::BinOpKind::BitOr => {
168 fn lint_misrefactored_assign_op(
169 cx: &LateContext<'_>,
170 expr: &hir::Expr<'_>,
173 assignee: &hir::Expr<'_>,
174 rhs_other: &hir::Expr<'_>,
178 MISREFACTORED_ASSIGN_OP,
180 "variable appears on both sides of an assignment operation",
182 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span)) {
183 let a = &sugg::Sugg::hir(cx, assignee, "..");
184 let r = &sugg::Sugg::hir(cx, rhs, "..");
185 let long = format!("{} = {}", snip_a, sugg::make_binop(op.node.into(), a, r));
186 diag.span_suggestion(
189 "did you mean `{} = {} {} {}` or `{}`? Consider replacing it with",
196 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
197 Applicability::MaybeIncorrect,
199 diag.span_suggestion(
203 Applicability::MaybeIncorrect, // snippet
211 fn is_commutative(op: hir::BinOpKind) -> bool {
212 use rustc_hir::BinOpKind::{
213 Add, And, BitAnd, BitOr, BitXor, Div, Eq, Ge, Gt, Le, Lt, Mul, Ne, Or, Rem, Shl, Shr, Sub,
216 Add | Mul | And | Or | BitXor | BitAnd | BitOr | Eq | Ne => true,
217 Sub | Div | Rem | Shl | Shr | Lt | Le | Ge | Gt => false,
221 struct ExprVisitor<'a, 'tcx> {
222 assignee: &'a hir::Expr<'a>,
224 cx: &'a LateContext<'tcx>,
227 impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
228 fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
229 if eq_expr_value(self.cx, self.assignee, expr) {
233 walk_expr(self, expr);