1 use if_chain::if_chain;
3 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_lint_pass, declare_tool_lint};
6 use rustc_errors::Applicability;
9 get_trait_def_id, implements_trait, snippet_opt, span_lint_and_then, trait_ref_of_method, SpanlessEq,
11 use crate::utils::{higher, sugg};
13 declare_clippy_lint! {
14 /// **What it does:** Checks for `a = a op b` or `a = b commutative_op a`
17 /// **Why is this bad?** These can be written as the shorter `a op= b`.
19 /// **Known problems:** While forbidden by the spec, `OpAssign` traits may have
20 /// implementations that differ from the regular `Op` impl.
29 pub ASSIGN_OP_PATTERN,
31 "assigning the result of an operation on a variable to that same variable"
34 declare_clippy_lint! {
35 /// **What it does:** Checks for `a op= a op b` or `a op= b op a` patterns.
37 /// **Why is this bad?** Most likely these are bugs where one meant to write `a
40 /// **Known problems:** Clippy cannot know for sure if `a op= a op b` should have
41 /// been `a = a op a op b` or `a = a op b`/`a op= b`. Therefore, it suggests both.
42 /// If `a op= a op b` is really the correct behaviour it should be
43 /// written as `a = a op a op b` as it's less confusing.
51 pub MISREFACTORED_ASSIGN_OP,
53 "having a variable on both sides of an assign op"
56 declare_lint_pass!(AssignOps => [ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP]);
58 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
59 #[allow(clippy::too_many_lines)]
60 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
62 hir::ExprKind::AssignOp(op, lhs, rhs) => {
63 if let hir::ExprKind::Binary(binop, l, r) = &rhs.node {
64 if op.node != binop.node {
68 if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
69 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, r);
71 // lhs op= l commutative_op r
72 if is_commutative(op.node) && SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, r) {
73 lint_misrefactored_assign_op(cx, expr, *op, rhs, lhs, l);
77 hir::ExprKind::Assign(assignee, e) => {
78 if let hir::ExprKind::Binary(op, l, r) = &e.node {
79 #[allow(clippy::cognitive_complexity)]
80 let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
81 let ty = cx.tables.expr_ty(assignee);
82 let rty = cx.tables.expr_ty(rhs);
88 $($trait_name:ident),+) => {
90 $(hir::BinOpKind::$trait_name => {
91 let [krate, module] = crate::utils::paths::OPS_MODULE;
92 let path: [&str; 3] = [krate, module, concat!(stringify!($trait_name), "Assign")];
93 let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
96 return; // useless if the trait doesn't exist
98 // check that we are not inside an `impl AssignOp` of this exact operation
99 let parent_fn = cx.tcx.hir().get_parent_item(e.hir_id);
101 if let Some(trait_ref) = trait_ref_of_method(cx, parent_fn);
102 if trait_ref.path.res.def_id() == trait_id;
105 implements_trait($cx, $ty, trait_id, &[$rty])
133 "manual implementation of an assign operation",
135 if let (Some(snip_a), Some(snip_r)) =
136 (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs.span))
141 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
142 Applicability::MachineApplicable,
150 let mut visitor = ExprVisitor {
156 walk_expr(&mut visitor, e);
158 if visitor.counter == 1 {
160 if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
163 // a = b commutative_op a
164 // Limited to primitive type as these ops are know to be commutative
165 if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r)
166 && cx.tables.expr_ty(assignee).is_primitive_ty()
170 | hir::BinOpKind::Mul
171 | hir::BinOpKind::And
173 | hir::BinOpKind::BitXor
174 | hir::BinOpKind::BitAnd
175 | hir::BinOpKind::BitOr => {
189 fn lint_misrefactored_assign_op(
190 cx: &LateContext<'_, '_>,
194 assignee: &hir::Expr,
195 rhs_other: &hir::Expr,
199 MISREFACTORED_ASSIGN_OP,
201 "variable appears on both sides of an assignment operation",
203 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span), snippet_opt(cx, rhs_other.span)) {
204 let a = &sugg::Sugg::hir(cx, assignee, "..");
205 let r = &sugg::Sugg::hir(cx, rhs, "..");
206 let long = format!("{} = {}", snip_a, sugg::make_binop(higher::binop(op.node), a, r));
210 "Did you mean {} = {} {} {} or {}? Consider replacing it with",
217 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r),
218 Applicability::MachineApplicable,
224 Applicability::MachineApplicable, // snippet
231 fn is_commutative(op: hir::BinOpKind) -> bool {
232 use rustc::hir::BinOpKind::*;
234 Add | Mul | And | Or | BitXor | BitAnd | BitOr | Eq | Ne => true,
235 Sub | Div | Rem | Shl | Shr | Lt | Le | Ge | Gt => false,
239 struct ExprVisitor<'a, 'tcx> {
240 assignee: &'a hir::Expr,
242 cx: &'a LateContext<'a, 'tcx>,
245 impl<'a, 'tcx> Visitor<'tcx> for ExprVisitor<'a, 'tcx> {
246 fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
247 if SpanlessEq::new(self.cx).ignore_fn().eq_expr(self.assignee, expr) {
251 walk_expr(self, expr);
253 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
254 NestedVisitorMap::None