3 use utils::{span_lint_and_then, snippet_opt, SpanlessEq, get_trait_def_id, implements_trait};
4 use utils::{higher, sugg};
6 /// **What it does:** Checks for compound assignment operations (`+=` and similar).
8 /// **Why is this bad?** Projects with many developers from languages without
9 /// those operations may find them unreadable and not worth their weight.
11 /// **Known problems:** Types implementing `OpAssign` don't necessarily implement `Op`.
17 declare_restriction_lint! {
19 "any compound assignment operation"
22 /// **What it does:** Checks for `a = a op b` or `a = b commutative_op a` patterns.
24 /// **Why is this bad?** These can be written as the shorter `a op= b`.
26 /// **Known problems:** While forbidden by the spec, `OpAssign` traits may have
27 /// implementations that differ from the regular `Op` impl.
36 pub ASSIGN_OP_PATTERN,
38 "assigning the result of an operation on a variable to that same variable"
41 /// **What it does:** Checks for `a op= a op b` or `a op= b op a` patterns.
43 /// **Why is this bad?** Most likely these are bugs where one meant to write `a op= b`.
45 /// **Known problems:** Someone might actually mean `a op= a op b`, but that
46 /// should rather be written as `a = (2 * a) op b` where applicable.
55 pub MISREFACTORED_ASSIGN_OP,
57 "having a variable on both sides of an assign op"
60 #[derive(Copy, Clone, Default)]
63 impl LintPass for AssignOps {
64 fn get_lints(&self) -> LintArray {
65 lint_array!(ASSIGN_OPS, ASSIGN_OP_PATTERN, MISREFACTORED_ASSIGN_OP)
69 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssignOps {
70 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
72 hir::ExprAssignOp(op, ref lhs, ref rhs) => {
73 span_lint_and_then(cx, ASSIGN_OPS, expr.span, "assign operation detected", |db| {
74 let lhs = &sugg::Sugg::hir(cx, lhs, "..");
75 let rhs = &sugg::Sugg::hir(cx, rhs, "..");
77 db.span_suggestion(expr.span,
79 format!("{} = {}", lhs, sugg::make_binop(higher::binop(op.node), lhs, rhs)));
81 if let hir::ExprBinary(binop, ref l, ref r) = rhs.node {
82 if op.node == binop.node {
83 let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
84 let ty = cx.tcx.tables().expr_ty(assignee);
85 if ty.walk_shallow().next().is_some() {
86 return; // implements_trait does not work with generics
88 let rty = cx.tcx.tables().expr_ty(rhs);
89 if rty.walk_shallow().next().is_some() {
90 return; // implements_trait does not work with generics
92 span_lint_and_then(cx,
93 MISREFACTORED_ASSIGN_OP,
95 "variable appears on both sides of an assignment operation",
97 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span),
98 snippet_opt(cx, rhs.span)) {
99 db.span_suggestion(expr.span,
101 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r));
106 if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, l) {
109 // lhs op= l commutative_op r
110 if is_commutative(op.node) && SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, r) {
116 hir::ExprAssign(ref assignee, ref e) => {
117 if let hir::ExprBinary(op, ref l, ref r) = e.node {
118 let lint = |assignee: &hir::Expr, rhs: &hir::Expr| {
119 let ty = cx.tcx.tables().expr_ty(assignee);
120 if ty.walk_shallow().next().is_some() {
121 return; // implements_trait does not work with generics
123 let rty = cx.tcx.tables().expr_ty(rhs);
124 if rty.walk_shallow().next().is_some() {
125 return; // implements_trait does not work with generics
128 ($op:expr, $cx:expr, $ty:expr, $rty:expr, $($trait_name:ident:$full_trait_name:ident),+) => {
130 $(hir::$full_trait_name => {
131 let [krate, module] = ::utils::paths::OPS_MODULE;
132 let path = [krate, module, concat!(stringify!($trait_name), "Assign")];
133 let trait_id = if let Some(trait_id) = get_trait_def_id($cx, &path) {
136 return; // useless if the trait doesn't exist
138 implements_trait($cx, $ty, trait_id, vec![$rty])
160 span_lint_and_then(cx,
163 "manual implementation of an assign operation",
165 if let (Some(snip_a), Some(snip_r)) = (snippet_opt(cx, assignee.span),
166 snippet_opt(cx, rhs.span)) {
167 db.span_suggestion(expr.span,
169 format!("{} {}= {}", snip_a, op.node.as_str(), snip_r));
175 if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, l) {
178 // a = b commutative_op a
179 if SpanlessEq::new(cx).ignore_fn().eq_expr(assignee, r) {
181 hir::BiAdd | hir::BiMul | hir::BiAnd | hir::BiOr | hir::BiBitXor | hir::BiBitAnd |
195 fn is_commutative(op: hir::BinOp_) -> bool {
196 use rustc::hir::BinOp_::*;