1 use crate::utils::SpanlessEq;
2 use crate::utils::{get_item_name, higher, match_type, paths, snippet, span_lint_and_then, walk_ptrs_ty};
3 use if_chain::if_chain;
4 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
6 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
7 use rustc::{declare_lint_pass, declare_tool_lint};
8 use rustc_errors::Applicability;
9 use syntax::source_map::Span;
11 declare_clippy_lint! {
12 /// **What it does:** Checks for uses of `contains_key` + `insert` on `HashMap`
15 /// **Why is this bad?** Using `entry` is more efficient.
17 /// **Known problems:** Some false negatives, eg.:
20 /// if !m.contains_key(k) {
21 /// m.insert(k.clone(), v);
27 /// if !m.contains_key(&k) {
31 /// can be rewritten as:
33 /// m.entry(k).or_insert(v);
37 "use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
40 declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
42 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HashMapPass {
43 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
44 if let Some((ref check, ref then_block, ref else_block)) = higher::if_block(&expr) {
45 if let ExprKind::Unary(UnOp::UnNot, ref check) = check.node {
46 if let Some((ty, map, key)) = check_cond(cx, check) {
47 // in case of `if !m.contains_key(&k) { m.insert(k, v); }`
48 // we can give a better error message
51 && if let ExprKind::Block(ref then_block, _) = then_block.node {
52 (then_block.expr.is_some() as usize) + then_block.stmts.len() == 1
58 let mut visitor = InsertVisitor {
67 walk_expr(&mut visitor, &**then_block);
69 } else if let Some(ref else_block) = *else_block {
70 if let Some((ty, map, key)) = check_cond(cx, check) {
71 let mut visitor = InsertVisitor {
80 walk_expr(&mut visitor, else_block);
87 fn check_cond<'a, 'tcx, 'b>(
88 cx: &'a LateContext<'a, 'tcx>,
90 ) -> Option<(&'static str, &'b Expr, &'b Expr)> {
92 if let ExprKind::MethodCall(ref path, _, ref params) = check.node;
94 if path.ident.name == sym!(contains_key);
95 if let ExprKind::AddrOf(_, ref key) = params[1].node;
98 let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(map));
100 return if match_type(cx, obj_ty, &paths::BTREEMAP) {
101 Some(("BTreeMap", map, key))
103 else if match_type(cx, obj_ty, &paths::HASHMAP) {
104 Some(("HashMap", map, key))
115 struct InsertVisitor<'a, 'tcx: 'a, 'b> {
116 cx: &'a LateContext<'a, 'tcx>,
124 impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> {
125 fn visit_expr(&mut self, expr: &'tcx Expr) {
127 if let ExprKind::MethodCall(ref path, _, ref params) = expr.node;
128 if params.len() == 3;
129 if path.ident.name == sym!(insert);
130 if get_item_name(self.cx, self.map) == get_item_name(self.cx, ¶ms[0]);
131 if SpanlessEq::new(self.cx).eq_expr(self.key, ¶ms[1]);
133 span_lint_and_then(self.cx, MAP_ENTRY, self.span,
134 &format!("usage of `contains_key` followed by `insert` on a `{}`", self.ty), |db| {
136 let help = format!("{}.entry({}).or_insert({})",
137 snippet(self.cx, self.map.span, "map"),
138 snippet(self.cx, params[1].span, ".."),
139 snippet(self.cx, params[2].span, ".."));
145 Applicability::MachineApplicable, // snippet
149 let help = format!("{}.entry({})",
150 snippet(self.cx, self.map.span, "map"),
151 snippet(self.cx, params[1].span, ".."));
157 Applicability::MachineApplicable, // snippet
165 walk_expr(self, expr);
168 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
169 NestedVisitorMap::None