2016-04-07 10:46:48 -05:00
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use rustc::hir::*;
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2017-09-05 04:33:04 -05:00
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use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
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2016-04-14 11:13:15 -05:00
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use rustc::lint::*;
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2015-12-21 17:35:56 -06:00
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use syntax::codemap::Span;
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2016-02-06 13:13:25 -06:00
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use utils::SpanlessEq;
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2016-04-14 11:13:15 -05:00
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use utils::{get_item_name, match_type, paths, snippet, span_lint_and_then, walk_ptrs_ty};
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2015-12-21 17:35:56 -06:00
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2016-08-06 02:55:04 -05:00
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/// **What it does:** Checks for uses of `contains_key` + `insert` on `HashMap`
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/// or `BTreeMap`.
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2015-12-21 17:35:56 -06:00
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///
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2016-01-12 13:23:28 -06:00
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/// **Why is this bad?** Using `entry` is more efficient.
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2015-12-21 17:35:56 -06:00
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///
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2016-01-03 09:31:28 -06:00
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/// **Known problems:** Some false negatives, eg.:
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2016-07-29 13:36:33 -05:00
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/// ```rust
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2016-01-03 09:31:28 -06:00
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/// let k = &key;
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/// if !m.contains_key(k) { m.insert(k.clone(), v); }
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/// ```
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2015-12-21 17:35:56 -06:00
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///
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2016-01-03 10:19:49 -06:00
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/// **Example:**
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/// ```rust
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/// if !m.contains_key(&k) { m.insert(k, v) }
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/// ```
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/// can be rewritten as:
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/// ```rust
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/// m.entry(k).or_insert(v);
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/// ```
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2016-01-12 13:23:28 -06:00
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pub MAP_ENTRY,
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2018-03-28 08:24:26 -05:00
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perf,
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2016-01-12 13:23:28 -06:00
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"use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
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2015-12-21 17:35:56 -06:00
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}
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2017-08-09 02:30:56 -05:00
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#[derive(Copy, Clone)]
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2015-12-21 17:35:56 -06:00
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pub struct HashMapLint;
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impl LintPass for HashMapLint {
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fn get_lints(&self) -> LintArray {
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2016-01-12 13:23:28 -06:00
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lint_array!(MAP_ENTRY)
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2015-12-21 17:35:56 -06:00
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}
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}
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2016-12-07 06:13:40 -06:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HashMapLint {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
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2016-02-18 13:19:16 -06:00
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if let ExprIf(ref check, ref then_block, ref else_block) = expr.node {
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if let ExprUnary(UnOp::UnNot, ref check) = check.node {
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if let Some((ty, map, key)) = check_cond(cx, check) {
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// in case of `if !m.contains_key(&k) { m.insert(k, v); }`
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// we can give a better error message
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2017-04-12 04:06:32 -05:00
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let sole_expr = {
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2018-05-17 04:21:15 -05:00
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else_block.is_none() && if let ExprBlock(ref then_block, _) = then_block.node {
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2017-09-05 04:33:04 -05:00
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(then_block.expr.is_some() as usize) + then_block.stmts.len() == 1
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} else {
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true
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}
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2017-03-31 16:36:45 -05:00
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};
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2016-01-03 10:19:49 -06:00
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2016-02-18 13:19:16 -06:00
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let mut visitor = InsertVisitor {
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2018-03-15 10:07:15 -05:00
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cx,
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2016-02-18 13:19:16 -06:00
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span: expr.span,
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2018-03-15 10:07:15 -05:00
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ty,
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map,
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key,
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sole_expr,
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2016-02-18 13:19:16 -06:00
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};
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2016-01-03 09:31:28 -06:00
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2017-03-31 12:23:35 -05:00
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walk_expr(&mut visitor, &**then_block);
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2016-01-12 13:23:28 -06:00
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}
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2016-02-18 13:19:16 -06:00
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} else if let Some(ref else_block) = *else_block {
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if let Some((ty, map, key)) = check_cond(cx, check) {
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let mut visitor = InsertVisitor {
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2018-03-15 10:07:15 -05:00
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cx,
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2016-02-18 13:19:16 -06:00
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span: expr.span,
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2018-03-15 10:07:15 -05:00
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ty,
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map,
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key,
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2016-02-18 13:19:16 -06:00
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sole_expr: false,
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};
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2016-01-12 13:23:28 -06:00
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2016-02-18 13:19:16 -06:00
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walk_expr(&mut visitor, else_block);
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2015-12-21 17:35:56 -06:00
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}
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}
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}
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}
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}
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2016-12-21 05:14:54 -06:00
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fn check_cond<'a, 'tcx, 'b>(
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cx: &'a LateContext<'a, 'tcx>,
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2017-08-09 02:30:56 -05:00
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check: &'b Expr,
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2016-12-21 05:14:54 -06:00
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) -> Option<(&'static str, &'b Expr, &'b Expr)> {
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2017-10-23 14:18:02 -05:00
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if_chain! {
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if let ExprMethodCall(ref path, _, ref params) = check.node;
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if params.len() >= 2;
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if path.name == "contains_key";
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if let ExprAddrOf(_, ref key) = params[1].node;
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then {
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let map = ¶ms[0];
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let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(map));
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2017-11-04 14:55:56 -05:00
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2017-10-23 14:18:02 -05:00
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return if match_type(cx, obj_ty, &paths::BTREEMAP) {
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Some(("BTreeMap", map, key))
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}
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else if match_type(cx, obj_ty, &paths::HASHMAP) {
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Some(("HashMap", map, key))
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}
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else {
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None
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};
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2016-02-18 13:19:16 -06:00
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}
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2017-10-23 14:18:02 -05:00
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}
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2016-02-18 13:19:16 -06:00
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None
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}
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struct InsertVisitor<'a, 'tcx: 'a, 'b> {
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cx: &'a LateContext<'a, 'tcx>,
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span: Span,
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ty: &'static str,
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map: &'b Expr,
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key: &'b Expr,
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sole_expr: bool,
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}
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2016-12-06 04:32:21 -06:00
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impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> {
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fn visit_expr(&mut self, expr: &'tcx Expr) {
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2017-10-23 14:18:02 -05:00
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if_chain! {
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if let ExprMethodCall(ref path, _, ref params) = expr.node;
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if params.len() == 3;
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if path.name == "insert";
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if get_item_name(self.cx, self.map) == get_item_name(self.cx, ¶ms[0]);
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if SpanlessEq::new(self.cx).eq_expr(self.key, ¶ms[1]);
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then {
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span_lint_and_then(self.cx, MAP_ENTRY, self.span,
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&format!("usage of `contains_key` followed by `insert` on a `{}`", self.ty), |db| {
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if self.sole_expr {
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let help = format!("{}.entry({}).or_insert({})",
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snippet(self.cx, self.map.span, "map"),
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snippet(self.cx, params[1].span, ".."),
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snippet(self.cx, params[2].span, ".."));
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2017-11-04 14:55:56 -05:00
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2017-10-23 14:18:02 -05:00
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db.span_suggestion(self.span, "consider using", help);
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}
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else {
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let help = format!("{}.entry({})",
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snippet(self.cx, self.map.span, "map"),
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snippet(self.cx, params[1].span, ".."));
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2017-11-04 14:55:56 -05:00
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2017-10-23 14:18:02 -05:00
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db.span_suggestion(self.span, "consider using", help);
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}
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});
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}
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}
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2016-02-18 13:19:16 -06:00
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if !self.sole_expr {
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walk_expr(self, expr);
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2015-12-21 17:35:56 -06:00
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}
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}
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2016-12-06 04:32:21 -06:00
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fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
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2017-05-12 05:02:42 -05:00
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NestedVisitorMap::None
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2016-12-06 04:32:21 -06:00
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}
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2015-12-21 17:35:56 -06:00
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}
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