| use crate::utils::SpanlessEq; |
| use crate::utils::{get_item_name, higher, match_type, paths, snippet, snippet_opt}; |
| use crate::utils::{snippet_with_applicability, span_lint_and_then, walk_ptrs_ty}; |
| use if_chain::if_chain; |
| use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor}; |
| use rustc::hir::*; |
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; |
| use rustc::{declare_lint_pass, declare_tool_lint}; |
| use rustc_errors::Applicability; |
| use syntax::source_map::Span; |
| |
| declare_clippy_lint! { |
| /// **What it does:** Checks for uses of `contains_key` + `insert` on `HashMap` |
| /// or `BTreeMap`. |
| /// |
| /// **Why is this bad?** Using `entry` is more efficient. |
| /// |
| /// **Known problems:** Some false negatives, eg.: |
| /// ```rust |
| /// # use std::collections::HashMap; |
| /// # let mut map = HashMap::new(); |
| /// # let v = 1; |
| /// # let k = 1; |
| /// if !map.contains_key(&k) { |
| /// map.insert(k.clone(), v); |
| /// } |
| /// ``` |
| /// |
| /// **Example:** |
| /// ```rust |
| /// # use std::collections::HashMap; |
| /// # let mut map = HashMap::new(); |
| /// # let k = 1; |
| /// # let v = 1; |
| /// if !map.contains_key(&k) { |
| /// map.insert(k, v); |
| /// } |
| /// ``` |
| /// can both be rewritten as: |
| /// ```rust |
| /// # use std::collections::HashMap; |
| /// # let mut map = HashMap::new(); |
| /// # let k = 1; |
| /// # let v = 1; |
| /// map.entry(k).or_insert(v); |
| /// ``` |
| pub MAP_ENTRY, |
| perf, |
| "use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`" |
| } |
| |
| declare_lint_pass!(HashMapPass => [MAP_ENTRY]); |
| |
| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HashMapPass { |
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { |
| if let Some((ref check, ref then_block, ref else_block)) = higher::if_block(&expr) { |
| if let ExprKind::Unary(UnOp::UnNot, ref check) = check.kind { |
| if let Some((ty, map, key)) = check_cond(cx, check) { |
| // in case of `if !m.contains_key(&k) { m.insert(k, v); }` |
| // we can give a better error message |
| let sole_expr = { |
| else_block.is_none() |
| && if let ExprKind::Block(ref then_block, _) = then_block.kind { |
| (then_block.expr.is_some() as usize) + then_block.stmts.len() == 1 |
| } else { |
| true |
| } |
| // XXXManishearth we can also check for if/else blocks containing `None`. |
| }; |
| |
| let mut visitor = InsertVisitor { |
| cx, |
| span: expr.span, |
| ty, |
| map, |
| key, |
| sole_expr, |
| }; |
| |
| walk_expr(&mut visitor, &**then_block); |
| } |
| } else if let Some(ref else_block) = *else_block { |
| if let Some((ty, map, key)) = check_cond(cx, check) { |
| let mut visitor = InsertVisitor { |
| cx, |
| span: expr.span, |
| ty, |
| map, |
| key, |
| sole_expr: false, |
| }; |
| |
| walk_expr(&mut visitor, else_block); |
| } |
| } |
| } |
| } |
| } |
| |
| fn check_cond<'a, 'tcx, 'b>( |
| cx: &'a LateContext<'a, 'tcx>, |
| check: &'b Expr, |
| ) -> Option<(&'static str, &'b Expr, &'b Expr)> { |
| if_chain! { |
| if let ExprKind::MethodCall(ref path, _, ref params) = check.kind; |
| if params.len() >= 2; |
| if path.ident.name == sym!(contains_key); |
| if let ExprKind::AddrOf(_, ref key) = params[1].kind; |
| then { |
| let map = ¶ms[0]; |
| let obj_ty = walk_ptrs_ty(cx.tables.expr_ty(map)); |
| |
| return if match_type(cx, obj_ty, &paths::BTREEMAP) { |
| Some(("BTreeMap", map, key)) |
| } |
| else if match_type(cx, obj_ty, &paths::HASHMAP) { |
| Some(("HashMap", map, key)) |
| } |
| else { |
| None |
| }; |
| } |
| } |
| |
| None |
| } |
| |
| struct InsertVisitor<'a, 'tcx, 'b> { |
| cx: &'a LateContext<'a, 'tcx>, |
| span: Span, |
| ty: &'static str, |
| map: &'b Expr, |
| key: &'b Expr, |
| sole_expr: bool, |
| } |
| |
| impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> { |
| fn visit_expr(&mut self, expr: &'tcx Expr) { |
| if_chain! { |
| if let ExprKind::MethodCall(ref path, _, ref params) = expr.kind; |
| if params.len() == 3; |
| if path.ident.name == sym!(insert); |
| if get_item_name(self.cx, self.map) == get_item_name(self.cx, ¶ms[0]); |
| if SpanlessEq::new(self.cx).eq_expr(self.key, ¶ms[1]); |
| if snippet_opt(self.cx, self.map.span) == snippet_opt(self.cx, params[0].span); |
| then { |
| span_lint_and_then(self.cx, MAP_ENTRY, self.span, |
| &format!("usage of `contains_key` followed by `insert` on a `{}`", self.ty), |db| { |
| if self.sole_expr { |
| let mut app = Applicability::MachineApplicable; |
| let help = format!("{}.entry({}).or_insert({});", |
| snippet_with_applicability(self.cx, self.map.span, "map", &mut app), |
| snippet_with_applicability(self.cx, params[1].span, "..", &mut app), |
| snippet_with_applicability(self.cx, params[2].span, "..", &mut app)); |
| |
| db.span_suggestion( |
| self.span, |
| "consider using", |
| help, |
| Applicability::MachineApplicable, // snippet |
| ); |
| } |
| else { |
| let help = format!("consider using `{}.entry({})`", |
| snippet(self.cx, self.map.span, "map"), |
| snippet(self.cx, params[1].span, "..")); |
| |
| db.span_label( |
| self.span, |
| &help, |
| ); |
| } |
| }); |
| } |
| } |
| |
| if !self.sole_expr { |
| walk_expr(self, expr); |
| } |
| } |
| fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { |
| NestedVisitorMap::None |
| } |
| } |