use clippy_utils::diagnostics::span_lint_and_then; use clippy_utils::source::{snippet, snippet_opt, snippet_with_applicability}; use clippy_utils::ty::{is_type_diagnostic_item, match_type}; use clippy_utils::SpanlessEq; use clippy_utils::{get_item_name, paths}; use if_chain::if_chain; use rustc_errors::Applicability; use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor}; use rustc_hir::{BorrowKind, Expr, ExprKind, UnOp}; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::hir::map::Map; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; use rustc_span::sym; 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<'tcx> LateLintPass<'tcx> for HashMapPass { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { if let ExprKind::If(check, then_block, ref else_block) = expr.kind { if let ExprKind::Unary(UnOp::Not, 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(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(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>(cx: &LateContext<'_>, check: &'a Expr<'a>) -> Option<(&'static str, &'a Expr<'a>, &'a Expr<'a>)> { if_chain! { if let ExprKind::MethodCall(path, _, params, _) = check.kind; if params.len() >= 2; if path.ident.name == sym!(contains_key); if let ExprKind::AddrOf(BorrowKind::Ref, _, key) = params[1].kind; then { let map = ¶ms[0]; let obj_ty = cx.typeck_results().expr_ty(map).peel_refs(); return if match_type(cx, obj_ty, &paths::BTREEMAP) { Some(("BTreeMap", map, key)) } else if is_type_diagnostic_item(cx, obj_ty, sym::hashmap_type) { Some(("HashMap", map, key)) } else { None }; } } None } struct InsertVisitor<'a, 'tcx, 'b> { cx: &'a LateContext<'tcx>, span: Span, ty: &'static str, map: &'b Expr<'b>, key: &'b Expr<'b>, sole_expr: bool, } impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> { type Map = Map<'tcx>; fn visit_expr(&mut self, expr: &'tcx Expr<'_>) { if_chain! { if let ExprKind::MethodCall(path, _, 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), |diag| { 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)); diag.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, "..")); diag.span_label( self.span, &help, ); } }); } } if !self.sole_expr { walk_expr(self, expr); } } fn nested_visit_map(&mut self) -> NestedVisitorMap { NestedVisitorMap::None } }