mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
0480ff861a
In particular for: * `VecDeque` * `String` * `Mutex` * `HashMap` * `HashSet` cc https://github.com/rust-lang/rust/pull/71414 https://github.com/rust-lang/rust-clippy/issues/5393
187 lines
6.7 KiB
Rust
187 lines
6.7 KiB
Rust
use crate::utils::SpanlessEq;
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use crate::utils::{get_item_name, higher, is_type_diagnostic_item, match_type, paths, snippet, snippet_opt};
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use crate::utils::{snippet_with_applicability, span_lint_and_then, walk_ptrs_ty};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
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use rustc_hir::{BorrowKind, Expr, ExprKind, UnOp};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::hir::map::Map;
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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declare_clippy_lint! {
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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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///
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/// **Why is this bad?** Using `entry` is more efficient.
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///
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/// **Known problems:** Some false negatives, eg.:
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/// ```rust
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/// # use std::collections::HashMap;
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/// # let mut map = HashMap::new();
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/// # let v = 1;
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/// # let k = 1;
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/// if !map.contains_key(&k) {
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/// map.insert(k.clone(), v);
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/// }
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/// ```
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///
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/// **Example:**
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/// ```rust
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/// # use std::collections::HashMap;
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/// # let mut map = HashMap::new();
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/// # let k = 1;
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/// # let v = 1;
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/// if !map.contains_key(&k) {
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/// map.insert(k, v);
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/// }
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/// ```
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/// can both be rewritten as:
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/// ```rust
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/// # use std::collections::HashMap;
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/// # let mut map = HashMap::new();
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/// # let k = 1;
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/// # let v = 1;
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/// map.entry(k).or_insert(v);
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/// ```
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pub MAP_ENTRY,
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perf,
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"use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
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}
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declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for HashMapPass {
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fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
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if let Some((ref check, ref then_block, ref else_block)) = higher::if_block(&expr) {
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if let ExprKind::Unary(UnOp::UnNot, ref check) = check.kind {
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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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let sole_expr = {
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else_block.is_none()
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&& if let ExprKind::Block(ref then_block, _) = then_block.kind {
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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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// XXXManishearth we can also check for if/else blocks containing `None`.
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};
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let mut visitor = InsertVisitor {
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cx,
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span: expr.span,
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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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};
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walk_expr(&mut visitor, &**then_block);
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}
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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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cx,
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span: expr.span,
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ty,
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map,
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key,
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sole_expr: false,
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};
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walk_expr(&mut visitor, else_block);
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}
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}
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}
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}
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}
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fn check_cond<'a, 'tcx, 'b>(
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cx: &'a LateContext<'a, 'tcx>,
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check: &'b Expr<'b>,
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) -> Option<(&'static str, &'b Expr<'b>, &'b Expr<'b>)> {
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if_chain! {
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if let ExprKind::MethodCall(ref path, _, ref params) = check.kind;
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if params.len() >= 2;
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if path.ident.name == sym!(contains_key);
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if let ExprKind::AddrOf(BorrowKind::Ref, _, ref key) = params[1].kind;
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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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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 is_type_diagnostic_item(cx, obj_ty, sym!(hashmap_type)) {
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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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}
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}
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None
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}
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struct InsertVisitor<'a, 'tcx, '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<'b>,
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key: &'b Expr<'b>,
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sole_expr: bool,
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}
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impl<'a, 'tcx, 'b> Visitor<'tcx> for InsertVisitor<'a, 'tcx, 'b> {
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type Map = Map<'tcx>;
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fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
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if_chain! {
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if let ExprKind::MethodCall(ref path, _, ref params) = expr.kind;
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if params.len() == 3;
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if path.ident.name == sym!(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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if snippet_opt(self.cx, self.map.span) == snippet_opt(self.cx, params[0].span);
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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), |diag| {
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if self.sole_expr {
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let mut app = Applicability::MachineApplicable;
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let help = format!("{}.entry({}).or_insert({});",
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snippet_with_applicability(self.cx, self.map.span, "map", &mut app),
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snippet_with_applicability(self.cx, params[1].span, "..", &mut app),
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snippet_with_applicability(self.cx, params[2].span, "..", &mut app));
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diag.span_suggestion(
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self.span,
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"consider using",
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help,
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Applicability::MachineApplicable, // snippet
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);
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}
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else {
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let help = format!("consider using `{}.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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diag.span_label(
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self.span,
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&help,
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);
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}
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});
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}
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}
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if !self.sole_expr {
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walk_expr(self, expr);
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}
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}
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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}
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