2 can_move_expr_to_closure_no_visit,
3 diagnostics::span_lint_and_sugg,
4 is_expr_final_block_expr, is_expr_used_or_unified, match_def_path, paths, peel_hir_expr_while,
5 source::{reindent_multiline, snippet_indent, snippet_with_applicability, snippet_with_context},
8 use rustc_errors::Applicability;
10 intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
11 Block, Expr, ExprKind, Guard, HirId, Local, Stmt, StmtKind, UnOp,
13 use rustc_lint::{LateContext, LateLintPass};
14 use rustc_session::{declare_lint_pass, declare_tool_lint};
15 use rustc_span::{Span, SyntaxContext, DUMMY_SP};
18 declare_clippy_lint! {
20 /// Checks for uses of `contains_key` + `insert` on `HashMap`
23 /// ### Why is this bad?
24 /// Using `entry` is more efficient.
26 /// ### Known problems
27 /// The suggestion may have type inference errors in some cases. e.g.
29 /// let mut map = std::collections::HashMap::new();
30 /// let _ = if !map.contains_key(&0) {
39 /// # use std::collections::HashMap;
40 /// # let mut map = HashMap::new();
43 /// if !map.contains_key(&k) {
47 /// can both be rewritten as:
49 /// # use std::collections::HashMap;
50 /// # let mut map = HashMap::new();
53 /// map.entry(k).or_insert(v);
57 "use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
60 declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
62 impl<'tcx> LateLintPass<'tcx> for HashMapPass {
63 #[allow(clippy::too_many_lines)]
64 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
65 let (cond_expr, then_expr, else_expr) = match expr.kind {
66 ExprKind::If(c, t, e) => (c, t, e),
69 let (map_ty, contains_expr) = match try_parse_contains(cx, cond_expr) {
74 let then_search = match find_insert_calls(cx, &contains_expr, then_expr) {
79 let mut app = Applicability::MachineApplicable;
80 let map_str = snippet_with_context(cx, contains_expr.map.span, contains_expr.call_ctxt, "..", &mut app).0;
81 let key_str = snippet_with_context(cx, contains_expr.key.span, contains_expr.call_ctxt, "..", &mut app).0;
82 let sugg = if let Some(else_expr) = else_expr {
83 let else_search = match find_insert_calls(cx, &contains_expr, else_expr) {
84 Some(search) => search,
88 if then_search.edits.is_empty() && else_search.edits.is_empty() {
91 } else if then_search.edits.is_empty() || else_search.edits.is_empty() {
92 // if .. { insert } else { .. } or if .. { .. } else { insert }
93 let ((then_str, entry_kind), else_str) = match (else_search.edits.is_empty(), contains_expr.negated) {
95 then_search.snippet_vacant(cx, then_expr.span, &mut app),
96 snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
99 then_search.snippet_occupied(cx, then_expr.span, &mut app),
100 snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
103 else_search.snippet_occupied(cx, else_expr.span, &mut app),
104 snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
107 else_search.snippet_vacant(cx, else_expr.span, &mut app),
108 snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
112 "if let {}::{} = {}.entry({}) {} else {}",
121 // if .. { insert } else { insert }
122 let ((then_str, then_entry), (else_str, else_entry)) = if contains_expr.negated {
124 then_search.snippet_vacant(cx, then_expr.span, &mut app),
125 else_search.snippet_occupied(cx, else_expr.span, &mut app),
129 then_search.snippet_occupied(cx, then_expr.span, &mut app),
130 else_search.snippet_vacant(cx, else_expr.span, &mut app),
133 let indent_str = snippet_indent(cx, expr.span);
134 let indent_str = indent_str.as_deref().unwrap_or("");
136 "match {}.entry({}) {{\n{indent} {entry}::{} => {}\n\
137 {indent} {entry}::{} => {}\n{indent}}}",
141 reindent_multiline(then_str.into(), true, Some(4 + indent_str.len())),
143 reindent_multiline(else_str.into(), true, Some(4 + indent_str.len())),
144 entry = map_ty.entry_path(),
149 if then_search.edits.is_empty() {
155 if !then_search.allow_insert_closure {
156 let (body_str, entry_kind) = if contains_expr.negated {
157 then_search.snippet_vacant(cx, then_expr.span, &mut app)
159 then_search.snippet_occupied(cx, then_expr.span, &mut app)
162 "if let {}::{} = {}.entry({}) {}",
169 } else if let Some(insertion) = then_search.as_single_insertion() {
170 let value_str = snippet_with_context(cx, insertion.value.span, then_expr.span.ctxt(), "..", &mut app).0;
171 if contains_expr.negated {
172 if insertion.value.can_have_side_effects() {
173 format!("{}.entry({}).or_insert_with(|| {});", map_str, key_str, value_str)
175 format!("{}.entry({}).or_insert({});", map_str, key_str, value_str)
178 // TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
179 // This would need to be a different lint.
183 let block_str = then_search.snippet_closure(cx, then_expr.span, &mut app);
184 if contains_expr.negated {
185 format!("{}.entry({}).or_insert_with(|| {});", map_str, key_str, block_str)
187 // TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
188 // This would need to be a different lint.
198 &format!("usage of `contains_key` followed by `insert` on a `{}`", map_ty.name()),
206 #[derive(Clone, Copy)]
212 fn name(self) -> &'static str {
214 Self::Hash => "HashMap",
215 Self::BTree => "BTreeMap",
218 fn entry_path(self) -> &'static str {
220 Self::Hash => "std::collections::hash_map::Entry",
221 Self::BTree => "std::collections::btree_map::Entry",
226 struct ContainsExpr<'tcx> {
228 map: &'tcx Expr<'tcx>,
229 key: &'tcx Expr<'tcx>,
230 call_ctxt: SyntaxContext,
232 fn try_parse_contains(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<(MapType, ContainsExpr<'tcx>)> {
233 let mut negated = false;
234 let expr = peel_hir_expr_while(expr, |e| match e.kind {
235 ExprKind::Unary(UnOp::Not, e) => {
242 ExprKind::MethodCall(
246 kind: ExprKind::AddrOf(_, _, key),
251 ) if key_span.ctxt() == expr.span.ctxt() => {
252 let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
253 let expr = ContainsExpr {
257 call_ctxt: expr.span.ctxt(),
259 if match_def_path(cx, id, &paths::BTREEMAP_CONTAINS_KEY) {
260 Some((MapType::BTree, expr))
261 } else if match_def_path(cx, id, &paths::HASHMAP_CONTAINS_KEY) {
262 Some((MapType::Hash, expr))
271 struct InsertExpr<'tcx> {
272 map: &'tcx Expr<'tcx>,
273 key: &'tcx Expr<'tcx>,
274 value: &'tcx Expr<'tcx>,
276 fn try_parse_insert(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> {
277 if let ExprKind::MethodCall(_, _, [map, key, value], _) = expr.kind {
278 let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
279 if match_def_path(cx, id, &paths::BTREEMAP_INSERT) || match_def_path(cx, id, &paths::HASHMAP_INSERT) {
280 Some(InsertExpr { map, key, value })
289 /// An edit that will need to be made to move the expression to use the entry api
290 #[derive(Clone, Copy)]
292 /// A semicolon that needs to be removed. Used to create a closure for `insert_with`.
294 /// An insertion into the map.
295 Insertion(Insertion<'tcx>),
298 fn as_insertion(self) -> Option<Insertion<'tcx>> {
299 if let Self::Insertion(i) = self { Some(i) } else { None }
302 #[derive(Clone, Copy)]
303 struct Insertion<'tcx> {
304 call: &'tcx Expr<'tcx>,
305 value: &'tcx Expr<'tcx>,
308 /// This visitor needs to do a multiple things:
309 /// * Find all usages of the map. An insertion can only be made before any other usages of the map.
310 /// * Determine if there's an insertion using the same key. There's no need for the entry api
312 /// * Determine if the final statement executed is an insertion. This is needed to use
313 /// `or_insert_with`.
314 /// * Determine if there's any sub-expression that can't be placed in a closure.
315 /// * Determine if there's only a single insert statement. `or_insert` can be used in this case.
316 #[allow(clippy::struct_excessive_bools)]
317 struct InsertSearcher<'cx, 'tcx> {
318 cx: &'cx LateContext<'tcx>,
319 /// The map expression used in the contains call.
320 map: &'tcx Expr<'tcx>,
321 /// The key expression used in the contains call.
322 key: &'tcx Expr<'tcx>,
323 /// The context of the top level block. All insert calls must be in the same context.
325 /// Whether this expression can be safely moved into a closure.
326 allow_insert_closure: bool,
327 /// Whether this expression can use the entry api.
329 /// Whether this expression is the final expression in this code path. This may be a statement.
331 // Is this expression a single insert. A slightly better suggestion can be made in this case.
332 is_single_insert: bool,
333 /// If the visitor has seen the map being used.
335 /// The locations where changes need to be made for the suggestion.
336 edits: Vec<Edit<'tcx>>,
337 /// A stack of loops the visitor is currently in.
340 impl<'tcx> InsertSearcher<'_, 'tcx> {
341 /// Visit the expression as a branch in control flow. Multiple insert calls can be used, but
342 /// only if they are on separate code paths. This will return whether the map was used in the
343 /// given expression.
344 fn visit_cond_arm(&mut self, e: &'tcx Expr<'_>) -> bool {
345 let is_map_used = self.is_map_used;
346 let in_tail_pos = self.in_tail_pos;
348 let res = self.is_map_used;
349 self.is_map_used = is_map_used;
350 self.in_tail_pos = in_tail_pos;
354 /// Visits an expression which is not itself in a tail position, but other sibling expressions
355 /// may be. e.g. if conditions
356 fn visit_non_tail_expr(&mut self, e: &'tcx Expr<'_>) {
357 let in_tail_pos = self.in_tail_pos;
358 self.in_tail_pos = false;
360 self.in_tail_pos = in_tail_pos;
363 impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> {
364 type Map = ErasedMap<'tcx>;
365 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
366 NestedVisitorMap::None
369 fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
371 StmtKind::Semi(e) => {
374 if self.in_tail_pos && self.allow_insert_closure {
375 // The spans are used to slice the top level expression into multiple parts. This requires that
376 // they all come from the same part of the source code.
377 if stmt.span.ctxt() == self.ctxt && e.span.ctxt() == self.ctxt {
379 .push(Edit::RemoveSemi(stmt.span.trim_start(e.span).unwrap_or(DUMMY_SP)));
381 self.allow_insert_closure = false;
385 StmtKind::Expr(e) => self.visit_expr(e),
386 StmtKind::Local(Local { init: Some(e), .. }) => {
387 self.allow_insert_closure &= !self.in_tail_pos;
388 self.in_tail_pos = false;
389 self.is_single_insert = false;
393 self.allow_insert_closure &= !self.in_tail_pos;
394 self.is_single_insert = false;
399 fn visit_block(&mut self, block: &'tcx Block<'_>) {
400 // If the block is in a tail position, then the last expression (possibly a statement) is in the
401 // tail position. The rest, however, are not.
402 match (block.stmts, block.expr) {
404 self.allow_insert_closure &= !self.in_tail_pos;
406 ([], Some(expr)) => self.visit_expr(expr),
407 (stmts, Some(expr)) => {
408 let in_tail_pos = self.in_tail_pos;
409 self.in_tail_pos = false;
411 self.visit_stmt(stmt);
413 self.in_tail_pos = in_tail_pos;
414 self.visit_expr(expr);
416 ([stmts @ .., stmt], None) => {
417 let in_tail_pos = self.in_tail_pos;
418 self.in_tail_pos = false;
420 self.visit_stmt(stmt);
422 self.in_tail_pos = in_tail_pos;
423 self.visit_stmt(stmt);
428 fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
429 if !self.can_use_entry {
433 match try_parse_insert(self.cx, expr) {
434 Some(insert_expr) if SpanlessEq::new(self.cx).eq_expr(self.map, insert_expr.map) => {
435 // Multiple inserts, inserts with a different key, and inserts from a macro can't use the entry api.
437 || !SpanlessEq::new(self.cx).eq_expr(self.key, insert_expr.key)
438 || expr.span.ctxt() != self.ctxt
440 self.can_use_entry = false;
444 self.edits.push(Edit::Insertion(Insertion {
446 value: insert_expr.value,
448 self.is_map_used = true;
449 self.allow_insert_closure &= self.in_tail_pos;
451 // The value doesn't affect whether there is only a single insert expression.
452 let is_single_insert = self.is_single_insert;
453 self.visit_non_tail_expr(insert_expr.value);
454 self.is_single_insert = is_single_insert;
456 _ if SpanlessEq::new(self.cx).eq_expr(self.map, expr) => {
457 self.is_map_used = true;
459 _ => match expr.kind {
460 ExprKind::If(cond_expr, then_expr, Some(else_expr)) => {
461 self.is_single_insert = false;
462 self.visit_non_tail_expr(cond_expr);
463 // Each branch may contain it's own insert expression.
464 let mut is_map_used = self.visit_cond_arm(then_expr);
465 is_map_used |= self.visit_cond_arm(else_expr);
466 self.is_map_used = is_map_used;
468 ExprKind::Match(scrutinee_expr, arms, _) => {
469 self.is_single_insert = false;
470 self.visit_non_tail_expr(scrutinee_expr);
471 // Each branch may contain it's own insert expression.
472 let mut is_map_used = self.is_map_used;
474 if let Some(Guard::If(guard) | Guard::IfLet(_, guard)) = arm.guard {
475 self.visit_non_tail_expr(guard);
477 is_map_used |= self.visit_cond_arm(arm.body);
479 self.is_map_used = is_map_used;
481 ExprKind::Loop(block, ..) => {
482 self.loops.push(expr.hir_id);
483 self.is_single_insert = false;
484 self.allow_insert_closure &= !self.in_tail_pos;
485 // Don't allow insertions inside of a loop.
486 let edit_len = self.edits.len();
487 self.visit_block(block);
488 if self.edits.len() != edit_len {
489 self.can_use_entry = false;
493 ExprKind::Block(block, _) => self.visit_block(block),
494 ExprKind::InlineAsm(_) | ExprKind::LlvmInlineAsm(_) => {
495 self.can_use_entry = false;
498 self.allow_insert_closure &= !self.in_tail_pos;
499 self.allow_insert_closure &= can_move_expr_to_closure_no_visit(self.cx, expr, &self.loops);
500 // Sub expressions are no longer in the tail position.
501 self.is_single_insert = false;
502 self.in_tail_pos = false;
503 walk_expr(self, expr);
510 struct InsertSearchResults<'tcx> {
511 edits: Vec<Edit<'tcx>>,
512 allow_insert_closure: bool,
513 is_single_insert: bool,
515 impl InsertSearchResults<'tcx> {
516 fn as_single_insertion(&self) -> Option<Insertion<'tcx>> {
517 self.is_single_insert.then(|| self.edits[0].as_insertion().unwrap())
522 cx: &LateContext<'_>,
524 app: &mut Applicability,
525 write_wrapped: impl Fn(&mut String, Insertion<'_>, SyntaxContext, &mut Applicability),
527 let ctxt = span.ctxt();
528 let mut res = String::new();
529 for insertion in self.edits.iter().filter_map(|e| e.as_insertion()) {
530 res.push_str(&snippet_with_applicability(
532 span.until(insertion.call.span),
536 if is_expr_used_or_unified(cx.tcx, insertion.call) {
537 write_wrapped(&mut res, insertion, ctxt, app);
542 snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
545 span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
547 res.push_str(&snippet_with_applicability(cx, span, "..", app));
551 fn snippet_occupied(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
553 self.snippet(cx, span, app, |res, insertion, ctxt, app| {
554 // Insertion into a map would return `Some(&mut value)`, but the entry returns `&mut value`
557 "Some(e.insert({}))",
558 snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
565 fn snippet_vacant(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
567 self.snippet(cx, span, app, |res, insertion, ctxt, app| {
568 // Insertion into a map would return `None`, but the entry returns a mutable reference.
569 let _ = if is_expr_final_block_expr(cx.tcx, insertion.call) {
572 "e.insert({});\n{}None",
573 snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
574 snippet_indent(cx, insertion.call.span).as_deref().unwrap_or(""),
579 "{{ e.insert({}); None }}",
580 snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
588 fn snippet_closure(&self, cx: &LateContext<'_>, mut span: Span, app: &mut Applicability) -> String {
589 let ctxt = span.ctxt();
590 let mut res = String::new();
591 for edit in &self.edits {
593 Edit::Insertion(insertion) => {
594 // Cut out the value from `map.insert(key, value)`
595 res.push_str(&snippet_with_applicability(
597 span.until(insertion.call.span),
601 res.push_str(&snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0);
602 span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
604 Edit::RemoveSemi(semi_span) => {
605 // Cut out the semicolon. This allows the value to be returned from the closure.
606 res.push_str(&snippet_with_applicability(cx, span.until(semi_span), "..", app));
607 span = span.trim_start(semi_span).unwrap_or(DUMMY_SP);
611 res.push_str(&snippet_with_applicability(cx, span, "..", app));
616 fn find_insert_calls(
617 cx: &LateContext<'tcx>,
618 contains_expr: &ContainsExpr<'tcx>,
619 expr: &'tcx Expr<'_>,
620 ) -> Option<InsertSearchResults<'tcx>> {
621 let mut s = InsertSearcher {
623 map: contains_expr.map,
624 key: contains_expr.key,
625 ctxt: expr.span.ctxt(),
628 allow_insert_closure: true,
631 is_single_insert: true,
635 let allow_insert_closure = s.allow_insert_closure;
636 let is_single_insert = s.is_single_insert;
638 s.can_use_entry.then(|| InsertSearchResults {
640 allow_insert_closure,