src/tools/clippy/clippy_lints/src/entry.rs

   1 use clippy_utils::higher;
   2 use clippy_utils::{
   3     can_move_expr_to_closure_no_visit,
   4     diagnostics::span_lint_and_sugg,
   5     is_expr_final_block_expr, is_expr_used_or_unified, match_def_path, paths, peel_hir_expr_while,
   6     source::{reindent_multiline, snippet_indent, snippet_with_applicability, snippet_with_context},
   7     SpanlessEq,
   8 };
   9 use core::fmt::Write;
  10 use rustc_errors::Applicability;
  11 use rustc_hir::{
  12     hir_id::HirIdSet,
  13     intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
  14     Block, Expr, ExprKind, Guard, HirId, Pat, Stmt, StmtKind, UnOp,
  15 };
  16 use rustc_lint::{LateContext, LateLintPass};
  17 use rustc_session::{declare_lint_pass, declare_tool_lint};
  18 use rustc_span::{Span, SyntaxContext, DUMMY_SP};
  19
  20 declare_clippy_lint! {
  21     /// ### What it does
  22     /// Checks for uses of `contains_key` + `insert` on `HashMap`
  23     /// or `BTreeMap`.
  24     ///
  25     /// ### Why is this bad?
  26     /// Using `entry` is more efficient.
  27     ///
  28     /// ### Known problems
  29     /// The suggestion may have type inference errors in some cases. e.g.
  30     /// ```rust
  31     /// let mut map = std::collections::HashMap::new();
  32     /// let _ = if !map.contains_key(&0) {
  33     ///     map.insert(0, 0)
  34     /// } else {
  35     ///     None
  36     /// };
  37     /// ```
  38     ///
  39     /// ### Example
  40     /// ```rust
  41     /// # use std::collections::HashMap;
  42     /// # let mut map = HashMap::new();
  43     /// # let k = 1;
  44     /// # let v = 1;
  45     /// if !map.contains_key(&k) {
  46     ///     map.insert(k, v);
  47     /// }
  48     /// ```
  49     /// can both be rewritten as:
  50     /// ```rust
  51     /// # use std::collections::HashMap;
  52     /// # let mut map = HashMap::new();
  53     /// # let k = 1;
  54     /// # let v = 1;
  55     /// map.entry(k).or_insert(v);
  56     /// ```
  57     #[clippy::version = "pre 1.29.0"]
  58     pub MAP_ENTRY,
  59     perf,
  60     "use of `contains_key` followed by `insert` on a `HashMap` or `BTreeMap`"
  61 }
  62
  63 declare_lint_pass!(HashMapPass => [MAP_ENTRY]);
  64
  65 impl<'tcx> LateLintPass<'tcx> for HashMapPass {
  66     #[allow(clippy::too_many_lines)]
  67     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
  68         let (cond_expr, then_expr, else_expr) = match higher::If::hir(expr) {
  69             Some(higher::If { cond, then, r#else }) => (cond, then, r#else),
  70             _ => return,
  71         };
  72
  73         let (map_ty, contains_expr) = match try_parse_contains(cx, cond_expr) {
  74             Some(x) => x,
  75             None => return,
  76         };
  77
  78         let then_search = match find_insert_calls(cx, &contains_expr, then_expr) {
  79             Some(x) => x,
  80             None => return,
  81         };
  82
  83         let mut app = Applicability::MachineApplicable;
  84         let map_str = snippet_with_context(cx, contains_expr.map.span, contains_expr.call_ctxt, "..", &mut app).0;
  85         let key_str = snippet_with_context(cx, contains_expr.key.span, contains_expr.call_ctxt, "..", &mut app).0;
  86         let sugg = if let Some(else_expr) = else_expr {
  87             let else_search = match find_insert_calls(cx, &contains_expr, else_expr) {
  88                 Some(search) => search,
  89                 None => return,
  90             };
  91
  92             if then_search.edits.is_empty() && else_search.edits.is_empty() {
  93                 // No insertions
  94                 return;
  95             } else if then_search.edits.is_empty() || else_search.edits.is_empty() {
  96                 // if .. { insert } else { .. } or if .. { .. } else { insert }
  97                 let ((then_str, entry_kind), else_str) = match (else_search.edits.is_empty(), contains_expr.negated) {
  98                     (true, true) => (
  99                         then_search.snippet_vacant(cx, then_expr.span, &mut app),
 100                         snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
 101                     ),
 102                     (true, false) => (
 103                         then_search.snippet_occupied(cx, then_expr.span, &mut app),
 104                         snippet_with_applicability(cx, else_expr.span, "{ .. }", &mut app),
 105                     ),
 106                     (false, true) => (
 107                         else_search.snippet_occupied(cx, else_expr.span, &mut app),
 108                         snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
 109                     ),
 110                     (false, false) => (
 111                         else_search.snippet_vacant(cx, else_expr.span, &mut app),
 112                         snippet_with_applicability(cx, then_expr.span, "{ .. }", &mut app),
 113                     ),
 114                 };
 115                 format!(
 116                     "if let {}::{} = {}.entry({}) {} else {}",
 117                     map_ty.entry_path(),
 118                     entry_kind,
 119                     map_str,
 120                     key_str,
 121                     then_str,
 122                     else_str,
 123                 )
 124             } else {
 125                 // if .. { insert } else { insert }
 126                 let ((then_str, then_entry), (else_str, else_entry)) = if contains_expr.negated {
 127                     (
 128                         then_search.snippet_vacant(cx, then_expr.span, &mut app),
 129                         else_search.snippet_occupied(cx, else_expr.span, &mut app),
 130                     )
 131                 } else {
 132                     (
 133                         then_search.snippet_occupied(cx, then_expr.span, &mut app),
 134                         else_search.snippet_vacant(cx, else_expr.span, &mut app),
 135                     )
 136                 };
 137                 let indent_str = snippet_indent(cx, expr.span);
 138                 let indent_str = indent_str.as_deref().unwrap_or("");
 139                 format!(
 140                     "match {}.entry({}) {{\n{indent}    {entry}::{} => {}\n\
 141                         {indent}    {entry}::{} => {}\n{indent}}}",
 142                     map_str,
 143                     key_str,
 144                     then_entry,
 145                     reindent_multiline(then_str.into(), true, Some(4 + indent_str.len())),
 146                     else_entry,
 147                     reindent_multiline(else_str.into(), true, Some(4 + indent_str.len())),
 148                     entry = map_ty.entry_path(),
 149                     indent = indent_str,
 150                 )
 151             }
 152         } else {
 153             if then_search.edits.is_empty() {
 154                 // no insertions
 155                 return;
 156             }
 157
 158             // if .. { insert }
 159             if !then_search.allow_insert_closure {
 160                 let (body_str, entry_kind) = if contains_expr.negated {
 161                     then_search.snippet_vacant(cx, then_expr.span, &mut app)
 162                 } else {
 163                     then_search.snippet_occupied(cx, then_expr.span, &mut app)
 164                 };
 165                 format!(
 166                     "if let {}::{} = {}.entry({}) {}",
 167                     map_ty.entry_path(),
 168                     entry_kind,
 169                     map_str,
 170                     key_str,
 171                     body_str,
 172                 )
 173             } else if let Some(insertion) = then_search.as_single_insertion() {
 174                 let value_str = snippet_with_context(cx, insertion.value.span, then_expr.span.ctxt(), "..", &mut app).0;
 175                 if contains_expr.negated {
 176                     if insertion.value.can_have_side_effects() {
 177                         format!("{}.entry({}).or_insert_with(|| {});", map_str, key_str, value_str)
 178                     } else {
 179                         format!("{}.entry({}).or_insert({});", map_str, key_str, value_str)
 180                     }
 181                 } else {
 182                     // TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
 183                     // This would need to be a different lint.
 184                     return;
 185                 }
 186             } else {
 187                 let block_str = then_search.snippet_closure(cx, then_expr.span, &mut app);
 188                 if contains_expr.negated {
 189                     format!("{}.entry({}).or_insert_with(|| {});", map_str, key_str, block_str)
 190                 } else {
 191                     // TODO: suggest using `if let Some(v) = map.get_mut(k) { .. }` here.
 192                     // This would need to be a different lint.
 193                     return;
 194                 }
 195             }
 196         };
 197
 198         span_lint_and_sugg(
 199             cx,
 200             MAP_ENTRY,
 201             expr.span,
 202             &format!("usage of `contains_key` followed by `insert` on a `{}`", map_ty.name()),
 203             "try this",
 204             sugg,
 205             app,
 206         );
 207     }
 208 }
 209
 210 #[derive(Clone, Copy)]
 211 enum MapType {
 212     Hash,
 213     BTree,
 214 }
 215 impl MapType {
 216     fn name(self) -> &'static str {
 217         match self {
 218             Self::Hash => "HashMap",
 219             Self::BTree => "BTreeMap",
 220         }
 221     }
 222     fn entry_path(self) -> &'static str {
 223         match self {
 224             Self::Hash => "std::collections::hash_map::Entry",
 225             Self::BTree => "std::collections::btree_map::Entry",
 226         }
 227     }
 228 }
 229
 230 struct ContainsExpr<'tcx> {
 231     negated: bool,
 232     map: &'tcx Expr<'tcx>,
 233     key: &'tcx Expr<'tcx>,
 234     call_ctxt: SyntaxContext,
 235 }
 236 fn try_parse_contains(cx: &LateContext<'_>, expr: &'tcx Expr<'_>) -> Option<(MapType, ContainsExpr<'tcx>)> {
 237     let mut negated = false;
 238     let expr = peel_hir_expr_while(expr, |e| match e.kind {
 239         ExprKind::Unary(UnOp::Not, e) => {
 240             negated = !negated;
 241             Some(e)
 242         },
 243         _ => None,
 244     });
 245     match expr.kind {
 246         ExprKind::MethodCall(
 247             _,
 248             _,
 249             [
 250                 map,
 251                 Expr {
 252                     kind: ExprKind::AddrOf(_, _, key),
 253                     span: key_span,
 254                     ..
 255                 },
 256             ],
 257             _,
 258         ) if key_span.ctxt() == expr.span.ctxt() => {
 259             let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
 260             let expr = ContainsExpr {
 261                 negated,
 262                 map,
 263                 key,
 264                 call_ctxt: expr.span.ctxt(),
 265             };
 266             if match_def_path(cx, id, &paths::BTREEMAP_CONTAINS_KEY) {
 267                 Some((MapType::BTree, expr))
 268             } else if match_def_path(cx, id, &paths::HASHMAP_CONTAINS_KEY) {
 269                 Some((MapType::Hash, expr))
 270             } else {
 271                 None
 272             }
 273         },
 274         _ => None,
 275     }
 276 }
 277
 278 struct InsertExpr<'tcx> {
 279     map: &'tcx Expr<'tcx>,
 280     key: &'tcx Expr<'tcx>,
 281     value: &'tcx Expr<'tcx>,
 282 }
 283 fn try_parse_insert(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<InsertExpr<'tcx>> {
 284     if let ExprKind::MethodCall(_, _, [map, key, value], _) = expr.kind {
 285         let id = cx.typeck_results().type_dependent_def_id(expr.hir_id)?;
 286         if match_def_path(cx, id, &paths::BTREEMAP_INSERT) || match_def_path(cx, id, &paths::HASHMAP_INSERT) {
 287             Some(InsertExpr { map, key, value })
 288         } else {
 289             None
 290         }
 291     } else {
 292         None
 293     }
 294 }
 295
 296 /// An edit that will need to be made to move the expression to use the entry api
 297 #[derive(Clone, Copy)]
 298 enum Edit<'tcx> {
 299     /// A semicolon that needs to be removed. Used to create a closure for `insert_with`.
 300     RemoveSemi(Span),
 301     /// An insertion into the map.
 302     Insertion(Insertion<'tcx>),
 303 }
 304 impl Edit<'tcx> {
 305     fn as_insertion(self) -> Option<Insertion<'tcx>> {
 306         if let Self::Insertion(i) = self { Some(i) } else { None }
 307     }
 308 }
 309 #[derive(Clone, Copy)]
 310 struct Insertion<'tcx> {
 311     call: &'tcx Expr<'tcx>,
 312     value: &'tcx Expr<'tcx>,
 313 }
 314
 315 /// This visitor needs to do a multiple things:
 316 /// * Find all usages of the map. An insertion can only be made before any other usages of the map.
 317 /// * Determine if there's an insertion using the same key. There's no need for the entry api
 318 ///   otherwise.
 319 /// * Determine if the final statement executed is an insertion. This is needed to use
 320 ///   `or_insert_with`.
 321 /// * Determine if there's any sub-expression that can't be placed in a closure.
 322 /// * Determine if there's only a single insert statement. `or_insert` can be used in this case.
 323 #[allow(clippy::struct_excessive_bools)]
 324 struct InsertSearcher<'cx, 'tcx> {
 325     cx: &'cx LateContext<'tcx>,
 326     /// The map expression used in the contains call.
 327     map: &'tcx Expr<'tcx>,
 328     /// The key expression used in the contains call.
 329     key: &'tcx Expr<'tcx>,
 330     /// The context of the top level block. All insert calls must be in the same context.
 331     ctxt: SyntaxContext,
 332     /// Whether this expression can be safely moved into a closure.
 333     allow_insert_closure: bool,
 334     /// Whether this expression can use the entry api.
 335     can_use_entry: bool,
 336     /// Whether this expression is the final expression in this code path. This may be a statement.
 337     in_tail_pos: bool,
 338     // Is this expression a single insert. A slightly better suggestion can be made in this case.
 339     is_single_insert: bool,
 340     /// If the visitor has seen the map being used.
 341     is_map_used: bool,
 342     /// The locations where changes need to be made for the suggestion.
 343     edits: Vec<Edit<'tcx>>,
 344     /// A stack of loops the visitor is currently in.
 345     loops: Vec<HirId>,
 346     /// Local variables created in the expression. These don't need to be captured.
 347     locals: HirIdSet,
 348 }
 349 impl<'tcx> InsertSearcher<'_, 'tcx> {
 350     /// Visit the expression as a branch in control flow. Multiple insert calls can be used, but
 351     /// only if they are on separate code paths. This will return whether the map was used in the
 352     /// given expression.
 353     fn visit_cond_arm(&mut self, e: &'tcx Expr<'_>) -> bool {
 354         let is_map_used = self.is_map_used;
 355         let in_tail_pos = self.in_tail_pos;
 356         self.visit_expr(e);
 357         let res = self.is_map_used;
 358         self.is_map_used = is_map_used;
 359         self.in_tail_pos = in_tail_pos;
 360         res
 361     }
 362
 363     /// Visits an expression which is not itself in a tail position, but other sibling expressions
 364     /// may be. e.g. if conditions
 365     fn visit_non_tail_expr(&mut self, e: &'tcx Expr<'_>) {
 366         let in_tail_pos = self.in_tail_pos;
 367         self.in_tail_pos = false;
 368         self.visit_expr(e);
 369         self.in_tail_pos = in_tail_pos;
 370     }
 371 }
 372 impl<'tcx> Visitor<'tcx> for InsertSearcher<'_, 'tcx> {
 373     type Map = ErasedMap<'tcx>;
 374     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 375         NestedVisitorMap::None
 376     }
 377
 378     fn visit_stmt(&mut self, stmt: &'tcx Stmt<'_>) {
 379         match stmt.kind {
 380             StmtKind::Semi(e) => {
 381                 self.visit_expr(e);
 382
 383                 if self.in_tail_pos && self.allow_insert_closure {
 384                     // The spans are used to slice the top level expression into multiple parts. This requires that
 385                     // they all come from the same part of the source code.
 386                     if stmt.span.ctxt() == self.ctxt && e.span.ctxt() == self.ctxt {
 387                         self.edits
 388                             .push(Edit::RemoveSemi(stmt.span.trim_start(e.span).unwrap_or(DUMMY_SP)));
 389                     } else {
 390                         self.allow_insert_closure = false;
 391                     }
 392                 }
 393             },
 394             StmtKind::Expr(e) => self.visit_expr(e),
 395             StmtKind::Local(l) => {
 396                 self.visit_pat(l.pat);
 397                 if let Some(e) = l.init {
 398                     self.allow_insert_closure &= !self.in_tail_pos;
 399                     self.in_tail_pos = false;
 400                     self.is_single_insert = false;
 401                     self.visit_expr(e);
 402                 }
 403             },
 404             StmtKind::Item(_) => {
 405                 self.allow_insert_closure &= !self.in_tail_pos;
 406                 self.is_single_insert = false;
 407             },
 408         }
 409     }
 410
 411     fn visit_block(&mut self, block: &'tcx Block<'_>) {
 412         // If the block is in a tail position, then the last expression (possibly a statement) is in the
 413         // tail position. The rest, however, are not.
 414         match (block.stmts, block.expr) {
 415             ([], None) => {
 416                 self.allow_insert_closure &= !self.in_tail_pos;
 417             },
 418             ([], Some(expr)) => self.visit_expr(expr),
 419             (stmts, Some(expr)) => {
 420                 let in_tail_pos = self.in_tail_pos;
 421                 self.in_tail_pos = false;
 422                 for stmt in stmts {
 423                     self.visit_stmt(stmt);
 424                 }
 425                 self.in_tail_pos = in_tail_pos;
 426                 self.visit_expr(expr);
 427             },
 428             ([stmts @ .., stmt], None) => {
 429                 let in_tail_pos = self.in_tail_pos;
 430                 self.in_tail_pos = false;
 431                 for stmt in stmts {
 432                     self.visit_stmt(stmt);
 433                 }
 434                 self.in_tail_pos = in_tail_pos;
 435                 self.visit_stmt(stmt);
 436             },
 437         }
 438     }
 439
 440     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
 441         if !self.can_use_entry {
 442             return;
 443         }
 444
 445         match try_parse_insert(self.cx, expr) {
 446             Some(insert_expr) if SpanlessEq::new(self.cx).eq_expr(self.map, insert_expr.map) => {
 447                 // Multiple inserts, inserts with a different key, and inserts from a macro can't use the entry api.
 448                 if self.is_map_used
 449                     || !SpanlessEq::new(self.cx).eq_expr(self.key, insert_expr.key)
 450                     || expr.span.ctxt() != self.ctxt
 451                 {
 452                     self.can_use_entry = false;
 453                     return;
 454                 }
 455
 456                 self.edits.push(Edit::Insertion(Insertion {
 457                     call: expr,
 458                     value: insert_expr.value,
 459                 }));
 460                 self.is_map_used = true;
 461                 self.allow_insert_closure &= self.in_tail_pos;
 462
 463                 // The value doesn't affect whether there is only a single insert expression.
 464                 let is_single_insert = self.is_single_insert;
 465                 self.visit_non_tail_expr(insert_expr.value);
 466                 self.is_single_insert = is_single_insert;
 467             },
 468             _ if SpanlessEq::new(self.cx).eq_expr(self.map, expr) => {
 469                 self.is_map_used = true;
 470             },
 471             _ => match expr.kind {
 472                 ExprKind::If(cond_expr, then_expr, Some(else_expr)) => {
 473                     self.is_single_insert = false;
 474                     self.visit_non_tail_expr(cond_expr);
 475                     // Each branch may contain it's own insert expression.
 476                     let mut is_map_used = self.visit_cond_arm(then_expr);
 477                     is_map_used |= self.visit_cond_arm(else_expr);
 478                     self.is_map_used = is_map_used;
 479                 },
 480                 ExprKind::Match(scrutinee_expr, arms, _) => {
 481                     self.is_single_insert = false;
 482                     self.visit_non_tail_expr(scrutinee_expr);
 483                     // Each branch may contain it's own insert expression.
 484                     let mut is_map_used = self.is_map_used;
 485                     for arm in arms {
 486                         self.visit_pat(arm.pat);
 487                         if let Some(Guard::If(guard) | Guard::IfLet(_, guard)) = arm.guard {
 488                             self.visit_non_tail_expr(guard);
 489                         }
 490                         is_map_used |= self.visit_cond_arm(arm.body);
 491                     }
 492                     self.is_map_used = is_map_used;
 493                 },
 494                 ExprKind::Loop(block, ..) => {
 495                     self.loops.push(expr.hir_id);
 496                     self.is_single_insert = false;
 497                     self.allow_insert_closure &= !self.in_tail_pos;
 498                     // Don't allow insertions inside of a loop.
 499                     let edit_len = self.edits.len();
 500                     self.visit_block(block);
 501                     if self.edits.len() != edit_len {
 502                         self.can_use_entry = false;
 503                     }
 504                     self.loops.pop();
 505                 },
 506                 ExprKind::Block(block, _) => self.visit_block(block),
 507                 ExprKind::InlineAsm(_) | ExprKind::LlvmInlineAsm(_) => {
 508                     self.can_use_entry = false;
 509                 },
 510                 _ => {
 511                     self.allow_insert_closure &= !self.in_tail_pos;
 512                     self.allow_insert_closure &=
 513                         can_move_expr_to_closure_no_visit(self.cx, expr, &self.loops, &self.locals);
 514                     // Sub expressions are no longer in the tail position.
 515                     self.is_single_insert = false;
 516                     self.in_tail_pos = false;
 517                     walk_expr(self, expr);
 518                 },
 519             },
 520         }
 521     }
 522
 523     fn visit_pat(&mut self, p: &'tcx Pat<'tcx>) {
 524         p.each_binding_or_first(&mut |_, id, _, _| {
 525             self.locals.insert(id);
 526         });
 527     }
 528 }
 529
 530 struct InsertSearchResults<'tcx> {
 531     edits: Vec<Edit<'tcx>>,
 532     allow_insert_closure: bool,
 533     is_single_insert: bool,
 534 }
 535 impl InsertSearchResults<'tcx> {
 536     fn as_single_insertion(&self) -> Option<Insertion<'tcx>> {
 537         self.is_single_insert.then(|| self.edits[0].as_insertion().unwrap())
 538     }
 539
 540     fn snippet(
 541         &self,
 542         cx: &LateContext<'_>,
 543         mut span: Span,
 544         app: &mut Applicability,
 545         write_wrapped: impl Fn(&mut String, Insertion<'_>, SyntaxContext, &mut Applicability),
 546     ) -> String {
 547         let ctxt = span.ctxt();
 548         let mut res = String::new();
 549         for insertion in self.edits.iter().filter_map(|e| e.as_insertion()) {
 550             res.push_str(&snippet_with_applicability(
 551                 cx,
 552                 span.until(insertion.call.span),
 553                 "..",
 554                 app,
 555             ));
 556             if is_expr_used_or_unified(cx.tcx, insertion.call) {
 557                 write_wrapped(&mut res, insertion, ctxt, app);
 558             } else {
 559                 let _ = write!(
 560                     res,
 561                     "e.insert({})",
 562                     snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
 563                 );
 564             }
 565             span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
 566         }
 567         res.push_str(&snippet_with_applicability(cx, span, "..", app));
 568         res
 569     }
 570
 571     fn snippet_occupied(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
 572         (
 573             self.snippet(cx, span, app, |res, insertion, ctxt, app| {
 574                 // Insertion into a map would return `Some(&mut value)`, but the entry returns `&mut value`
 575                 let _ = write!(
 576                     res,
 577                     "Some(e.insert({}))",
 578                     snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0
 579                 );
 580             }),
 581             "Occupied(mut e)",
 582         )
 583     }
 584
 585     fn snippet_vacant(&self, cx: &LateContext<'_>, span: Span, app: &mut Applicability) -> (String, &'static str) {
 586         (
 587             self.snippet(cx, span, app, |res, insertion, ctxt, app| {
 588                 // Insertion into a map would return `None`, but the entry returns a mutable reference.
 589                 let _ = if is_expr_final_block_expr(cx.tcx, insertion.call) {
 590                     write!(
 591                         res,
 592                         "e.insert({});\n{}None",
 593                         snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
 594                         snippet_indent(cx, insertion.call.span).as_deref().unwrap_or(""),
 595                     )
 596                 } else {
 597                     write!(
 598                         res,
 599                         "{{ e.insert({}); None }}",
 600                         snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0,
 601                     )
 602                 };
 603             }),
 604             "Vacant(e)",
 605         )
 606     }
 607
 608     fn snippet_closure(&self, cx: &LateContext<'_>, mut span: Span, app: &mut Applicability) -> String {
 609         let ctxt = span.ctxt();
 610         let mut res = String::new();
 611         for edit in &self.edits {
 612             match *edit {
 613                 Edit::Insertion(insertion) => {
 614                     // Cut out the value from `map.insert(key, value)`
 615                     res.push_str(&snippet_with_applicability(
 616                         cx,
 617                         span.until(insertion.call.span),
 618                         "..",
 619                         app,
 620                     ));
 621                     res.push_str(&snippet_with_context(cx, insertion.value.span, ctxt, "..", app).0);
 622                     span = span.trim_start(insertion.call.span).unwrap_or(DUMMY_SP);
 623                 },
 624                 Edit::RemoveSemi(semi_span) => {
 625                     // Cut out the semicolon. This allows the value to be returned from the closure.
 626                     res.push_str(&snippet_with_applicability(cx, span.until(semi_span), "..", app));
 627                     span = span.trim_start(semi_span).unwrap_or(DUMMY_SP);
 628                 },
 629             }
 630         }
 631         res.push_str(&snippet_with_applicability(cx, span, "..", app));
 632         res
 633     }
 634 }
 635
 636 fn find_insert_calls(
 637     cx: &LateContext<'tcx>,
 638     contains_expr: &ContainsExpr<'tcx>,
 639     expr: &'tcx Expr<'_>,
 640 ) -> Option<InsertSearchResults<'tcx>> {
 641     let mut s = InsertSearcher {
 642         cx,
 643         map: contains_expr.map,
 644         key: contains_expr.key,
 645         ctxt: expr.span.ctxt(),
 646         edits: Vec::new(),
 647         is_map_used: false,
 648         allow_insert_closure: true,
 649         can_use_entry: true,
 650         in_tail_pos: true,
 651         is_single_insert: true,
 652         loops: Vec::new(),
 653         locals: HirIdSet::default(),
 654     };
 655     s.visit_expr(expr);
 656     let allow_insert_closure = s.allow_insert_closure;
 657     let is_single_insert = s.is_single_insert;
 658     let edits = s.edits;
 659     s.can_use_entry.then(|| InsertSearchResults {
 660         edits,
 661         allow_insert_closure,
 662         is_single_insert,
 663     })
 664 }