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