crates/ide/src/syntax_highlighting/highlight.rs

   1 //! Computes color for a single element.
   2
   3 use hir::{AsAssocItem, Semantics};
   4 use ide_db::{
   5     defs::{Definition, NameClass, NameRefClass},
   6     RootDatabase, SymbolKind,
   7 };
   8 use rustc_hash::FxHashMap;
   9 use syntax::{
  10     ast, AstNode, AstToken, NodeOrToken, SyntaxElement,
  11     SyntaxKind::{self, *},
  12     SyntaxNode, SyntaxToken, T,
  13 };
  14
  15 use crate::{
  16     syntax_highlighting::tags::{HlOperator, HlPunct},
  17     Highlight, HlMod, HlTag,
  18 };
  19
  20 pub(super) fn element(
  21     sema: &Semantics<RootDatabase>,
  22     krate: Option<hir::Crate>,
  23     bindings_shadow_count: &mut FxHashMap<hir::Name, u32>,
  24     syntactic_name_ref_highlighting: bool,
  25     element: SyntaxElement,
  26 ) -> Option<(Highlight, Option<u64>)> {
  27     let db = sema.db;
  28     let mut binding_hash = None;
  29     let highlight: Highlight = match element.kind() {
  30         FN => {
  31             bindings_shadow_count.clear();
  32             return None;
  33         }
  34
  35         // Highlight definitions depending on the "type" of the definition.
  36         NAME => {
  37             let name = element.into_node().and_then(ast::Name::cast).unwrap();
  38             let name_kind = NameClass::classify(sema, &name);
  39
  40             if let Some(NameClass::Definition(Definition::Local(local))) = &name_kind {
  41                 if let Some(name) = local.name(db) {
  42                     let shadow_count = bindings_shadow_count.entry(name.clone()).or_default();
  43                     *shadow_count += 1;
  44                     binding_hash = Some(calc_binding_hash(&name, *shadow_count))
  45                 }
  46             };
  47
  48             match name_kind {
  49                 Some(NameClass::ExternCrate(_)) => SymbolKind::Module.into(),
  50                 Some(NameClass::Definition(def)) => {
  51                     highlight_def(db, krate, def) | HlMod::Definition
  52                 }
  53                 Some(NameClass::ConstReference(def)) => highlight_def(db, krate, def),
  54                 Some(NameClass::PatFieldShorthand { field_ref, .. }) => {
  55                     let mut h = HlTag::Symbol(SymbolKind::Field).into();
  56                     if let Definition::Field(field) = field_ref {
  57                         if let hir::VariantDef::Union(_) = field.parent_def(db) {
  58                             h |= HlMod::Unsafe;
  59                         }
  60                     }
  61                     h
  62                 }
  63                 None => highlight_name_by_syntax(name) | HlMod::Definition,
  64             }
  65         }
  66         // Highlight references like the definitions they resolve to
  67         NAME_REF if element.ancestors().any(|it| it.kind() == ATTR) => {
  68             // even though we track whether we are in an attribute or not we still need this special case
  69             // as otherwise we would emit unresolved references for name refs inside attributes
  70             SymbolKind::Function.into()
  71         }
  72         NAME_REF => {
  73             let name_ref = element.into_node().and_then(ast::NameRef::cast).unwrap();
  74             highlight_func_by_name_ref(sema, krate, &name_ref).unwrap_or_else(|| {
  75                 let is_self = name_ref.self_token().is_some();
  76                 let h = match NameRefClass::classify(sema, &name_ref) {
  77                     Some(name_kind) => match name_kind {
  78                         NameRefClass::ExternCrate(_) => SymbolKind::Module.into(),
  79                         NameRefClass::Definition(def) => {
  80                             if let Definition::Local(local) = &def {
  81                                 if let Some(name) = local.name(db) {
  82                                     let shadow_count =
  83                                         bindings_shadow_count.entry(name.clone()).or_default();
  84                                     binding_hash = Some(calc_binding_hash(&name, *shadow_count))
  85                                 }
  86                             };
  87
  88                             let mut h = highlight_def(db, krate, def);
  89
  90                             if let Definition::Local(local) = &def {
  91                                 if is_consumed_lvalue(name_ref.syntax().clone().into(), local, db) {
  92                                     h |= HlMod::Consuming;
  93                                 }
  94                             }
  95
  96                             if let Some(parent) = name_ref.syntax().parent() {
  97                                 if matches!(parent.kind(), FIELD_EXPR | RECORD_PAT_FIELD) {
  98                                     if let Definition::Field(field) = def {
  99                                         if let hir::VariantDef::Union(_) = field.parent_def(db) {
 100                                             h |= HlMod::Unsafe;
 101                                         }
 102                                     }
 103                                 }
 104                             }
 105
 106                             h
 107                         }
 108                         NameRefClass::FieldShorthand { .. } => SymbolKind::Field.into(),
 109                     },
 110                     None if syntactic_name_ref_highlighting => {
 111                         highlight_name_ref_by_syntax(name_ref, sema, krate)
 112                     }
 113                     None => HlTag::UnresolvedReference.into(),
 114                 };
 115                 if h.tag == HlTag::Symbol(SymbolKind::Module) && is_self {
 116                     SymbolKind::SelfParam.into()
 117                 } else {
 118                     h
 119                 }
 120             })
 121         }
 122
 123         // Simple token-based highlighting
 124         COMMENT => {
 125             let comment = element.into_token().and_then(ast::Comment::cast)?;
 126             let h = HlTag::Comment;
 127             match comment.kind().doc {
 128                 Some(_) => h | HlMod::Documentation,
 129                 None => h.into(),
 130             }
 131         }
 132         STRING | BYTE_STRING => HlTag::StringLiteral.into(),
 133         ATTR => HlTag::Attribute.into(),
 134         INT_NUMBER | FLOAT_NUMBER => HlTag::NumericLiteral.into(),
 135         BYTE => HlTag::ByteLiteral.into(),
 136         CHAR => HlTag::CharLiteral.into(),
 137         QUESTION => HlTag::Operator(HlOperator::Other) | HlMod::ControlFlow,
 138         LIFETIME => {
 139             let lifetime = element.into_node().and_then(ast::Lifetime::cast).unwrap();
 140
 141             match NameClass::classify_lifetime(sema, &lifetime) {
 142                 Some(NameClass::Definition(def)) => {
 143                     highlight_def(db, krate, def) | HlMod::Definition
 144                 }
 145                 None => match NameRefClass::classify_lifetime(sema, &lifetime) {
 146                     Some(NameRefClass::Definition(def)) => highlight_def(db, krate, def),
 147                     _ => SymbolKind::LifetimeParam.into(),
 148                 },
 149                 _ => Highlight::from(SymbolKind::LifetimeParam) | HlMod::Definition,
 150             }
 151         }
 152         p if p.is_punct() => match p {
 153             T![&] if parent_matches::<ast::BinExpr>(&element) => HlOperator::Bitwise.into(),
 154             T![&] => {
 155                 let h = HlTag::Operator(HlOperator::Other).into();
 156                 let is_unsafe = element
 157                     .parent()
 158                     .and_then(ast::RefExpr::cast)
 159                     .map_or(false, |ref_expr| sema.is_unsafe_ref_expr(&ref_expr));
 160                 if is_unsafe {
 161                     h | HlMod::Unsafe
 162                 } else {
 163                     h
 164                 }
 165             }
 166             T![::] | T![->] | T![=>] | T![..] | T![=] | T![@] | T![.] => HlOperator::Other.into(),
 167             T![!] if parent_matches::<ast::MacroCall>(&element) => SymbolKind::Macro.into(),
 168             T![!] if parent_matches::<ast::NeverType>(&element) => HlTag::BuiltinType.into(),
 169             T![!] if parent_matches::<ast::PrefixExpr>(&element) => HlOperator::Logical.into(),
 170             T![*] if parent_matches::<ast::PtrType>(&element) => HlTag::Keyword.into(),
 171             T![*] if parent_matches::<ast::PrefixExpr>(&element) => {
 172                 let prefix_expr = element.parent().and_then(ast::PrefixExpr::cast)?;
 173
 174                 let expr = prefix_expr.expr()?;
 175                 let ty = sema.type_of_expr(&expr)?;
 176                 if ty.is_raw_ptr() {
 177                     HlTag::Operator(HlOperator::Other) | HlMod::Unsafe
 178                 } else if let Some(ast::PrefixOp::Deref) = prefix_expr.op_kind() {
 179                     HlOperator::Other.into()
 180                 } else {
 181                     HlPunct::Other.into()
 182                 }
 183             }
 184             T![-] if parent_matches::<ast::PrefixExpr>(&element) => {
 185                 let prefix_expr = element.parent().and_then(ast::PrefixExpr::cast)?;
 186
 187                 let expr = prefix_expr.expr()?;
 188                 match expr {
 189                     ast::Expr::Literal(_) => HlTag::NumericLiteral,
 190                     _ => HlTag::Operator(HlOperator::Other),
 191                 }
 192                 .into()
 193             }
 194             _ if parent_matches::<ast::PrefixExpr>(&element) => HlOperator::Other.into(),
 195             T![+] | T![-] | T![*] | T![/] | T![+=] | T![-=] | T![*=] | T![/=]
 196                 if parent_matches::<ast::BinExpr>(&element) =>
 197             {
 198                 HlOperator::Arithmetic.into()
 199             }
 200             T![|] | T![&] | T![!] | T![^] | T![|=] | T![&=] | T![^=]
 201                 if parent_matches::<ast::BinExpr>(&element) =>
 202             {
 203                 HlOperator::Bitwise.into()
 204             }
 205             T![&&] | T![||] if parent_matches::<ast::BinExpr>(&element) => {
 206                 HlOperator::Logical.into()
 207             }
 208             T![>] | T![<] | T![==] | T![>=] | T![<=] | T![!=]
 209                 if parent_matches::<ast::BinExpr>(&element) =>
 210             {
 211                 HlOperator::Comparison.into()
 212             }
 213             _ if parent_matches::<ast::BinExpr>(&element) => HlOperator::Other.into(),
 214             _ if parent_matches::<ast::RangeExpr>(&element) => HlOperator::Other.into(),
 215             _ if parent_matches::<ast::RangePat>(&element) => HlOperator::Other.into(),
 216             _ if parent_matches::<ast::RestPat>(&element) => HlOperator::Other.into(),
 217             _ if parent_matches::<ast::Attr>(&element) => HlTag::Attribute.into(),
 218             kind => match kind {
 219                 T!['['] | T![']'] => HlPunct::Bracket,
 220                 T!['{'] | T!['}'] => HlPunct::Brace,
 221                 T!['('] | T![')'] => HlPunct::Parenthesis,
 222                 T![<] | T![>] => HlPunct::Angle,
 223                 T![,] => HlPunct::Comma,
 224                 T![:] => HlPunct::Colon,
 225                 T![;] => HlPunct::Semi,
 226                 T![.] => HlPunct::Dot,
 227                 _ => HlPunct::Other,
 228             }
 229             .into(),
 230         },
 231
 232         k if k.is_keyword() => {
 233             let h = Highlight::new(HlTag::Keyword);
 234             match k {
 235                 T![await] => h | HlMod::Async | HlMod::ControlFlow,
 236                 T![break]
 237                 | T![continue]
 238                 | T![else]
 239                 | T![if]
 240                 | T![in]
 241                 | T![loop]
 242                 | T![match]
 243                 | T![return]
 244                 | T![while]
 245                 | T![yield] => h | HlMod::ControlFlow,
 246                 T![for] if !is_child_of_impl(&element) => h | HlMod::ControlFlow,
 247                 T![unsafe] => h | HlMod::Unsafe,
 248                 T![true] | T![false] => HlTag::BoolLiteral.into(),
 249                 // self is handled as either a Name or NameRef already
 250                 T![self] => return None,
 251                 T![ref] => element
 252                     .parent()
 253                     .and_then(ast::IdentPat::cast)
 254                     .and_then(|ident_pat| {
 255                         if sema.is_unsafe_ident_pat(&ident_pat) {
 256                             Some(HlMod::Unsafe)
 257                         } else {
 258                             None
 259                         }
 260                     })
 261                     .map(|modifier| h | modifier)
 262                     .unwrap_or(h),
 263                 T![async] => h | HlMod::Async,
 264                 _ => h,
 265             }
 266         }
 267
 268         _ => return None,
 269     };
 270
 271     return Some((highlight, binding_hash));
 272
 273     fn calc_binding_hash(name: &hir::Name, shadow_count: u32) -> u64 {
 274         fn hash<T: std::hash::Hash + std::fmt::Debug>(x: T) -> u64 {
 275             use std::{collections::hash_map::DefaultHasher, hash::Hasher};
 276
 277             let mut hasher = DefaultHasher::new();
 278             x.hash(&mut hasher);
 279             hasher.finish()
 280         }
 281
 282         hash((name, shadow_count))
 283     }
 284 }
 285 fn highlight_def(db: &RootDatabase, krate: Option<hir::Crate>, def: Definition) -> Highlight {
 286     let mut h = match def {
 287         Definition::Macro(_) => Highlight::new(HlTag::Symbol(SymbolKind::Macro)),
 288         Definition::Field(_) => Highlight::new(HlTag::Symbol(SymbolKind::Field)),
 289         Definition::ModuleDef(def) => match def {
 290             hir::ModuleDef::Module(_) => Highlight::new(HlTag::Symbol(SymbolKind::Module)),
 291             hir::ModuleDef::Function(func) => {
 292                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Function));
 293                 if let Some(item) = func.as_assoc_item(db) {
 294                     h |= HlMod::Associated;
 295                     match func.self_param(db) {
 296                         Some(sp) => {
 297                             if let hir::Access::Exclusive = sp.access(db) {
 298                                 h |= HlMod::Mutable;
 299                             }
 300                         }
 301                         None => h |= HlMod::Static,
 302                     }
 303
 304                     match item.container(db) {
 305                         hir::AssocItemContainer::Impl(i) => {
 306                             if i.trait_(db).is_some() {
 307                                 h |= HlMod::Trait;
 308                             }
 309                         }
 310                         hir::AssocItemContainer::Trait(_t) => {
 311                             h |= HlMod::Trait;
 312                         }
 313                     }
 314                 }
 315
 316                 if func.is_unsafe(db) {
 317                     h |= HlMod::Unsafe;
 318                 }
 319                 if func.is_async(db) {
 320                     h |= HlMod::Async;
 321                 }
 322
 323                 h
 324             }
 325             hir::ModuleDef::Adt(adt) => {
 326                 let h = match adt {
 327                     hir::Adt::Struct(_) => HlTag::Symbol(SymbolKind::Struct),
 328                     hir::Adt::Enum(_) => HlTag::Symbol(SymbolKind::Enum),
 329                     hir::Adt::Union(_) => HlTag::Symbol(SymbolKind::Union),
 330                 };
 331
 332                 Highlight::new(h)
 333             }
 334             hir::ModuleDef::Variant(_) => Highlight::new(HlTag::Symbol(SymbolKind::Variant)),
 335             hir::ModuleDef::Const(konst) => {
 336                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Const));
 337
 338                 if let Some(item) = konst.as_assoc_item(db) {
 339                     h |= HlMod::Associated;
 340                     match item.container(db) {
 341                         hir::AssocItemContainer::Impl(i) => {
 342                             if i.trait_(db).is_some() {
 343                                 h |= HlMod::Trait;
 344                             }
 345                         }
 346                         hir::AssocItemContainer::Trait(_t) => {
 347                             h |= HlMod::Trait;
 348                         }
 349                     }
 350                 }
 351
 352                 h
 353             }
 354             hir::ModuleDef::Trait(trait_) => {
 355                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Trait));
 356
 357                 if trait_.is_unsafe(db) {
 358                     h |= HlMod::Unsafe;
 359                 }
 360
 361                 h
 362             }
 363             hir::ModuleDef::TypeAlias(type_) => {
 364                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::TypeAlias));
 365
 366                 if let Some(item) = type_.as_assoc_item(db) {
 367                     h |= HlMod::Associated;
 368                     match item.container(db) {
 369                         hir::AssocItemContainer::Impl(i) => {
 370                             if i.trait_(db).is_some() {
 371                                 h |= HlMod::Trait;
 372                             }
 373                         }
 374                         hir::AssocItemContainer::Trait(_t) => {
 375                             h |= HlMod::Trait;
 376                         }
 377                     }
 378                 }
 379
 380                 h
 381             }
 382             hir::ModuleDef::BuiltinType(_) => Highlight::new(HlTag::BuiltinType),
 383             hir::ModuleDef::Static(s) => {
 384                 let mut h = Highlight::new(HlTag::Symbol(SymbolKind::Static));
 385
 386                 if s.is_mut(db) {
 387                     h |= HlMod::Mutable;
 388                     h |= HlMod::Unsafe;
 389                 }
 390
 391                 h
 392             }
 393         },
 394         Definition::SelfType(_) => Highlight::new(HlTag::Symbol(SymbolKind::Impl)),
 395         Definition::GenericParam(it) => match it {
 396             hir::GenericParam::TypeParam(_) => Highlight::new(HlTag::Symbol(SymbolKind::TypeParam)),
 397             hir::GenericParam::ConstParam(_) => {
 398                 Highlight::new(HlTag::Symbol(SymbolKind::ConstParam))
 399             }
 400             hir::GenericParam::LifetimeParam(_) => {
 401                 Highlight::new(HlTag::Symbol(SymbolKind::LifetimeParam))
 402             }
 403         },
 404         Definition::Local(local) => {
 405             let tag = if local.is_self(db) {
 406                 HlTag::Symbol(SymbolKind::SelfParam)
 407             } else if local.is_param(db) {
 408                 HlTag::Symbol(SymbolKind::ValueParam)
 409             } else {
 410                 HlTag::Symbol(SymbolKind::Local)
 411             };
 412             let mut h = Highlight::new(tag);
 413             let ty = local.ty(db);
 414             if local.is_mut(db) || ty.is_mutable_reference() {
 415                 h |= HlMod::Mutable;
 416             }
 417             if ty.as_callable(db).is_some() || ty.impls_fnonce(db) {
 418                 h |= HlMod::Callable;
 419             }
 420             h
 421         }
 422         Definition::Label(_) => Highlight::new(HlTag::Symbol(SymbolKind::Label)),
 423     };
 424
 425     let is_from_other_crate = def.module(db).map(hir::Module::krate) != krate;
 426     let is_builtin_type = matches!(def, Definition::ModuleDef(hir::ModuleDef::BuiltinType(_)));
 427
 428     if is_from_other_crate && !is_builtin_type {
 429         h |= HlMod::Library;
 430     }
 431
 432     h
 433 }
 434
 435 fn highlight_func_by_name_ref(
 436     sema: &Semantics<RootDatabase>,
 437     krate: Option<hir::Crate>,
 438     name_ref: &ast::NameRef,
 439 ) -> Option<Highlight> {
 440     let mc = name_ref.syntax().parent().and_then(ast::MethodCallExpr::cast)?;
 441     highlight_method_call(sema, krate, &mc)
 442 }
 443
 444 fn highlight_method_call(
 445     sema: &Semantics<RootDatabase>,
 446     krate: Option<hir::Crate>,
 447     method_call: &ast::MethodCallExpr,
 448 ) -> Option<Highlight> {
 449     let func = sema.resolve_method_call(&method_call)?;
 450
 451     let mut h = SymbolKind::Function.into();
 452     h |= HlMod::Associated;
 453
 454     if func.is_unsafe(sema.db) || sema.is_unsafe_method_call(&method_call) {
 455         h |= HlMod::Unsafe;
 456     }
 457     if func.is_async(sema.db) {
 458         h |= HlMod::Async;
 459     }
 460     if func.as_assoc_item(sema.db).and_then(|it| it.containing_trait(sema.db)).is_some() {
 461         h |= HlMod::Trait;
 462     }
 463     if Some(func.module(sema.db).krate()) != krate {
 464         h |= HlMod::Library;
 465     }
 466
 467     if let Some(self_param) = func.self_param(sema.db) {
 468         match self_param.access(sema.db) {
 469             hir::Access::Shared => (),
 470             hir::Access::Exclusive => h |= HlMod::Mutable,
 471             hir::Access::Owned => {
 472                 if let Some(receiver_ty) =
 473                     method_call.receiver().and_then(|it| sema.type_of_expr(&it))
 474                 {
 475                     if !receiver_ty.is_copy(sema.db) {
 476                         h |= HlMod::Consuming
 477                     }
 478                 }
 479             }
 480         }
 481     }
 482     Some(h)
 483 }
 484
 485 fn highlight_name_by_syntax(name: ast::Name) -> Highlight {
 486     let default = HlTag::UnresolvedReference;
 487
 488     let parent = match name.syntax().parent() {
 489         Some(it) => it,
 490         _ => return default.into(),
 491     };
 492
 493     let tag = match parent.kind() {
 494         STRUCT => SymbolKind::Struct,
 495         ENUM => SymbolKind::Enum,
 496         VARIANT => SymbolKind::Variant,
 497         UNION => SymbolKind::Union,
 498         TRAIT => SymbolKind::Trait,
 499         TYPE_ALIAS => SymbolKind::TypeAlias,
 500         TYPE_PARAM => SymbolKind::TypeParam,
 501         RECORD_FIELD => SymbolKind::Field,
 502         MODULE => SymbolKind::Module,
 503         FN => SymbolKind::Function,
 504         CONST => SymbolKind::Const,
 505         STATIC => SymbolKind::Static,
 506         IDENT_PAT => SymbolKind::Local,
 507         _ => return default.into(),
 508     };
 509
 510     tag.into()
 511 }
 512
 513 fn highlight_name_ref_by_syntax(
 514     name: ast::NameRef,
 515     sema: &Semantics<RootDatabase>,
 516     krate: Option<hir::Crate>,
 517 ) -> Highlight {
 518     let default = HlTag::UnresolvedReference;
 519
 520     let parent = match name.syntax().parent() {
 521         Some(it) => it,
 522         _ => return default.into(),
 523     };
 524
 525     match parent.kind() {
 526         METHOD_CALL_EXPR => {
 527             return ast::MethodCallExpr::cast(parent)
 528                 .and_then(|it| highlight_method_call(sema, krate, &it))
 529                 .unwrap_or_else(|| SymbolKind::Function.into());
 530         }
 531         FIELD_EXPR => {
 532             let h = HlTag::Symbol(SymbolKind::Field);
 533             let is_union = ast::FieldExpr::cast(parent)
 534                 .and_then(|field_expr| sema.resolve_field(&field_expr))
 535                 .map_or(false, |field| {
 536                     matches!(field.parent_def(sema.db), hir::VariantDef::Union(_))
 537                 });
 538             if is_union {
 539                 h | HlMod::Unsafe
 540             } else {
 541                 h.into()
 542             }
 543         }
 544         PATH_SEGMENT => {
 545             let path = match parent.parent().and_then(ast::Path::cast) {
 546                 Some(it) => it,
 547                 _ => return default.into(),
 548             };
 549             let expr = match path.syntax().parent().and_then(ast::PathExpr::cast) {
 550                 Some(it) => it,
 551                 _ => {
 552                     // within path, decide whether it is module or adt by checking for uppercase name
 553                     return if name.text().chars().next().unwrap_or_default().is_uppercase() {
 554                         SymbolKind::Struct
 555                     } else {
 556                         SymbolKind::Module
 557                     }
 558                     .into();
 559                 }
 560             };
 561             let parent = match expr.syntax().parent() {
 562                 Some(it) => it,
 563                 None => return default.into(),
 564             };
 565
 566             match parent.kind() {
 567                 CALL_EXPR => SymbolKind::Function.into(),
 568                 _ => if name.text().chars().next().unwrap_or_default().is_uppercase() {
 569                     SymbolKind::Struct
 570                 } else {
 571                     SymbolKind::Const
 572                 }
 573                 .into(),
 574             }
 575         }
 576         _ => default.into(),
 577     }
 578 }
 579
 580 fn is_consumed_lvalue(
 581     node: NodeOrToken<SyntaxNode, SyntaxToken>,
 582     local: &hir::Local,
 583     db: &RootDatabase,
 584 ) -> bool {
 585     // When lvalues are passed as arguments and they're not Copy, then mark them as Consuming.
 586     parents_match(node, &[PATH_SEGMENT, PATH, PATH_EXPR, ARG_LIST]) && !local.ty(db).is_copy(db)
 587 }
 588
 589 /// Returns true if the parent nodes of `node` all match the `SyntaxKind`s in `kinds` exactly.
 590 fn parents_match(mut node: NodeOrToken<SyntaxNode, SyntaxToken>, mut kinds: &[SyntaxKind]) -> bool {
 591     while let (Some(parent), [kind, rest @ ..]) = (&node.parent(), kinds) {
 592         if parent.kind() != *kind {
 593             return false;
 594         }
 595
 596         // FIXME: Would be nice to get parent out of the match, but binding by-move and by-value
 597         // in the same pattern is unstable: rust-lang/rust#68354.
 598         node = node.parent().unwrap().into();
 599         kinds = rest;
 600     }
 601
 602     // Only true if we matched all expected kinds
 603     kinds.len() == 0
 604 }
 605
 606 #[inline]
 607 fn parent_matches<N: AstNode>(element: &SyntaxElement) -> bool {
 608     element.parent().map_or(false, |it| N::can_cast(it.kind()))
 609 }
 610
 611 fn is_child_of_impl(element: &SyntaxElement) -> bool {
 612     match element.parent() {
 613         Some(e) => e.kind() == IMPL,
 614         _ => false,
 615     }
 616 }