crates/ide_completion/src/context.rs

   1 //! See `CompletionContext` structure.
   2
   3 use base_db::SourceDatabaseExt;
   4 use hir::{Local, Name, ScopeDef, Semantics, SemanticsScope, Type, TypeInfo};
   5 use ide_db::{
   6     base_db::{FilePosition, SourceDatabase},
   7     call_info::ActiveParameter,
   8     RootDatabase,
   9 };
  10 use syntax::{
  11     algo::find_node_at_offset,
  12     ast::{self, HasName, NameOrNameRef},
  13     match_ast, AstNode, NodeOrToken,
  14     SyntaxKind::{self, *},
  15     SyntaxNode, SyntaxToken, TextRange, TextSize, T,
  16 };
  17 use text_edit::Indel;
  18
  19 use crate::{
  20     patterns::{
  21         determine_location, determine_prev_sibling, for_is_prev2, inside_impl_trait_block,
  22         is_in_loop_body, previous_token, ImmediateLocation, ImmediatePrevSibling,
  23     },
  24     CompletionConfig,
  25 };
  26
  27 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  28 pub(crate) enum PatternRefutability {
  29     Refutable,
  30     Irrefutable,
  31 }
  32
  33 #[derive(Debug)]
  34 pub(super) enum PathKind {
  35     Expr,
  36     Type,
  37 }
  38
  39 #[derive(Debug)]
  40 pub(crate) struct PathCompletionContext {
  41     /// If this is a call with () already there
  42     call_kind: Option<CallKind>,
  43     /// A single-indent path, like `foo`. `::foo` should not be considered a trivial path.
  44     pub(super) is_trivial_path: bool,
  45     /// If not a trivial path, the prefix (qualifier).
  46     pub(super) qualifier: Option<ast::Path>,
  47     /// Whether the qualifier comes from a use tree parent or not
  48     pub(super) use_tree_parent: bool,
  49     pub(super) kind: Option<PathKind>,
  50     /// Whether the path segment has type args or not.
  51     pub(super) has_type_args: bool,
  52     /// `true` if we are a statement or a last expr in the block.
  53     pub(super) can_be_stmt: bool,
  54     pub(super) in_loop_body: bool,
  55 }
  56
  57 #[derive(Debug)]
  58 pub(super) struct PatternContext {
  59     pub(super) refutability: PatternRefutability,
  60     pub(super) is_param: Option<ParamKind>,
  61     pub(super) has_type_ascription: bool,
  62 }
  63
  64 #[derive(Debug)]
  65 pub(super) enum LifetimeContext {
  66     LifetimeParam(Option<ast::LifetimeParam>),
  67     Lifetime,
  68     LabelRef,
  69     LabelDef,
  70 }
  71
  72 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  73 pub(crate) enum CallKind {
  74     Pat,
  75     Mac,
  76     Expr,
  77 }
  78
  79 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  80 pub(crate) enum ParamKind {
  81     Function,
  82     Closure,
  83 }
  84 /// `CompletionContext` is created early during completion to figure out, where
  85 /// exactly is the cursor, syntax-wise.
  86 #[derive(Debug)]
  87 pub(crate) struct CompletionContext<'a> {
  88     pub(super) sema: Semantics<'a, RootDatabase>,
  89     pub(super) scope: SemanticsScope<'a>,
  90     pub(super) db: &'a RootDatabase,
  91     pub(super) config: &'a CompletionConfig,
  92     pub(super) position: FilePosition,
  93     /// The token before the cursor, in the original file.
  94     pub(super) original_token: SyntaxToken,
  95     /// The token before the cursor, in the macro-expanded file.
  96     pub(super) token: SyntaxToken,
  97     /// The crate of the current file.
  98     pub(super) krate: Option<hir::Crate>,
  99     pub(super) expected_name: Option<NameOrNameRef>,
 100     pub(super) expected_type: Option<Type>,
 101
 102     /// The parent function of the cursor position if it exists.
 103     pub(super) function_def: Option<ast::Fn>,
 104     /// The parent impl of the cursor position if it exists.
 105     pub(super) impl_def: Option<ast::Impl>,
 106     /// The NameLike under the cursor in the original file if it exists.
 107     pub(super) name_syntax: Option<ast::NameLike>,
 108     pub(super) incomplete_let: bool,
 109
 110     pub(super) completion_location: Option<ImmediateLocation>,
 111     pub(super) prev_sibling: Option<ImmediatePrevSibling>,
 112     pub(super) attribute_under_caret: Option<ast::Attr>,
 113     pub(super) previous_token: Option<SyntaxToken>,
 114
 115     pub(super) lifetime_ctx: Option<LifetimeContext>,
 116     pub(super) pattern_ctx: Option<PatternContext>,
 117     pub(super) path_context: Option<PathCompletionContext>,
 118     pub(super) locals: Vec<(Name, Local)>,
 119
 120     no_completion_required: bool,
 121 }
 122
 123 impl<'a> CompletionContext<'a> {
 124     /// Checks whether completions in that particular case don't make much sense.
 125     /// Examples:
 126     /// - `fn $0` -- we expect function name, it's unlikely that "hint" will be helpful.
 127     ///   Exception for this case is `impl Trait for Foo`, where we would like to hint trait method names.
 128     /// - `for _ i$0` -- obviously, it'll be "in" keyword.
 129     pub(crate) fn no_completion_required(&self) -> bool {
 130         self.no_completion_required
 131     }
 132
 133     /// The range of the identifier that is being completed.
 134     pub(crate) fn source_range(&self) -> TextRange {
 135         // check kind of macro-expanded token, but use range of original token
 136         let kind = self.token.kind();
 137         if kind == IDENT || kind == LIFETIME_IDENT || kind == UNDERSCORE || kind.is_keyword() {
 138             self.original_token.text_range()
 139         } else if kind == CHAR {
 140             // assume we are completing a lifetime but the user has only typed the '
 141             cov_mark::hit!(completes_if_lifetime_without_idents);
 142             TextRange::at(self.original_token.text_range().start(), TextSize::from(1))
 143         } else {
 144             TextRange::empty(self.position.offset)
 145         }
 146     }
 147
 148     pub(crate) fn previous_token_is(&self, kind: SyntaxKind) -> bool {
 149         self.previous_token.as_ref().map_or(false, |tok| tok.kind() == kind)
 150     }
 151
 152     pub(crate) fn dot_receiver(&self) -> Option<&ast::Expr> {
 153         match &self.completion_location {
 154             Some(
 155                 ImmediateLocation::MethodCall { receiver, .. }
 156                 | ImmediateLocation::FieldAccess { receiver, .. },
 157             ) => receiver.as_ref(),
 158             _ => None,
 159         }
 160     }
 161
 162     pub(crate) fn has_dot_receiver(&self) -> bool {
 163         matches!(
 164             &self.completion_location,
 165             Some(ImmediateLocation::FieldAccess { receiver, .. } | ImmediateLocation::MethodCall { receiver,.. })
 166                 if receiver.is_some()
 167         )
 168     }
 169
 170     pub(crate) fn expects_assoc_item(&self) -> bool {
 171         matches!(self.completion_location, Some(ImmediateLocation::Trait | ImmediateLocation::Impl))
 172     }
 173
 174     pub(crate) fn expects_non_trait_assoc_item(&self) -> bool {
 175         matches!(self.completion_location, Some(ImmediateLocation::Impl))
 176     }
 177
 178     pub(crate) fn expects_item(&self) -> bool {
 179         matches!(self.completion_location, Some(ImmediateLocation::ItemList))
 180     }
 181
 182     pub(crate) fn expects_generic_arg(&self) -> bool {
 183         matches!(self.completion_location, Some(ImmediateLocation::GenericArgList(_)))
 184     }
 185
 186     pub(crate) fn has_block_expr_parent(&self) -> bool {
 187         matches!(self.completion_location, Some(ImmediateLocation::StmtList))
 188     }
 189
 190     pub(crate) fn expects_ident_pat_or_ref_expr(&self) -> bool {
 191         matches!(
 192             self.completion_location,
 193             Some(ImmediateLocation::IdentPat | ImmediateLocation::RefExpr)
 194         )
 195     }
 196
 197     pub(crate) fn expect_field(&self) -> bool {
 198         matches!(
 199             self.completion_location,
 200             Some(ImmediateLocation::RecordField | ImmediateLocation::TupleField)
 201         )
 202     }
 203
 204     pub(crate) fn in_use_tree(&self) -> bool {
 205         matches!(
 206             self.completion_location,
 207             Some(ImmediateLocation::Use | ImmediateLocation::UseTree)
 208         )
 209     }
 210
 211     pub(crate) fn has_impl_or_trait_prev_sibling(&self) -> bool {
 212         matches!(
 213             self.prev_sibling,
 214             Some(ImmediatePrevSibling::ImplDefType | ImmediatePrevSibling::TraitDefName)
 215         )
 216     }
 217
 218     pub(crate) fn has_impl_prev_sibling(&self) -> bool {
 219         matches!(self.prev_sibling, Some(ImmediatePrevSibling::ImplDefType))
 220     }
 221
 222     pub(crate) fn has_visibility_prev_sibling(&self) -> bool {
 223         matches!(self.prev_sibling, Some(ImmediatePrevSibling::Visibility))
 224     }
 225
 226     pub(crate) fn after_if(&self) -> bool {
 227         matches!(self.prev_sibling, Some(ImmediatePrevSibling::IfExpr))
 228     }
 229
 230     pub(crate) fn is_path_disallowed(&self) -> bool {
 231         self.attribute_under_caret.is_some()
 232             || self.previous_token_is(T![unsafe])
 233             || matches!(
 234                 self.prev_sibling,
 235                 Some(ImmediatePrevSibling::Attribute | ImmediatePrevSibling::Visibility)
 236             )
 237             || matches!(
 238                 self.completion_location,
 239                 Some(
 240                     ImmediateLocation::Attribute(_)
 241                         | ImmediateLocation::ModDeclaration(_)
 242                         | ImmediateLocation::RecordPat(_)
 243                         | ImmediateLocation::RecordExpr(_)
 244                         | ImmediateLocation::Rename
 245                 )
 246             )
 247     }
 248
 249     pub(crate) fn expects_expression(&self) -> bool {
 250         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Expr), .. }))
 251     }
 252
 253     pub(crate) fn expects_type(&self) -> bool {
 254         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Type), .. }))
 255     }
 256
 257     pub(crate) fn path_call_kind(&self) -> Option<CallKind> {
 258         self.path_context.as_ref().and_then(|it| it.call_kind)
 259     }
 260
 261     pub(crate) fn is_trivial_path(&self) -> bool {
 262         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: true, .. }))
 263     }
 264
 265     pub(crate) fn is_non_trivial_path(&self) -> bool {
 266         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: false, .. }))
 267     }
 268
 269     pub(crate) fn path_qual(&self) -> Option<&ast::Path> {
 270         self.path_context.as_ref().and_then(|it| it.qualifier.as_ref())
 271     }
 272
 273     /// Checks if an item is visible and not `doc(hidden)` at the completion site.
 274     pub(crate) fn is_visible<I>(&self, item: &I) -> bool
 275     where
 276         I: hir::HasVisibility + hir::HasAttrs + hir::HasCrate + Copy,
 277     {
 278         self.is_visible_impl(&item.visibility(self.db), &item.attrs(self.db), item.krate(self.db))
 279     }
 280
 281     pub(crate) fn is_scope_def_hidden(&self, scope_def: &ScopeDef) -> bool {
 282         if let (Some(attrs), Some(krate)) = (scope_def.attrs(self.db), scope_def.krate(self.db)) {
 283             return self.is_doc_hidden(&attrs, krate);
 284         }
 285
 286         false
 287     }
 288
 289     /// Check if an item is `#[doc(hidden)]`.
 290     pub(crate) fn is_item_hidden(&self, item: &hir::ItemInNs) -> bool {
 291         let attrs = item.attrs(self.db);
 292         let krate = item.krate(self.db);
 293         match (attrs, krate) {
 294             (Some(attrs), Some(krate)) => self.is_doc_hidden(&attrs, krate),
 295             _ => false,
 296         }
 297     }
 298
 299     pub(crate) fn is_immediately_after_macro_bang(&self) -> bool {
 300         self.token.kind() == BANG && self.token.parent().map_or(false, |it| it.kind() == MACRO_CALL)
 301     }
 302
 303     /// A version of [`SemanticsScope::process_all_names`] that filters out `#[doc(hidden)]` items.
 304     pub(crate) fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
 305         self.scope.process_all_names(&mut |name, def| {
 306             if self.is_scope_def_hidden(&def) {
 307                 return;
 308             }
 309
 310             f(name, def);
 311         })
 312     }
 313
 314     fn is_visible_impl(
 315         &self,
 316         vis: &hir::Visibility,
 317         attrs: &hir::Attrs,
 318         defining_crate: hir::Crate,
 319     ) -> bool {
 320         let module = match self.scope.module() {
 321             Some(it) => it,
 322             None => return false,
 323         };
 324         if !vis.is_visible_from(self.db, module.into()) {
 325             // If the definition location is editable, also show private items
 326             let root_file = defining_crate.root_file(self.db);
 327             let source_root_id = self.db.file_source_root(root_file);
 328             let is_editable = !self.db.source_root(source_root_id).is_library;
 329             return is_editable;
 330         }
 331
 332         !self.is_doc_hidden(attrs, defining_crate)
 333     }
 334
 335     fn is_doc_hidden(&self, attrs: &hir::Attrs, defining_crate: hir::Crate) -> bool {
 336         let krate = match self.krate {
 337             Some(it) => it,
 338             None => return true,
 339         };
 340         if krate != defining_crate && attrs.has_doc_hidden() {
 341             // `doc(hidden)` items are only completed within the defining crate.
 342             return true;
 343         }
 344
 345         false
 346     }
 347 }
 348
 349 // CompletionContext construction
 350 impl<'a> CompletionContext<'a> {
 351     pub(super) fn new(
 352         db: &'a RootDatabase,
 353         position: FilePosition,
 354         config: &'a CompletionConfig,
 355     ) -> Option<CompletionContext<'a>> {
 356         let sema = Semantics::new(db);
 357
 358         let original_file = sema.parse(position.file_id);
 359
 360         // Insert a fake ident to get a valid parse tree. We will use this file
 361         // to determine context, though the original_file will be used for
 362         // actual completion.
 363         let file_with_fake_ident = {
 364             let parse = db.parse(position.file_id);
 365             let edit = Indel::insert(position.offset, "intellijRulezz".to_string());
 366             parse.reparse(&edit).tree()
 367         };
 368         let fake_ident_token =
 369             file_with_fake_ident.syntax().token_at_offset(position.offset).right_biased().unwrap();
 370
 371         let original_token =
 372             original_file.syntax().token_at_offset(position.offset).left_biased()?;
 373         let token = sema.descend_into_macros_single(original_token.clone());
 374         let scope = sema.scope_at_offset(&token, position.offset);
 375         let krate = scope.krate();
 376         let mut locals = vec![];
 377         scope.process_all_names(&mut |name, scope| {
 378             if let ScopeDef::Local(local) = scope {
 379                 locals.push((name, local));
 380             }
 381         });
 382         let mut ctx = CompletionContext {
 383             sema,
 384             scope,
 385             db,
 386             config,
 387             position,
 388             original_token,
 389             token,
 390             krate,
 391             expected_name: None,
 392             expected_type: None,
 393             function_def: None,
 394             impl_def: None,
 395             name_syntax: None,
 396             lifetime_ctx: None,
 397             pattern_ctx: None,
 398             completion_location: None,
 399             prev_sibling: None,
 400             attribute_under_caret: None,
 401             previous_token: None,
 402             path_context: None,
 403             locals,
 404             incomplete_let: false,
 405             no_completion_required: false,
 406         };
 407         ctx.expand_and_fill(
 408             original_file.syntax().clone(),
 409             file_with_fake_ident.syntax().clone(),
 410             position.offset,
 411             fake_ident_token,
 412         );
 413         Some(ctx)
 414     }
 415
 416     /// Do the attribute expansion at the current cursor position for both original file and fake file
 417     /// as long as possible. As soon as one of the two expansions fail we stop to stay in sync.
 418     fn expand_and_fill(
 419         &mut self,
 420         mut original_file: SyntaxNode,
 421         mut speculative_file: SyntaxNode,
 422         mut offset: TextSize,
 423         mut fake_ident_token: SyntaxToken,
 424     ) {
 425         loop {
 426             // Expand attributes
 427             if let (Some(actual_item), Some(item_with_fake_ident)) = (
 428                 find_node_at_offset::<ast::Item>(&original_file, offset),
 429                 find_node_at_offset::<ast::Item>(&speculative_file, offset),
 430             ) {
 431                 match (
 432                     self.sema.expand_attr_macro(&actual_item),
 433                     self.sema.speculative_expand_attr_macro(
 434                         &actual_item,
 435                         &item_with_fake_ident,
 436                         fake_ident_token.clone(),
 437                     ),
 438                 ) {
 439                     (Some(actual_expansion), Some(speculative_expansion)) => {
 440                         let new_offset = speculative_expansion.1.text_range().start();
 441                         if new_offset > actual_expansion.text_range().end() {
 442                             break;
 443                         }
 444                         original_file = actual_expansion;
 445                         speculative_file = speculative_expansion.0;
 446                         fake_ident_token = speculative_expansion.1;
 447                         offset = new_offset;
 448                         continue;
 449                     }
 450                     (None, None) => (),
 451                     _ => break,
 452                 }
 453             }
 454
 455             // Expand fn-like macro calls
 456             if let (Some(actual_macro_call), Some(macro_call_with_fake_ident)) = (
 457                 find_node_at_offset::<ast::MacroCall>(&original_file, offset),
 458                 find_node_at_offset::<ast::MacroCall>(&speculative_file, offset),
 459             ) {
 460                 let mac_call_path0 = actual_macro_call.path().as_ref().map(|s| s.syntax().text());
 461                 let mac_call_path1 =
 462                     macro_call_with_fake_ident.path().as_ref().map(|s| s.syntax().text());
 463                 if mac_call_path0 != mac_call_path1 {
 464                     break;
 465                 }
 466                 let speculative_args = match macro_call_with_fake_ident.token_tree() {
 467                     Some(tt) => tt,
 468                     None => break,
 469                 };
 470
 471                 if let (Some(actual_expansion), Some(speculative_expansion)) = (
 472                     self.sema.expand(&actual_macro_call),
 473                     self.sema.speculative_expand(
 474                         &actual_macro_call,
 475                         &speculative_args,
 476                         fake_ident_token,
 477                     ),
 478                 ) {
 479                     let new_offset = speculative_expansion.1.text_range().start();
 480                     if new_offset > actual_expansion.text_range().end() {
 481                         break;
 482                     }
 483                     original_file = actual_expansion;
 484                     speculative_file = speculative_expansion.0;
 485                     fake_ident_token = speculative_expansion.1;
 486                     offset = new_offset;
 487                 } else {
 488                     break;
 489                 }
 490             } else {
 491                 break;
 492             }
 493         }
 494
 495         self.fill(&original_file, speculative_file, offset);
 496     }
 497
 498     fn expected_type_and_name(&self) -> (Option<Type>, Option<NameOrNameRef>) {
 499         let mut node = match self.token.parent() {
 500             Some(it) => it,
 501             None => return (None, None),
 502         };
 503         loop {
 504             break match_ast! {
 505                 match node {
 506                     ast::LetStmt(it) => {
 507                         cov_mark::hit!(expected_type_let_with_leading_char);
 508                         cov_mark::hit!(expected_type_let_without_leading_char);
 509                         let ty = it.pat()
 510                             .and_then(|pat| self.sema.type_of_pat(&pat))
 511                             .or_else(|| it.initializer().and_then(|it| self.sema.type_of_expr(&it)))
 512                             .map(TypeInfo::original);
 513                         let name = match it.pat() {
 514                             Some(ast::Pat::IdentPat(ident)) => ident.name().map(NameOrNameRef::Name),
 515                             Some(_) | None => None,
 516                         };
 517
 518                         (ty, name)
 519                     },
 520                     ast::ArgList(_it) => {
 521                         cov_mark::hit!(expected_type_fn_param);
 522                         ActiveParameter::at_token(
 523                             &self.sema,
 524                             self.token.clone(),
 525                         ).map(|ap| {
 526                             let name = ap.ident().map(NameOrNameRef::Name);
 527                             let ty = if has_ref(&self.token) {
 528                                 cov_mark::hit!(expected_type_fn_param_ref);
 529                                 ap.ty.remove_ref()
 530                             } else {
 531                                 Some(ap.ty)
 532                             };
 533                             (ty, name)
 534                         })
 535                         .unwrap_or((None, None))
 536                     },
 537                     ast::RecordExprFieldList(it) => {
 538                         // wouldn't try {} be nice...
 539                         (|| {
 540                             if self.token.kind() == T![..]
 541                                 || self.token.prev_token().map(|t| t.kind()) == Some(T![..])
 542                             {
 543                                 cov_mark::hit!(expected_type_struct_func_update);
 544                                 let record_expr = it.syntax().parent().and_then(ast::RecordExpr::cast)?;
 545                                 let ty = self.sema.type_of_expr(&record_expr.into())?;
 546                                 Some((
 547                                     Some(ty.original),
 548                                     None
 549                                 ))
 550                             } else {
 551                                 cov_mark::hit!(expected_type_struct_field_without_leading_char);
 552                                 let expr_field = self.token.prev_sibling_or_token()?
 553                                     .into_node()
 554                                     .and_then(ast::RecordExprField::cast)?;
 555                                 let (_, _, ty) = self.sema.resolve_record_field(&expr_field)?;
 556                                 Some((
 557                                     Some(ty),
 558                                     expr_field.field_name().map(NameOrNameRef::NameRef),
 559                                 ))
 560                             }
 561                         })().unwrap_or((None, None))
 562                     },
 563                     ast::RecordExprField(it) => {
 564                         cov_mark::hit!(expected_type_struct_field_with_leading_char);
 565                         (
 566                             it.expr().as_ref().and_then(|e| self.sema.type_of_expr(e)).map(TypeInfo::original),
 567                             it.field_name().map(NameOrNameRef::NameRef),
 568                         )
 569                     },
 570                     ast::MatchExpr(it) => {
 571                         cov_mark::hit!(expected_type_match_arm_without_leading_char);
 572                         let ty = it.expr().and_then(|e| self.sema.type_of_expr(&e)).map(TypeInfo::original);
 573                         (ty, None)
 574                     },
 575                     ast::IfExpr(it) => {
 576                         cov_mark::hit!(expected_type_if_let_without_leading_char);
 577                         let ty = it.condition()
 578                             .and_then(|cond| cond.expr())
 579                             .and_then(|e| self.sema.type_of_expr(&e))
 580                             .map(TypeInfo::original);
 581                         (ty, None)
 582                     },
 583                     ast::IdentPat(it) => {
 584                         cov_mark::hit!(expected_type_if_let_with_leading_char);
 585                         cov_mark::hit!(expected_type_match_arm_with_leading_char);
 586                         let ty = self.sema.type_of_pat(&ast::Pat::from(it)).map(TypeInfo::original);
 587                         (ty, None)
 588                     },
 589                     ast::Fn(it) => {
 590                         cov_mark::hit!(expected_type_fn_ret_with_leading_char);
 591                         cov_mark::hit!(expected_type_fn_ret_without_leading_char);
 592                         let def = self.sema.to_def(&it);
 593                         (def.map(|def| def.ret_type(self.db)), None)
 594                     },
 595                     ast::ClosureExpr(it) => {
 596                         let ty = self.sema.type_of_expr(&it.into());
 597                         ty.and_then(|ty| ty.original.as_callable(self.db))
 598                             .map(|c| (Some(c.return_type()), None))
 599                             .unwrap_or((None, None))
 600                     },
 601                     ast::Stmt(_it) => (None, None),
 602                     ast::Item(__) => (None, None),
 603                     _ => {
 604                         match node.parent() {
 605                             Some(n) => {
 606                                 node = n;
 607                                 continue;
 608                             },
 609                             None => (None, None),
 610                         }
 611                     },
 612                 }
 613             };
 614         }
 615     }
 616
 617     fn fill(
 618         &mut self,
 619         original_file: &SyntaxNode,
 620         file_with_fake_ident: SyntaxNode,
 621         offset: TextSize,
 622     ) {
 623         let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
 624         let syntax_element = NodeOrToken::Token(fake_ident_token);
 625         self.previous_token = previous_token(syntax_element.clone());
 626         self.attribute_under_caret = syntax_element.ancestors().find_map(ast::Attr::cast);
 627         self.no_completion_required = {
 628             let inside_impl_trait_block = inside_impl_trait_block(syntax_element.clone());
 629             let fn_is_prev = self.previous_token_is(T![fn]);
 630             let for_is_prev2 = for_is_prev2(syntax_element.clone());
 631             (fn_is_prev && !inside_impl_trait_block) || for_is_prev2
 632         };
 633
 634         self.incomplete_let =
 635             syntax_element.ancestors().take(6).find_map(ast::LetStmt::cast).map_or(false, |it| {
 636                 it.syntax().text_range().end() == syntax_element.text_range().end()
 637             });
 638
 639         let (expected_type, expected_name) = self.expected_type_and_name();
 640         self.expected_type = expected_type;
 641         self.expected_name = expected_name;
 642
 643         let name_like = match find_node_at_offset(&file_with_fake_ident, offset) {
 644             Some(it) => it,
 645             None => return,
 646         };
 647         self.completion_location =
 648             determine_location(&self.sema, original_file, offset, &name_like);
 649         self.prev_sibling = determine_prev_sibling(&name_like);
 650         self.name_syntax =
 651             find_node_at_offset(original_file, name_like.syntax().text_range().start());
 652         self.impl_def = self
 653             .sema
 654             .token_ancestors_with_macros(self.token.clone())
 655             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 656             .find_map(ast::Impl::cast);
 657         self.function_def = self
 658             .sema
 659             .token_ancestors_with_macros(self.token.clone())
 660             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 661             .find_map(ast::Fn::cast);
 662         match name_like {
 663             ast::NameLike::Lifetime(lifetime) => {
 664                 self.lifetime_ctx =
 665                     Self::classify_lifetime(&self.sema, original_file, lifetime, offset);
 666             }
 667             ast::NameLike::NameRef(name_ref) => {
 668                 self.path_context = Self::classify_name_ref(&self.sema, original_file, name_ref);
 669             }
 670             ast::NameLike::Name(name) => {
 671                 self.pattern_ctx = Self::classify_name(&self.sema, name);
 672             }
 673         }
 674     }
 675
 676     fn classify_lifetime(
 677         sema: &Semantics<RootDatabase>,
 678         original_file: &SyntaxNode,
 679         lifetime: ast::Lifetime,
 680         offset: TextSize,
 681     ) -> Option<LifetimeContext> {
 682         let parent = lifetime.syntax().parent()?;
 683         if parent.kind() == ERROR {
 684             return None;
 685         }
 686
 687         Some(match_ast! {
 688             match parent {
 689                 ast::LifetimeParam(_it) => LifetimeContext::LifetimeParam(sema.find_node_at_offset_with_macros(original_file, offset)),
 690                 ast::BreakExpr(_it) => LifetimeContext::LabelRef,
 691                 ast::ContinueExpr(_it) => LifetimeContext::LabelRef,
 692                 ast::Label(_it) => LifetimeContext::LabelDef,
 693                 _ => LifetimeContext::Lifetime,
 694             }
 695         })
 696     }
 697
 698     fn classify_name(_sema: &Semantics<RootDatabase>, name: ast::Name) -> Option<PatternContext> {
 699         let bind_pat = name.syntax().parent().and_then(ast::IdentPat::cast)?;
 700         let is_name_in_field_pat = bind_pat
 701             .syntax()
 702             .parent()
 703             .and_then(ast::RecordPatField::cast)
 704             .map_or(false, |pat_field| pat_field.name_ref().is_none());
 705         if is_name_in_field_pat {
 706             return None;
 707         }
 708         if !bind_pat.is_simple_ident() {
 709             return None;
 710         }
 711         let mut is_param = None;
 712         let (refutability, has_type_ascription) = bind_pat
 713             .syntax()
 714             .ancestors()
 715             .skip_while(|it| ast::Pat::can_cast(it.kind()))
 716             .next()
 717             .map_or((PatternRefutability::Irrefutable, false), |node| {
 718                 let refutability = match_ast! {
 719                     match node {
 720                         ast::LetStmt(let_) => return (PatternRefutability::Irrefutable, let_.ty().is_some()),
 721                         ast::Param(param) => {
 722                             let is_closure_param = param
 723                                 .syntax()
 724                                 .ancestors()
 725                                 .nth(2)
 726                                 .and_then(ast::ClosureExpr::cast)
 727                                 .is_some();
 728                             is_param = Some(if is_closure_param {
 729                                 ParamKind::Closure
 730                             } else {
 731                                 ParamKind::Function
 732                             });
 733                             return (PatternRefutability::Irrefutable, param.ty().is_some())
 734                         },
 735                         ast::MatchArm(__) => PatternRefutability::Refutable,
 736                         ast::Condition(__) => PatternRefutability::Refutable,
 737                         ast::ForExpr(__) => PatternRefutability::Irrefutable,
 738                         _ => PatternRefutability::Irrefutable,
 739                     }
 740                 };
 741                 (refutability, false)
 742             });
 743         Some(PatternContext { refutability, is_param, has_type_ascription })
 744     }
 745
 746     fn classify_name_ref(
 747         _sema: &Semantics<RootDatabase>,
 748         original_file: &SyntaxNode,
 749         name_ref: ast::NameRef,
 750     ) -> Option<PathCompletionContext> {
 751         let parent = name_ref.syntax().parent()?;
 752         let segment = ast::PathSegment::cast(parent)?;
 753
 754         let mut path_ctx = PathCompletionContext {
 755             call_kind: None,
 756             is_trivial_path: false,
 757             qualifier: None,
 758             has_type_args: false,
 759             can_be_stmt: false,
 760             in_loop_body: false,
 761             use_tree_parent: false,
 762             kind: None,
 763         };
 764         path_ctx.in_loop_body = is_in_loop_body(name_ref.syntax());
 765         let path = segment.parent_path();
 766
 767         if let Some(p) = path.syntax().parent() {
 768             path_ctx.call_kind = match_ast! {
 769                 match p {
 770                     ast::PathExpr(it) => it.syntax().parent().and_then(ast::CallExpr::cast).map(|_| CallKind::Expr),
 771                     ast::MacroCall(it) => it.excl_token().and(Some(CallKind::Mac)),
 772                     ast::TupleStructPat(_it) => Some(CallKind::Pat),
 773                     _ => None
 774                 }
 775             };
 776         }
 777
 778         if let Some(parent) = path.syntax().parent() {
 779             path_ctx.kind = match_ast! {
 780                 match parent {
 781                     ast::PathType(_it) => Some(PathKind::Type),
 782                     ast::PathExpr(_it) => Some(PathKind::Expr),
 783                     _ => None,
 784                 }
 785             };
 786         }
 787         path_ctx.has_type_args = segment.generic_arg_list().is_some();
 788
 789         if let Some((path, use_tree_parent)) = path_or_use_tree_qualifier(&path) {
 790             path_ctx.use_tree_parent = use_tree_parent;
 791             path_ctx.qualifier = path
 792                 .segment()
 793                 .and_then(|it| {
 794                     find_node_with_range::<ast::PathSegment>(
 795                         original_file,
 796                         it.syntax().text_range(),
 797                     )
 798                 })
 799                 .map(|it| it.parent_path());
 800             return Some(path_ctx);
 801         }
 802
 803         if let Some(segment) = path.segment() {
 804             if segment.coloncolon_token().is_some() {
 805                 return Some(path_ctx);
 806             }
 807         }
 808
 809         path_ctx.is_trivial_path = true;
 810
 811         // Find either enclosing expr statement (thing with `;`) or a
 812         // block. If block, check that we are the last expr.
 813         path_ctx.can_be_stmt = name_ref
 814             .syntax()
 815             .ancestors()
 816             .find_map(|node| {
 817                 if let Some(stmt) = ast::ExprStmt::cast(node.clone()) {
 818                     return Some(stmt.syntax().text_range() == name_ref.syntax().text_range());
 819                 }
 820                 if let Some(stmt_list) = ast::StmtList::cast(node) {
 821                     return Some(
 822                         stmt_list.tail_expr().map(|e| e.syntax().text_range())
 823                             == Some(name_ref.syntax().text_range()),
 824                     );
 825                 }
 826                 None
 827             })
 828             .unwrap_or(false);
 829         Some(path_ctx)
 830     }
 831 }
 832
 833 fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Option<N> {
 834     syntax.covering_element(range).ancestors().find_map(N::cast)
 835 }
 836
 837 fn path_or_use_tree_qualifier(path: &ast::Path) -> Option<(ast::Path, bool)> {
 838     if let Some(qual) = path.qualifier() {
 839         return Some((qual, false));
 840     }
 841     let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
 842     let use_tree = use_tree_list.syntax().parent().and_then(ast::UseTree::cast)?;
 843     use_tree.path().zip(Some(true))
 844 }
 845
 846 fn has_ref(token: &SyntaxToken) -> bool {
 847     let mut token = token.clone();
 848     for skip in [WHITESPACE, IDENT, T![mut]] {
 849         if token.kind() == skip {
 850             token = match token.prev_token() {
 851                 Some(it) => it,
 852                 None => return false,
 853             }
 854         }
 855     }
 856     token.kind() == T![&]
 857 }
 858
 859 #[cfg(test)]
 860 mod tests {
 861     use expect_test::{expect, Expect};
 862     use hir::HirDisplay;
 863
 864     use crate::tests::{position, TEST_CONFIG};
 865
 866     use super::CompletionContext;
 867
 868     fn check_expected_type_and_name(ra_fixture: &str, expect: Expect) {
 869         let (db, pos) = position(ra_fixture);
 870         let config = TEST_CONFIG;
 871         let completion_context = CompletionContext::new(&db, pos, &config).unwrap();
 872
 873         let ty = completion_context
 874             .expected_type
 875             .map(|t| t.display_test(&db).to_string())
 876             .unwrap_or("?".to_owned());
 877
 878         let name = completion_context
 879             .expected_name
 880             .map_or_else(|| "?".to_owned(), |name| name.to_string());
 881
 882         expect.assert_eq(&format!("ty: {}, name: {}", ty, name));
 883     }
 884
 885     #[test]
 886     fn expected_type_let_without_leading_char() {
 887         cov_mark::check!(expected_type_let_without_leading_char);
 888         check_expected_type_and_name(
 889             r#"
 890 fn foo() {
 891     let x: u32 = $0;
 892 }
 893 "#,
 894             expect![[r#"ty: u32, name: x"#]],
 895         );
 896     }
 897
 898     #[test]
 899     fn expected_type_let_with_leading_char() {
 900         cov_mark::check!(expected_type_let_with_leading_char);
 901         check_expected_type_and_name(
 902             r#"
 903 fn foo() {
 904     let x: u32 = c$0;
 905 }
 906 "#,
 907             expect![[r#"ty: u32, name: x"#]],
 908         );
 909     }
 910
 911     #[test]
 912     fn expected_type_let_pat() {
 913         check_expected_type_and_name(
 914             r#"
 915 fn foo() {
 916     let x$0 = 0u32;
 917 }
 918 "#,
 919             expect![[r#"ty: u32, name: ?"#]],
 920         );
 921         check_expected_type_and_name(
 922             r#"
 923 fn foo() {
 924     let $0 = 0u32;
 925 }
 926 "#,
 927             expect![[r#"ty: u32, name: ?"#]],
 928         );
 929     }
 930
 931     #[test]
 932     fn expected_type_fn_param() {
 933         cov_mark::check!(expected_type_fn_param);
 934         check_expected_type_and_name(
 935             r#"
 936 fn foo() { bar($0); }
 937 fn bar(x: u32) {}
 938 "#,
 939             expect![[r#"ty: u32, name: x"#]],
 940         );
 941         check_expected_type_and_name(
 942             r#"
 943 fn foo() { bar(c$0); }
 944 fn bar(x: u32) {}
 945 "#,
 946             expect![[r#"ty: u32, name: x"#]],
 947         );
 948     }
 949
 950     #[test]
 951     fn expected_type_fn_param_ref() {
 952         cov_mark::check!(expected_type_fn_param_ref);
 953         check_expected_type_and_name(
 954             r#"
 955 fn foo() { bar(&$0); }
 956 fn bar(x: &u32) {}
 957 "#,
 958             expect![[r#"ty: u32, name: x"#]],
 959         );
 960         check_expected_type_and_name(
 961             r#"
 962 fn foo() { bar(&mut $0); }
 963 fn bar(x: &mut u32) {}
 964 "#,
 965             expect![[r#"ty: u32, name: x"#]],
 966         );
 967         check_expected_type_and_name(
 968             r#"
 969 fn foo() { bar(&c$0); }
 970 fn bar(x: &u32) {}
 971         "#,
 972             expect![[r#"ty: u32, name: x"#]],
 973         );
 974     }
 975
 976     #[test]
 977     fn expected_type_struct_field_without_leading_char() {
 978         cov_mark::check!(expected_type_struct_field_without_leading_char);
 979         check_expected_type_and_name(
 980             r#"
 981 struct Foo { a: u32 }
 982 fn foo() {
 983     Foo { a: $0 };
 984 }
 985 "#,
 986             expect![[r#"ty: u32, name: a"#]],
 987         )
 988     }
 989
 990     #[test]
 991     fn expected_type_generic_struct_field() {
 992         check_expected_type_and_name(
 993             r#"
 994 struct Foo<T> { a: T }
 995 fn foo() -> Foo<u32> {
 996     Foo { a: $0 }
 997 }
 998 "#,
 999             expect![[r#"ty: u32, name: a"#]],
1000         )
1001     }
1002
1003     #[test]
1004     fn expected_type_struct_field_with_leading_char() {
1005         cov_mark::check!(expected_type_struct_field_with_leading_char);
1006         check_expected_type_and_name(
1007             r#"
1008 struct Foo { a: u32 }
1009 fn foo() {
1010     Foo { a: c$0 };
1011 }
1012 "#,
1013             expect![[r#"ty: u32, name: a"#]],
1014         );
1015     }
1016
1017     #[test]
1018     fn expected_type_match_arm_without_leading_char() {
1019         cov_mark::check!(expected_type_match_arm_without_leading_char);
1020         check_expected_type_and_name(
1021             r#"
1022 enum E { X }
1023 fn foo() {
1024    match E::X { $0 }
1025 }
1026 "#,
1027             expect![[r#"ty: E, name: ?"#]],
1028         );
1029     }
1030
1031     #[test]
1032     fn expected_type_match_arm_with_leading_char() {
1033         cov_mark::check!(expected_type_match_arm_with_leading_char);
1034         check_expected_type_and_name(
1035             r#"
1036 enum E { X }
1037 fn foo() {
1038    match E::X { c$0 }
1039 }
1040 "#,
1041             expect![[r#"ty: E, name: ?"#]],
1042         );
1043     }
1044
1045     #[test]
1046     fn expected_type_if_let_without_leading_char() {
1047         cov_mark::check!(expected_type_if_let_without_leading_char);
1048         check_expected_type_and_name(
1049             r#"
1050 enum Foo { Bar, Baz, Quux }
1051
1052 fn foo() {
1053     let f = Foo::Quux;
1054     if let $0 = f { }
1055 }
1056 "#,
1057             expect![[r#"ty: Foo, name: ?"#]],
1058         )
1059     }
1060
1061     #[test]
1062     fn expected_type_if_let_with_leading_char() {
1063         cov_mark::check!(expected_type_if_let_with_leading_char);
1064         check_expected_type_and_name(
1065             r#"
1066 enum Foo { Bar, Baz, Quux }
1067
1068 fn foo() {
1069     let f = Foo::Quux;
1070     if let c$0 = f { }
1071 }
1072 "#,
1073             expect![[r#"ty: Foo, name: ?"#]],
1074         )
1075     }
1076
1077     #[test]
1078     fn expected_type_fn_ret_without_leading_char() {
1079         cov_mark::check!(expected_type_fn_ret_without_leading_char);
1080         check_expected_type_and_name(
1081             r#"
1082 fn foo() -> u32 {
1083     $0
1084 }
1085 "#,
1086             expect![[r#"ty: u32, name: ?"#]],
1087         )
1088     }
1089
1090     #[test]
1091     fn expected_type_fn_ret_with_leading_char() {
1092         cov_mark::check!(expected_type_fn_ret_with_leading_char);
1093         check_expected_type_and_name(
1094             r#"
1095 fn foo() -> u32 {
1096     c$0
1097 }
1098 "#,
1099             expect![[r#"ty: u32, name: ?"#]],
1100         )
1101     }
1102
1103     #[test]
1104     fn expected_type_fn_ret_fn_ref_fully_typed() {
1105         check_expected_type_and_name(
1106             r#"
1107 fn foo() -> u32 {
1108     foo$0
1109 }
1110 "#,
1111             expect![[r#"ty: u32, name: ?"#]],
1112         )
1113     }
1114
1115     #[test]
1116     fn expected_type_closure_param_return() {
1117         // FIXME: make this work with `|| $0`
1118         check_expected_type_and_name(
1119             r#"
1120 //- minicore: fn
1121 fn foo() {
1122     bar(|| a$0);
1123 }
1124
1125 fn bar(f: impl FnOnce() -> u32) {}
1126 "#,
1127             expect![[r#"ty: u32, name: ?"#]],
1128         );
1129     }
1130
1131     #[test]
1132     fn expected_type_generic_function() {
1133         check_expected_type_and_name(
1134             r#"
1135 fn foo() {
1136     bar::<u32>($0);
1137 }
1138
1139 fn bar<T>(t: T) {}
1140 "#,
1141             expect![[r#"ty: u32, name: t"#]],
1142         );
1143     }
1144
1145     #[test]
1146     fn expected_type_generic_method() {
1147         check_expected_type_and_name(
1148             r#"
1149 fn foo() {
1150     S(1u32).bar($0);
1151 }
1152
1153 struct S<T>(T);
1154 impl<T> S<T> {
1155     fn bar(self, t: T) {}
1156 }
1157 "#,
1158             expect![[r#"ty: u32, name: t"#]],
1159         );
1160     }
1161
1162     #[test]
1163     fn expected_type_functional_update() {
1164         cov_mark::check!(expected_type_struct_func_update);
1165         check_expected_type_and_name(
1166             r#"
1167 struct Foo { field: u32 }
1168 fn foo() {
1169     Foo {
1170         ..$0
1171     }
1172 }
1173 "#,
1174             expect![[r#"ty: Foo, name: ?"#]],
1175         );
1176     }
1177 }