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 }
  62
  63 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  64 pub(crate) enum CallKind {
  65     Pat,
  66     Mac,
  67     Expr,
  68 }
  69
  70 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  71 pub(crate) enum ParamKind {
  72     Function,
  73     Closure,
  74 }
  75 /// `CompletionContext` is created early during completion to figure out, where
  76 /// exactly is the cursor, syntax-wise.
  77 #[derive(Debug)]
  78 pub(crate) struct CompletionContext<'a> {
  79     pub(super) sema: Semantics<'a, RootDatabase>,
  80     pub(super) scope: SemanticsScope<'a>,
  81     pub(super) db: &'a RootDatabase,
  82     pub(super) config: &'a CompletionConfig,
  83     pub(super) position: FilePosition,
  84     /// The token before the cursor, in the original file.
  85     pub(super) original_token: SyntaxToken,
  86     /// The token before the cursor, in the macro-expanded file.
  87     pub(super) token: SyntaxToken,
  88     pub(super) krate: Option<hir::Crate>,
  89     pub(super) expected_name: Option<NameOrNameRef>,
  90     pub(super) expected_type: Option<Type>,
  91
  92     /// The parent function of the cursor position if it exists.
  93     pub(super) function_def: Option<ast::Fn>,
  94     /// The parent impl of the cursor position if it exists.
  95     pub(super) impl_def: Option<ast::Impl>,
  96     pub(super) name_syntax: Option<ast::NameLike>,
  97
  98     // potentially set if we are completing a lifetime
  99     pub(super) lifetime_param_syntax: Option<ast::LifetimeParam>,
 100     pub(super) lifetime_allowed: bool,
 101     pub(super) is_label_ref: bool,
 102
 103     pub(super) completion_location: Option<ImmediateLocation>,
 104     pub(super) prev_sibling: Option<ImmediatePrevSibling>,
 105     pub(super) attribute_under_caret: Option<ast::Attr>,
 106     pub(super) previous_token: Option<SyntaxToken>,
 107
 108     pub(super) pattern_ctx: Option<PatternContext>,
 109     pub(super) path_context: Option<PathCompletionContext>,
 110     pub(super) locals: Vec<(String, Local)>,
 111
 112     pub(super) incomplete_let: bool,
 113
 114     no_completion_required: bool,
 115 }
 116
 117 impl<'a> CompletionContext<'a> {
 118     pub(super) fn new(
 119         db: &'a RootDatabase,
 120         position: FilePosition,
 121         config: &'a CompletionConfig,
 122     ) -> Option<CompletionContext<'a>> {
 123         let sema = Semantics::new(db);
 124
 125         let original_file = sema.parse(position.file_id);
 126
 127         // Insert a fake ident to get a valid parse tree. We will use this file
 128         // to determine context, though the original_file will be used for
 129         // actual completion.
 130         let file_with_fake_ident = {
 131             let parse = db.parse(position.file_id);
 132             let edit = Indel::insert(position.offset, "intellijRulezz".to_string());
 133             parse.reparse(&edit).tree()
 134         };
 135         let fake_ident_token =
 136             file_with_fake_ident.syntax().token_at_offset(position.offset).right_biased().unwrap();
 137
 138         let krate = sema.to_module_def(position.file_id).map(|m| m.krate());
 139         let original_token =
 140             original_file.syntax().token_at_offset(position.offset).left_biased()?;
 141         let token = sema.descend_into_macros(original_token.clone());
 142         let scope = sema.scope_at_offset(&token, position.offset);
 143         let mut locals = vec![];
 144         scope.process_all_names(&mut |name, scope| {
 145             if let ScopeDef::Local(local) = scope {
 146                 locals.push((name.to_string(), local));
 147             }
 148         });
 149         let mut ctx = CompletionContext {
 150             sema,
 151             scope,
 152             db,
 153             config,
 154             position,
 155             original_token,
 156             token,
 157             krate,
 158             expected_name: None,
 159             expected_type: None,
 160             function_def: None,
 161             impl_def: None,
 162             name_syntax: None,
 163             lifetime_param_syntax: None,
 164             lifetime_allowed: false,
 165             is_label_ref: false,
 166             pattern_ctx: None,
 167             completion_location: None,
 168             prev_sibling: None,
 169             attribute_under_caret: None,
 170             previous_token: None,
 171             path_context: None,
 172             locals,
 173             incomplete_let: false,
 174             no_completion_required: false,
 175         };
 176         ctx.expand_and_fill(
 177             original_file.syntax().clone(),
 178             file_with_fake_ident.syntax().clone(),
 179             position.offset,
 180             fake_ident_token,
 181         );
 182         Some(ctx)
 183     }
 184
 185     fn expand_and_fill(
 186         &mut self,
 187         mut original_file: SyntaxNode,
 188         mut speculative_file: SyntaxNode,
 189         mut offset: TextSize,
 190         mut fake_ident_token: SyntaxToken,
 191     ) {
 192         loop {
 193             // Expand attributes
 194             if let (Some(actual_item), Some(item_with_fake_ident)) = (
 195                 find_node_at_offset::<ast::Item>(&original_file, offset),
 196                 find_node_at_offset::<ast::Item>(&speculative_file, offset),
 197             ) {
 198                 match (
 199                     self.sema.expand_attr_macro(&actual_item),
 200                     self.sema.speculative_expand_attr_macro(
 201                         &actual_item,
 202                         &item_with_fake_ident,
 203                         fake_ident_token.clone(),
 204                     ),
 205                 ) {
 206                     (Some(actual_expansion), Some(speculative_expansion)) => {
 207                         let new_offset = speculative_expansion.1.text_range().start();
 208                         if new_offset > actual_expansion.text_range().end() {
 209                             break;
 210                         }
 211                         original_file = actual_expansion;
 212                         speculative_file = speculative_expansion.0;
 213                         fake_ident_token = speculative_expansion.1;
 214                         offset = new_offset;
 215                         continue;
 216                     }
 217                     (None, None) => (),
 218                     _ => break,
 219                 }
 220             }
 221
 222             // Expand fn-like macro calls
 223             if let (Some(actual_macro_call), Some(macro_call_with_fake_ident)) = (
 224                 find_node_at_offset::<ast::MacroCall>(&original_file, offset),
 225                 find_node_at_offset::<ast::MacroCall>(&speculative_file, offset),
 226             ) {
 227                 let mac_call_path0 = actual_macro_call.path().as_ref().map(|s| s.syntax().text());
 228                 let mac_call_path1 =
 229                     macro_call_with_fake_ident.path().as_ref().map(|s| s.syntax().text());
 230                 if mac_call_path0 != mac_call_path1 {
 231                     break;
 232                 }
 233                 let speculative_args = match macro_call_with_fake_ident.token_tree() {
 234                     Some(tt) => tt,
 235                     None => break,
 236                 };
 237
 238                 if let (Some(actual_expansion), Some(speculative_expansion)) = (
 239                     self.sema.expand(&actual_macro_call),
 240                     self.sema.speculative_expand(
 241                         &actual_macro_call,
 242                         &speculative_args,
 243                         fake_ident_token,
 244                     ),
 245                 ) {
 246                     let new_offset = speculative_expansion.1.text_range().start();
 247                     if new_offset > actual_expansion.text_range().end() {
 248                         break;
 249                     }
 250                     original_file = actual_expansion;
 251                     speculative_file = speculative_expansion.0;
 252                     fake_ident_token = speculative_expansion.1;
 253                     offset = new_offset;
 254                 } else {
 255                     break;
 256                 }
 257             } else {
 258                 break;
 259             }
 260         }
 261
 262         self.fill(&original_file, speculative_file, offset);
 263     }
 264
 265     /// Checks whether completions in that particular case don't make much sense.
 266     /// Examples:
 267     /// - `fn $0` -- we expect function name, it's unlikely that "hint" will be helpful.
 268     ///   Exception for this case is `impl Trait for Foo`, where we would like to hint trait method names.
 269     /// - `for _ i$0` -- obviously, it'll be "in" keyword.
 270     pub(crate) fn no_completion_required(&self) -> bool {
 271         self.no_completion_required
 272     }
 273
 274     /// The range of the identifier that is being completed.
 275     pub(crate) fn source_range(&self) -> TextRange {
 276         // check kind of macro-expanded token, but use range of original token
 277         let kind = self.token.kind();
 278         if kind == IDENT || kind == LIFETIME_IDENT || kind == UNDERSCORE || kind.is_keyword() {
 279             cov_mark::hit!(completes_if_prefix_is_keyword);
 280             self.original_token.text_range()
 281         } else if kind == CHAR {
 282             // assume we are completing a lifetime but the user has only typed the '
 283             cov_mark::hit!(completes_if_lifetime_without_idents);
 284             TextRange::at(self.original_token.text_range().start(), TextSize::from(1))
 285         } else {
 286             TextRange::empty(self.position.offset)
 287         }
 288     }
 289
 290     pub(crate) fn previous_token_is(&self, kind: SyntaxKind) -> bool {
 291         self.previous_token.as_ref().map_or(false, |tok| tok.kind() == kind)
 292     }
 293
 294     pub(crate) fn expects_assoc_item(&self) -> bool {
 295         matches!(self.completion_location, Some(ImmediateLocation::Trait | ImmediateLocation::Impl))
 296     }
 297
 298     pub(crate) fn has_dot_receiver(&self) -> bool {
 299         matches!(
 300             &self.completion_location,
 301             Some(ImmediateLocation::FieldAccess { receiver, .. } | ImmediateLocation::MethodCall { receiver,.. })
 302                 if receiver.is_some()
 303         )
 304     }
 305
 306     pub(crate) fn dot_receiver(&self) -> Option<&ast::Expr> {
 307         match &self.completion_location {
 308             Some(
 309                 ImmediateLocation::MethodCall { receiver, .. }
 310                 | ImmediateLocation::FieldAccess { receiver, .. },
 311             ) => receiver.as_ref(),
 312             _ => None,
 313         }
 314     }
 315
 316     pub(crate) fn expects_non_trait_assoc_item(&self) -> bool {
 317         matches!(self.completion_location, Some(ImmediateLocation::Impl))
 318     }
 319
 320     pub(crate) fn expects_item(&self) -> bool {
 321         matches!(self.completion_location, Some(ImmediateLocation::ItemList))
 322     }
 323
 324     pub(crate) fn expects_generic_arg(&self) -> bool {
 325         matches!(self.completion_location, Some(ImmediateLocation::GenericArgList(_)))
 326     }
 327
 328     pub(crate) fn has_block_expr_parent(&self) -> bool {
 329         matches!(self.completion_location, Some(ImmediateLocation::StmtList))
 330     }
 331
 332     pub(crate) fn expects_ident_pat_or_ref_expr(&self) -> bool {
 333         matches!(
 334             self.completion_location,
 335             Some(ImmediateLocation::IdentPat | ImmediateLocation::RefExpr)
 336         )
 337     }
 338
 339     pub(crate) fn expect_field(&self) -> bool {
 340         matches!(
 341             self.completion_location,
 342             Some(ImmediateLocation::RecordField | ImmediateLocation::TupleField)
 343         )
 344     }
 345
 346     pub(crate) fn in_use_tree(&self) -> bool {
 347         matches!(
 348             self.completion_location,
 349             Some(ImmediateLocation::Use | ImmediateLocation::UseTree)
 350         )
 351     }
 352
 353     pub(crate) fn has_impl_or_trait_prev_sibling(&self) -> bool {
 354         matches!(
 355             self.prev_sibling,
 356             Some(ImmediatePrevSibling::ImplDefType | ImmediatePrevSibling::TraitDefName)
 357         )
 358     }
 359
 360     pub(crate) fn has_impl_prev_sibling(&self) -> bool {
 361         matches!(self.prev_sibling, Some(ImmediatePrevSibling::ImplDefType))
 362     }
 363
 364     pub(crate) fn has_visibility_prev_sibling(&self) -> bool {
 365         matches!(self.prev_sibling, Some(ImmediatePrevSibling::Visibility))
 366     }
 367
 368     pub(crate) fn after_if(&self) -> bool {
 369         matches!(self.prev_sibling, Some(ImmediatePrevSibling::IfExpr))
 370     }
 371
 372     pub(crate) fn is_path_disallowed(&self) -> bool {
 373         self.attribute_under_caret.is_some()
 374             || self.previous_token_is(T![unsafe])
 375             || matches!(
 376                 self.prev_sibling,
 377                 Some(ImmediatePrevSibling::Attribute | ImmediatePrevSibling::Visibility)
 378             )
 379             || matches!(
 380                 self.completion_location,
 381                 Some(
 382                     ImmediateLocation::Attribute(_)
 383                         | ImmediateLocation::ModDeclaration(_)
 384                         | ImmediateLocation::RecordPat(_)
 385                         | ImmediateLocation::RecordExpr(_)
 386                         | ImmediateLocation::Rename
 387                 )
 388             )
 389     }
 390
 391     pub(crate) fn expects_expression(&self) -> bool {
 392         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Expr), .. }))
 393     }
 394
 395     pub(crate) fn expects_type(&self) -> bool {
 396         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Type), .. }))
 397     }
 398
 399     pub(crate) fn path_call_kind(&self) -> Option<CallKind> {
 400         self.path_context.as_ref().and_then(|it| it.call_kind)
 401     }
 402
 403     pub(crate) fn is_trivial_path(&self) -> bool {
 404         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: true, .. }))
 405     }
 406
 407     pub(crate) fn is_non_trivial_path(&self) -> bool {
 408         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: false, .. }))
 409     }
 410
 411     pub(crate) fn path_qual(&self) -> Option<&ast::Path> {
 412         self.path_context.as_ref().and_then(|it| it.qualifier.as_ref())
 413     }
 414
 415     /// Checks if an item is visible and not `doc(hidden)` at the completion site.
 416     pub(crate) fn is_visible<I>(&self, item: &I) -> bool
 417     where
 418         I: hir::HasVisibility + hir::HasAttrs + hir::HasCrate + Copy,
 419     {
 420         self.is_visible_impl(&item.visibility(self.db), &item.attrs(self.db), item.krate(self.db))
 421     }
 422
 423     pub(crate) fn is_scope_def_hidden(&self, scope_def: &ScopeDef) -> bool {
 424         if let (Some(attrs), Some(krate)) = (scope_def.attrs(self.db), scope_def.krate(self.db)) {
 425             return self.is_doc_hidden(&attrs, krate);
 426         }
 427
 428         false
 429     }
 430
 431     pub(crate) fn is_item_hidden(&self, item: &hir::ItemInNs) -> bool {
 432         let attrs = item.attrs(self.db);
 433         let krate = item.krate(self.db);
 434         match (attrs, krate) {
 435             (Some(attrs), Some(krate)) => self.is_doc_hidden(&attrs, krate),
 436             _ => false,
 437         }
 438     }
 439
 440     pub(crate) fn is_immediately_after_macro_bang(&self) -> bool {
 441         self.token.kind() == BANG && self.token.parent().map_or(false, |it| it.kind() == MACRO_CALL)
 442     }
 443
 444     /// A version of [`SemanticsScope::process_all_names`] that filters out `#[doc(hidden)]` items.
 445     pub(crate) fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
 446         self.scope.process_all_names(&mut |name, def| {
 447             if self.is_scope_def_hidden(&def) {
 448                 return;
 449             }
 450
 451             f(name, def);
 452         })
 453     }
 454
 455     fn is_visible_impl(
 456         &self,
 457         vis: &hir::Visibility,
 458         attrs: &hir::Attrs,
 459         defining_crate: hir::Crate,
 460     ) -> bool {
 461         let module = match self.scope.module() {
 462             Some(it) => it,
 463             None => return false,
 464         };
 465         if !vis.is_visible_from(self.db, module.into()) {
 466             // If the definition location is editable, also show private items
 467             let root_file = defining_crate.root_file(self.db);
 468             let source_root_id = self.db.file_source_root(root_file);
 469             let is_editable = !self.db.source_root(source_root_id).is_library;
 470             return is_editable;
 471         }
 472
 473         !self.is_doc_hidden(attrs, defining_crate)
 474     }
 475
 476     fn is_doc_hidden(&self, attrs: &hir::Attrs, defining_crate: hir::Crate) -> bool {
 477         let module = match self.scope.module() {
 478             Some(it) => it,
 479             None => return true,
 480         };
 481         if module.krate() != defining_crate && attrs.has_doc_hidden() {
 482             // `doc(hidden)` items are only completed within the defining crate.
 483             return true;
 484         }
 485
 486         false
 487     }
 488
 489     fn fill_impl_def(&mut self) {
 490         self.impl_def = self
 491             .sema
 492             .token_ancestors_with_macros(self.token.clone())
 493             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 494             .find_map(ast::Impl::cast);
 495     }
 496
 497     fn expected_type_and_name(&self) -> (Option<Type>, Option<NameOrNameRef>) {
 498         let mut node = match self.token.parent() {
 499             Some(it) => it,
 500             None => return (None, None),
 501         };
 502         loop {
 503             break match_ast! {
 504                 match node {
 505                     ast::LetStmt(it) => {
 506                         cov_mark::hit!(expected_type_let_with_leading_char);
 507                         cov_mark::hit!(expected_type_let_without_leading_char);
 508                         let ty = it.pat()
 509                             .and_then(|pat| self.sema.type_of_pat(&pat))
 510                             .or_else(|| it.initializer().and_then(|it| self.sema.type_of_expr(&it)))
 511                             .map(TypeInfo::original);
 512                         let name = match it.pat() {
 513                             Some(ast::Pat::IdentPat(ident)) => ident.name().map(NameOrNameRef::Name),
 514                             Some(_) | None => None,
 515                         };
 516
 517                         (ty, name)
 518                     },
 519                     ast::ArgList(_it) => {
 520                         cov_mark::hit!(expected_type_fn_param);
 521                         ActiveParameter::at_token(
 522                             &self.sema,
 523                             self.token.clone(),
 524                         ).map(|ap| {
 525                             let name = ap.ident().map(NameOrNameRef::Name);
 526                             let ty = if has_ref(&self.token) {
 527                                 cov_mark::hit!(expected_type_fn_param_ref);
 528                                 ap.ty.remove_ref()
 529                             } else {
 530                                 Some(ap.ty)
 531                             };
 532                             (ty, name)
 533                         })
 534                         .unwrap_or((None, None))
 535                     },
 536                     ast::RecordExprFieldList(it) => {
 537                         // wouldn't try {} be nice...
 538                         (|| {
 539                             if self.token.kind() == T![..]
 540                                 || self.token.prev_token().map(|t| t.kind()) == Some(T![..])
 541                             {
 542                                 cov_mark::hit!(expected_type_struct_func_update);
 543                                 let record_expr = it.syntax().parent().and_then(ast::RecordExpr::cast)?;
 544                                 let ty = self.sema.type_of_expr(&record_expr.into())?;
 545                                 Some((
 546                                     Some(ty.original),
 547                                     None
 548                                 ))
 549                             } else {
 550                                 cov_mark::hit!(expected_type_struct_field_without_leading_char);
 551                                 let expr_field = self.token.prev_sibling_or_token()?
 552                                     .into_node()
 553                                     .and_then(ast::RecordExprField::cast)?;
 554                                 let (_, _, ty) = self.sema.resolve_record_field(&expr_field)?;
 555                                 Some((
 556                                     Some(ty),
 557                                     expr_field.field_name().map(NameOrNameRef::NameRef),
 558                                 ))
 559                             }
 560                         })().unwrap_or((None, None))
 561                     },
 562                     ast::RecordExprField(it) => {
 563                         cov_mark::hit!(expected_type_struct_field_with_leading_char);
 564                         (
 565                             it.expr().as_ref().and_then(|e| self.sema.type_of_expr(e)).map(TypeInfo::original),
 566                             it.field_name().map(NameOrNameRef::NameRef),
 567                         )
 568                     },
 569                     ast::MatchExpr(it) => {
 570                         cov_mark::hit!(expected_type_match_arm_without_leading_char);
 571                         let ty = it.expr().and_then(|e| self.sema.type_of_expr(&e)).map(TypeInfo::original);
 572                         (ty, None)
 573                     },
 574                     ast::IfExpr(it) => {
 575                         cov_mark::hit!(expected_type_if_let_without_leading_char);
 576                         let ty = it.condition()
 577                             .and_then(|cond| cond.expr())
 578                             .and_then(|e| self.sema.type_of_expr(&e))
 579                             .map(TypeInfo::original);
 580                         (ty, None)
 581                     },
 582                     ast::IdentPat(it) => {
 583                         cov_mark::hit!(expected_type_if_let_with_leading_char);
 584                         cov_mark::hit!(expected_type_match_arm_with_leading_char);
 585                         let ty = self.sema.type_of_pat(&ast::Pat::from(it)).map(TypeInfo::original);
 586                         (ty, None)
 587                     },
 588                     ast::Fn(it) => {
 589                         cov_mark::hit!(expected_type_fn_ret_with_leading_char);
 590                         cov_mark::hit!(expected_type_fn_ret_without_leading_char);
 591                         let def = self.sema.to_def(&it);
 592                         (def.map(|def| def.ret_type(self.db)), None)
 593                     },
 594                     ast::ClosureExpr(it) => {
 595                         let ty = self.sema.type_of_expr(&it.into());
 596                         ty.and_then(|ty| ty.original.as_callable(self.db))
 597                             .map(|c| (Some(c.return_type()), None))
 598                             .unwrap_or((None, None))
 599                     },
 600                     ast::Stmt(_it) => (None, None),
 601                     ast::Item(__) => (None, None),
 602                     _ => {
 603                         match node.parent() {
 604                             Some(n) => {
 605                                 node = n;
 606                                 continue;
 607                             },
 608                             None => (None, None),
 609                         }
 610                     },
 611                 }
 612             };
 613         }
 614     }
 615
 616     fn fill(
 617         &mut self,
 618         original_file: &SyntaxNode,
 619         file_with_fake_ident: SyntaxNode,
 620         offset: TextSize,
 621     ) {
 622         let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
 623         let syntax_element = NodeOrToken::Token(fake_ident_token);
 624         self.previous_token = previous_token(syntax_element.clone());
 625         self.attribute_under_caret = syntax_element.ancestors().find_map(ast::Attr::cast);
 626         self.no_completion_required = {
 627             let inside_impl_trait_block = inside_impl_trait_block(syntax_element.clone());
 628             let fn_is_prev = self.previous_token_is(T![fn]);
 629             let for_is_prev2 = for_is_prev2(syntax_element.clone());
 630             (fn_is_prev && !inside_impl_trait_block) || for_is_prev2
 631         };
 632
 633         self.incomplete_let =
 634             syntax_element.ancestors().take(6).find_map(ast::LetStmt::cast).map_or(false, |it| {
 635                 it.syntax().text_range().end() == syntax_element.text_range().end()
 636             });
 637
 638         let (expected_type, expected_name) = self.expected_type_and_name();
 639         self.expected_type = expected_type;
 640         self.expected_name = expected_name;
 641
 642         let name_like = match find_node_at_offset(&file_with_fake_ident, offset) {
 643             Some(it) => it,
 644             None => return,
 645         };
 646         self.completion_location =
 647             determine_location(&self.sema, original_file, offset, &name_like);
 648         self.prev_sibling = determine_prev_sibling(&name_like);
 649         self.name_syntax =
 650             find_node_at_offset(original_file, name_like.syntax().text_range().start());
 651         match name_like {
 652             ast::NameLike::Lifetime(lifetime) => {
 653                 self.classify_lifetime(original_file, lifetime, offset);
 654             }
 655             ast::NameLike::NameRef(name_ref) => {
 656                 self.classify_name_ref(original_file, name_ref);
 657             }
 658             ast::NameLike::Name(name) => {
 659                 self.classify_name(name);
 660             }
 661         }
 662     }
 663
 664     fn classify_lifetime(
 665         &mut self,
 666         original_file: &SyntaxNode,
 667         lifetime: ast::Lifetime,
 668         offset: TextSize,
 669     ) {
 670         if let Some(parent) = lifetime.syntax().parent() {
 671             if parent.kind() == ERROR {
 672                 return;
 673             }
 674
 675             match_ast! {
 676                 match parent {
 677                     ast::LifetimeParam(_it) => {
 678                         self.lifetime_allowed = true;
 679                         self.lifetime_param_syntax =
 680                             self.sema.find_node_at_offset_with_macros(original_file, offset);
 681                     },
 682                     ast::BreakExpr(_it) => self.is_label_ref = true,
 683                     ast::ContinueExpr(_it) => self.is_label_ref = true,
 684                     ast::Label(_it) => (),
 685                     _ => self.lifetime_allowed = true,
 686                 }
 687             }
 688         }
 689     }
 690
 691     fn classify_name(&mut self, name: ast::Name) {
 692         self.fill_impl_def();
 693
 694         if let Some(bind_pat) = name.syntax().parent().and_then(ast::IdentPat::cast) {
 695             let is_name_in_field_pat = bind_pat
 696                 .syntax()
 697                 .parent()
 698                 .and_then(ast::RecordPatField::cast)
 699                 .map_or(false, |pat_field| pat_field.name_ref().is_none());
 700             if is_name_in_field_pat {
 701                 return;
 702             }
 703             if bind_pat.is_simple_ident() {
 704                 let mut is_param = None;
 705                 let refutability = bind_pat
 706                     .syntax()
 707                     .ancestors()
 708                     .skip_while(|it| ast::Pat::can_cast(it.kind()))
 709                     .next()
 710                     .map_or(PatternRefutability::Irrefutable, |node| {
 711                         match_ast! {
 712                             match node {
 713                                 ast::LetStmt(__) => PatternRefutability::Irrefutable,
 714                                 ast::Param(param) => {
 715                                     let is_closure_param = param
 716                                         .syntax()
 717                                         .ancestors()
 718                                         .nth(2)
 719                                         .and_then(ast::ClosureExpr::cast)
 720                                         .is_some();
 721                                     is_param = Some(if is_closure_param {
 722                                         ParamKind::Closure
 723                                     } else {
 724                                         ParamKind::Function
 725                                     });
 726                                     PatternRefutability::Irrefutable
 727                                 },
 728                                 ast::MatchArm(__) => PatternRefutability::Refutable,
 729                                 ast::Condition(__) => PatternRefutability::Refutable,
 730                                 ast::ForExpr(__) => PatternRefutability::Irrefutable,
 731                                 _ => PatternRefutability::Irrefutable,
 732                             }
 733                         }
 734                     });
 735                 self.pattern_ctx = Some(PatternContext { refutability, is_param });
 736             }
 737         }
 738     }
 739
 740     fn classify_name_ref(&mut self, original_file: &SyntaxNode, name_ref: ast::NameRef) {
 741         self.fill_impl_def();
 742
 743         self.function_def = self
 744             .sema
 745             .token_ancestors_with_macros(self.token.clone())
 746             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 747             .find_map(ast::Fn::cast);
 748
 749         let parent = match name_ref.syntax().parent() {
 750             Some(it) => it,
 751             None => return,
 752         };
 753
 754         if let Some(segment) = ast::PathSegment::cast(parent) {
 755             let path_ctx = self.path_context.get_or_insert(PathCompletionContext {
 756                 call_kind: None,
 757                 is_trivial_path: false,
 758                 qualifier: None,
 759                 has_type_args: false,
 760                 can_be_stmt: false,
 761                 in_loop_body: false,
 762                 use_tree_parent: false,
 763                 kind: None,
 764             });
 765             path_ctx.in_loop_body = is_in_loop_body(name_ref.syntax());
 766             let path = segment.parent_path();
 767
 768             if let Some(p) = path.syntax().parent() {
 769                 path_ctx.call_kind = match_ast! {
 770                     match p {
 771                         ast::PathExpr(it) => it.syntax().parent().and_then(ast::CallExpr::cast).map(|_| CallKind::Expr),
 772                         ast::MacroCall(it) => it.excl_token().and(Some(CallKind::Mac)),
 773                         ast::TupleStructPat(_it) => Some(CallKind::Pat),
 774                         _ => None
 775                     }
 776                 };
 777             }
 778
 779             if let Some(parent) = path.syntax().parent() {
 780                 path_ctx.kind = match_ast! {
 781                     match parent {
 782                         ast::PathType(_it) => Some(PathKind::Type),
 783                         ast::PathExpr(_it) => Some(PathKind::Expr),
 784                         _ => None,
 785                     }
 786                 };
 787             }
 788             path_ctx.has_type_args = segment.generic_arg_list().is_some();
 789
 790             if let Some((path, use_tree_parent)) = path_or_use_tree_qualifier(&path) {
 791                 path_ctx.use_tree_parent = use_tree_parent;
 792                 path_ctx.qualifier = path
 793                     .segment()
 794                     .and_then(|it| {
 795                         find_node_with_range::<ast::PathSegment>(
 796                             original_file,
 797                             it.syntax().text_range(),
 798                         )
 799                     })
 800                     .map(|it| it.parent_path());
 801                 return;
 802             }
 803
 804             if let Some(segment) = path.segment() {
 805                 if segment.coloncolon_token().is_some() {
 806                     return;
 807                 }
 808             }
 809
 810             path_ctx.is_trivial_path = true;
 811
 812             // Find either enclosing expr statement (thing with `;`) or a
 813             // block. If block, check that we are the last expr.
 814             path_ctx.can_be_stmt = name_ref
 815                 .syntax()
 816                 .ancestors()
 817                 .find_map(|node| {
 818                     if let Some(stmt) = ast::ExprStmt::cast(node.clone()) {
 819                         return Some(stmt.syntax().text_range() == name_ref.syntax().text_range());
 820                     }
 821                     if let Some(stmt_list) = ast::StmtList::cast(node) {
 822                         return Some(
 823                             stmt_list.tail_expr().map(|e| e.syntax().text_range())
 824                                 == Some(name_ref.syntax().text_range()),
 825                         );
 826                     }
 827                     None
 828                 })
 829                 .unwrap_or(false);
 830         }
 831     }
 832 }
 833
 834 fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Option<N> {
 835     syntax.covering_element(range).ancestors().find_map(N::cast)
 836 }
 837
 838 fn path_or_use_tree_qualifier(path: &ast::Path) -> Option<(ast::Path, bool)> {
 839     if let Some(qual) = path.qualifier() {
 840         return Some((qual, false));
 841     }
 842     let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
 843     let use_tree = use_tree_list.syntax().parent().and_then(ast::UseTree::cast)?;
 844     use_tree.path().zip(Some(true))
 845 }
 846
 847 fn has_ref(token: &SyntaxToken) -> bool {
 848     let mut token = token.clone();
 849     for skip in [WHITESPACE, IDENT, T![mut]] {
 850         if token.kind() == skip {
 851             token = match token.prev_token() {
 852                 Some(it) => it,
 853                 None => return false,
 854             }
 855         }
 856     }
 857     token.kind() == T![&]
 858 }
 859
 860 #[cfg(test)]
 861 mod tests {
 862     use expect_test::{expect, Expect};
 863     use hir::HirDisplay;
 864
 865     use crate::tests::{position, TEST_CONFIG};
 866
 867     use super::CompletionContext;
 868
 869     fn check_expected_type_and_name(ra_fixture: &str, expect: Expect) {
 870         let (db, pos) = position(ra_fixture);
 871         let config = TEST_CONFIG;
 872         let completion_context = CompletionContext::new(&db, pos, &config).unwrap();
 873
 874         let ty = completion_context
 875             .expected_type
 876             .map(|t| t.display_test(&db).to_string())
 877             .unwrap_or("?".to_owned());
 878
 879         let name = completion_context
 880             .expected_name
 881             .map_or_else(|| "?".to_owned(), |name| name.to_string());
 882
 883         expect.assert_eq(&format!("ty: {}, name: {}", ty, name));
 884     }
 885
 886     #[test]
 887     fn expected_type_let_without_leading_char() {
 888         cov_mark::check!(expected_type_let_without_leading_char);
 889         check_expected_type_and_name(
 890             r#"
 891 fn foo() {
 892     let x: u32 = $0;
 893 }
 894 "#,
 895             expect![[r#"ty: u32, name: x"#]],
 896         );
 897     }
 898
 899     #[test]
 900     fn expected_type_let_with_leading_char() {
 901         cov_mark::check!(expected_type_let_with_leading_char);
 902         check_expected_type_and_name(
 903             r#"
 904 fn foo() {
 905     let x: u32 = c$0;
 906 }
 907 "#,
 908             expect![[r#"ty: u32, name: x"#]],
 909         );
 910     }
 911
 912     #[test]
 913     fn expected_type_let_pat() {
 914         check_expected_type_and_name(
 915             r#"
 916 fn foo() {
 917     let x$0 = 0u32;
 918 }
 919 "#,
 920             expect![[r#"ty: u32, name: ?"#]],
 921         );
 922         check_expected_type_and_name(
 923             r#"
 924 fn foo() {
 925     let $0 = 0u32;
 926 }
 927 "#,
 928             expect![[r#"ty: u32, name: ?"#]],
 929         );
 930     }
 931
 932     #[test]
 933     fn expected_type_fn_param() {
 934         cov_mark::check!(expected_type_fn_param);
 935         check_expected_type_and_name(
 936             r#"
 937 fn foo() { bar($0); }
 938 fn bar(x: u32) {}
 939 "#,
 940             expect![[r#"ty: u32, name: x"#]],
 941         );
 942         check_expected_type_and_name(
 943             r#"
 944 fn foo() { bar(c$0); }
 945 fn bar(x: u32) {}
 946 "#,
 947             expect![[r#"ty: u32, name: x"#]],
 948         );
 949     }
 950
 951     #[test]
 952     fn expected_type_fn_param_ref() {
 953         cov_mark::check!(expected_type_fn_param_ref);
 954         check_expected_type_and_name(
 955             r#"
 956 fn foo() { bar(&$0); }
 957 fn bar(x: &u32) {}
 958 "#,
 959             expect![[r#"ty: u32, name: x"#]],
 960         );
 961         check_expected_type_and_name(
 962             r#"
 963 fn foo() { bar(&mut $0); }
 964 fn bar(x: &mut u32) {}
 965 "#,
 966             expect![[r#"ty: u32, name: x"#]],
 967         );
 968         check_expected_type_and_name(
 969             r#"
 970 fn foo() { bar(&c$0); }
 971 fn bar(x: &u32) {}
 972         "#,
 973             expect![[r#"ty: u32, name: x"#]],
 974         );
 975     }
 976
 977     #[test]
 978     fn expected_type_struct_field_without_leading_char() {
 979         cov_mark::check!(expected_type_struct_field_without_leading_char);
 980         check_expected_type_and_name(
 981             r#"
 982 struct Foo { a: u32 }
 983 fn foo() {
 984     Foo { a: $0 };
 985 }
 986 "#,
 987             expect![[r#"ty: u32, name: a"#]],
 988         )
 989     }
 990
 991     #[test]
 992     fn expected_type_generic_struct_field() {
 993         check_expected_type_and_name(
 994             r#"
 995 struct Foo<T> { a: T }
 996 fn foo() -> Foo<u32> {
 997     Foo { a: $0 }
 998 }
 999 "#,
1000             expect![[r#"ty: u32, name: a"#]],
1001         )
1002     }
1003
1004     #[test]
1005     fn expected_type_struct_field_with_leading_char() {
1006         cov_mark::check!(expected_type_struct_field_with_leading_char);
1007         check_expected_type_and_name(
1008             r#"
1009 struct Foo { a: u32 }
1010 fn foo() {
1011     Foo { a: c$0 };
1012 }
1013 "#,
1014             expect![[r#"ty: u32, name: a"#]],
1015         );
1016     }
1017
1018     #[test]
1019     fn expected_type_match_arm_without_leading_char() {
1020         cov_mark::check!(expected_type_match_arm_without_leading_char);
1021         check_expected_type_and_name(
1022             r#"
1023 enum E { X }
1024 fn foo() {
1025    match E::X { $0 }
1026 }
1027 "#,
1028             expect![[r#"ty: E, name: ?"#]],
1029         );
1030     }
1031
1032     #[test]
1033     fn expected_type_match_arm_with_leading_char() {
1034         cov_mark::check!(expected_type_match_arm_with_leading_char);
1035         check_expected_type_and_name(
1036             r#"
1037 enum E { X }
1038 fn foo() {
1039    match E::X { c$0 }
1040 }
1041 "#,
1042             expect![[r#"ty: E, name: ?"#]],
1043         );
1044     }
1045
1046     #[test]
1047     fn expected_type_if_let_without_leading_char() {
1048         cov_mark::check!(expected_type_if_let_without_leading_char);
1049         check_expected_type_and_name(
1050             r#"
1051 enum Foo { Bar, Baz, Quux }
1052
1053 fn foo() {
1054     let f = Foo::Quux;
1055     if let $0 = f { }
1056 }
1057 "#,
1058             expect![[r#"ty: Foo, name: ?"#]],
1059         )
1060     }
1061
1062     #[test]
1063     fn expected_type_if_let_with_leading_char() {
1064         cov_mark::check!(expected_type_if_let_with_leading_char);
1065         check_expected_type_and_name(
1066             r#"
1067 enum Foo { Bar, Baz, Quux }
1068
1069 fn foo() {
1070     let f = Foo::Quux;
1071     if let c$0 = f { }
1072 }
1073 "#,
1074             expect![[r#"ty: Foo, name: ?"#]],
1075         )
1076     }
1077
1078     #[test]
1079     fn expected_type_fn_ret_without_leading_char() {
1080         cov_mark::check!(expected_type_fn_ret_without_leading_char);
1081         check_expected_type_and_name(
1082             r#"
1083 fn foo() -> u32 {
1084     $0
1085 }
1086 "#,
1087             expect![[r#"ty: u32, name: ?"#]],
1088         )
1089     }
1090
1091     #[test]
1092     fn expected_type_fn_ret_with_leading_char() {
1093         cov_mark::check!(expected_type_fn_ret_with_leading_char);
1094         check_expected_type_and_name(
1095             r#"
1096 fn foo() -> u32 {
1097     c$0
1098 }
1099 "#,
1100             expect![[r#"ty: u32, name: ?"#]],
1101         )
1102     }
1103
1104     #[test]
1105     fn expected_type_fn_ret_fn_ref_fully_typed() {
1106         check_expected_type_and_name(
1107             r#"
1108 fn foo() -> u32 {
1109     foo$0
1110 }
1111 "#,
1112             expect![[r#"ty: u32, name: ?"#]],
1113         )
1114     }
1115
1116     #[test]
1117     fn expected_type_closure_param_return() {
1118         // FIXME: make this work with `|| $0`
1119         check_expected_type_and_name(
1120             r#"
1121 //- minicore: fn
1122 fn foo() {
1123     bar(|| a$0);
1124 }
1125
1126 fn bar(f: impl FnOnce() -> u32) {}
1127 "#,
1128             expect![[r#"ty: u32, name: ?"#]],
1129         );
1130     }
1131
1132     #[test]
1133     fn expected_type_generic_function() {
1134         check_expected_type_and_name(
1135             r#"
1136 fn foo() {
1137     bar::<u32>($0);
1138 }
1139
1140 fn bar<T>(t: T) {}
1141 "#,
1142             expect![[r#"ty: u32, name: t"#]],
1143         );
1144     }
1145
1146     #[test]
1147     fn expected_type_generic_method() {
1148         check_expected_type_and_name(
1149             r#"
1150 fn foo() {
1151     S(1u32).bar($0);
1152 }
1153
1154 struct S<T>(T);
1155 impl<T> S<T> {
1156     fn bar(self, t: T) {}
1157 }
1158 "#,
1159             expect![[r#"ty: u32, name: t"#]],
1160         );
1161     }
1162
1163     #[test]
1164     fn expected_type_functional_update() {
1165         cov_mark::check!(expected_type_struct_func_update);
1166         check_expected_type_and_name(
1167             r#"
1168 struct Foo { field: u32 }
1169 fn foo() {
1170     Foo {
1171         ..$0
1172     }
1173 }
1174 "#,
1175             expect![[r#"ty: Foo, name: ?"#]],
1176         );
1177     }
1178 }