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     active_parameter::ActiveParameter,
   7     base_db::{FilePosition, SourceDatabase},
   8     helpers::FamousDefs,
   9     RootDatabase,
  10 };
  11 use syntax::{
  12     algo::find_node_at_offset,
  13     ast::{self, HasName, NameOrNameRef},
  14     match_ast, AstNode, NodeOrToken,
  15     SyntaxKind::{self, *},
  16     SyntaxNode, SyntaxToken, TextRange, TextSize, T,
  17 };
  18 use text_edit::Indel;
  19
  20 use crate::{
  21     patterns::{
  22         determine_location, determine_prev_sibling, for_is_prev2, inside_impl_trait_block,
  23         is_in_loop_body, previous_token, ImmediateLocation, ImmediatePrevSibling,
  24     },
  25     CompletionConfig,
  26 };
  27
  28 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  29 pub(crate) enum PatternRefutability {
  30     Refutable,
  31     Irrefutable,
  32 }
  33
  34 #[derive(Copy, Clone, Debug)]
  35 pub(super) enum PathKind {
  36     Expr,
  37     Type,
  38     Attr,
  39     Mac,
  40     Pat,
  41     Vis { has_in_token: bool },
  42     Use,
  43 }
  44
  45 #[derive(Debug)]
  46 pub(crate) struct PathCompletionContext {
  47     /// If this is a call with () already there
  48     has_call_parens: bool,
  49     /// A single-indent path, like `foo`. `::foo` should not be considered a trivial path.
  50     pub(super) is_trivial_path: bool,
  51     /// If not a trivial path, the prefix (qualifier).
  52     pub(super) qualifier: Option<ast::Path>,
  53     #[allow(dead_code)]
  54     /// If not a trivial path, the suffix (parent).
  55     pub(super) parent: Option<ast::Path>,
  56     /// Whether the qualifier comes from a use tree parent or not
  57     pub(super) use_tree_parent: bool,
  58     pub(super) kind: Option<PathKind>,
  59     /// Whether the path segment has type args or not.
  60     pub(super) has_type_args: bool,
  61     /// `true` if we are a statement or a last expr in the block.
  62     pub(super) can_be_stmt: bool,
  63     pub(super) in_loop_body: bool,
  64 }
  65
  66 #[derive(Debug)]
  67 pub(super) struct PatternContext {
  68     pub(super) refutability: PatternRefutability,
  69     pub(super) is_param: Option<ParamKind>,
  70     pub(super) has_type_ascription: bool,
  71 }
  72
  73 #[derive(Debug)]
  74 pub(super) enum LifetimeContext {
  75     LifetimeParam(Option<ast::LifetimeParam>),
  76     Lifetime,
  77     LabelRef,
  78     LabelDef,
  79 }
  80
  81 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  82 pub(crate) enum ParamKind {
  83     Function,
  84     Closure,
  85 }
  86 /// `CompletionContext` is created early during completion to figure out, where
  87 /// exactly is the cursor, syntax-wise.
  88 #[derive(Debug)]
  89 pub(crate) struct CompletionContext<'a> {
  90     pub(super) sema: Semantics<'a, RootDatabase>,
  91     pub(super) scope: SemanticsScope<'a>,
  92     pub(super) db: &'a RootDatabase,
  93     pub(super) config: &'a CompletionConfig,
  94     pub(super) position: FilePosition,
  95     /// The token before the cursor, in the original file.
  96     pub(super) original_token: SyntaxToken,
  97     /// The token before the cursor, in the macro-expanded file.
  98     pub(super) token: SyntaxToken,
  99     /// The crate of the current file.
 100     pub(super) krate: Option<hir::Crate>,
 101     pub(super) expected_name: Option<NameOrNameRef>,
 102     pub(super) expected_type: Option<Type>,
 103
 104     /// The parent function of the cursor position if it exists.
 105     pub(super) function_def: Option<ast::Fn>,
 106     /// The parent impl of the cursor position if it exists.
 107     pub(super) impl_def: Option<ast::Impl>,
 108     /// The NameLike under the cursor in the original file if it exists.
 109     pub(super) name_syntax: Option<ast::NameLike>,
 110     pub(super) incomplete_let: bool,
 111
 112     pub(super) completion_location: Option<ImmediateLocation>,
 113     pub(super) prev_sibling: Option<ImmediatePrevSibling>,
 114     pub(super) attribute_under_caret: Option<ast::Attr>,
 115     pub(super) previous_token: Option<SyntaxToken>,
 116
 117     pub(super) lifetime_ctx: Option<LifetimeContext>,
 118     pub(super) pattern_ctx: Option<PatternContext>,
 119     pub(super) path_context: Option<PathCompletionContext>,
 120     pub(super) locals: Vec<(Name, Local)>,
 121
 122     no_completion_required: bool,
 123 }
 124
 125 impl<'a> CompletionContext<'a> {
 126     /// Checks whether completions in that particular case don't make much sense.
 127     /// Examples:
 128     /// - `fn $0` -- we expect function name, it's unlikely that "hint" will be helpful.
 129     ///   Exception for this case is `impl Trait for Foo`, where we would like to hint trait method names.
 130     /// - `for _ i$0` -- obviously, it'll be "in" keyword.
 131     pub(crate) fn no_completion_required(&self) -> bool {
 132         self.no_completion_required
 133     }
 134
 135     /// The range of the identifier that is being completed.
 136     pub(crate) fn source_range(&self) -> TextRange {
 137         // check kind of macro-expanded token, but use range of original token
 138         let kind = self.token.kind();
 139         if kind == IDENT || kind == LIFETIME_IDENT || kind == UNDERSCORE || kind.is_keyword() {
 140             self.original_token.text_range()
 141         } else if kind == CHAR {
 142             // assume we are completing a lifetime but the user has only typed the '
 143             cov_mark::hit!(completes_if_lifetime_without_idents);
 144             TextRange::at(self.original_token.text_range().start(), TextSize::from(1))
 145         } else {
 146             TextRange::empty(self.position.offset)
 147         }
 148     }
 149
 150     pub(crate) fn previous_token_is(&self, kind: SyntaxKind) -> bool {
 151         self.previous_token.as_ref().map_or(false, |tok| tok.kind() == kind)
 152     }
 153
 154     pub(crate) fn famous_defs(&self) -> FamousDefs {
 155         FamousDefs(&self.sema, self.krate)
 156     }
 157
 158     pub(crate) fn dot_receiver(&self) -> Option<&ast::Expr> {
 159         match &self.completion_location {
 160             Some(
 161                 ImmediateLocation::MethodCall { receiver, .. }
 162                 | ImmediateLocation::FieldAccess { receiver, .. },
 163             ) => receiver.as_ref(),
 164             _ => None,
 165         }
 166     }
 167
 168     pub(crate) fn has_dot_receiver(&self) -> bool {
 169         matches!(
 170             &self.completion_location,
 171             Some(ImmediateLocation::FieldAccess { receiver, .. } | ImmediateLocation::MethodCall { receiver,.. })
 172                 if receiver.is_some()
 173         )
 174     }
 175
 176     pub(crate) fn expects_assoc_item(&self) -> bool {
 177         matches!(self.completion_location, Some(ImmediateLocation::Trait | ImmediateLocation::Impl))
 178     }
 179
 180     pub(crate) fn expects_variant(&self) -> bool {
 181         matches!(self.completion_location, Some(ImmediateLocation::Variant))
 182     }
 183
 184     pub(crate) fn expects_non_trait_assoc_item(&self) -> bool {
 185         matches!(self.completion_location, Some(ImmediateLocation::Impl))
 186     }
 187
 188     pub(crate) fn expects_item(&self) -> bool {
 189         matches!(self.completion_location, Some(ImmediateLocation::ItemList))
 190     }
 191
 192     pub(crate) fn expects_generic_arg(&self) -> bool {
 193         matches!(self.completion_location, Some(ImmediateLocation::GenericArgList(_)))
 194     }
 195
 196     pub(crate) fn has_block_expr_parent(&self) -> bool {
 197         matches!(self.completion_location, Some(ImmediateLocation::StmtList))
 198     }
 199
 200     pub(crate) fn expects_ident_pat_or_ref_expr(&self) -> bool {
 201         matches!(
 202             self.completion_location,
 203             Some(ImmediateLocation::IdentPat | ImmediateLocation::RefExpr)
 204         )
 205     }
 206
 207     pub(crate) fn expect_field(&self) -> bool {
 208         matches!(
 209             self.completion_location,
 210             Some(ImmediateLocation::RecordField | ImmediateLocation::TupleField)
 211         )
 212     }
 213
 214     pub(crate) fn has_impl_or_trait_prev_sibling(&self) -> bool {
 215         matches!(
 216             self.prev_sibling,
 217             Some(ImmediatePrevSibling::ImplDefType | ImmediatePrevSibling::TraitDefName)
 218         )
 219     }
 220
 221     pub(crate) fn has_impl_prev_sibling(&self) -> bool {
 222         matches!(self.prev_sibling, Some(ImmediatePrevSibling::ImplDefType))
 223     }
 224
 225     pub(crate) fn has_visibility_prev_sibling(&self) -> bool {
 226         matches!(self.prev_sibling, Some(ImmediatePrevSibling::Visibility))
 227     }
 228
 229     pub(crate) fn after_if(&self) -> bool {
 230         matches!(self.prev_sibling, Some(ImmediatePrevSibling::IfExpr))
 231     }
 232
 233     pub(crate) fn is_path_disallowed(&self) -> bool {
 234         self.previous_token_is(T![unsafe])
 235             || matches!(
 236                 self.prev_sibling,
 237                 Some(ImmediatePrevSibling::Attribute | ImmediatePrevSibling::Visibility)
 238             )
 239             || matches!(
 240                 self.completion_location,
 241                 Some(
 242                     ImmediateLocation::ModDeclaration(_)
 243                         | ImmediateLocation::RecordPat(_)
 244                         | ImmediateLocation::RecordExpr(_)
 245                         | ImmediateLocation::Rename
 246                 )
 247             )
 248     }
 249
 250     pub(crate) fn expects_expression(&self) -> bool {
 251         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Expr), .. }))
 252     }
 253
 254     pub(crate) fn expects_type(&self) -> bool {
 255         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Type), .. }))
 256     }
 257
 258     pub(crate) fn path_is_call(&self) -> bool {
 259         self.path_context.as_ref().map_or(false, |it| it.has_call_parens)
 260     }
 261
 262     pub(crate) fn is_trivial_path(&self) -> bool {
 263         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: true, .. }))
 264     }
 265
 266     pub(crate) fn is_non_trivial_path(&self) -> bool {
 267         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: false, .. }))
 268     }
 269
 270     pub(crate) fn path_qual(&self) -> Option<&ast::Path> {
 271         self.path_context.as_ref().and_then(|it| it.qualifier.as_ref())
 272     }
 273
 274     pub(crate) fn path_kind(&self) -> Option<PathKind> {
 275         self.path_context.as_ref().and_then(|it| it.kind)
 276     }
 277
 278     /// Checks if an item is visible and not `doc(hidden)` at the completion site.
 279     pub(crate) fn is_visible<I>(&self, item: &I) -> bool
 280     where
 281         I: hir::HasVisibility + hir::HasAttrs + hir::HasCrate + Copy,
 282     {
 283         self.is_visible_impl(&item.visibility(self.db), &item.attrs(self.db), item.krate(self.db))
 284     }
 285
 286     pub(crate) fn is_scope_def_hidden(&self, scope_def: ScopeDef) -> bool {
 287         if let (Some(attrs), Some(krate)) = (scope_def.attrs(self.db), scope_def.krate(self.db)) {
 288             return self.is_doc_hidden(&attrs, krate);
 289         }
 290
 291         false
 292     }
 293
 294     /// Check if an item is `#[doc(hidden)]`.
 295     pub(crate) fn is_item_hidden(&self, item: &hir::ItemInNs) -> bool {
 296         let attrs = item.attrs(self.db);
 297         let krate = item.krate(self.db);
 298         match (attrs, krate) {
 299             (Some(attrs), Some(krate)) => self.is_doc_hidden(&attrs, krate),
 300             _ => false,
 301         }
 302     }
 303
 304     pub(crate) fn is_immediately_after_macro_bang(&self) -> bool {
 305         self.token.kind() == BANG && self.token.parent().map_or(false, |it| it.kind() == MACRO_CALL)
 306     }
 307
 308     /// A version of [`SemanticsScope::process_all_names`] that filters out `#[doc(hidden)]` items.
 309     pub(crate) fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
 310         self.scope.process_all_names(&mut |name, def| {
 311             if self.is_scope_def_hidden(def) {
 312                 return;
 313             }
 314
 315             f(name, def);
 316         })
 317     }
 318
 319     fn is_visible_impl(
 320         &self,
 321         vis: &hir::Visibility,
 322         attrs: &hir::Attrs,
 323         defining_crate: hir::Crate,
 324     ) -> bool {
 325         let module = match self.scope.module() {
 326             Some(it) => it,
 327             None => return false,
 328         };
 329         if !vis.is_visible_from(self.db, module.into()) {
 330             // If the definition location is editable, also show private items
 331             let root_file = defining_crate.root_file(self.db);
 332             let source_root_id = self.db.file_source_root(root_file);
 333             let is_editable = !self.db.source_root(source_root_id).is_library;
 334             return is_editable;
 335         }
 336
 337         !self.is_doc_hidden(attrs, defining_crate)
 338     }
 339
 340     fn is_doc_hidden(&self, attrs: &hir::Attrs, defining_crate: hir::Crate) -> bool {
 341         let krate = match self.krate {
 342             Some(it) => it,
 343             None => return true,
 344         };
 345         if krate != defining_crate && attrs.has_doc_hidden() {
 346             // `doc(hidden)` items are only completed within the defining crate.
 347             return true;
 348         }
 349
 350         false
 351     }
 352 }
 353
 354 // CompletionContext construction
 355 impl<'a> CompletionContext<'a> {
 356     pub(super) fn new(
 357         db: &'a RootDatabase,
 358         position @ FilePosition { file_id, offset }: FilePosition,
 359         config: &'a CompletionConfig,
 360     ) -> Option<CompletionContext<'a>> {
 361         let _p = profile::span("CompletionContext::new");
 362         let sema = Semantics::new(db);
 363
 364         let original_file = sema.parse(file_id);
 365
 366         // Insert a fake ident to get a valid parse tree. We will use this file
 367         // to determine context, though the original_file will be used for
 368         // actual completion.
 369         let file_with_fake_ident = {
 370             let parse = db.parse(file_id);
 371             let edit = Indel::insert(offset, "intellijRulezz".to_string());
 372             parse.reparse(&edit).tree()
 373         };
 374         let fake_ident_token =
 375             file_with_fake_ident.syntax().token_at_offset(offset).right_biased()?;
 376
 377         let original_token = original_file.syntax().token_at_offset(offset).left_biased()?;
 378         let token = sema.descend_into_macros_single(original_token.clone());
 379         let scope = sema.scope_at_offset(&token, offset);
 380         let krate = scope.krate();
 381         let mut locals = vec![];
 382         scope.process_all_names(&mut |name, scope| {
 383             if let ScopeDef::Local(local) = scope {
 384                 locals.push((name, local));
 385             }
 386         });
 387         let mut ctx = CompletionContext {
 388             sema,
 389             scope,
 390             db,
 391             config,
 392             position,
 393             original_token,
 394             token,
 395             krate,
 396             expected_name: None,
 397             expected_type: None,
 398             function_def: None,
 399             impl_def: None,
 400             name_syntax: None,
 401             lifetime_ctx: None,
 402             pattern_ctx: None,
 403             completion_location: None,
 404             prev_sibling: None,
 405             attribute_under_caret: None,
 406             previous_token: None,
 407             path_context: None,
 408             locals,
 409             incomplete_let: false,
 410             no_completion_required: false,
 411         };
 412         ctx.expand_and_fill(
 413             original_file.syntax().clone(),
 414             file_with_fake_ident.syntax().clone(),
 415             offset,
 416             fake_ident_token,
 417         );
 418         Some(ctx)
 419     }
 420
 421     /// Do the attribute expansion at the current cursor position for both original file and fake file
 422     /// as long as possible. As soon as one of the two expansions fail we stop to stay in sync.
 423     fn expand_and_fill(
 424         &mut self,
 425         mut original_file: SyntaxNode,
 426         mut speculative_file: SyntaxNode,
 427         mut offset: TextSize,
 428         mut fake_ident_token: SyntaxToken,
 429     ) {
 430         loop {
 431             // Expand attributes
 432             if let (Some(actual_item), Some(item_with_fake_ident)) = (
 433                 find_node_at_offset::<ast::Item>(&original_file, offset),
 434                 find_node_at_offset::<ast::Item>(&speculative_file, offset),
 435             ) {
 436                 match (
 437                     self.sema.expand_attr_macro(&actual_item),
 438                     self.sema.speculative_expand_attr_macro(
 439                         &actual_item,
 440                         &item_with_fake_ident,
 441                         fake_ident_token.clone(),
 442                     ),
 443                 ) {
 444                     (Some(actual_expansion), Some(speculative_expansion)) => {
 445                         let new_offset = speculative_expansion.1.text_range().start();
 446                         if new_offset > actual_expansion.text_range().end() {
 447                             break;
 448                         }
 449                         original_file = actual_expansion;
 450                         speculative_file = speculative_expansion.0;
 451                         fake_ident_token = speculative_expansion.1;
 452                         offset = new_offset;
 453                         continue;
 454                     }
 455                     (None, None) => (),
 456                     _ => break,
 457                 }
 458             }
 459
 460             // Expand fn-like macro calls
 461             if let (Some(actual_macro_call), Some(macro_call_with_fake_ident)) = (
 462                 find_node_at_offset::<ast::MacroCall>(&original_file, offset),
 463                 find_node_at_offset::<ast::MacroCall>(&speculative_file, offset),
 464             ) {
 465                 let mac_call_path0 = actual_macro_call.path().as_ref().map(|s| s.syntax().text());
 466                 let mac_call_path1 =
 467                     macro_call_with_fake_ident.path().as_ref().map(|s| s.syntax().text());
 468                 if mac_call_path0 != mac_call_path1 {
 469                     break;
 470                 }
 471                 let speculative_args = match macro_call_with_fake_ident.token_tree() {
 472                     Some(tt) => tt,
 473                     None => break,
 474                 };
 475
 476                 if let (Some(actual_expansion), Some(speculative_expansion)) = (
 477                     self.sema.expand(&actual_macro_call),
 478                     self.sema.speculative_expand(
 479                         &actual_macro_call,
 480                         &speculative_args,
 481                         fake_ident_token,
 482                     ),
 483                 ) {
 484                     let new_offset = speculative_expansion.1.text_range().start();
 485                     if new_offset > actual_expansion.text_range().end() {
 486                         break;
 487                     }
 488                     original_file = actual_expansion;
 489                     speculative_file = speculative_expansion.0;
 490                     fake_ident_token = speculative_expansion.1;
 491                     offset = new_offset;
 492                 } else {
 493                     break;
 494                 }
 495             } else {
 496                 break;
 497             }
 498         }
 499
 500         self.fill(&original_file, speculative_file, offset);
 501     }
 502
 503     fn expected_type_and_name(&self) -> (Option<Type>, Option<NameOrNameRef>) {
 504         let mut node = match self.token.parent() {
 505             Some(it) => it,
 506             None => return (None, None),
 507         };
 508         loop {
 509             break match_ast! {
 510                 match node {
 511                     ast::LetStmt(it) => {
 512                         cov_mark::hit!(expected_type_let_with_leading_char);
 513                         cov_mark::hit!(expected_type_let_without_leading_char);
 514                         let ty = it.pat()
 515                             .and_then(|pat| self.sema.type_of_pat(&pat))
 516                             .or_else(|| it.initializer().and_then(|it| self.sema.type_of_expr(&it)))
 517                             .map(TypeInfo::original);
 518                         let name = match it.pat() {
 519                             Some(ast::Pat::IdentPat(ident)) => ident.name().map(NameOrNameRef::Name),
 520                             Some(_) | None => None,
 521                         };
 522
 523                         (ty, name)
 524                     },
 525                     ast::ArgList(_) => {
 526                         cov_mark::hit!(expected_type_fn_param);
 527                         ActiveParameter::at_token(
 528                             &self.sema,
 529                             self.token.clone(),
 530                         ).map(|ap| {
 531                             let name = ap.ident().map(NameOrNameRef::Name);
 532                             let ty = if has_ref(&self.token) {
 533                                 cov_mark::hit!(expected_type_fn_param_ref);
 534                                 ap.ty.remove_ref()
 535                             } else {
 536                                 Some(ap.ty)
 537                             };
 538                             (ty, name)
 539                         })
 540                         .unwrap_or((None, None))
 541                     },
 542                     ast::RecordExprFieldList(it) => {
 543                         // wouldn't try {} be nice...
 544                         (|| {
 545                             if self.token.kind() == T![..]
 546                                 || self.token.prev_token().map(|t| t.kind()) == Some(T![..])
 547                             {
 548                                 cov_mark::hit!(expected_type_struct_func_update);
 549                                 let record_expr = it.syntax().parent().and_then(ast::RecordExpr::cast)?;
 550                                 let ty = self.sema.type_of_expr(&record_expr.into())?;
 551                                 Some((
 552                                     Some(ty.original),
 553                                     None
 554                                 ))
 555                             } else {
 556                                 cov_mark::hit!(expected_type_struct_field_without_leading_char);
 557                                 let expr_field = self.token.prev_sibling_or_token()?
 558                                     .into_node()
 559                                     .and_then(ast::RecordExprField::cast)?;
 560                                 let (_, _, ty) = self.sema.resolve_record_field(&expr_field)?;
 561                                 Some((
 562                                     Some(ty),
 563                                     expr_field.field_name().map(NameOrNameRef::NameRef),
 564                                 ))
 565                             }
 566                         })().unwrap_or((None, None))
 567                     },
 568                     ast::RecordExprField(it) => {
 569                         if let Some(expr) = it.expr() {
 570                             cov_mark::hit!(expected_type_struct_field_with_leading_char);
 571                             (
 572                                 self.sema.type_of_expr(&expr).map(TypeInfo::original),
 573                                 it.field_name().map(NameOrNameRef::NameRef),
 574                             )
 575                         } else {
 576                             cov_mark::hit!(expected_type_struct_field_followed_by_comma);
 577                             let ty = self.sema.resolve_record_field(&it)
 578                                 .map(|(_, _, ty)| ty);
 579                             (
 580                                 ty,
 581                                 it.field_name().map(NameOrNameRef::NameRef),
 582                             )
 583                         }
 584                     },
 585                     ast::MatchExpr(it) => {
 586                         cov_mark::hit!(expected_type_match_arm_without_leading_char);
 587                         let ty = it.expr().and_then(|e| self.sema.type_of_expr(&e)).map(TypeInfo::original);
 588                         (ty, None)
 589                     },
 590                     ast::IfExpr(it) => {
 591                         cov_mark::hit!(expected_type_if_let_without_leading_char);
 592                         let ty = it.condition()
 593                             .and_then(|cond| cond.expr())
 594                             .and_then(|e| self.sema.type_of_expr(&e))
 595                             .map(TypeInfo::original);
 596                         (ty, None)
 597                     },
 598                     ast::IdentPat(it) => {
 599                         cov_mark::hit!(expected_type_if_let_with_leading_char);
 600                         cov_mark::hit!(expected_type_match_arm_with_leading_char);
 601                         let ty = self.sema.type_of_pat(&ast::Pat::from(it)).map(TypeInfo::original);
 602                         (ty, None)
 603                     },
 604                     ast::Fn(it) => {
 605                         cov_mark::hit!(expected_type_fn_ret_with_leading_char);
 606                         cov_mark::hit!(expected_type_fn_ret_without_leading_char);
 607                         let def = self.sema.to_def(&it);
 608                         (def.map(|def| def.ret_type(self.db)), None)
 609                     },
 610                     ast::ClosureExpr(it) => {
 611                         let ty = self.sema.type_of_expr(&it.into());
 612                         ty.and_then(|ty| ty.original.as_callable(self.db))
 613                             .map(|c| (Some(c.return_type()), None))
 614                             .unwrap_or((None, None))
 615                     },
 616                     ast::ParamList(_) => (None, None),
 617                     ast::Stmt(_) => (None, None),
 618                     ast::Item(_) => (None, None),
 619                     _ => {
 620                         match node.parent() {
 621                             Some(n) => {
 622                                 node = n;
 623                                 continue;
 624                             },
 625                             None => (None, None),
 626                         }
 627                     },
 628                 }
 629             };
 630         }
 631     }
 632
 633     fn fill(
 634         &mut self,
 635         original_file: &SyntaxNode,
 636         file_with_fake_ident: SyntaxNode,
 637         offset: TextSize,
 638     ) {
 639         let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
 640         let syntax_element = NodeOrToken::Token(fake_ident_token);
 641         self.previous_token = previous_token(syntax_element.clone());
 642         self.attribute_under_caret = syntax_element.ancestors().find_map(ast::Attr::cast);
 643         self.no_completion_required = {
 644             let inside_impl_trait_block = inside_impl_trait_block(syntax_element.clone());
 645             let fn_is_prev = self.previous_token_is(T![fn]);
 646             let for_is_prev2 = for_is_prev2(syntax_element.clone());
 647             (fn_is_prev && !inside_impl_trait_block) || for_is_prev2
 648         };
 649
 650         self.incomplete_let =
 651             syntax_element.ancestors().take(6).find_map(ast::LetStmt::cast).map_or(false, |it| {
 652                 it.syntax().text_range().end() == syntax_element.text_range().end()
 653             });
 654
 655         let (expected_type, expected_name) = self.expected_type_and_name();
 656         self.expected_type = expected_type;
 657         self.expected_name = expected_name;
 658
 659         let name_like = match find_node_at_offset(&file_with_fake_ident, offset) {
 660             Some(it) => it,
 661             None => return,
 662         };
 663         self.completion_location =
 664             determine_location(&self.sema, original_file, offset, &name_like);
 665         self.prev_sibling = determine_prev_sibling(&name_like);
 666         self.name_syntax =
 667             find_node_at_offset(original_file, name_like.syntax().text_range().start());
 668         self.impl_def = self
 669             .sema
 670             .token_ancestors_with_macros(self.token.clone())
 671             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 672             .find_map(ast::Impl::cast);
 673         self.function_def = self
 674             .sema
 675             .token_ancestors_with_macros(self.token.clone())
 676             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 677             .find_map(ast::Fn::cast);
 678         match name_like {
 679             ast::NameLike::Lifetime(lifetime) => {
 680                 self.lifetime_ctx =
 681                     Self::classify_lifetime(&self.sema, original_file, lifetime, offset);
 682             }
 683             ast::NameLike::NameRef(name_ref) => {
 684                 if let Some((path_ctx, pat_ctx)) =
 685                     Self::classify_name_ref(&self.sema, original_file, name_ref)
 686                 {
 687                     self.path_context = Some(path_ctx);
 688                     self.pattern_ctx = pat_ctx;
 689                 }
 690             }
 691             ast::NameLike::Name(name) => {
 692                 self.pattern_ctx = Self::classify_name(&self.sema, name);
 693             }
 694         }
 695     }
 696
 697     fn classify_lifetime(
 698         sema: &Semantics<RootDatabase>,
 699         original_file: &SyntaxNode,
 700         lifetime: ast::Lifetime,
 701         offset: TextSize,
 702     ) -> Option<LifetimeContext> {
 703         let parent = lifetime.syntax().parent()?;
 704         if parent.kind() == ERROR {
 705             return None;
 706         }
 707
 708         Some(match_ast! {
 709             match parent {
 710                 ast::LifetimeParam(_) => LifetimeContext::LifetimeParam(sema.find_node_at_offset_with_macros(original_file, offset)),
 711                 ast::BreakExpr(_) => LifetimeContext::LabelRef,
 712                 ast::ContinueExpr(_) => LifetimeContext::LabelRef,
 713                 ast::Label(_) => LifetimeContext::LabelDef,
 714                 _ => LifetimeContext::Lifetime,
 715             }
 716         })
 717     }
 718
 719     fn classify_name(_sema: &Semantics<RootDatabase>, name: ast::Name) -> Option<PatternContext> {
 720         let bind_pat = name.syntax().parent().and_then(ast::IdentPat::cast)?;
 721         let is_name_in_field_pat = bind_pat
 722             .syntax()
 723             .parent()
 724             .and_then(ast::RecordPatField::cast)
 725             .map_or(false, |pat_field| pat_field.name_ref().is_none());
 726         if is_name_in_field_pat {
 727             return None;
 728         }
 729         if !bind_pat.is_simple_ident() {
 730             return None;
 731         }
 732         Some(pattern_context_for(bind_pat.into()))
 733     }
 734
 735     fn classify_name_ref(
 736         _sema: &Semantics<RootDatabase>,
 737         original_file: &SyntaxNode,
 738         name_ref: ast::NameRef,
 739     ) -> Option<(PathCompletionContext, Option<PatternContext>)> {
 740         let parent = name_ref.syntax().parent()?;
 741         let segment = ast::PathSegment::cast(parent)?;
 742         let path = segment.parent_path();
 743
 744         let mut path_ctx = PathCompletionContext {
 745             has_call_parens: false,
 746             is_trivial_path: false,
 747             qualifier: None,
 748             parent: None,
 749             has_type_args: false,
 750             can_be_stmt: false,
 751             in_loop_body: false,
 752             use_tree_parent: false,
 753             kind: None,
 754         };
 755         let mut pat_ctx = None;
 756         path_ctx.in_loop_body = is_in_loop_body(name_ref.syntax());
 757
 758         path_ctx.kind  = path.syntax().ancestors().find_map(|it| {
 759             match_ast! {
 760                 match it {
 761                     ast::PathType(_) => Some(PathKind::Type),
 762                     ast::PathExpr(it) => {
 763                         path_ctx.has_call_parens = it.syntax().parent().map_or(false, |it| ast::CallExpr::can_cast(it.kind()));
 764                         Some(PathKind::Expr)
 765                     },
 766                     ast::TupleStructPat(it) => {
 767                         path_ctx.has_call_parens = true;
 768                         pat_ctx = Some(pattern_context_for(it.into()));
 769                         Some(PathKind::Pat)
 770                     },
 771                     ast::RecordPat(it) => {
 772                         pat_ctx = Some(pattern_context_for(it.into()));
 773                         Some(PathKind::Pat)
 774                     },
 775                     ast::PathPat(it) => {
 776                         pat_ctx = Some(pattern_context_for(it.into()));
 777                         Some(PathKind::Pat)
 778                     },
 779                     ast::MacroCall(it) => it.excl_token().and(Some(PathKind::Mac)),
 780                     ast::Meta(_) => Some(PathKind::Attr),
 781                     ast::Visibility(it) => Some(PathKind::Vis { has_in_token: it.in_token().is_some() }),
 782                     ast::UseTree(_) => Some(PathKind::Use),
 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, pat_ctx));
 801         }
 802
 803         if let Some(segment) = path.segment() {
 804             if segment.coloncolon_token().is_some() {
 805                 return Some((path_ctx, pat_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, pat_ctx))
 830     }
 831 }
 832
 833 fn pattern_context_for(pat: ast::Pat) -> PatternContext {
 834     let mut is_param = None;
 835     let (refutability, has_type_ascription) =
 836     pat
 837         .syntax()
 838         .ancestors()
 839         .skip_while(|it| ast::Pat::can_cast(it.kind()))
 840         .next()
 841         .map_or((PatternRefutability::Irrefutable, false), |node| {
 842             let refutability = match_ast! {
 843                 match node {
 844                     ast::LetStmt(let_) => return (PatternRefutability::Irrefutable, let_.ty().is_some()),
 845                     ast::Param(param) => {
 846                         let is_closure_param = param
 847                             .syntax()
 848                             .ancestors()
 849                             .nth(2)
 850                             .and_then(ast::ClosureExpr::cast)
 851                             .is_some();
 852                         is_param = Some(if is_closure_param {
 853                             ParamKind::Closure
 854                         } else {
 855                             ParamKind::Function
 856                         });
 857                         return (PatternRefutability::Irrefutable, param.ty().is_some())
 858                     },
 859                     ast::MatchArm(_) => PatternRefutability::Refutable,
 860                     ast::Condition(_) => PatternRefutability::Refutable,
 861                     ast::ForExpr(_) => PatternRefutability::Irrefutable,
 862                     _ => PatternRefutability::Irrefutable,
 863                 }
 864             };
 865             (refutability, false)
 866         });
 867     PatternContext { refutability, is_param, has_type_ascription }
 868 }
 869 fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Option<N> {
 870     syntax.covering_element(range).ancestors().find_map(N::cast)
 871 }
 872
 873 fn path_or_use_tree_qualifier(path: &ast::Path) -> Option<(ast::Path, bool)> {
 874     if let Some(qual) = path.qualifier() {
 875         return Some((qual, false));
 876     }
 877     let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
 878     let use_tree = use_tree_list.syntax().parent().and_then(ast::UseTree::cast)?;
 879     use_tree.path().zip(Some(true))
 880 }
 881
 882 fn has_ref(token: &SyntaxToken) -> bool {
 883     let mut token = token.clone();
 884     for skip in [WHITESPACE, IDENT, T![mut]] {
 885         if token.kind() == skip {
 886             token = match token.prev_token() {
 887                 Some(it) => it,
 888                 None => return false,
 889             }
 890         }
 891     }
 892     token.kind() == T![&]
 893 }
 894
 895 #[cfg(test)]
 896 mod tests {
 897     use expect_test::{expect, Expect};
 898     use hir::HirDisplay;
 899
 900     use crate::tests::{position, TEST_CONFIG};
 901
 902     use super::CompletionContext;
 903
 904     fn check_expected_type_and_name(ra_fixture: &str, expect: Expect) {
 905         let (db, pos) = position(ra_fixture);
 906         let config = TEST_CONFIG;
 907         let completion_context = CompletionContext::new(&db, pos, &config).unwrap();
 908
 909         let ty = completion_context
 910             .expected_type
 911             .map(|t| t.display_test(&db).to_string())
 912             .unwrap_or("?".to_owned());
 913
 914         let name = completion_context
 915             .expected_name
 916             .map_or_else(|| "?".to_owned(), |name| name.to_string());
 917
 918         expect.assert_eq(&format!("ty: {}, name: {}", ty, name));
 919     }
 920
 921     #[test]
 922     fn expected_type_let_without_leading_char() {
 923         cov_mark::check!(expected_type_let_without_leading_char);
 924         check_expected_type_and_name(
 925             r#"
 926 fn foo() {
 927     let x: u32 = $0;
 928 }
 929 "#,
 930             expect![[r#"ty: u32, name: x"#]],
 931         );
 932     }
 933
 934     #[test]
 935     fn expected_type_let_with_leading_char() {
 936         cov_mark::check!(expected_type_let_with_leading_char);
 937         check_expected_type_and_name(
 938             r#"
 939 fn foo() {
 940     let x: u32 = c$0;
 941 }
 942 "#,
 943             expect![[r#"ty: u32, name: x"#]],
 944         );
 945     }
 946
 947     #[test]
 948     fn expected_type_let_pat() {
 949         check_expected_type_and_name(
 950             r#"
 951 fn foo() {
 952     let x$0 = 0u32;
 953 }
 954 "#,
 955             expect![[r#"ty: u32, name: ?"#]],
 956         );
 957         check_expected_type_and_name(
 958             r#"
 959 fn foo() {
 960     let $0 = 0u32;
 961 }
 962 "#,
 963             expect![[r#"ty: u32, name: ?"#]],
 964         );
 965     }
 966
 967     #[test]
 968     fn expected_type_fn_param() {
 969         cov_mark::check!(expected_type_fn_param);
 970         check_expected_type_and_name(
 971             r#"
 972 fn foo() { bar($0); }
 973 fn bar(x: u32) {}
 974 "#,
 975             expect![[r#"ty: u32, name: x"#]],
 976         );
 977         check_expected_type_and_name(
 978             r#"
 979 fn foo() { bar(c$0); }
 980 fn bar(x: u32) {}
 981 "#,
 982             expect![[r#"ty: u32, name: x"#]],
 983         );
 984     }
 985
 986     #[test]
 987     fn expected_type_fn_param_ref() {
 988         cov_mark::check!(expected_type_fn_param_ref);
 989         check_expected_type_and_name(
 990             r#"
 991 fn foo() { bar(&$0); }
 992 fn bar(x: &u32) {}
 993 "#,
 994             expect![[r#"ty: u32, name: x"#]],
 995         );
 996         check_expected_type_and_name(
 997             r#"
 998 fn foo() { bar(&mut $0); }
 999 fn bar(x: &mut u32) {}
1000 "#,
1001             expect![[r#"ty: u32, name: x"#]],
1002         );
1003         check_expected_type_and_name(
1004             r#"
1005 fn foo() { bar(&c$0); }
1006 fn bar(x: &u32) {}
1007         "#,
1008             expect![[r#"ty: u32, name: x"#]],
1009         );
1010     }
1011
1012     #[test]
1013     fn expected_type_struct_field_without_leading_char() {
1014         cov_mark::check!(expected_type_struct_field_without_leading_char);
1015         check_expected_type_and_name(
1016             r#"
1017 struct Foo { a: u32 }
1018 fn foo() {
1019     Foo { a: $0 };
1020 }
1021 "#,
1022             expect![[r#"ty: u32, name: a"#]],
1023         )
1024     }
1025
1026     #[test]
1027     fn expected_type_struct_field_followed_by_comma() {
1028         cov_mark::check!(expected_type_struct_field_followed_by_comma);
1029         check_expected_type_and_name(
1030             r#"
1031 struct Foo { a: u32 }
1032 fn foo() {
1033     Foo { a: $0, };
1034 }
1035 "#,
1036             expect![[r#"ty: u32, name: a"#]],
1037         )
1038     }
1039
1040     #[test]
1041     fn expected_type_generic_struct_field() {
1042         check_expected_type_and_name(
1043             r#"
1044 struct Foo<T> { a: T }
1045 fn foo() -> Foo<u32> {
1046     Foo { a: $0 }
1047 }
1048 "#,
1049             expect![[r#"ty: u32, name: a"#]],
1050         )
1051     }
1052
1053     #[test]
1054     fn expected_type_struct_field_with_leading_char() {
1055         cov_mark::check!(expected_type_struct_field_with_leading_char);
1056         check_expected_type_and_name(
1057             r#"
1058 struct Foo { a: u32 }
1059 fn foo() {
1060     Foo { a: c$0 };
1061 }
1062 "#,
1063             expect![[r#"ty: u32, name: a"#]],
1064         );
1065     }
1066
1067     #[test]
1068     fn expected_type_match_arm_without_leading_char() {
1069         cov_mark::check!(expected_type_match_arm_without_leading_char);
1070         check_expected_type_and_name(
1071             r#"
1072 enum E { X }
1073 fn foo() {
1074    match E::X { $0 }
1075 }
1076 "#,
1077             expect![[r#"ty: E, name: ?"#]],
1078         );
1079     }
1080
1081     #[test]
1082     fn expected_type_match_arm_with_leading_char() {
1083         cov_mark::check!(expected_type_match_arm_with_leading_char);
1084         check_expected_type_and_name(
1085             r#"
1086 enum E { X }
1087 fn foo() {
1088    match E::X { c$0 }
1089 }
1090 "#,
1091             expect![[r#"ty: E, name: ?"#]],
1092         );
1093     }
1094
1095     #[test]
1096     fn expected_type_if_let_without_leading_char() {
1097         cov_mark::check!(expected_type_if_let_without_leading_char);
1098         check_expected_type_and_name(
1099             r#"
1100 enum Foo { Bar, Baz, Quux }
1101
1102 fn foo() {
1103     let f = Foo::Quux;
1104     if let $0 = f { }
1105 }
1106 "#,
1107             expect![[r#"ty: Foo, name: ?"#]],
1108         )
1109     }
1110
1111     #[test]
1112     fn expected_type_if_let_with_leading_char() {
1113         cov_mark::check!(expected_type_if_let_with_leading_char);
1114         check_expected_type_and_name(
1115             r#"
1116 enum Foo { Bar, Baz, Quux }
1117
1118 fn foo() {
1119     let f = Foo::Quux;
1120     if let c$0 = f { }
1121 }
1122 "#,
1123             expect![[r#"ty: Foo, name: ?"#]],
1124         )
1125     }
1126
1127     #[test]
1128     fn expected_type_fn_ret_without_leading_char() {
1129         cov_mark::check!(expected_type_fn_ret_without_leading_char);
1130         check_expected_type_and_name(
1131             r#"
1132 fn foo() -> u32 {
1133     $0
1134 }
1135 "#,
1136             expect![[r#"ty: u32, name: ?"#]],
1137         )
1138     }
1139
1140     #[test]
1141     fn expected_type_fn_ret_with_leading_char() {
1142         cov_mark::check!(expected_type_fn_ret_with_leading_char);
1143         check_expected_type_and_name(
1144             r#"
1145 fn foo() -> u32 {
1146     c$0
1147 }
1148 "#,
1149             expect![[r#"ty: u32, name: ?"#]],
1150         )
1151     }
1152
1153     #[test]
1154     fn expected_type_fn_ret_fn_ref_fully_typed() {
1155         check_expected_type_and_name(
1156             r#"
1157 fn foo() -> u32 {
1158     foo$0
1159 }
1160 "#,
1161             expect![[r#"ty: u32, name: ?"#]],
1162         )
1163     }
1164
1165     #[test]
1166     fn expected_type_closure_param_return() {
1167         // FIXME: make this work with `|| $0`
1168         check_expected_type_and_name(
1169             r#"
1170 //- minicore: fn
1171 fn foo() {
1172     bar(|| a$0);
1173 }
1174
1175 fn bar(f: impl FnOnce() -> u32) {}
1176 "#,
1177             expect![[r#"ty: u32, name: ?"#]],
1178         );
1179     }
1180
1181     #[test]
1182     fn expected_type_generic_function() {
1183         check_expected_type_and_name(
1184             r#"
1185 fn foo() {
1186     bar::<u32>($0);
1187 }
1188
1189 fn bar<T>(t: T) {}
1190 "#,
1191             expect![[r#"ty: u32, name: t"#]],
1192         );
1193     }
1194
1195     #[test]
1196     fn expected_type_generic_method() {
1197         check_expected_type_and_name(
1198             r#"
1199 fn foo() {
1200     S(1u32).bar($0);
1201 }
1202
1203 struct S<T>(T);
1204 impl<T> S<T> {
1205     fn bar(self, t: T) {}
1206 }
1207 "#,
1208             expect![[r#"ty: u32, name: t"#]],
1209         );
1210     }
1211
1212     #[test]
1213     fn expected_type_functional_update() {
1214         cov_mark::check!(expected_type_struct_func_update);
1215         check_expected_type_and_name(
1216             r#"
1217 struct Foo { field: u32 }
1218 fn foo() {
1219     Foo {
1220         ..$0
1221     }
1222 }
1223 "#,
1224             expect![[r#"ty: Foo, name: ?"#]],
1225         );
1226     }
1227
1228     #[test]
1229     fn expected_type_param_pat() {
1230         check_expected_type_and_name(
1231             r#"
1232 struct Foo { field: u32 }
1233 fn foo(a$0: Foo) {}
1234 "#,
1235             expect![[r#"ty: Foo, name: ?"#]],
1236         );
1237         check_expected_type_and_name(
1238             r#"
1239 struct Foo { field: u32 }
1240 fn foo($0: Foo) {}
1241 "#,
1242             // FIXME make this work, currently fails due to pattern recovery eating the `:`
1243             expect![[r#"ty: ?, name: ?"#]],
1244         );
1245     }
1246 }