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     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(Copy, Clone, Debug)]
  34 pub(super) enum PathKind {
  35     Expr,
  36     Type,
  37     Attr,
  38     Mac,
  39     Pat,
  40     Vis { has_in_token: bool },
  41     Use,
  42 }
  43
  44 #[derive(Debug)]
  45 pub(crate) struct PathCompletionContext {
  46     /// If this is a call with () already there
  47     has_call_parens: bool,
  48     /// A single-indent path, like `foo`. `::foo` should not be considered a trivial path.
  49     pub(super) is_trivial_path: bool,
  50     /// If not a trivial path, the prefix (qualifier).
  51     pub(super) qualifier: Option<ast::Path>,
  52     #[allow(dead_code)]
  53     /// If not a trivial path, the suffix (parent).
  54     pub(super) parent: Option<ast::Path>,
  55     /// Whether the qualifier comes from a use tree parent or not
  56     pub(super) use_tree_parent: bool,
  57     pub(super) kind: Option<PathKind>,
  58     /// Whether the path segment has type args or not.
  59     pub(super) has_type_args: bool,
  60     /// `true` if we are a statement or a last expr in the block.
  61     pub(super) can_be_stmt: bool,
  62     pub(super) in_loop_body: bool,
  63 }
  64
  65 #[derive(Debug)]
  66 pub(super) struct PatternContext {
  67     pub(super) refutability: PatternRefutability,
  68     pub(super) is_param: Option<ParamKind>,
  69     pub(super) has_type_ascription: bool,
  70 }
  71
  72 #[derive(Debug)]
  73 pub(super) enum LifetimeContext {
  74     LifetimeParam(Option<ast::LifetimeParam>),
  75     Lifetime,
  76     LabelRef,
  77     LabelDef,
  78 }
  79
  80 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
  81 pub(crate) enum ParamKind {
  82     Function,
  83     Closure,
  84 }
  85 /// `CompletionContext` is created early during completion to figure out, where
  86 /// exactly is the cursor, syntax-wise.
  87 #[derive(Debug)]
  88 pub(crate) struct CompletionContext<'a> {
  89     pub(super) sema: Semantics<'a, RootDatabase>,
  90     pub(super) scope: SemanticsScope<'a>,
  91     pub(super) db: &'a RootDatabase,
  92     pub(super) config: &'a CompletionConfig,
  93     pub(super) position: FilePosition,
  94     /// The token before the cursor, in the original file.
  95     pub(super) original_token: SyntaxToken,
  96     /// The token before the cursor, in the macro-expanded file.
  97     pub(super) token: SyntaxToken,
  98     /// The crate of the current file.
  99     pub(super) krate: Option<hir::Crate>,
 100     pub(super) expected_name: Option<NameOrNameRef>,
 101     pub(super) expected_type: Option<Type>,
 102
 103     /// The parent function of the cursor position if it exists.
 104     pub(super) function_def: Option<ast::Fn>,
 105     /// The parent impl of the cursor position if it exists.
 106     pub(super) impl_def: Option<ast::Impl>,
 107     /// The NameLike under the cursor in the original file if it exists.
 108     pub(super) name_syntax: Option<ast::NameLike>,
 109     pub(super) incomplete_let: bool,
 110
 111     pub(super) completion_location: Option<ImmediateLocation>,
 112     pub(super) prev_sibling: Option<ImmediatePrevSibling>,
 113     pub(super) attribute_under_caret: Option<ast::Attr>,
 114     pub(super) previous_token: Option<SyntaxToken>,
 115
 116     pub(super) lifetime_ctx: Option<LifetimeContext>,
 117     pub(super) pattern_ctx: Option<PatternContext>,
 118     pub(super) path_context: Option<PathCompletionContext>,
 119     pub(super) locals: Vec<(Name, Local)>,
 120
 121     no_completion_required: bool,
 122 }
 123
 124 impl<'a> CompletionContext<'a> {
 125     /// Checks whether completions in that particular case don't make much sense.
 126     /// Examples:
 127     /// - `fn $0` -- we expect function name, it's unlikely that "hint" will be helpful.
 128     ///   Exception for this case is `impl Trait for Foo`, where we would like to hint trait method names.
 129     /// - `for _ i$0` -- obviously, it'll be "in" keyword.
 130     pub(crate) fn no_completion_required(&self) -> bool {
 131         self.no_completion_required
 132     }
 133
 134     /// The range of the identifier that is being completed.
 135     pub(crate) fn source_range(&self) -> TextRange {
 136         // check kind of macro-expanded token, but use range of original token
 137         let kind = self.token.kind();
 138         if kind == IDENT || kind == LIFETIME_IDENT || kind == UNDERSCORE || kind.is_keyword() {
 139             self.original_token.text_range()
 140         } else if kind == CHAR {
 141             // assume we are completing a lifetime but the user has only typed the '
 142             cov_mark::hit!(completes_if_lifetime_without_idents);
 143             TextRange::at(self.original_token.text_range().start(), TextSize::from(1))
 144         } else {
 145             TextRange::empty(self.position.offset)
 146         }
 147     }
 148
 149     pub(crate) fn previous_token_is(&self, kind: SyntaxKind) -> bool {
 150         self.previous_token.as_ref().map_or(false, |tok| tok.kind() == kind)
 151     }
 152
 153     pub(crate) fn dot_receiver(&self) -> Option<&ast::Expr> {
 154         match &self.completion_location {
 155             Some(
 156                 ImmediateLocation::MethodCall { receiver, .. }
 157                 | ImmediateLocation::FieldAccess { receiver, .. },
 158             ) => receiver.as_ref(),
 159             _ => None,
 160         }
 161     }
 162
 163     pub(crate) fn has_dot_receiver(&self) -> bool {
 164         matches!(
 165             &self.completion_location,
 166             Some(ImmediateLocation::FieldAccess { receiver, .. } | ImmediateLocation::MethodCall { receiver,.. })
 167                 if receiver.is_some()
 168         )
 169     }
 170
 171     pub(crate) fn expects_assoc_item(&self) -> bool {
 172         matches!(self.completion_location, Some(ImmediateLocation::Trait | ImmediateLocation::Impl))
 173     }
 174
 175     pub(crate) fn expects_variant(&self) -> bool {
 176         matches!(self.completion_location, Some(ImmediateLocation::Variant))
 177     }
 178
 179     pub(crate) fn expects_non_trait_assoc_item(&self) -> bool {
 180         matches!(self.completion_location, Some(ImmediateLocation::Impl))
 181     }
 182
 183     pub(crate) fn expects_item(&self) -> bool {
 184         matches!(self.completion_location, Some(ImmediateLocation::ItemList))
 185     }
 186
 187     pub(crate) fn expects_generic_arg(&self) -> bool {
 188         matches!(self.completion_location, Some(ImmediateLocation::GenericArgList(_)))
 189     }
 190
 191     pub(crate) fn has_block_expr_parent(&self) -> bool {
 192         matches!(self.completion_location, Some(ImmediateLocation::StmtList))
 193     }
 194
 195     pub(crate) fn expects_ident_pat_or_ref_expr(&self) -> bool {
 196         matches!(
 197             self.completion_location,
 198             Some(ImmediateLocation::IdentPat | ImmediateLocation::RefExpr)
 199         )
 200     }
 201
 202     pub(crate) fn expect_field(&self) -> bool {
 203         matches!(
 204             self.completion_location,
 205             Some(ImmediateLocation::RecordField | ImmediateLocation::TupleField)
 206         )
 207     }
 208
 209     pub(crate) fn has_impl_or_trait_prev_sibling(&self) -> bool {
 210         matches!(
 211             self.prev_sibling,
 212             Some(ImmediatePrevSibling::ImplDefType | ImmediatePrevSibling::TraitDefName)
 213         )
 214     }
 215
 216     pub(crate) fn has_impl_prev_sibling(&self) -> bool {
 217         matches!(self.prev_sibling, Some(ImmediatePrevSibling::ImplDefType))
 218     }
 219
 220     pub(crate) fn has_visibility_prev_sibling(&self) -> bool {
 221         matches!(self.prev_sibling, Some(ImmediatePrevSibling::Visibility))
 222     }
 223
 224     pub(crate) fn after_if(&self) -> bool {
 225         matches!(self.prev_sibling, Some(ImmediatePrevSibling::IfExpr))
 226     }
 227
 228     pub(crate) fn is_path_disallowed(&self) -> bool {
 229         self.previous_token_is(T![unsafe])
 230             || matches!(
 231                 self.prev_sibling,
 232                 Some(ImmediatePrevSibling::Attribute | ImmediatePrevSibling::Visibility)
 233             )
 234             || matches!(
 235                 self.completion_location,
 236                 Some(
 237                     ImmediateLocation::ModDeclaration(_)
 238                         | ImmediateLocation::RecordPat(_)
 239                         | ImmediateLocation::RecordExpr(_)
 240                         | ImmediateLocation::Rename
 241                 )
 242             )
 243     }
 244
 245     pub(crate) fn expects_expression(&self) -> bool {
 246         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Expr), .. }))
 247     }
 248
 249     pub(crate) fn expects_type(&self) -> bool {
 250         matches!(self.path_context, Some(PathCompletionContext { kind: Some(PathKind::Type), .. }))
 251     }
 252
 253     pub(crate) fn path_is_call(&self) -> bool {
 254         self.path_context.as_ref().map_or(false, |it| it.has_call_parens)
 255     }
 256
 257     pub(crate) fn is_trivial_path(&self) -> bool {
 258         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: true, .. }))
 259     }
 260
 261     pub(crate) fn is_non_trivial_path(&self) -> bool {
 262         matches!(self.path_context, Some(PathCompletionContext { is_trivial_path: false, .. }))
 263     }
 264
 265     pub(crate) fn path_qual(&self) -> Option<&ast::Path> {
 266         self.path_context.as_ref().and_then(|it| it.qualifier.as_ref())
 267     }
 268
 269     pub(crate) fn path_kind(&self) -> Option<PathKind> {
 270         self.path_context.as_ref().and_then(|it| it.kind)
 271     }
 272
 273     /// Checks if an item is visible and not `doc(hidden)` at the completion site.
 274     pub(crate) fn is_visible<I>(&self, item: &I) -> bool
 275     where
 276         I: hir::HasVisibility + hir::HasAttrs + hir::HasCrate + Copy,
 277     {
 278         self.is_visible_impl(&item.visibility(self.db), &item.attrs(self.db), item.krate(self.db))
 279     }
 280
 281     pub(crate) fn is_scope_def_hidden(&self, scope_def: ScopeDef) -> bool {
 282         if let (Some(attrs), Some(krate)) = (scope_def.attrs(self.db), scope_def.krate(self.db)) {
 283             return self.is_doc_hidden(&attrs, krate);
 284         }
 285
 286         false
 287     }
 288
 289     /// Check if an item is `#[doc(hidden)]`.
 290     pub(crate) fn is_item_hidden(&self, item: &hir::ItemInNs) -> bool {
 291         let attrs = item.attrs(self.db);
 292         let krate = item.krate(self.db);
 293         match (attrs, krate) {
 294             (Some(attrs), Some(krate)) => self.is_doc_hidden(&attrs, krate),
 295             _ => false,
 296         }
 297     }
 298
 299     pub(crate) fn is_immediately_after_macro_bang(&self) -> bool {
 300         self.token.kind() == BANG && self.token.parent().map_or(false, |it| it.kind() == MACRO_CALL)
 301     }
 302
 303     /// A version of [`SemanticsScope::process_all_names`] that filters out `#[doc(hidden)]` items.
 304     pub(crate) fn process_all_names(&self, f: &mut dyn FnMut(Name, ScopeDef)) {
 305         self.scope.process_all_names(&mut |name, def| {
 306             if self.is_scope_def_hidden(def) {
 307                 return;
 308             }
 309
 310             f(name, def);
 311         })
 312     }
 313
 314     fn is_visible_impl(
 315         &self,
 316         vis: &hir::Visibility,
 317         attrs: &hir::Attrs,
 318         defining_crate: hir::Crate,
 319     ) -> bool {
 320         let module = match self.scope.module() {
 321             Some(it) => it,
 322             None => return false,
 323         };
 324         if !vis.is_visible_from(self.db, module.into()) {
 325             // If the definition location is editable, also show private items
 326             let root_file = defining_crate.root_file(self.db);
 327             let source_root_id = self.db.file_source_root(root_file);
 328             let is_editable = !self.db.source_root(source_root_id).is_library;
 329             return is_editable;
 330         }
 331
 332         !self.is_doc_hidden(attrs, defining_crate)
 333     }
 334
 335     fn is_doc_hidden(&self, attrs: &hir::Attrs, defining_crate: hir::Crate) -> bool {
 336         let krate = match self.krate {
 337             Some(it) => it,
 338             None => return true,
 339         };
 340         if krate != defining_crate && attrs.has_doc_hidden() {
 341             // `doc(hidden)` items are only completed within the defining crate.
 342             return true;
 343         }
 344
 345         false
 346     }
 347 }
 348
 349 // CompletionContext construction
 350 impl<'a> CompletionContext<'a> {
 351     pub(super) fn new(
 352         db: &'a RootDatabase,
 353         position @ FilePosition { file_id, offset }: FilePosition,
 354         config: &'a CompletionConfig,
 355     ) -> Option<CompletionContext<'a>> {
 356         let _p = profile::span("CompletionContext::new");
 357         let sema = Semantics::new(db);
 358
 359         let original_file = sema.parse(file_id);
 360
 361         // Insert a fake ident to get a valid parse tree. We will use this file
 362         // to determine context, though the original_file will be used for
 363         // actual completion.
 364         let file_with_fake_ident = {
 365             let parse = db.parse(file_id);
 366             let edit = Indel::insert(offset, "intellijRulezz".to_string());
 367             parse.reparse(&edit).tree()
 368         };
 369         let fake_ident_token =
 370             file_with_fake_ident.syntax().token_at_offset(offset).right_biased()?;
 371
 372         let original_token = original_file.syntax().token_at_offset(offset).left_biased()?;
 373         let token = sema.descend_into_macros_single(original_token.clone());
 374         let scope = sema.scope_at_offset(&token, offset);
 375         let krate = scope.krate();
 376         let mut locals = vec![];
 377         scope.process_all_names(&mut |name, scope| {
 378             if let ScopeDef::Local(local) = scope {
 379                 locals.push((name, local));
 380             }
 381         });
 382         let mut ctx = CompletionContext {
 383             sema,
 384             scope,
 385             db,
 386             config,
 387             position,
 388             original_token,
 389             token,
 390             krate,
 391             expected_name: None,
 392             expected_type: None,
 393             function_def: None,
 394             impl_def: None,
 395             name_syntax: None,
 396             lifetime_ctx: None,
 397             pattern_ctx: None,
 398             completion_location: None,
 399             prev_sibling: None,
 400             attribute_under_caret: None,
 401             previous_token: None,
 402             path_context: None,
 403             locals,
 404             incomplete_let: false,
 405             no_completion_required: false,
 406         };
 407         ctx.expand_and_fill(
 408             original_file.syntax().clone(),
 409             file_with_fake_ident.syntax().clone(),
 410             offset,
 411             fake_ident_token,
 412         );
 413         Some(ctx)
 414     }
 415
 416     /// Do the attribute expansion at the current cursor position for both original file and fake file
 417     /// as long as possible. As soon as one of the two expansions fail we stop to stay in sync.
 418     fn expand_and_fill(
 419         &mut self,
 420         mut original_file: SyntaxNode,
 421         mut speculative_file: SyntaxNode,
 422         mut offset: TextSize,
 423         mut fake_ident_token: SyntaxToken,
 424     ) {
 425         loop {
 426             // Expand attributes
 427             if let (Some(actual_item), Some(item_with_fake_ident)) = (
 428                 find_node_at_offset::<ast::Item>(&original_file, offset),
 429                 find_node_at_offset::<ast::Item>(&speculative_file, offset),
 430             ) {
 431                 match (
 432                     self.sema.expand_attr_macro(&actual_item),
 433                     self.sema.speculative_expand_attr_macro(
 434                         &actual_item,
 435                         &item_with_fake_ident,
 436                         fake_ident_token.clone(),
 437                     ),
 438                 ) {
 439                     (Some(actual_expansion), Some(speculative_expansion)) => {
 440                         let new_offset = speculative_expansion.1.text_range().start();
 441                         if new_offset > actual_expansion.text_range().end() {
 442                             break;
 443                         }
 444                         original_file = actual_expansion;
 445                         speculative_file = speculative_expansion.0;
 446                         fake_ident_token = speculative_expansion.1;
 447                         offset = new_offset;
 448                         continue;
 449                     }
 450                     (None, None) => (),
 451                     _ => break,
 452                 }
 453             }
 454
 455             // Expand fn-like macro calls
 456             if let (Some(actual_macro_call), Some(macro_call_with_fake_ident)) = (
 457                 find_node_at_offset::<ast::MacroCall>(&original_file, offset),
 458                 find_node_at_offset::<ast::MacroCall>(&speculative_file, offset),
 459             ) {
 460                 let mac_call_path0 = actual_macro_call.path().as_ref().map(|s| s.syntax().text());
 461                 let mac_call_path1 =
 462                     macro_call_with_fake_ident.path().as_ref().map(|s| s.syntax().text());
 463                 if mac_call_path0 != mac_call_path1 {
 464                     break;
 465                 }
 466                 let speculative_args = match macro_call_with_fake_ident.token_tree() {
 467                     Some(tt) => tt,
 468                     None => break,
 469                 };
 470
 471                 if let (Some(actual_expansion), Some(speculative_expansion)) = (
 472                     self.sema.expand(&actual_macro_call),
 473                     self.sema.speculative_expand(
 474                         &actual_macro_call,
 475                         &speculative_args,
 476                         fake_ident_token,
 477                     ),
 478                 ) {
 479                     let new_offset = speculative_expansion.1.text_range().start();
 480                     if new_offset > actual_expansion.text_range().end() {
 481                         break;
 482                     }
 483                     original_file = actual_expansion;
 484                     speculative_file = speculative_expansion.0;
 485                     fake_ident_token = speculative_expansion.1;
 486                     offset = new_offset;
 487                 } else {
 488                     break;
 489                 }
 490             } else {
 491                 break;
 492             }
 493         }
 494
 495         self.fill(&original_file, speculative_file, offset);
 496     }
 497
 498     fn expected_type_and_name(&self) -> (Option<Type>, Option<NameOrNameRef>) {
 499         let mut node = match self.token.parent() {
 500             Some(it) => it,
 501             None => return (None, None),
 502         };
 503         loop {
 504             break match_ast! {
 505                 match node {
 506                     ast::LetStmt(it) => {
 507                         cov_mark::hit!(expected_type_let_with_leading_char);
 508                         cov_mark::hit!(expected_type_let_without_leading_char);
 509                         let ty = it.pat()
 510                             .and_then(|pat| self.sema.type_of_pat(&pat))
 511                             .or_else(|| it.initializer().and_then(|it| self.sema.type_of_expr(&it)))
 512                             .map(TypeInfo::original);
 513                         let name = match it.pat() {
 514                             Some(ast::Pat::IdentPat(ident)) => ident.name().map(NameOrNameRef::Name),
 515                             Some(_) | None => None,
 516                         };
 517
 518                         (ty, name)
 519                     },
 520                     ast::ArgList(_) => {
 521                         cov_mark::hit!(expected_type_fn_param);
 522                         ActiveParameter::at_token(
 523                             &self.sema,
 524                             self.token.clone(),
 525                         ).map(|ap| {
 526                             let name = ap.ident().map(NameOrNameRef::Name);
 527                             let ty = if has_ref(&self.token) {
 528                                 cov_mark::hit!(expected_type_fn_param_ref);
 529                                 ap.ty.remove_ref()
 530                             } else {
 531                                 Some(ap.ty)
 532                             };
 533                             (ty, name)
 534                         })
 535                         .unwrap_or((None, None))
 536                     },
 537                     ast::RecordExprFieldList(it) => {
 538                         // wouldn't try {} be nice...
 539                         (|| {
 540                             if self.token.kind() == T![..]
 541                                 || self.token.prev_token().map(|t| t.kind()) == Some(T![..])
 542                             {
 543                                 cov_mark::hit!(expected_type_struct_func_update);
 544                                 let record_expr = it.syntax().parent().and_then(ast::RecordExpr::cast)?;
 545                                 let ty = self.sema.type_of_expr(&record_expr.into())?;
 546                                 Some((
 547                                     Some(ty.original),
 548                                     None
 549                                 ))
 550                             } else {
 551                                 cov_mark::hit!(expected_type_struct_field_without_leading_char);
 552                                 let expr_field = self.token.prev_sibling_or_token()?
 553                                     .into_node()
 554                                     .and_then(ast::RecordExprField::cast)?;
 555                                 let (_, _, ty) = self.sema.resolve_record_field(&expr_field)?;
 556                                 Some((
 557                                     Some(ty),
 558                                     expr_field.field_name().map(NameOrNameRef::NameRef),
 559                                 ))
 560                             }
 561                         })().unwrap_or((None, None))
 562                     },
 563                     ast::RecordExprField(it) => {
 564                         if let Some(expr) = it.expr() {
 565                             cov_mark::hit!(expected_type_struct_field_with_leading_char);
 566                             (
 567                                 self.sema.type_of_expr(&expr).map(TypeInfo::original),
 568                                 it.field_name().map(NameOrNameRef::NameRef),
 569                             )
 570                         } else {
 571                             cov_mark::hit!(expected_type_struct_field_followed_by_comma);
 572                             let ty = self.sema.resolve_record_field(&it)
 573                                 .map(|(_, _, ty)| ty);
 574                             (
 575                                 ty,
 576                                 it.field_name().map(NameOrNameRef::NameRef),
 577                             )
 578                         }
 579                     },
 580                     ast::MatchExpr(it) => {
 581                         cov_mark::hit!(expected_type_match_arm_without_leading_char);
 582                         let ty = it.expr().and_then(|e| self.sema.type_of_expr(&e)).map(TypeInfo::original);
 583                         (ty, None)
 584                     },
 585                     ast::IfExpr(it) => {
 586                         cov_mark::hit!(expected_type_if_let_without_leading_char);
 587                         let ty = it.condition()
 588                             .and_then(|cond| cond.expr())
 589                             .and_then(|e| self.sema.type_of_expr(&e))
 590                             .map(TypeInfo::original);
 591                         (ty, None)
 592                     },
 593                     ast::IdentPat(it) => {
 594                         cov_mark::hit!(expected_type_if_let_with_leading_char);
 595                         cov_mark::hit!(expected_type_match_arm_with_leading_char);
 596                         let ty = self.sema.type_of_pat(&ast::Pat::from(it)).map(TypeInfo::original);
 597                         (ty, None)
 598                     },
 599                     ast::Fn(it) => {
 600                         cov_mark::hit!(expected_type_fn_ret_with_leading_char);
 601                         cov_mark::hit!(expected_type_fn_ret_without_leading_char);
 602                         let def = self.sema.to_def(&it);
 603                         (def.map(|def| def.ret_type(self.db)), None)
 604                     },
 605                     ast::ClosureExpr(it) => {
 606                         let ty = self.sema.type_of_expr(&it.into());
 607                         ty.and_then(|ty| ty.original.as_callable(self.db))
 608                             .map(|c| (Some(c.return_type()), None))
 609                             .unwrap_or((None, None))
 610                     },
 611                     ast::ParamList(_) => (None, None),
 612                     ast::Stmt(_) => (None, None),
 613                     ast::Item(_) => (None, None),
 614                     _ => {
 615                         match node.parent() {
 616                             Some(n) => {
 617                                 node = n;
 618                                 continue;
 619                             },
 620                             None => (None, None),
 621                         }
 622                     },
 623                 }
 624             };
 625         }
 626     }
 627
 628     fn fill(
 629         &mut self,
 630         original_file: &SyntaxNode,
 631         file_with_fake_ident: SyntaxNode,
 632         offset: TextSize,
 633     ) {
 634         let fake_ident_token = file_with_fake_ident.token_at_offset(offset).right_biased().unwrap();
 635         let syntax_element = NodeOrToken::Token(fake_ident_token);
 636         self.previous_token = previous_token(syntax_element.clone());
 637         self.attribute_under_caret = syntax_element.ancestors().find_map(ast::Attr::cast);
 638         self.no_completion_required = {
 639             let inside_impl_trait_block = inside_impl_trait_block(syntax_element.clone());
 640             let fn_is_prev = self.previous_token_is(T![fn]);
 641             let for_is_prev2 = for_is_prev2(syntax_element.clone());
 642             (fn_is_prev && !inside_impl_trait_block) || for_is_prev2
 643         };
 644
 645         self.incomplete_let =
 646             syntax_element.ancestors().take(6).find_map(ast::LetStmt::cast).map_or(false, |it| {
 647                 it.syntax().text_range().end() == syntax_element.text_range().end()
 648             });
 649
 650         let (expected_type, expected_name) = self.expected_type_and_name();
 651         self.expected_type = expected_type;
 652         self.expected_name = expected_name;
 653
 654         let name_like = match find_node_at_offset(&file_with_fake_ident, offset) {
 655             Some(it) => it,
 656             None => return,
 657         };
 658         self.completion_location =
 659             determine_location(&self.sema, original_file, offset, &name_like);
 660         self.prev_sibling = determine_prev_sibling(&name_like);
 661         self.name_syntax =
 662             find_node_at_offset(original_file, name_like.syntax().text_range().start());
 663         self.impl_def = self
 664             .sema
 665             .token_ancestors_with_macros(self.token.clone())
 666             .take_while(|it| it.kind() != SOURCE_FILE && it.kind() != MODULE)
 667             .find_map(ast::Impl::cast);
 668         self.function_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::Fn::cast);
 673         match name_like {
 674             ast::NameLike::Lifetime(lifetime) => {
 675                 self.lifetime_ctx =
 676                     Self::classify_lifetime(&self.sema, original_file, lifetime, offset);
 677             }
 678             ast::NameLike::NameRef(name_ref) => {
 679                 if let Some((path_ctx, pat_ctx)) =
 680                     Self::classify_name_ref(&self.sema, original_file, name_ref)
 681                 {
 682                     self.path_context = Some(path_ctx);
 683                     self.pattern_ctx = pat_ctx;
 684                 }
 685             }
 686             ast::NameLike::Name(name) => {
 687                 self.pattern_ctx = Self::classify_name(&self.sema, name);
 688             }
 689         }
 690     }
 691
 692     fn classify_lifetime(
 693         sema: &Semantics<RootDatabase>,
 694         original_file: &SyntaxNode,
 695         lifetime: ast::Lifetime,
 696         offset: TextSize,
 697     ) -> Option<LifetimeContext> {
 698         let parent = lifetime.syntax().parent()?;
 699         if parent.kind() == ERROR {
 700             return None;
 701         }
 702
 703         Some(match_ast! {
 704             match parent {
 705                 ast::LifetimeParam(_) => LifetimeContext::LifetimeParam(sema.find_node_at_offset_with_macros(original_file, offset)),
 706                 ast::BreakExpr(_) => LifetimeContext::LabelRef,
 707                 ast::ContinueExpr(_) => LifetimeContext::LabelRef,
 708                 ast::Label(_) => LifetimeContext::LabelDef,
 709                 _ => LifetimeContext::Lifetime,
 710             }
 711         })
 712     }
 713
 714     fn classify_name(_sema: &Semantics<RootDatabase>, name: ast::Name) -> Option<PatternContext> {
 715         let bind_pat = name.syntax().parent().and_then(ast::IdentPat::cast)?;
 716         let is_name_in_field_pat = bind_pat
 717             .syntax()
 718             .parent()
 719             .and_then(ast::RecordPatField::cast)
 720             .map_or(false, |pat_field| pat_field.name_ref().is_none());
 721         if is_name_in_field_pat {
 722             return None;
 723         }
 724         if !bind_pat.is_simple_ident() {
 725             return None;
 726         }
 727         Some(pattern_context_for(bind_pat.into()))
 728     }
 729
 730     fn classify_name_ref(
 731         _sema: &Semantics<RootDatabase>,
 732         original_file: &SyntaxNode,
 733         name_ref: ast::NameRef,
 734     ) -> Option<(PathCompletionContext, Option<PatternContext>)> {
 735         let parent = name_ref.syntax().parent()?;
 736         let segment = ast::PathSegment::cast(parent)?;
 737         let path = segment.parent_path();
 738
 739         let mut path_ctx = PathCompletionContext {
 740             has_call_parens: false,
 741             is_trivial_path: false,
 742             qualifier: None,
 743             parent: None,
 744             has_type_args: false,
 745             can_be_stmt: false,
 746             in_loop_body: false,
 747             use_tree_parent: false,
 748             kind: None,
 749         };
 750         let mut pat_ctx = None;
 751         path_ctx.in_loop_body = is_in_loop_body(name_ref.syntax());
 752
 753         path_ctx.kind  = path.syntax().ancestors().find_map(|it| {
 754             match_ast! {
 755                 match it {
 756                     ast::PathType(_) => Some(PathKind::Type),
 757                     ast::PathExpr(it) => {
 758                         path_ctx.has_call_parens = it.syntax().parent().map_or(false, |it| ast::CallExpr::can_cast(it.kind()));
 759                         Some(PathKind::Expr)
 760                     },
 761                     ast::TupleStructPat(it) => {
 762                         path_ctx.has_call_parens = true;
 763                         pat_ctx = Some(pattern_context_for(it.into()));
 764                         Some(PathKind::Pat)
 765                     },
 766                     ast::RecordPat(it) => {
 767                         pat_ctx = Some(pattern_context_for(it.into()));
 768                         Some(PathKind::Pat)
 769                     },
 770                     ast::PathPat(it) => {
 771                         pat_ctx = Some(pattern_context_for(it.into()));
 772                         Some(PathKind::Pat)
 773                     },
 774                     ast::MacroCall(it) => it.excl_token().and(Some(PathKind::Mac)),
 775                     ast::Meta(_) => Some(PathKind::Attr),
 776                     ast::Visibility(it) => Some(PathKind::Vis { has_in_token: it.in_token().is_some() }),
 777                     ast::UseTree(_) => Some(PathKind::Use),
 778                     _ => None,
 779                 }
 780             }
 781         });
 782         path_ctx.has_type_args = segment.generic_arg_list().is_some();
 783
 784         if let Some((path, use_tree_parent)) = path_or_use_tree_qualifier(&path) {
 785             path_ctx.use_tree_parent = use_tree_parent;
 786             path_ctx.qualifier = path
 787                 .segment()
 788                 .and_then(|it| {
 789                     find_node_with_range::<ast::PathSegment>(
 790                         original_file,
 791                         it.syntax().text_range(),
 792                     )
 793                 })
 794                 .map(|it| it.parent_path());
 795             return Some((path_ctx, pat_ctx));
 796         }
 797
 798         if let Some(segment) = path.segment() {
 799             if segment.coloncolon_token().is_some() {
 800                 return Some((path_ctx, pat_ctx));
 801             }
 802         }
 803
 804         path_ctx.is_trivial_path = true;
 805
 806         // Find either enclosing expr statement (thing with `;`) or a
 807         // block. If block, check that we are the last expr.
 808         path_ctx.can_be_stmt = name_ref
 809             .syntax()
 810             .ancestors()
 811             .find_map(|node| {
 812                 if let Some(stmt) = ast::ExprStmt::cast(node.clone()) {
 813                     return Some(stmt.syntax().text_range() == name_ref.syntax().text_range());
 814                 }
 815                 if let Some(stmt_list) = ast::StmtList::cast(node) {
 816                     return Some(
 817                         stmt_list.tail_expr().map(|e| e.syntax().text_range())
 818                             == Some(name_ref.syntax().text_range()),
 819                     );
 820                 }
 821                 None
 822             })
 823             .unwrap_or(false);
 824         Some((path_ctx, pat_ctx))
 825     }
 826 }
 827
 828 fn pattern_context_for(pat: ast::Pat) -> PatternContext {
 829     let mut is_param = None;
 830     let (refutability, has_type_ascription) =
 831     pat
 832         .syntax()
 833         .ancestors()
 834         .skip_while(|it| ast::Pat::can_cast(it.kind()))
 835         .next()
 836         .map_or((PatternRefutability::Irrefutable, false), |node| {
 837             let refutability = match_ast! {
 838                 match node {
 839                     ast::LetStmt(let_) => return (PatternRefutability::Irrefutable, let_.ty().is_some()),
 840                     ast::Param(param) => {
 841                         let is_closure_param = param
 842                             .syntax()
 843                             .ancestors()
 844                             .nth(2)
 845                             .and_then(ast::ClosureExpr::cast)
 846                             .is_some();
 847                         is_param = Some(if is_closure_param {
 848                             ParamKind::Closure
 849                         } else {
 850                             ParamKind::Function
 851                         });
 852                         return (PatternRefutability::Irrefutable, param.ty().is_some())
 853                     },
 854                     ast::MatchArm(_) => PatternRefutability::Refutable,
 855                     ast::Condition(_) => PatternRefutability::Refutable,
 856                     ast::ForExpr(_) => PatternRefutability::Irrefutable,
 857                     _ => PatternRefutability::Irrefutable,
 858                 }
 859             };
 860             (refutability, false)
 861         });
 862     PatternContext { refutability, is_param, has_type_ascription }
 863 }
 864 fn find_node_with_range<N: AstNode>(syntax: &SyntaxNode, range: TextRange) -> Option<N> {
 865     syntax.covering_element(range).ancestors().find_map(N::cast)
 866 }
 867
 868 fn path_or_use_tree_qualifier(path: &ast::Path) -> Option<(ast::Path, bool)> {
 869     if let Some(qual) = path.qualifier() {
 870         return Some((qual, false));
 871     }
 872     let use_tree_list = path.syntax().ancestors().find_map(ast::UseTreeList::cast)?;
 873     let use_tree = use_tree_list.syntax().parent().and_then(ast::UseTree::cast)?;
 874     use_tree.path().zip(Some(true))
 875 }
 876
 877 fn has_ref(token: &SyntaxToken) -> bool {
 878     let mut token = token.clone();
 879     for skip in [WHITESPACE, IDENT, T![mut]] {
 880         if token.kind() == skip {
 881             token = match token.prev_token() {
 882                 Some(it) => it,
 883                 None => return false,
 884             }
 885         }
 886     }
 887     token.kind() == T![&]
 888 }
 889
 890 #[cfg(test)]
 891 mod tests {
 892     use expect_test::{expect, Expect};
 893     use hir::HirDisplay;
 894
 895     use crate::tests::{position, TEST_CONFIG};
 896
 897     use super::CompletionContext;
 898
 899     fn check_expected_type_and_name(ra_fixture: &str, expect: Expect) {
 900         let (db, pos) = position(ra_fixture);
 901         let config = TEST_CONFIG;
 902         let completion_context = CompletionContext::new(&db, pos, &config).unwrap();
 903
 904         let ty = completion_context
 905             .expected_type
 906             .map(|t| t.display_test(&db).to_string())
 907             .unwrap_or("?".to_owned());
 908
 909         let name = completion_context
 910             .expected_name
 911             .map_or_else(|| "?".to_owned(), |name| name.to_string());
 912
 913         expect.assert_eq(&format!("ty: {}, name: {}", ty, name));
 914     }
 915
 916     #[test]
 917     fn expected_type_let_without_leading_char() {
 918         cov_mark::check!(expected_type_let_without_leading_char);
 919         check_expected_type_and_name(
 920             r#"
 921 fn foo() {
 922     let x: u32 = $0;
 923 }
 924 "#,
 925             expect![[r#"ty: u32, name: x"#]],
 926         );
 927     }
 928
 929     #[test]
 930     fn expected_type_let_with_leading_char() {
 931         cov_mark::check!(expected_type_let_with_leading_char);
 932         check_expected_type_and_name(
 933             r#"
 934 fn foo() {
 935     let x: u32 = c$0;
 936 }
 937 "#,
 938             expect![[r#"ty: u32, name: x"#]],
 939         );
 940     }
 941
 942     #[test]
 943     fn expected_type_let_pat() {
 944         check_expected_type_and_name(
 945             r#"
 946 fn foo() {
 947     let x$0 = 0u32;
 948 }
 949 "#,
 950             expect![[r#"ty: u32, name: ?"#]],
 951         );
 952         check_expected_type_and_name(
 953             r#"
 954 fn foo() {
 955     let $0 = 0u32;
 956 }
 957 "#,
 958             expect![[r#"ty: u32, name: ?"#]],
 959         );
 960     }
 961
 962     #[test]
 963     fn expected_type_fn_param() {
 964         cov_mark::check!(expected_type_fn_param);
 965         check_expected_type_and_name(
 966             r#"
 967 fn foo() { bar($0); }
 968 fn bar(x: u32) {}
 969 "#,
 970             expect![[r#"ty: u32, name: x"#]],
 971         );
 972         check_expected_type_and_name(
 973             r#"
 974 fn foo() { bar(c$0); }
 975 fn bar(x: u32) {}
 976 "#,
 977             expect![[r#"ty: u32, name: x"#]],
 978         );
 979     }
 980
 981     #[test]
 982     fn expected_type_fn_param_ref() {
 983         cov_mark::check!(expected_type_fn_param_ref);
 984         check_expected_type_and_name(
 985             r#"
 986 fn foo() { bar(&$0); }
 987 fn bar(x: &u32) {}
 988 "#,
 989             expect![[r#"ty: u32, name: x"#]],
 990         );
 991         check_expected_type_and_name(
 992             r#"
 993 fn foo() { bar(&mut $0); }
 994 fn bar(x: &mut u32) {}
 995 "#,
 996             expect![[r#"ty: u32, name: x"#]],
 997         );
 998         check_expected_type_and_name(
 999             r#"
1000 fn foo() { bar(&c$0); }
1001 fn bar(x: &u32) {}
1002         "#,
1003             expect![[r#"ty: u32, name: x"#]],
1004         );
1005     }
1006
1007     #[test]
1008     fn expected_type_struct_field_without_leading_char() {
1009         cov_mark::check!(expected_type_struct_field_without_leading_char);
1010         check_expected_type_and_name(
1011             r#"
1012 struct Foo { a: u32 }
1013 fn foo() {
1014     Foo { a: $0 };
1015 }
1016 "#,
1017             expect![[r#"ty: u32, name: a"#]],
1018         )
1019     }
1020
1021     #[test]
1022     fn expected_type_struct_field_followed_by_comma() {
1023         cov_mark::check!(expected_type_struct_field_followed_by_comma);
1024         check_expected_type_and_name(
1025             r#"
1026 struct Foo { a: u32 }
1027 fn foo() {
1028     Foo { a: $0, };
1029 }
1030 "#,
1031             expect![[r#"ty: u32, name: a"#]],
1032         )
1033     }
1034
1035     #[test]
1036     fn expected_type_generic_struct_field() {
1037         check_expected_type_and_name(
1038             r#"
1039 struct Foo<T> { a: T }
1040 fn foo() -> Foo<u32> {
1041     Foo { a: $0 }
1042 }
1043 "#,
1044             expect![[r#"ty: u32, name: a"#]],
1045         )
1046     }
1047
1048     #[test]
1049     fn expected_type_struct_field_with_leading_char() {
1050         cov_mark::check!(expected_type_struct_field_with_leading_char);
1051         check_expected_type_and_name(
1052             r#"
1053 struct Foo { a: u32 }
1054 fn foo() {
1055     Foo { a: c$0 };
1056 }
1057 "#,
1058             expect![[r#"ty: u32, name: a"#]],
1059         );
1060     }
1061
1062     #[test]
1063     fn expected_type_match_arm_without_leading_char() {
1064         cov_mark::check!(expected_type_match_arm_without_leading_char);
1065         check_expected_type_and_name(
1066             r#"
1067 enum E { X }
1068 fn foo() {
1069    match E::X { $0 }
1070 }
1071 "#,
1072             expect![[r#"ty: E, name: ?"#]],
1073         );
1074     }
1075
1076     #[test]
1077     fn expected_type_match_arm_with_leading_char() {
1078         cov_mark::check!(expected_type_match_arm_with_leading_char);
1079         check_expected_type_and_name(
1080             r#"
1081 enum E { X }
1082 fn foo() {
1083    match E::X { c$0 }
1084 }
1085 "#,
1086             expect![[r#"ty: E, name: ?"#]],
1087         );
1088     }
1089
1090     #[test]
1091     fn expected_type_if_let_without_leading_char() {
1092         cov_mark::check!(expected_type_if_let_without_leading_char);
1093         check_expected_type_and_name(
1094             r#"
1095 enum Foo { Bar, Baz, Quux }
1096
1097 fn foo() {
1098     let f = Foo::Quux;
1099     if let $0 = f { }
1100 }
1101 "#,
1102             expect![[r#"ty: Foo, name: ?"#]],
1103         )
1104     }
1105
1106     #[test]
1107     fn expected_type_if_let_with_leading_char() {
1108         cov_mark::check!(expected_type_if_let_with_leading_char);
1109         check_expected_type_and_name(
1110             r#"
1111 enum Foo { Bar, Baz, Quux }
1112
1113 fn foo() {
1114     let f = Foo::Quux;
1115     if let c$0 = f { }
1116 }
1117 "#,
1118             expect![[r#"ty: Foo, name: ?"#]],
1119         )
1120     }
1121
1122     #[test]
1123     fn expected_type_fn_ret_without_leading_char() {
1124         cov_mark::check!(expected_type_fn_ret_without_leading_char);
1125         check_expected_type_and_name(
1126             r#"
1127 fn foo() -> u32 {
1128     $0
1129 }
1130 "#,
1131             expect![[r#"ty: u32, name: ?"#]],
1132         )
1133     }
1134
1135     #[test]
1136     fn expected_type_fn_ret_with_leading_char() {
1137         cov_mark::check!(expected_type_fn_ret_with_leading_char);
1138         check_expected_type_and_name(
1139             r#"
1140 fn foo() -> u32 {
1141     c$0
1142 }
1143 "#,
1144             expect![[r#"ty: u32, name: ?"#]],
1145         )
1146     }
1147
1148     #[test]
1149     fn expected_type_fn_ret_fn_ref_fully_typed() {
1150         check_expected_type_and_name(
1151             r#"
1152 fn foo() -> u32 {
1153     foo$0
1154 }
1155 "#,
1156             expect![[r#"ty: u32, name: ?"#]],
1157         )
1158     }
1159
1160     #[test]
1161     fn expected_type_closure_param_return() {
1162         // FIXME: make this work with `|| $0`
1163         check_expected_type_and_name(
1164             r#"
1165 //- minicore: fn
1166 fn foo() {
1167     bar(|| a$0);
1168 }
1169
1170 fn bar(f: impl FnOnce() -> u32) {}
1171 "#,
1172             expect![[r#"ty: u32, name: ?"#]],
1173         );
1174     }
1175
1176     #[test]
1177     fn expected_type_generic_function() {
1178         check_expected_type_and_name(
1179             r#"
1180 fn foo() {
1181     bar::<u32>($0);
1182 }
1183
1184 fn bar<T>(t: T) {}
1185 "#,
1186             expect![[r#"ty: u32, name: t"#]],
1187         );
1188     }
1189
1190     #[test]
1191     fn expected_type_generic_method() {
1192         check_expected_type_and_name(
1193             r#"
1194 fn foo() {
1195     S(1u32).bar($0);
1196 }
1197
1198 struct S<T>(T);
1199 impl<T> S<T> {
1200     fn bar(self, t: T) {}
1201 }
1202 "#,
1203             expect![[r#"ty: u32, name: t"#]],
1204         );
1205     }
1206
1207     #[test]
1208     fn expected_type_functional_update() {
1209         cov_mark::check!(expected_type_struct_func_update);
1210         check_expected_type_and_name(
1211             r#"
1212 struct Foo { field: u32 }
1213 fn foo() {
1214     Foo {
1215         ..$0
1216     }
1217 }
1218 "#,
1219             expect![[r#"ty: Foo, name: ?"#]],
1220         );
1221     }
1222
1223     #[test]
1224     fn expected_type_param_pat() {
1225         check_expected_type_and_name(
1226             r#"
1227 struct Foo { field: u32 }
1228 fn foo(a$0: Foo) {}
1229 "#,
1230             expect![[r#"ty: Foo, name: ?"#]],
1231         );
1232         check_expected_type_and_name(
1233             r#"
1234 struct Foo { field: u32 }
1235 fn foo($0: Foo) {}
1236 "#,
1237             // FIXME make this work, currently fails due to pattern recovery eating the `:`
1238             expect![[r#"ty: ?, name: ?"#]],
1239         );
1240     }
1241 }