crates/ide_completion/src/context.rs

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