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