crates/hir_ty/src/display.rs

   1 //! FIXME: write short doc here
   2
   3 use std::{array, fmt};
   4
   5 use chalk_ir::Mutability;
   6 use hir_def::{
   7     db::DefDatabase,
   8     find_path,
   9     generics::TypeParamProvenance,
  10     item_scope::ItemInNs,
  11     path::{Path, PathKind},
  12     type_ref::{TypeBound, TypeRef},
  13     visibility::Visibility,
  14     AssocContainerId, Lookup, ModuleId, TraitId,
  15 };
  16 use hir_expand::name::Name;
  17
  18 use crate::{
  19     db::HirDatabase, from_assoc_type_id, from_foreign_def_id, from_placeholder_idx, primitive,
  20     to_assoc_type_id, traits::chalk::from_chalk, utils::generics, AdtId, AliasEq, AliasTy,
  21     CallableDefId, CallableSig, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime, OpaqueTy,
  22     ProjectionTy, QuantifiedWhereClause, Scalar, TraitRef, Ty, TyExt, TyKind, WhereClause,
  23 };
  24
  25 pub struct HirFormatter<'a> {
  26     pub db: &'a dyn HirDatabase,
  27     fmt: &'a mut dyn fmt::Write,
  28     buf: String,
  29     curr_size: usize,
  30     pub(crate) max_size: Option<usize>,
  31     omit_verbose_types: bool,
  32     display_target: DisplayTarget,
  33 }
  34
  35 pub trait HirDisplay {
  36     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError>;
  37
  38     /// Returns a `Display`able type that is human-readable.
  39     fn into_displayable<'a>(
  40         &'a self,
  41         db: &'a dyn HirDatabase,
  42         max_size: Option<usize>,
  43         omit_verbose_types: bool,
  44         display_target: DisplayTarget,
  45     ) -> HirDisplayWrapper<'a, Self>
  46     where
  47         Self: Sized,
  48     {
  49         HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
  50     }
  51
  52     /// Returns a `Display`able type that is human-readable.
  53     /// Use this for showing types to the user (e.g. diagnostics)
  54     fn display<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
  55     where
  56         Self: Sized,
  57     {
  58         HirDisplayWrapper {
  59             db,
  60             t: self,
  61             max_size: None,
  62             omit_verbose_types: false,
  63             display_target: DisplayTarget::Diagnostics,
  64         }
  65     }
  66
  67     /// Returns a `Display`able type that is human-readable and tries to be succinct.
  68     /// Use this for showing types to the user where space is constrained (e.g. doc popups)
  69     fn display_truncated<'a>(
  70         &'a self,
  71         db: &'a dyn HirDatabase,
  72         max_size: Option<usize>,
  73     ) -> HirDisplayWrapper<'a, Self>
  74     where
  75         Self: Sized,
  76     {
  77         HirDisplayWrapper {
  78             db,
  79             t: self,
  80             max_size,
  81             omit_verbose_types: true,
  82             display_target: DisplayTarget::Diagnostics,
  83         }
  84     }
  85
  86     /// Returns a String representation of `self` that can be inserted into the given module.
  87     /// Use this when generating code (e.g. assists)
  88     fn display_source_code<'a>(
  89         &'a self,
  90         db: &'a dyn HirDatabase,
  91         module_id: ModuleId,
  92     ) -> Result<String, DisplaySourceCodeError> {
  93         let mut result = String::new();
  94         match self.hir_fmt(&mut HirFormatter {
  95             db,
  96             fmt: &mut result,
  97             buf: String::with_capacity(20),
  98             curr_size: 0,
  99             max_size: None,
 100             omit_verbose_types: false,
 101             display_target: DisplayTarget::SourceCode { module_id },
 102         }) {
 103             Ok(()) => {}
 104             Err(HirDisplayError::FmtError) => panic!("Writing to String can't fail!"),
 105             Err(HirDisplayError::DisplaySourceCodeError(e)) => return Err(e),
 106         };
 107         Ok(result)
 108     }
 109
 110     /// Returns a String representation of `self` for test purposes
 111     fn display_test<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
 112     where
 113         Self: Sized,
 114     {
 115         HirDisplayWrapper {
 116             db,
 117             t: self,
 118             max_size: None,
 119             omit_verbose_types: false,
 120             display_target: DisplayTarget::Test,
 121         }
 122     }
 123 }
 124
 125 impl<'a> HirFormatter<'a> {
 126     pub fn write_joined<T: HirDisplay>(
 127         &mut self,
 128         iter: impl IntoIterator<Item = T>,
 129         sep: &str,
 130     ) -> Result<(), HirDisplayError> {
 131         let mut first = true;
 132         for e in iter {
 133             if !first {
 134                 write!(self, "{}", sep)?;
 135             }
 136             first = false;
 137             e.hir_fmt(self)?;
 138         }
 139         Ok(())
 140     }
 141
 142     /// This allows using the `write!` macro directly with a `HirFormatter`.
 143     pub fn write_fmt(&mut self, args: fmt::Arguments) -> Result<(), HirDisplayError> {
 144         // We write to a buffer first to track output size
 145         self.buf.clear();
 146         fmt::write(&mut self.buf, args)?;
 147         self.curr_size += self.buf.len();
 148
 149         // Then we write to the internal formatter from the buffer
 150         self.fmt.write_str(&self.buf).map_err(HirDisplayError::from)
 151     }
 152
 153     pub fn should_truncate(&self) -> bool {
 154         if let Some(max_size) = self.max_size {
 155             self.curr_size >= max_size
 156         } else {
 157             false
 158         }
 159     }
 160
 161     pub fn omit_verbose_types(&self) -> bool {
 162         self.omit_verbose_types
 163     }
 164 }
 165
 166 #[derive(Clone, Copy)]
 167 pub enum DisplayTarget {
 168     /// Display types for inlays, doc popups, autocompletion, etc...
 169     /// Showing `{unknown}` or not qualifying paths is fine here.
 170     /// There's no reason for this to fail.
 171     Diagnostics,
 172     /// Display types for inserting them in source files.
 173     /// The generated code should compile, so paths need to be qualified.
 174     SourceCode { module_id: ModuleId },
 175     /// Only for test purpose to keep real types
 176     Test,
 177 }
 178
 179 impl DisplayTarget {
 180     fn is_source_code(&self) -> bool {
 181         matches!(self, Self::SourceCode { .. })
 182     }
 183     fn is_test(&self) -> bool {
 184         matches!(self, Self::Test)
 185     }
 186 }
 187
 188 #[derive(Debug)]
 189 pub enum DisplaySourceCodeError {
 190     PathNotFound,
 191     UnknownType,
 192     Closure,
 193 }
 194
 195 pub enum HirDisplayError {
 196     /// Errors that can occur when generating source code
 197     DisplaySourceCodeError(DisplaySourceCodeError),
 198     /// `FmtError` is required to be compatible with std::fmt::Display
 199     FmtError,
 200 }
 201 impl From<fmt::Error> for HirDisplayError {
 202     fn from(_: fmt::Error) -> Self {
 203         Self::FmtError
 204     }
 205 }
 206
 207 pub struct HirDisplayWrapper<'a, T> {
 208     db: &'a dyn HirDatabase,
 209     t: &'a T,
 210     max_size: Option<usize>,
 211     omit_verbose_types: bool,
 212     display_target: DisplayTarget,
 213 }
 214
 215 impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
 216 where
 217     T: HirDisplay,
 218 {
 219     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 220         match self.t.hir_fmt(&mut HirFormatter {
 221             db: self.db,
 222             fmt: f,
 223             buf: String::with_capacity(20),
 224             curr_size: 0,
 225             max_size: self.max_size,
 226             omit_verbose_types: self.omit_verbose_types,
 227             display_target: self.display_target,
 228         }) {
 229             Ok(()) => Ok(()),
 230             Err(HirDisplayError::FmtError) => Err(fmt::Error),
 231             Err(HirDisplayError::DisplaySourceCodeError(_)) => {
 232                 // This should never happen
 233                 panic!("HirDisplay failed when calling Display::fmt!")
 234             }
 235         }
 236     }
 237 }
 238
 239 const TYPE_HINT_TRUNCATION: &str = "…";
 240
 241 impl<T: HirDisplay> HirDisplay for &'_ T {
 242     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 243         HirDisplay::hir_fmt(*self, f)
 244     }
 245 }
 246
 247 impl HirDisplay for ProjectionTy {
 248     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 249         if f.should_truncate() {
 250             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 251         }
 252
 253         let trait_ = f.db.trait_data(self.trait_(f.db));
 254         let first_parameter = self.self_type_parameter().into_displayable(
 255             f.db,
 256             f.max_size,
 257             f.omit_verbose_types,
 258             f.display_target,
 259         );
 260         write!(f, "<{} as {}", first_parameter, trait_.name)?;
 261         if self.substitution.len(&Interner) > 1 {
 262             write!(f, "<")?;
 263             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 264             write!(f, ">")?;
 265         }
 266         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
 267         Ok(())
 268     }
 269 }
 270
 271 impl HirDisplay for OpaqueTy {
 272     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 273         if f.should_truncate() {
 274             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 275         }
 276
 277         self.substitution.at(&Interner, 0).hir_fmt(f)
 278     }
 279 }
 280
 281 impl HirDisplay for GenericArg {
 282     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 283         match self.interned() {
 284             crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
 285         }
 286     }
 287 }
 288
 289 impl HirDisplay for Ty {
 290     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 291         if f.should_truncate() {
 292             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 293         }
 294
 295         match self.kind(&Interner) {
 296             TyKind::Never => write!(f, "!")?,
 297             TyKind::Str => write!(f, "str")?,
 298             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
 299             TyKind::Scalar(Scalar::Char) => write!(f, "char")?,
 300             &TyKind::Scalar(Scalar::Float(t)) => write!(f, "{}", primitive::float_ty_to_string(t))?,
 301             &TyKind::Scalar(Scalar::Int(t)) => write!(f, "{}", primitive::int_ty_to_string(t))?,
 302             &TyKind::Scalar(Scalar::Uint(t)) => write!(f, "{}", primitive::uint_ty_to_string(t))?,
 303             TyKind::Slice(t) => {
 304                 write!(f, "[")?;
 305                 t.hir_fmt(f)?;
 306                 write!(f, "]")?;
 307             }
 308             TyKind::Array(t) => {
 309                 write!(f, "[")?;
 310                 t.hir_fmt(f)?;
 311                 write!(f, "; _]")?;
 312             }
 313             TyKind::Raw(m, t) | TyKind::Ref(m, t) => {
 314                 let ty_display =
 315                     t.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 316
 317                 if matches!(self.kind(&Interner), TyKind::Raw(..)) {
 318                     write!(
 319                         f,
 320                         "*{}",
 321                         match m {
 322                             Mutability::Not => "const ",
 323                             Mutability::Mut => "mut ",
 324                         }
 325                     )?;
 326                 } else {
 327                     write!(
 328                         f,
 329                         "&{}",
 330                         match m {
 331                             Mutability::Not => "",
 332                             Mutability::Mut => "mut ",
 333                         }
 334                     )?;
 335                 }
 336
 337                 // FIXME: all this just to decide whether to use parentheses...
 338                 let datas;
 339                 let predicates: Vec<_> = match t.kind(&Interner) {
 340                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
 341                         dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
 342                     }
 343                     &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
 344                         opaque_ty_id,
 345                         substitution: ref parameters,
 346                     })) => {
 347                         let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty_id.into());
 348                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
 349                             datas =
 350                                 f.db.return_type_impl_traits(func)
 351                                     .expect("impl trait id without data");
 352                             let data = (*datas)
 353                                 .as_ref()
 354                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 355                             let bounds = data.subst(parameters);
 356                             bounds.value
 357                         } else {
 358                             Vec::new()
 359                         }
 360                     }
 361                     _ => Vec::new(),
 362                 };
 363
 364                 if let Some(WhereClause::Implemented(trait_ref)) =
 365                     predicates.get(0).map(|b| b.skip_binders())
 366                 {
 367                     let trait_ = trait_ref.hir_trait_id();
 368                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
 369                         && predicates.len() <= 2
 370                     {
 371                         return write!(f, "{}", ty_display);
 372                     }
 373                 }
 374
 375                 if predicates.len() > 1 {
 376                     write!(f, "(")?;
 377                     write!(f, "{}", ty_display)?;
 378                     write!(f, ")")?;
 379                 } else {
 380                     write!(f, "{}", ty_display)?;
 381                 }
 382             }
 383             TyKind::Tuple(_, substs) => {
 384                 if substs.len(&Interner) == 1 {
 385                     write!(f, "(")?;
 386                     substs.at(&Interner, 0).hir_fmt(f)?;
 387                     write!(f, ",)")?;
 388                 } else {
 389                     write!(f, "(")?;
 390                     f.write_joined(&*substs.interned(), ", ")?;
 391                     write!(f, ")")?;
 392                 }
 393             }
 394             TyKind::Function(fn_ptr) => {
 395                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 396                 sig.hir_fmt(f)?;
 397             }
 398             TyKind::FnDef(def, parameters) => {
 399                 let def = from_chalk(f.db, *def);
 400                 let sig = f.db.callable_item_signature(def).subst(parameters);
 401                 match def {
 402                     CallableDefId::FunctionId(ff) => {
 403                         write!(f, "fn {}", f.db.function_data(ff).name)?
 404                     }
 405                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 406                     CallableDefId::EnumVariantId(e) => {
 407                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 408                     }
 409                 };
 410                 if parameters.len(&Interner) > 0 {
 411                     let generics = generics(f.db.upcast(), def.into());
 412                     let (parent_params, self_param, type_params, _impl_trait_params) =
 413                         generics.provenance_split();
 414                     let total_len = parent_params + self_param + type_params;
 415                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 416                     if total_len > 0 {
 417                         write!(f, "<")?;
 418                         f.write_joined(&parameters.interned()[..total_len], ", ")?;
 419                         write!(f, ">")?;
 420                     }
 421                 }
 422                 write!(f, "(")?;
 423                 f.write_joined(sig.params(), ", ")?;
 424                 write!(f, ")")?;
 425                 let ret = sig.ret();
 426                 if !ret.is_unit() {
 427                     let ret_display = ret.into_displayable(
 428                         f.db,
 429                         f.max_size,
 430                         f.omit_verbose_types,
 431                         f.display_target,
 432                     );
 433
 434                     write!(f, " -> {}", ret_display)?;
 435                 }
 436             }
 437             TyKind::Adt(AdtId(def_id), parameters) => {
 438                 match f.display_target {
 439                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 440                         let name = match *def_id {
 441                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 442                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 443                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 444                         };
 445                         write!(f, "{}", name)?;
 446                     }
 447                     DisplayTarget::SourceCode { module_id } => {
 448                         if let Some(path) = find_path::find_path(
 449                             f.db.upcast(),
 450                             ItemInNs::Types((*def_id).into()),
 451                             module_id,
 452                         ) {
 453                             write!(f, "{}", path)?;
 454                         } else {
 455                             return Err(HirDisplayError::DisplaySourceCodeError(
 456                                 DisplaySourceCodeError::PathNotFound,
 457                             ));
 458                         }
 459                     }
 460                 }
 461
 462                 if parameters.len(&Interner) > 0 {
 463                     let parameters_to_write = if f.display_target.is_source_code()
 464                         || f.omit_verbose_types()
 465                     {
 466                         match self
 467                             .as_generic_def(f.db)
 468                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 469                             .filter(|defaults| !defaults.is_empty())
 470                         {
 471                             None => parameters.interned().as_ref(),
 472                             Some(default_parameters) => {
 473                                 let mut default_from = 0;
 474                                 for (i, parameter) in parameters.iter(&Interner).enumerate() {
 475                                     match (
 476                                         parameter.assert_ty_ref(&Interner).kind(&Interner),
 477                                         default_parameters.get(i),
 478                                     ) {
 479                                         (&TyKind::Unknown, _) | (_, None) => {
 480                                             default_from = i + 1;
 481                                         }
 482                                         (_, Some(default_parameter)) => {
 483                                             let actual_default = default_parameter
 484                                                 .clone()
 485                                                 .subst(&parameters.prefix(i));
 486                                             if parameter.assert_ty_ref(&Interner) != &actual_default
 487                                             {
 488                                                 default_from = i + 1;
 489                                             }
 490                                         }
 491                                     }
 492                                 }
 493                                 &parameters.interned()[0..default_from]
 494                             }
 495                         }
 496                     } else {
 497                         parameters.interned().as_ref()
 498                     };
 499                     if !parameters_to_write.is_empty() {
 500                         write!(f, "<")?;
 501                         f.write_joined(parameters_to_write, ", ")?;
 502                         write!(f, ">")?;
 503                     }
 504                 }
 505             }
 506             TyKind::AssociatedType(assoc_type_id, parameters) => {
 507                 let type_alias = from_assoc_type_id(*assoc_type_id);
 508                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 509                     AssocContainerId::TraitId(it) => it,
 510                     _ => panic!("not an associated type"),
 511                 };
 512                 let trait_ = f.db.trait_data(trait_);
 513                 let type_alias_data = f.db.type_alias_data(type_alias);
 514
 515                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 516                 if f.display_target.is_test() {
 517                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 518                     if parameters.len(&Interner) > 0 {
 519                         write!(f, "<")?;
 520                         f.write_joined(&*parameters.interned(), ", ")?;
 521                         write!(f, ">")?;
 522                     }
 523                 } else {
 524                     let projection_ty = ProjectionTy {
 525                         associated_ty_id: to_assoc_type_id(type_alias),
 526                         substitution: parameters.clone(),
 527                     };
 528
 529                     projection_ty.hir_fmt(f)?;
 530                 }
 531             }
 532             TyKind::ForeignType(type_alias) => {
 533                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 534                 write!(f, "{}", type_alias.name)?;
 535             }
 536             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 537                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 538                 match impl_trait_id {
 539                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 540                         let datas =
 541                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 542                         let data = (*datas)
 543                             .as_ref()
 544                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 545                         let bounds = data.subst(&parameters);
 546                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
 547                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 548                     }
 549                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 550                         write!(f, "impl Future<Output = ")?;
 551                         parameters.at(&Interner, 0).hir_fmt(f)?;
 552                         write!(f, ">")?;
 553                     }
 554                 }
 555             }
 556             TyKind::Closure(.., substs) => {
 557                 if f.display_target.is_source_code() {
 558                     return Err(HirDisplayError::DisplaySourceCodeError(
 559                         DisplaySourceCodeError::Closure,
 560                     ));
 561                 }
 562                 let sig = substs.at(&Interner, 0).assert_ty_ref(&Interner).callable_sig(f.db);
 563                 if let Some(sig) = sig {
 564                     if sig.params().is_empty() {
 565                         write!(f, "||")?;
 566                     } else if f.omit_verbose_types() {
 567                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 568                     } else {
 569                         write!(f, "|")?;
 570                         f.write_joined(sig.params(), ", ")?;
 571                         write!(f, "|")?;
 572                     };
 573
 574                     let ret_display = sig.ret().into_displayable(
 575                         f.db,
 576                         f.max_size,
 577                         f.omit_verbose_types,
 578                         f.display_target,
 579                     );
 580                     write!(f, " -> {}", ret_display)?;
 581                 } else {
 582                     write!(f, "{{closure}}")?;
 583                 }
 584             }
 585             TyKind::Placeholder(idx) => {
 586                 let id = from_placeholder_idx(f.db, *idx);
 587                 let generics = generics(f.db.upcast(), id.parent);
 588                 let param_data = &generics.params.types[id.local_id];
 589                 match param_data.provenance {
 590                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 591                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 592                     }
 593                     TypeParamProvenance::ArgumentImplTrait => {
 594                         let substs = generics.type_params_subst(f.db);
 595                         let bounds = f
 596                             .db
 597                             .generic_predicates(id.parent)
 598                             .into_iter()
 599                             .map(|pred| pred.clone().subst(&substs))
 600                             .filter(|wc| match &wc.skip_binders() {
 601                                 WhereClause::Implemented(tr) => tr.self_type_parameter() == self,
 602                                 WhereClause::AliasEq(AliasEq {
 603                                     alias: AliasTy::Projection(proj),
 604                                     ty: _,
 605                                 }) => proj.self_type_parameter() == self,
 606                                 _ => false,
 607                             })
 608                             .collect::<Vec<_>>();
 609                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds, f)?;
 610                     }
 611                 }
 612             }
 613             TyKind::BoundVar(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index)?,
 614             TyKind::Dyn(dyn_ty) => {
 615                 write_bounds_like_dyn_trait_with_prefix(
 616                     "dyn",
 617                     dyn_ty.bounds.skip_binders().interned(),
 618                     f,
 619                 )?;
 620             }
 621             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 622             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 623                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 624                 match impl_trait_id {
 625                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 626                         let datas =
 627                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 628                         let data = (*datas)
 629                             .as_ref()
 630                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 631                         let bounds = data.subst(&opaque_ty.substitution);
 632                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
 633                     }
 634                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 635                         write!(f, "{{async block}}")?;
 636                     }
 637                 };
 638             }
 639             TyKind::Unknown => {
 640                 if f.display_target.is_source_code() {
 641                     return Err(HirDisplayError::DisplaySourceCodeError(
 642                         DisplaySourceCodeError::UnknownType,
 643                     ));
 644                 }
 645                 write!(f, "{{unknown}}")?;
 646             }
 647             TyKind::InferenceVar(..) => write!(f, "_")?,
 648         }
 649         Ok(())
 650     }
 651 }
 652
 653 impl HirDisplay for CallableSig {
 654     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 655         write!(f, "fn(")?;
 656         f.write_joined(self.params(), ", ")?;
 657         if self.is_varargs {
 658             if self.params().is_empty() {
 659                 write!(f, "...")?;
 660             } else {
 661                 write!(f, ", ...")?;
 662             }
 663         }
 664         write!(f, ")")?;
 665         let ret = self.ret();
 666         if !ret.is_unit() {
 667             let ret_display =
 668                 ret.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 669             write!(f, " -> {}", ret_display)?;
 670         }
 671         Ok(())
 672     }
 673 }
 674
 675 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 676     let krate = trait_.lookup(db).container.krate();
 677     let fn_traits = [
 678         db.lang_item(krate, "fn".into()),
 679         db.lang_item(krate, "fn_mut".into()),
 680         db.lang_item(krate, "fn_once".into()),
 681     ];
 682     array::IntoIter::new(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 683 }
 684
 685 pub fn write_bounds_like_dyn_trait_with_prefix(
 686     prefix: &str,
 687     predicates: &[QuantifiedWhereClause],
 688     f: &mut HirFormatter,
 689 ) -> Result<(), HirDisplayError> {
 690     write!(f, "{}", prefix)?;
 691     if !predicates.is_empty() {
 692         write!(f, " ")?;
 693         write_bounds_like_dyn_trait(predicates, f)
 694     } else {
 695         Ok(())
 696     }
 697 }
 698
 699 fn write_bounds_like_dyn_trait(
 700     predicates: &[QuantifiedWhereClause],
 701     f: &mut HirFormatter,
 702 ) -> Result<(), HirDisplayError> {
 703     // Note: This code is written to produce nice results (i.e.
 704     // corresponding to surface Rust) for types that can occur in
 705     // actual Rust. It will have weird results if the predicates
 706     // aren't as expected (i.e. self types = $0, projection
 707     // predicates for a certain trait come after the Implemented
 708     // predicate for that trait).
 709     let mut first = true;
 710     let mut angle_open = false;
 711     let mut is_fn_trait = false;
 712     for p in predicates.iter() {
 713         match p.skip_binders() {
 714             WhereClause::Implemented(trait_ref) => {
 715                 let trait_ = trait_ref.hir_trait_id();
 716                 if !is_fn_trait {
 717                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 718                 }
 719                 if !is_fn_trait && angle_open {
 720                     write!(f, ">")?;
 721                     angle_open = false;
 722                 }
 723                 if !first {
 724                     write!(f, " + ")?;
 725                 }
 726                 // We assume that the self type is $0 (i.e. the
 727                 // existential) here, which is the only thing that's
 728                 // possible in actual Rust, and hence don't print it
 729                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 730                 if let [_, params @ ..] = &*trait_ref.substitution.interned() {
 731                     if is_fn_trait {
 732                         if let Some(args) =
 733                             params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
 734                         {
 735                             write!(f, "(")?;
 736                             f.write_joined(&*args.interned(), ", ")?;
 737                             write!(f, ")")?;
 738                         }
 739                     } else if !params.is_empty() {
 740                         write!(f, "<")?;
 741                         f.write_joined(params, ", ")?;
 742                         // there might be assoc type bindings, so we leave the angle brackets open
 743                         angle_open = true;
 744                     }
 745                 }
 746             }
 747             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 748                 is_fn_trait = false;
 749                 write!(f, " -> ")?;
 750                 alias_eq.ty.hir_fmt(f)?;
 751             }
 752             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 753                 // in types in actual Rust, these will always come
 754                 // after the corresponding Implemented predicate
 755                 if angle_open {
 756                     write!(f, ", ")?;
 757                 } else {
 758                     write!(f, "<")?;
 759                     angle_open = true;
 760                 }
 761                 if let AliasTy::Projection(proj) = alias {
 762                     let type_alias =
 763                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 764                     write!(f, "{} = ", type_alias.name)?;
 765                 }
 766                 ty.hir_fmt(f)?;
 767             }
 768         }
 769         first = false;
 770     }
 771     if angle_open {
 772         write!(f, ">")?;
 773     }
 774     Ok(())
 775 }
 776
 777 impl TraitRef {
 778     fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 779         if f.should_truncate() {
 780             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 781         }
 782
 783         self.self_type_parameter().hir_fmt(f)?;
 784         if use_as {
 785             write!(f, " as ")?;
 786         } else {
 787             write!(f, ": ")?;
 788         }
 789         write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
 790         if self.substitution.len(&Interner) > 1 {
 791             write!(f, "<")?;
 792             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 793             write!(f, ">")?;
 794         }
 795         Ok(())
 796     }
 797 }
 798
 799 impl HirDisplay for TraitRef {
 800     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 801         self.hir_fmt_ext(f, false)
 802     }
 803 }
 804
 805 impl HirDisplay for WhereClause {
 806     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 807         if f.should_truncate() {
 808             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 809         }
 810
 811         match self {
 812             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 813             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 814                 write!(f, "<")?;
 815                 projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
 816                 write!(
 817                     f,
 818                     ">::{} = ",
 819                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 820                 )?;
 821                 ty.hir_fmt(f)?;
 822             }
 823             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 824         }
 825         Ok(())
 826     }
 827 }
 828
 829 impl HirDisplay for Lifetime {
 830     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 831         match self {
 832             Lifetime::Parameter(id) => {
 833                 let generics = generics(f.db.upcast(), id.parent);
 834                 let param_data = &generics.params.lifetimes[id.local_id];
 835                 write!(f, "{}", &param_data.name)
 836             }
 837             Lifetime::Static => write!(f, "'static"),
 838         }
 839     }
 840 }
 841
 842 impl HirDisplay for DomainGoal {
 843     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 844         match self {
 845             DomainGoal::Holds(wc) => {
 846                 write!(f, "Holds(")?;
 847                 wc.hir_fmt(f)?;
 848                 write!(f, ")")
 849             }
 850         }
 851     }
 852 }
 853
 854 pub fn write_visibility(
 855     module_id: ModuleId,
 856     vis: Visibility,
 857     f: &mut HirFormatter,
 858 ) -> Result<(), HirDisplayError> {
 859     match vis {
 860         Visibility::Public => write!(f, "pub "),
 861         Visibility::Module(vis_id) => {
 862             let def_map = module_id.def_map(f.db.upcast());
 863             let root_module_id = def_map.module_id(def_map.root());
 864             if vis_id == module_id {
 865                 // pub(self) or omitted
 866                 Ok(())
 867             } else if root_module_id == vis_id {
 868                 write!(f, "pub(crate) ")
 869             } else if module_id.containing_module(f.db.upcast()) == Some(vis_id) {
 870                 write!(f, "pub(super) ")
 871             } else {
 872                 write!(f, "pub(in ...) ")
 873             }
 874         }
 875     }
 876 }
 877
 878 impl HirDisplay for TypeRef {
 879     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 880         match self {
 881             TypeRef::Never => write!(f, "!")?,
 882             TypeRef::Placeholder => write!(f, "_")?,
 883             TypeRef::Tuple(elems) => {
 884                 write!(f, "(")?;
 885                 f.write_joined(elems, ", ")?;
 886                 if elems.len() == 1 {
 887                     write!(f, ",")?;
 888                 }
 889                 write!(f, ")")?;
 890             }
 891             TypeRef::Path(path) => path.hir_fmt(f)?,
 892             TypeRef::RawPtr(inner, mutability) => {
 893                 let mutability = match mutability {
 894                     hir_def::type_ref::Mutability::Shared => "*const ",
 895                     hir_def::type_ref::Mutability::Mut => "*mut ",
 896                 };
 897                 write!(f, "{}", mutability)?;
 898                 inner.hir_fmt(f)?;
 899             }
 900             TypeRef::Reference(inner, lifetime, mutability) => {
 901                 let mutability = match mutability {
 902                     hir_def::type_ref::Mutability::Shared => "",
 903                     hir_def::type_ref::Mutability::Mut => "mut ",
 904                 };
 905                 write!(f, "&")?;
 906                 if let Some(lifetime) = lifetime {
 907                     write!(f, "{} ", lifetime.name)?;
 908                 }
 909                 write!(f, "{}", mutability)?;
 910                 inner.hir_fmt(f)?;
 911             }
 912             TypeRef::Array(inner) => {
 913                 write!(f, "[")?;
 914                 inner.hir_fmt(f)?;
 915                 // FIXME: Array length?
 916                 write!(f, "; _]")?;
 917             }
 918             TypeRef::Slice(inner) => {
 919                 write!(f, "[")?;
 920                 inner.hir_fmt(f)?;
 921                 write!(f, "]")?;
 922             }
 923             TypeRef::Fn(tys, is_varargs) => {
 924                 // FIXME: Function pointer qualifiers.
 925                 write!(f, "fn(")?;
 926                 f.write_joined(&tys[..tys.len() - 1], ", ")?;
 927                 if *is_varargs {
 928                     write!(f, "{}...", if tys.len() == 1 { "" } else { ", " })?;
 929                 }
 930                 write!(f, ")")?;
 931                 let ret_ty = tys.last().unwrap();
 932                 match ret_ty {
 933                     TypeRef::Tuple(tup) if tup.is_empty() => {}
 934                     _ => {
 935                         write!(f, " -> ")?;
 936                         ret_ty.hir_fmt(f)?;
 937                     }
 938                 }
 939             }
 940             TypeRef::ImplTrait(bounds) => {
 941                 write!(f, "impl ")?;
 942                 f.write_joined(bounds, " + ")?;
 943             }
 944             TypeRef::DynTrait(bounds) => {
 945                 write!(f, "dyn ")?;
 946                 f.write_joined(bounds, " + ")?;
 947             }
 948             TypeRef::Error => write!(f, "{{error}}")?,
 949         }
 950         Ok(())
 951     }
 952 }
 953
 954 impl HirDisplay for TypeBound {
 955     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 956         match self {
 957             TypeBound::Path(path) => path.hir_fmt(f),
 958             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
 959             TypeBound::Error => write!(f, "{{error}}"),
 960         }
 961     }
 962 }
 963
 964 impl HirDisplay for Path {
 965     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 966         match (self.type_anchor(), self.kind()) {
 967             (Some(anchor), _) => {
 968                 write!(f, "<")?;
 969                 anchor.hir_fmt(f)?;
 970                 write!(f, ">")?;
 971             }
 972             (_, PathKind::Plain) => {}
 973             (_, PathKind::Abs) => write!(f, "::")?,
 974             (_, PathKind::Crate) => write!(f, "crate")?,
 975             (_, PathKind::Super(0)) => write!(f, "self")?,
 976             (_, PathKind::Super(n)) => {
 977                 write!(f, "super")?;
 978                 for _ in 0..*n {
 979                     write!(f, "::super")?;
 980                 }
 981             }
 982             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
 983         }
 984
 985         for (seg_idx, segment) in self.segments().iter().enumerate() {
 986             if seg_idx != 0 {
 987                 write!(f, "::")?;
 988             }
 989             write!(f, "{}", segment.name)?;
 990             if let Some(generic_args) = segment.args_and_bindings {
 991                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
 992                 // Do we actually format expressions?
 993                 write!(f, "<")?;
 994                 let mut first = true;
 995                 for arg in &generic_args.args {
 996                     if first {
 997                         first = false;
 998                         if generic_args.has_self_type {
 999                             // FIXME: Convert to `<Ty as Trait>` form.
1000                             write!(f, "Self = ")?;
1001                         }
1002                     } else {
1003                         write!(f, ", ")?;
1004                     }
1005                     arg.hir_fmt(f)?;
1006                 }
1007                 for binding in &generic_args.bindings {
1008                     if first {
1009                         first = false;
1010                     } else {
1011                         write!(f, ", ")?;
1012                     }
1013                     write!(f, "{}", binding.name)?;
1014                     match &binding.type_ref {
1015                         Some(ty) => {
1016                             write!(f, " = ")?;
1017                             ty.hir_fmt(f)?
1018                         }
1019                         None => {
1020                             write!(f, ": ")?;
1021                             f.write_joined(&binding.bounds, " + ")?;
1022                         }
1023                     }
1024                 }
1025                 write!(f, ">")?;
1026             }
1027         }
1028         Ok(())
1029     }
1030 }
1031
1032 impl HirDisplay for hir_def::path::GenericArg {
1033     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1034         match self {
1035             hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
1036             hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1037         }
1038     }
1039 }