crates/hir_ty/src/display.rs

   1 //! FIXME: write short doc here
   2
   3 use std::{
   4     array,
   5     fmt::{self, Debug},
   6 };
   7
   8 use hir_def::{
   9     db::DefDatabase,
  10     find_path,
  11     generics::TypeParamProvenance,
  12     item_scope::ItemInNs,
  13     path::{Path, PathKind},
  14     type_ref::{TypeBound, TypeRef},
  15     visibility::Visibility,
  16     AssocContainerId, Lookup, ModuleId, TraitId,
  17 };
  18 use hir_expand::name::Name;
  19
  20 use crate::{
  21     db::HirDatabase, from_assoc_type_id, from_foreign_def_id, from_placeholder_idx,
  22     lt_from_placeholder_idx, primitive, to_assoc_type_id, traits::chalk::from_chalk,
  23     utils::generics, AdtId, AliasEq, AliasTy, CallableDefId, CallableSig, DomainGoal, GenericArg,
  24     ImplTraitId, Interner, Lifetime, LifetimeData, LifetimeOutlives, Mutability, OpaqueTy,
  25     ProjectionTy, ProjectionTyExt, QuantifiedWhereClause, Scalar, TraitRef, Ty, TyExt, TyKind,
  26     WhereClause,
  27 };
  28
  29 pub struct HirFormatter<'a> {
  30     pub db: &'a dyn HirDatabase,
  31     fmt: &'a mut dyn fmt::Write,
  32     buf: String,
  33     curr_size: usize,
  34     pub(crate) max_size: Option<usize>,
  35     omit_verbose_types: bool,
  36     display_target: DisplayTarget,
  37 }
  38
  39 pub trait HirDisplay {
  40     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError>;
  41
  42     /// Returns a `Display`able type that is human-readable.
  43     fn into_displayable<'a>(
  44         &'a self,
  45         db: &'a dyn HirDatabase,
  46         max_size: Option<usize>,
  47         omit_verbose_types: bool,
  48         display_target: DisplayTarget,
  49     ) -> HirDisplayWrapper<'a, Self>
  50     where
  51         Self: Sized,
  52     {
  53         HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
  54     }
  55
  56     /// Returns a `Display`able type that is human-readable.
  57     /// Use this for showing types to the user (e.g. diagnostics)
  58     fn display<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
  59     where
  60         Self: Sized,
  61     {
  62         HirDisplayWrapper {
  63             db,
  64             t: self,
  65             max_size: None,
  66             omit_verbose_types: false,
  67             display_target: DisplayTarget::Diagnostics,
  68         }
  69     }
  70
  71     /// Returns a `Display`able type that is human-readable and tries to be succinct.
  72     /// Use this for showing types to the user where space is constrained (e.g. doc popups)
  73     fn display_truncated<'a>(
  74         &'a self,
  75         db: &'a dyn HirDatabase,
  76         max_size: Option<usize>,
  77     ) -> HirDisplayWrapper<'a, Self>
  78     where
  79         Self: Sized,
  80     {
  81         HirDisplayWrapper {
  82             db,
  83             t: self,
  84             max_size,
  85             omit_verbose_types: true,
  86             display_target: DisplayTarget::Diagnostics,
  87         }
  88     }
  89
  90     /// Returns a String representation of `self` that can be inserted into the given module.
  91     /// Use this when generating code (e.g. assists)
  92     fn display_source_code<'a>(
  93         &'a self,
  94         db: &'a dyn HirDatabase,
  95         module_id: ModuleId,
  96     ) -> Result<String, DisplaySourceCodeError> {
  97         let mut result = String::new();
  98         match self.hir_fmt(&mut HirFormatter {
  99             db,
 100             fmt: &mut result,
 101             buf: String::with_capacity(20),
 102             curr_size: 0,
 103             max_size: None,
 104             omit_verbose_types: false,
 105             display_target: DisplayTarget::SourceCode { module_id },
 106         }) {
 107             Ok(()) => {}
 108             Err(HirDisplayError::FmtError) => panic!("Writing to String can't fail!"),
 109             Err(HirDisplayError::DisplaySourceCodeError(e)) => return Err(e),
 110         };
 111         Ok(result)
 112     }
 113
 114     /// Returns a String representation of `self` for test purposes
 115     fn display_test<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
 116     where
 117         Self: Sized,
 118     {
 119         HirDisplayWrapper {
 120             db,
 121             t: self,
 122             max_size: None,
 123             omit_verbose_types: false,
 124             display_target: DisplayTarget::Test,
 125         }
 126     }
 127 }
 128
 129 impl<'a> HirFormatter<'a> {
 130     pub fn write_joined<T: HirDisplay>(
 131         &mut self,
 132         iter: impl IntoIterator<Item = T>,
 133         sep: &str,
 134     ) -> Result<(), HirDisplayError> {
 135         let mut first = true;
 136         for e in iter {
 137             if !first {
 138                 write!(self, "{}", sep)?;
 139             }
 140             first = false;
 141             e.hir_fmt(self)?;
 142         }
 143         Ok(())
 144     }
 145
 146     /// This allows using the `write!` macro directly with a `HirFormatter`.
 147     pub fn write_fmt(&mut self, args: fmt::Arguments) -> Result<(), HirDisplayError> {
 148         // We write to a buffer first to track output size
 149         self.buf.clear();
 150         fmt::write(&mut self.buf, args)?;
 151         self.curr_size += self.buf.len();
 152
 153         // Then we write to the internal formatter from the buffer
 154         self.fmt.write_str(&self.buf).map_err(HirDisplayError::from)
 155     }
 156
 157     pub fn should_truncate(&self) -> bool {
 158         if let Some(max_size) = self.max_size {
 159             self.curr_size >= max_size
 160         } else {
 161             false
 162         }
 163     }
 164
 165     pub fn omit_verbose_types(&self) -> bool {
 166         self.omit_verbose_types
 167     }
 168 }
 169
 170 #[derive(Clone, Copy)]
 171 pub enum DisplayTarget {
 172     /// Display types for inlays, doc popups, autocompletion, etc...
 173     /// Showing `{unknown}` or not qualifying paths is fine here.
 174     /// There's no reason for this to fail.
 175     Diagnostics,
 176     /// Display types for inserting them in source files.
 177     /// The generated code should compile, so paths need to be qualified.
 178     SourceCode { module_id: ModuleId },
 179     /// Only for test purpose to keep real types
 180     Test,
 181 }
 182
 183 impl DisplayTarget {
 184     fn is_source_code(&self) -> bool {
 185         matches!(self, Self::SourceCode { .. })
 186     }
 187     fn is_test(&self) -> bool {
 188         matches!(self, Self::Test)
 189     }
 190 }
 191
 192 #[derive(Debug)]
 193 pub enum DisplaySourceCodeError {
 194     PathNotFound,
 195     UnknownType,
 196     Closure,
 197 }
 198
 199 pub enum HirDisplayError {
 200     /// Errors that can occur when generating source code
 201     DisplaySourceCodeError(DisplaySourceCodeError),
 202     /// `FmtError` is required to be compatible with std::fmt::Display
 203     FmtError,
 204 }
 205 impl From<fmt::Error> for HirDisplayError {
 206     fn from(_: fmt::Error) -> Self {
 207         Self::FmtError
 208     }
 209 }
 210
 211 pub struct HirDisplayWrapper<'a, T> {
 212     db: &'a dyn HirDatabase,
 213     t: &'a T,
 214     max_size: Option<usize>,
 215     omit_verbose_types: bool,
 216     display_target: DisplayTarget,
 217 }
 218
 219 impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
 220 where
 221     T: HirDisplay,
 222 {
 223     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 224         match self.t.hir_fmt(&mut HirFormatter {
 225             db: self.db,
 226             fmt: f,
 227             buf: String::with_capacity(20),
 228             curr_size: 0,
 229             max_size: self.max_size,
 230             omit_verbose_types: self.omit_verbose_types,
 231             display_target: self.display_target,
 232         }) {
 233             Ok(()) => Ok(()),
 234             Err(HirDisplayError::FmtError) => Err(fmt::Error),
 235             Err(HirDisplayError::DisplaySourceCodeError(_)) => {
 236                 // This should never happen
 237                 panic!("HirDisplay failed when calling Display::fmt!")
 238             }
 239         }
 240     }
 241 }
 242
 243 const TYPE_HINT_TRUNCATION: &str = "…";
 244
 245 impl<T: HirDisplay> HirDisplay for &'_ T {
 246     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 247         HirDisplay::hir_fmt(*self, f)
 248     }
 249 }
 250
 251 impl HirDisplay for ProjectionTy {
 252     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 253         if f.should_truncate() {
 254             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 255         }
 256
 257         let trait_ = f.db.trait_data(self.trait_(f.db));
 258         let first_parameter = self.self_type_parameter(&Interner).into_displayable(
 259             f.db,
 260             f.max_size,
 261             f.omit_verbose_types,
 262             f.display_target,
 263         );
 264         write!(f, "<{} as {}", first_parameter, trait_.name)?;
 265         if self.substitution.len(&Interner) > 1 {
 266             write!(f, "<")?;
 267             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 268             write!(f, ">")?;
 269         }
 270         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
 271         Ok(())
 272     }
 273 }
 274
 275 impl HirDisplay for OpaqueTy {
 276     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 277         if f.should_truncate() {
 278             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 279         }
 280
 281         self.substitution.at(&Interner, 0).hir_fmt(f)
 282     }
 283 }
 284
 285 impl HirDisplay for GenericArg {
 286     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 287         match self.interned() {
 288             crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
 289         }
 290     }
 291 }
 292
 293 impl HirDisplay for Ty {
 294     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 295         if f.should_truncate() {
 296             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 297         }
 298
 299         match self.kind(&Interner) {
 300             TyKind::Never => write!(f, "!")?,
 301             TyKind::Str => write!(f, "str")?,
 302             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
 303             TyKind::Scalar(Scalar::Char) => write!(f, "char")?,
 304             &TyKind::Scalar(Scalar::Float(t)) => write!(f, "{}", primitive::float_ty_to_string(t))?,
 305             &TyKind::Scalar(Scalar::Int(t)) => write!(f, "{}", primitive::int_ty_to_string(t))?,
 306             &TyKind::Scalar(Scalar::Uint(t)) => write!(f, "{}", primitive::uint_ty_to_string(t))?,
 307             TyKind::Slice(t) => {
 308                 write!(f, "[")?;
 309                 t.hir_fmt(f)?;
 310                 write!(f, "]")?;
 311             }
 312             TyKind::Array(t) => {
 313                 write!(f, "[")?;
 314                 t.hir_fmt(f)?;
 315                 write!(f, "; _]")?;
 316             }
 317             TyKind::Raw(m, t) | TyKind::Ref(m, t) => {
 318                 let ty_display =
 319                     t.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 320
 321                 if matches!(self.kind(&Interner), TyKind::Raw(..)) {
 322                     write!(
 323                         f,
 324                         "*{}",
 325                         match m {
 326                             Mutability::Not => "const ",
 327                             Mutability::Mut => "mut ",
 328                         }
 329                     )?;
 330                 } else {
 331                     write!(
 332                         f,
 333                         "&{}",
 334                         match m {
 335                             Mutability::Not => "",
 336                             Mutability::Mut => "mut ",
 337                         }
 338                     )?;
 339                 }
 340
 341                 // FIXME: all this just to decide whether to use parentheses...
 342                 let datas;
 343                 let predicates: Vec<_> = match t.kind(&Interner) {
 344                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
 345                         dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
 346                     }
 347                     &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
 348                         opaque_ty_id,
 349                         substitution: ref parameters,
 350                     })) => {
 351                         let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty_id.into());
 352                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
 353                             datas =
 354                                 f.db.return_type_impl_traits(func)
 355                                     .expect("impl trait id without data");
 356                             let data = (*datas)
 357                                 .as_ref()
 358                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 359                             let bounds = data.substitute(&Interner, parameters);
 360                             bounds.into_value_and_skipped_binders().0
 361                         } else {
 362                             Vec::new()
 363                         }
 364                     }
 365                     _ => Vec::new(),
 366                 };
 367
 368                 if let Some(WhereClause::Implemented(trait_ref)) =
 369                     predicates.get(0).map(|b| b.skip_binders())
 370                 {
 371                     let trait_ = trait_ref.hir_trait_id();
 372                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
 373                         && predicates.len() <= 2
 374                     {
 375                         return write!(f, "{}", ty_display);
 376                     }
 377                 }
 378
 379                 if predicates.len() > 1 {
 380                     write!(f, "(")?;
 381                     write!(f, "{}", ty_display)?;
 382                     write!(f, ")")?;
 383                 } else {
 384                     write!(f, "{}", ty_display)?;
 385                 }
 386             }
 387             TyKind::Tuple(_, substs) => {
 388                 if substs.len(&Interner) == 1 {
 389                     write!(f, "(")?;
 390                     substs.at(&Interner, 0).hir_fmt(f)?;
 391                     write!(f, ",)")?;
 392                 } else {
 393                     write!(f, "(")?;
 394                     f.write_joined(&*substs.interned(), ", ")?;
 395                     write!(f, ")")?;
 396                 }
 397             }
 398             TyKind::Function(fn_ptr) => {
 399                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 400                 sig.hir_fmt(f)?;
 401             }
 402             TyKind::FnDef(def, parameters) => {
 403                 let def = from_chalk(f.db, *def);
 404                 let sig = f.db.callable_item_signature(def).substitute(&Interner, parameters);
 405                 match def {
 406                     CallableDefId::FunctionId(ff) => {
 407                         write!(f, "fn {}", f.db.function_data(ff).name)?
 408                     }
 409                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 410                     CallableDefId::EnumVariantId(e) => {
 411                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 412                     }
 413                 };
 414                 if parameters.len(&Interner) > 0 {
 415                     let generics = generics(f.db.upcast(), def.into());
 416                     let (parent_params, self_param, type_params, _impl_trait_params) =
 417                         generics.provenance_split();
 418                     let total_len = parent_params + self_param + type_params;
 419                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 420                     if total_len > 0 {
 421                         write!(f, "<")?;
 422                         f.write_joined(&parameters.interned()[..total_len], ", ")?;
 423                         write!(f, ">")?;
 424                     }
 425                 }
 426                 write!(f, "(")?;
 427                 f.write_joined(sig.params(), ", ")?;
 428                 write!(f, ")")?;
 429                 let ret = sig.ret();
 430                 if !ret.is_unit() {
 431                     let ret_display = ret.into_displayable(
 432                         f.db,
 433                         f.max_size,
 434                         f.omit_verbose_types,
 435                         f.display_target,
 436                     );
 437
 438                     write!(f, " -> {}", ret_display)?;
 439                 }
 440             }
 441             TyKind::Adt(AdtId(def_id), parameters) => {
 442                 match f.display_target {
 443                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 444                         let name = match *def_id {
 445                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 446                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 447                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 448                         };
 449                         write!(f, "{}", name)?;
 450                     }
 451                     DisplayTarget::SourceCode { module_id } => {
 452                         if let Some(path) = find_path::find_path(
 453                             f.db.upcast(),
 454                             ItemInNs::Types((*def_id).into()),
 455                             module_id,
 456                         ) {
 457                             write!(f, "{}", path)?;
 458                         } else {
 459                             return Err(HirDisplayError::DisplaySourceCodeError(
 460                                 DisplaySourceCodeError::PathNotFound,
 461                             ));
 462                         }
 463                     }
 464                 }
 465
 466                 if parameters.len(&Interner) > 0 {
 467                     let parameters_to_write = if f.display_target.is_source_code()
 468                         || f.omit_verbose_types()
 469                     {
 470                         match self
 471                             .as_generic_def(f.db)
 472                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 473                             .filter(|defaults| !defaults.is_empty())
 474                         {
 475                             None => parameters.interned().as_ref(),
 476                             Some(default_parameters) => {
 477                                 let mut default_from = 0;
 478                                 for (i, parameter) in parameters.iter(&Interner).enumerate() {
 479                                     match (
 480                                         parameter.assert_ty_ref(&Interner).kind(&Interner),
 481                                         default_parameters.get(i),
 482                                     ) {
 483                                         (&TyKind::Error, _) | (_, None) => {
 484                                             default_from = i + 1;
 485                                         }
 486                                         (_, Some(default_parameter)) => {
 487                                             let actual_default = default_parameter
 488                                                 .clone()
 489                                                 .substitute(&Interner, &parameters.prefix(i));
 490                                             if parameter.assert_ty_ref(&Interner) != &actual_default
 491                                             {
 492                                                 default_from = i + 1;
 493                                             }
 494                                         }
 495                                     }
 496                                 }
 497                                 &parameters.interned()[0..default_from]
 498                             }
 499                         }
 500                     } else {
 501                         parameters.interned().as_ref()
 502                     };
 503                     if !parameters_to_write.is_empty() {
 504                         write!(f, "<")?;
 505                         f.write_joined(parameters_to_write, ", ")?;
 506                         write!(f, ">")?;
 507                     }
 508                 }
 509             }
 510             TyKind::AssociatedType(assoc_type_id, parameters) => {
 511                 let type_alias = from_assoc_type_id(*assoc_type_id);
 512                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 513                     AssocContainerId::TraitId(it) => it,
 514                     _ => panic!("not an associated type"),
 515                 };
 516                 let trait_ = f.db.trait_data(trait_);
 517                 let type_alias_data = f.db.type_alias_data(type_alias);
 518
 519                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 520                 if f.display_target.is_test() {
 521                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 522                     if parameters.len(&Interner) > 0 {
 523                         write!(f, "<")?;
 524                         f.write_joined(&*parameters.interned(), ", ")?;
 525                         write!(f, ">")?;
 526                     }
 527                 } else {
 528                     let projection_ty = ProjectionTy {
 529                         associated_ty_id: to_assoc_type_id(type_alias),
 530                         substitution: parameters.clone(),
 531                     };
 532
 533                     projection_ty.hir_fmt(f)?;
 534                 }
 535             }
 536             TyKind::Foreign(type_alias) => {
 537                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 538                 write!(f, "{}", type_alias.name)?;
 539             }
 540             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 541                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 542                 match impl_trait_id {
 543                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 544                         let datas =
 545                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 546                         let data = (*datas)
 547                             .as_ref()
 548                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 549                         let bounds = data.substitute(&Interner, &parameters);
 550                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 551                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 552                     }
 553                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 554                         write!(f, "impl Future<Output = ")?;
 555                         parameters.at(&Interner, 0).hir_fmt(f)?;
 556                         write!(f, ">")?;
 557                     }
 558                 }
 559             }
 560             TyKind::Closure(.., substs) => {
 561                 if f.display_target.is_source_code() {
 562                     return Err(HirDisplayError::DisplaySourceCodeError(
 563                         DisplaySourceCodeError::Closure,
 564                     ));
 565                 }
 566                 let sig = substs.at(&Interner, 0).assert_ty_ref(&Interner).callable_sig(f.db);
 567                 if let Some(sig) = sig {
 568                     if sig.params().is_empty() {
 569                         write!(f, "||")?;
 570                     } else if f.omit_verbose_types() {
 571                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 572                     } else {
 573                         write!(f, "|")?;
 574                         f.write_joined(sig.params(), ", ")?;
 575                         write!(f, "|")?;
 576                     };
 577
 578                     let ret_display = sig.ret().into_displayable(
 579                         f.db,
 580                         f.max_size,
 581                         f.omit_verbose_types,
 582                         f.display_target,
 583                     );
 584                     write!(f, " -> {}", ret_display)?;
 585                 } else {
 586                     write!(f, "{{closure}}")?;
 587                 }
 588             }
 589             TyKind::Placeholder(idx) => {
 590                 let id = from_placeholder_idx(f.db, *idx);
 591                 let generics = generics(f.db.upcast(), id.parent);
 592                 let param_data = &generics.params.types[id.local_id];
 593                 match param_data.provenance {
 594                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 595                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 596                     }
 597                     TypeParamProvenance::ArgumentImplTrait => {
 598                         let substs = generics.type_params_subst(f.db);
 599                         let bounds =
 600                             f.db.generic_predicates(id.parent)
 601                                 .into_iter()
 602                                 .map(|pred| pred.clone().substitute(&Interner, &substs))
 603                                 .filter(|wc| match &wc.skip_binders() {
 604                                     WhereClause::Implemented(tr) => {
 605                                         tr.self_type_parameter(&Interner) == self
 606                                     }
 607                                     WhereClause::AliasEq(AliasEq {
 608                                         alias: AliasTy::Projection(proj),
 609                                         ty: _,
 610                                     }) => proj.self_type_parameter(&Interner) == self,
 611                                     _ => false,
 612                                 })
 613                                 .collect::<Vec<_>>();
 614                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds, f)?;
 615                     }
 616                 }
 617             }
 618             TyKind::BoundVar(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index)?,
 619             TyKind::Dyn(dyn_ty) => {
 620                 write_bounds_like_dyn_trait_with_prefix(
 621                     "dyn",
 622                     dyn_ty.bounds.skip_binders().interned(),
 623                     f,
 624                 )?;
 625             }
 626             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 627             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 628                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 629                 match impl_trait_id {
 630                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 631                         let datas =
 632                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 633                         let data = (*datas)
 634                             .as_ref()
 635                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 636                         let bounds = data.substitute(&Interner, &opaque_ty.substitution);
 637                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 638                     }
 639                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 640                         write!(f, "{{async block}}")?;
 641                     }
 642                 };
 643             }
 644             TyKind::Error => {
 645                 if f.display_target.is_source_code() {
 646                     return Err(HirDisplayError::DisplaySourceCodeError(
 647                         DisplaySourceCodeError::UnknownType,
 648                     ));
 649                 }
 650                 write!(f, "{{unknown}}")?;
 651             }
 652             TyKind::InferenceVar(..) => write!(f, "_")?,
 653         }
 654         Ok(())
 655     }
 656 }
 657
 658 impl HirDisplay for CallableSig {
 659     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 660         write!(f, "fn(")?;
 661         f.write_joined(self.params(), ", ")?;
 662         if self.is_varargs {
 663             if self.params().is_empty() {
 664                 write!(f, "...")?;
 665             } else {
 666                 write!(f, ", ...")?;
 667             }
 668         }
 669         write!(f, ")")?;
 670         let ret = self.ret();
 671         if !ret.is_unit() {
 672             let ret_display =
 673                 ret.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 674             write!(f, " -> {}", ret_display)?;
 675         }
 676         Ok(())
 677     }
 678 }
 679
 680 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 681     let krate = trait_.lookup(db).container.krate();
 682     let fn_traits = [
 683         db.lang_item(krate, "fn".into()),
 684         db.lang_item(krate, "fn_mut".into()),
 685         db.lang_item(krate, "fn_once".into()),
 686     ];
 687     array::IntoIter::new(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 688 }
 689
 690 pub fn write_bounds_like_dyn_trait_with_prefix(
 691     prefix: &str,
 692     predicates: &[QuantifiedWhereClause],
 693     f: &mut HirFormatter,
 694 ) -> Result<(), HirDisplayError> {
 695     write!(f, "{}", prefix)?;
 696     if !predicates.is_empty() {
 697         write!(f, " ")?;
 698         write_bounds_like_dyn_trait(predicates, f)
 699     } else {
 700         Ok(())
 701     }
 702 }
 703
 704 fn write_bounds_like_dyn_trait(
 705     predicates: &[QuantifiedWhereClause],
 706     f: &mut HirFormatter,
 707 ) -> Result<(), HirDisplayError> {
 708     // Note: This code is written to produce nice results (i.e.
 709     // corresponding to surface Rust) for types that can occur in
 710     // actual Rust. It will have weird results if the predicates
 711     // aren't as expected (i.e. self types = $0, projection
 712     // predicates for a certain trait come after the Implemented
 713     // predicate for that trait).
 714     let mut first = true;
 715     let mut angle_open = false;
 716     let mut is_fn_trait = false;
 717     for p in predicates.iter() {
 718         match p.skip_binders() {
 719             WhereClause::Implemented(trait_ref) => {
 720                 let trait_ = trait_ref.hir_trait_id();
 721                 if !is_fn_trait {
 722                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 723                 }
 724                 if !is_fn_trait && angle_open {
 725                     write!(f, ">")?;
 726                     angle_open = false;
 727                 }
 728                 if !first {
 729                     write!(f, " + ")?;
 730                 }
 731                 // We assume that the self type is $0 (i.e. the
 732                 // existential) here, which is the only thing that's
 733                 // possible in actual Rust, and hence don't print it
 734                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 735                 if let [_, params @ ..] = &*trait_ref.substitution.interned() {
 736                     if is_fn_trait {
 737                         if let Some(args) =
 738                             params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
 739                         {
 740                             write!(f, "(")?;
 741                             f.write_joined(&*args.interned(), ", ")?;
 742                             write!(f, ")")?;
 743                         }
 744                     } else if !params.is_empty() {
 745                         write!(f, "<")?;
 746                         f.write_joined(params, ", ")?;
 747                         // there might be assoc type bindings, so we leave the angle brackets open
 748                         angle_open = true;
 749                     }
 750                 }
 751             }
 752             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 753                 is_fn_trait = false;
 754                 write!(f, " -> ")?;
 755                 alias_eq.ty.hir_fmt(f)?;
 756             }
 757             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 758                 // in types in actual Rust, these will always come
 759                 // after the corresponding Implemented predicate
 760                 if angle_open {
 761                     write!(f, ", ")?;
 762                 } else {
 763                     write!(f, "<")?;
 764                     angle_open = true;
 765                 }
 766                 if let AliasTy::Projection(proj) = alias {
 767                     let type_alias =
 768                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 769                     write!(f, "{} = ", type_alias.name)?;
 770                 }
 771                 ty.hir_fmt(f)?;
 772             }
 773         }
 774         first = false;
 775     }
 776     if angle_open {
 777         write!(f, ">")?;
 778     }
 779     Ok(())
 780 }
 781
 782 impl TraitRef {
 783     fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 784         if f.should_truncate() {
 785             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 786         }
 787
 788         self.self_type_parameter(&Interner).hir_fmt(f)?;
 789         if use_as {
 790             write!(f, " as ")?;
 791         } else {
 792             write!(f, ": ")?;
 793         }
 794         write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
 795         if self.substitution.len(&Interner) > 1 {
 796             write!(f, "<")?;
 797             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 798             write!(f, ">")?;
 799         }
 800         Ok(())
 801     }
 802 }
 803
 804 impl HirDisplay for TraitRef {
 805     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 806         self.hir_fmt_ext(f, false)
 807     }
 808 }
 809
 810 impl HirDisplay for WhereClause {
 811     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 812         if f.should_truncate() {
 813             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 814         }
 815
 816         match self {
 817             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 818             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 819                 write!(f, "<")?;
 820                 projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
 821                 write!(
 822                     f,
 823                     ">::{} = ",
 824                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 825                 )?;
 826                 ty.hir_fmt(f)?;
 827             }
 828             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 829         }
 830         Ok(())
 831     }
 832 }
 833
 834 impl HirDisplay for LifetimeOutlives {
 835     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 836         self.a.hir_fmt(f)?;
 837         write!(f, ": ")?;
 838         self.b.hir_fmt(f)
 839     }
 840 }
 841
 842 impl HirDisplay for Lifetime {
 843     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 844         self.interned().hir_fmt(f)
 845     }
 846 }
 847
 848 impl HirDisplay for LifetimeData {
 849     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 850         match self {
 851             LifetimeData::BoundVar(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index),
 852             LifetimeData::InferenceVar(_) => write!(f, "_"),
 853             LifetimeData::Placeholder(idx) => {
 854                 let id = lt_from_placeholder_idx(f.db, *idx);
 855                 let generics = generics(f.db.upcast(), id.parent);
 856                 let param_data = &generics.params.lifetimes[id.local_id];
 857                 write!(f, "{}", param_data.name)
 858             }
 859             LifetimeData::Static => write!(f, "'static"),
 860             LifetimeData::Empty(_) => Ok(()),
 861             LifetimeData::Erased => Ok(()),
 862             LifetimeData::Phantom(_, _) => Ok(()),
 863         }
 864     }
 865 }
 866
 867 impl HirDisplay for DomainGoal {
 868     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 869         match self {
 870             DomainGoal::Holds(wc) => {
 871                 write!(f, "Holds(")?;
 872                 wc.hir_fmt(f)?;
 873                 write!(f, ")")
 874             }
 875         }
 876     }
 877 }
 878
 879 pub fn write_visibility(
 880     module_id: ModuleId,
 881     vis: Visibility,
 882     f: &mut HirFormatter,
 883 ) -> Result<(), HirDisplayError> {
 884     match vis {
 885         Visibility::Public => write!(f, "pub "),
 886         Visibility::Module(vis_id) => {
 887             let def_map = module_id.def_map(f.db.upcast());
 888             let root_module_id = def_map.module_id(def_map.root());
 889             if vis_id == module_id {
 890                 // pub(self) or omitted
 891                 Ok(())
 892             } else if root_module_id == vis_id {
 893                 write!(f, "pub(crate) ")
 894             } else if module_id.containing_module(f.db.upcast()) == Some(vis_id) {
 895                 write!(f, "pub(super) ")
 896             } else {
 897                 write!(f, "pub(in ...) ")
 898             }
 899         }
 900     }
 901 }
 902
 903 impl HirDisplay for TypeRef {
 904     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 905         match self {
 906             TypeRef::Never => write!(f, "!")?,
 907             TypeRef::Placeholder => write!(f, "_")?,
 908             TypeRef::Tuple(elems) => {
 909                 write!(f, "(")?;
 910                 f.write_joined(elems, ", ")?;
 911                 if elems.len() == 1 {
 912                     write!(f, ",")?;
 913                 }
 914                 write!(f, ")")?;
 915             }
 916             TypeRef::Path(path) => path.hir_fmt(f)?,
 917             TypeRef::RawPtr(inner, mutability) => {
 918                 let mutability = match mutability {
 919                     hir_def::type_ref::Mutability::Shared => "*const ",
 920                     hir_def::type_ref::Mutability::Mut => "*mut ",
 921                 };
 922                 write!(f, "{}", mutability)?;
 923                 inner.hir_fmt(f)?;
 924             }
 925             TypeRef::Reference(inner, lifetime, mutability) => {
 926                 let mutability = match mutability {
 927                     hir_def::type_ref::Mutability::Shared => "",
 928                     hir_def::type_ref::Mutability::Mut => "mut ",
 929                 };
 930                 write!(f, "&")?;
 931                 if let Some(lifetime) = lifetime {
 932                     write!(f, "{} ", lifetime.name)?;
 933                 }
 934                 write!(f, "{}", mutability)?;
 935                 inner.hir_fmt(f)?;
 936             }
 937             TypeRef::Array(inner) => {
 938                 write!(f, "[")?;
 939                 inner.hir_fmt(f)?;
 940                 // FIXME: Array length?
 941                 write!(f, "; _]")?;
 942             }
 943             TypeRef::Slice(inner) => {
 944                 write!(f, "[")?;
 945                 inner.hir_fmt(f)?;
 946                 write!(f, "]")?;
 947             }
 948             TypeRef::Fn(tys, is_varargs) => {
 949                 // FIXME: Function pointer qualifiers.
 950                 write!(f, "fn(")?;
 951                 f.write_joined(&tys[..tys.len() - 1], ", ")?;
 952                 if *is_varargs {
 953                     write!(f, "{}...", if tys.len() == 1 { "" } else { ", " })?;
 954                 }
 955                 write!(f, ")")?;
 956                 let ret_ty = tys.last().unwrap();
 957                 match ret_ty {
 958                     TypeRef::Tuple(tup) if tup.is_empty() => {}
 959                     _ => {
 960                         write!(f, " -> ")?;
 961                         ret_ty.hir_fmt(f)?;
 962                     }
 963                 }
 964             }
 965             TypeRef::ImplTrait(bounds) => {
 966                 write!(f, "impl ")?;
 967                 f.write_joined(bounds, " + ")?;
 968             }
 969             TypeRef::DynTrait(bounds) => {
 970                 write!(f, "dyn ")?;
 971                 f.write_joined(bounds, " + ")?;
 972             }
 973             TypeRef::Error => write!(f, "{{error}}")?,
 974         }
 975         Ok(())
 976     }
 977 }
 978
 979 impl HirDisplay for TypeBound {
 980     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 981         match self {
 982             TypeBound::Path(path) => path.hir_fmt(f),
 983             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
 984             TypeBound::Error => write!(f, "{{error}}"),
 985         }
 986     }
 987 }
 988
 989 impl HirDisplay for Path {
 990     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 991         match (self.type_anchor(), self.kind()) {
 992             (Some(anchor), _) => {
 993                 write!(f, "<")?;
 994                 anchor.hir_fmt(f)?;
 995                 write!(f, ">")?;
 996             }
 997             (_, PathKind::Plain) => {}
 998             (_, PathKind::Abs) => write!(f, "::")?,
 999             (_, PathKind::Crate) => write!(f, "crate")?,
1000             (_, PathKind::Super(0)) => write!(f, "self")?,
1001             (_, PathKind::Super(n)) => {
1002                 write!(f, "super")?;
1003                 for _ in 0..*n {
1004                     write!(f, "::super")?;
1005                 }
1006             }
1007             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
1008         }
1009
1010         for (seg_idx, segment) in self.segments().iter().enumerate() {
1011             if seg_idx != 0 {
1012                 write!(f, "::")?;
1013             }
1014             write!(f, "{}", segment.name)?;
1015             if let Some(generic_args) = segment.args_and_bindings {
1016                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
1017                 // Do we actually format expressions?
1018                 write!(f, "<")?;
1019                 let mut first = true;
1020                 for arg in &generic_args.args {
1021                     if first {
1022                         first = false;
1023                         if generic_args.has_self_type {
1024                             // FIXME: Convert to `<Ty as Trait>` form.
1025                             write!(f, "Self = ")?;
1026                         }
1027                     } else {
1028                         write!(f, ", ")?;
1029                     }
1030                     arg.hir_fmt(f)?;
1031                 }
1032                 for binding in &generic_args.bindings {
1033                     if first {
1034                         first = false;
1035                     } else {
1036                         write!(f, ", ")?;
1037                     }
1038                     write!(f, "{}", binding.name)?;
1039                     match &binding.type_ref {
1040                         Some(ty) => {
1041                             write!(f, " = ")?;
1042                             ty.hir_fmt(f)?
1043                         }
1044                         None => {
1045                             write!(f, ": ")?;
1046                             f.write_joined(&binding.bounds, " + ")?;
1047                         }
1048                     }
1049                 }
1050                 write!(f, ">")?;
1051             }
1052         }
1053         Ok(())
1054     }
1055 }
1056
1057 impl HirDisplay for hir_def::path::GenericArg {
1058     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1059         match self {
1060             hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
1061             hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1062         }
1063     }
1064 }