crates/hir_ty/src/display.rs

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