crates/hir_ty/src/display.rs

   1 //! FIXME: write short doc here
   2
   3 use std::{borrow::Cow, 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, 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 = match t.interned(&Interner) {
 332                     TyKind::Dyn(predicates) if predicates.len() > 1 => {
 333                         Cow::Borrowed(predicates.as_ref())
 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                             Cow::Owned(bounds.value)
 349                         } else {
 350                             Cow::Borrowed(&[][..])
 351                         }
 352                     }
 353                     _ => Cow::Borrowed(&[][..]),
 354                 };
 355
 356                 if let [WhereClause::Implemented(trait_ref), _] = predicates.as_ref() {
 357                     let trait_ = trait_ref.hir_trait_id();
 358                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_) {
 359                         return write!(f, "{}", ty_display);
 360                     }
 361                 }
 362
 363                 if predicates.len() > 1 {
 364                     write!(f, "(")?;
 365                     write!(f, "{}", ty_display)?;
 366                     write!(f, ")")?;
 367                 } else {
 368                     write!(f, "{}", ty_display)?;
 369                 }
 370             }
 371             TyKind::Tuple(_, substs) => {
 372                 if substs.len() == 1 {
 373                     write!(f, "(")?;
 374                     substs[0].hir_fmt(f)?;
 375                     write!(f, ",)")?;
 376                 } else {
 377                     write!(f, "(")?;
 378                     f.write_joined(&*substs.0, ", ")?;
 379                     write!(f, ")")?;
 380                 }
 381             }
 382             TyKind::Function(fn_ptr) => {
 383                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 384                 sig.hir_fmt(f)?;
 385             }
 386             TyKind::FnDef(def, parameters) => {
 387                 let def = from_chalk(f.db, *def);
 388                 let sig = f.db.callable_item_signature(def).subst(parameters);
 389                 match def {
 390                     CallableDefId::FunctionId(ff) => {
 391                         write!(f, "fn {}", f.db.function_data(ff).name)?
 392                     }
 393                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 394                     CallableDefId::EnumVariantId(e) => {
 395                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 396                     }
 397                 };
 398                 if parameters.len() > 0 {
 399                     let generics = generics(f.db.upcast(), def.into());
 400                     let (parent_params, self_param, type_params, _impl_trait_params) =
 401                         generics.provenance_split();
 402                     let total_len = parent_params + self_param + type_params;
 403                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 404                     if total_len > 0 {
 405                         write!(f, "<")?;
 406                         f.write_joined(&parameters.0[..total_len], ", ")?;
 407                         write!(f, ">")?;
 408                     }
 409                 }
 410                 write!(f, "(")?;
 411                 f.write_joined(sig.params(), ", ")?;
 412                 write!(f, ")")?;
 413                 let ret = sig.ret();
 414                 if *ret != Ty::unit() {
 415                     let ret_display = ret.into_displayable(
 416                         f.db,
 417                         f.max_size,
 418                         f.omit_verbose_types,
 419                         f.display_target,
 420                     );
 421
 422                     write!(f, " -> {}", ret_display)?;
 423                 }
 424             }
 425             TyKind::Adt(AdtId(def_id), parameters) => {
 426                 match f.display_target {
 427                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 428                         let name = match *def_id {
 429                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 430                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 431                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 432                         };
 433                         write!(f, "{}", name)?;
 434                     }
 435                     DisplayTarget::SourceCode { module_id } => {
 436                         if let Some(path) = find_path::find_path(
 437                             f.db.upcast(),
 438                             ItemInNs::Types((*def_id).into()),
 439                             module_id,
 440                         ) {
 441                             write!(f, "{}", path)?;
 442                         } else {
 443                             return Err(HirDisplayError::DisplaySourceCodeError(
 444                                 DisplaySourceCodeError::PathNotFound,
 445                             ));
 446                         }
 447                     }
 448                 }
 449
 450                 if parameters.len() > 0 {
 451                     let parameters_to_write = if f.display_target.is_source_code()
 452                         || f.omit_verbose_types()
 453                     {
 454                         match self
 455                             .as_generic_def(f.db)
 456                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 457                             .filter(|defaults| !defaults.is_empty())
 458                         {
 459                             None => parameters.0.as_ref(),
 460                             Some(default_parameters) => {
 461                                 let mut default_from = 0;
 462                                 for (i, parameter) in parameters.iter().enumerate() {
 463                                     match (parameter.interned(&Interner), default_parameters.get(i))
 464                                     {
 465                                         (&TyKind::Unknown, _) | (_, None) => {
 466                                             default_from = i + 1;
 467                                         }
 468                                         (_, Some(default_parameter)) => {
 469                                             let actual_default = default_parameter
 470                                                 .clone()
 471                                                 .subst(&parameters.prefix(i));
 472                                             if parameter != &actual_default {
 473                                                 default_from = i + 1;
 474                                             }
 475                                         }
 476                                     }
 477                                 }
 478                                 &parameters.0[0..default_from]
 479                             }
 480                         }
 481                     } else {
 482                         parameters.0.as_ref()
 483                     };
 484                     if !parameters_to_write.is_empty() {
 485                         write!(f, "<")?;
 486                         f.write_joined(parameters_to_write, ", ")?;
 487                         write!(f, ">")?;
 488                     }
 489                 }
 490             }
 491             TyKind::AssociatedType(assoc_type_id, parameters) => {
 492                 let type_alias = from_assoc_type_id(*assoc_type_id);
 493                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 494                     AssocContainerId::TraitId(it) => it,
 495                     _ => panic!("not an associated type"),
 496                 };
 497                 let trait_ = f.db.trait_data(trait_);
 498                 let type_alias_data = f.db.type_alias_data(type_alias);
 499
 500                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 501                 if f.display_target.is_test() {
 502                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 503                     if parameters.len() > 0 {
 504                         write!(f, "<")?;
 505                         f.write_joined(&*parameters.0, ", ")?;
 506                         write!(f, ">")?;
 507                     }
 508                 } else {
 509                     let projection_ty = ProjectionTy {
 510                         associated_ty_id: to_assoc_type_id(type_alias),
 511                         substitution: parameters.clone(),
 512                     };
 513
 514                     projection_ty.hir_fmt(f)?;
 515                 }
 516             }
 517             TyKind::ForeignType(type_alias) => {
 518                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 519                 write!(f, "{}", type_alias.name)?;
 520             }
 521             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 522                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 523                 match impl_trait_id {
 524                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 525                         let datas =
 526                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 527                         let data = (*datas)
 528                             .as_ref()
 529                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 530                         let bounds = data.subst(&parameters);
 531                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
 532                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 533                     }
 534                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 535                         write!(f, "impl Future<Output = ")?;
 536                         parameters[0].hir_fmt(f)?;
 537                         write!(f, ">")?;
 538                     }
 539                 }
 540             }
 541             TyKind::Closure(.., substs) => {
 542                 let sig = substs[0].callable_sig(f.db);
 543                 if let Some(sig) = sig {
 544                     if sig.params().is_empty() {
 545                         write!(f, "||")?;
 546                     } else if f.omit_verbose_types() {
 547                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 548                     } else {
 549                         write!(f, "|")?;
 550                         f.write_joined(sig.params(), ", ")?;
 551                         write!(f, "|")?;
 552                     };
 553
 554                     let ret_display = sig.ret().into_displayable(
 555                         f.db,
 556                         f.max_size,
 557                         f.omit_verbose_types,
 558                         f.display_target,
 559                     );
 560                     write!(f, " -> {}", ret_display)?;
 561                 } else {
 562                     write!(f, "{{closure}}")?;
 563                 }
 564             }
 565             TyKind::Placeholder(idx) => {
 566                 let id = from_placeholder_idx(f.db, *idx);
 567                 let generics = generics(f.db.upcast(), id.parent);
 568                 let param_data = &generics.params.types[id.local_id];
 569                 match param_data.provenance {
 570                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 571                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 572                     }
 573                     TypeParamProvenance::ArgumentImplTrait => {
 574                         let bounds = f.db.generic_predicates_for_param(id);
 575                         let substs = Substitution::type_params_for_generics(f.db, &generics);
 576                         write_bounds_like_dyn_trait_with_prefix(
 577                             "impl",
 578                             &bounds.iter().map(|b| b.clone().subst(&substs)).collect::<Vec<_>>(),
 579                             f,
 580                         )?;
 581                     }
 582                 }
 583             }
 584             TyKind::BoundVar(idx) => write!(f, "?{}.{}", idx.debruijn.depth(), idx.index)?,
 585             TyKind::Dyn(predicates) => {
 586                 write_bounds_like_dyn_trait_with_prefix("dyn", predicates, f)?;
 587             }
 588             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 589             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 590                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 591                 match impl_trait_id {
 592                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 593                         let datas =
 594                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 595                         let data = (*datas)
 596                             .as_ref()
 597                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 598                         let bounds = data.subst(&opaque_ty.substitution);
 599                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds.value, f)?;
 600                     }
 601                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 602                         write!(f, "{{async block}}")?;
 603                     }
 604                 };
 605             }
 606             TyKind::Unknown => {
 607                 if f.display_target.is_source_code() {
 608                     return Err(HirDisplayError::DisplaySourceCodeError(
 609                         DisplaySourceCodeError::UnknownType,
 610                     ));
 611                 }
 612                 write!(f, "{{unknown}}")?;
 613             }
 614             TyKind::InferenceVar(..) => write!(f, "_")?,
 615         }
 616         Ok(())
 617     }
 618 }
 619
 620 impl HirDisplay for CallableSig {
 621     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 622         write!(f, "fn(")?;
 623         f.write_joined(self.params(), ", ")?;
 624         if self.is_varargs {
 625             if self.params().is_empty() {
 626                 write!(f, "...")?;
 627             } else {
 628                 write!(f, ", ...")?;
 629             }
 630         }
 631         write!(f, ")")?;
 632         let ret = self.ret();
 633         if *ret != Ty::unit() {
 634             let ret_display =
 635                 ret.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 636             write!(f, " -> {}", ret_display)?;
 637         }
 638         Ok(())
 639     }
 640 }
 641
 642 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 643     let krate = trait_.lookup(db).container.krate();
 644     let fn_traits = [
 645         db.lang_item(krate, "fn".into()),
 646         db.lang_item(krate, "fn_mut".into()),
 647         db.lang_item(krate, "fn_once".into()),
 648     ];
 649     // FIXME: Replace ArrayVec when into_iter is a thing on arrays
 650     ArrayVec::from(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 651 }
 652
 653 pub fn write_bounds_like_dyn_trait_with_prefix(
 654     prefix: &str,
 655     predicates: &[WhereClause],
 656     f: &mut HirFormatter,
 657 ) -> Result<(), HirDisplayError> {
 658     write!(f, "{}", prefix)?;
 659     if !predicates.is_empty() {
 660         write!(f, " ")?;
 661         write_bounds_like_dyn_trait(predicates, f)
 662     } else {
 663         Ok(())
 664     }
 665 }
 666
 667 fn write_bounds_like_dyn_trait(
 668     predicates: &[WhereClause],
 669     f: &mut HirFormatter,
 670 ) -> Result<(), HirDisplayError> {
 671     // Note: This code is written to produce nice results (i.e.
 672     // corresponding to surface Rust) for types that can occur in
 673     // actual Rust. It will have weird results if the predicates
 674     // aren't as expected (i.e. self types = $0, projection
 675     // predicates for a certain trait come after the Implemented
 676     // predicate for that trait).
 677     let mut first = true;
 678     let mut angle_open = false;
 679     let mut is_fn_trait = false;
 680     for p in predicates.iter() {
 681         match p {
 682             WhereClause::Implemented(trait_ref) => {
 683                 let trait_ = trait_ref.hir_trait_id();
 684                 if !is_fn_trait {
 685                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 686                 }
 687                 if !is_fn_trait && angle_open {
 688                     write!(f, ">")?;
 689                     angle_open = false;
 690                 }
 691                 if !first {
 692                     write!(f, " + ")?;
 693                 }
 694                 // We assume that the self type is $0 (i.e. the
 695                 // existential) here, which is the only thing that's
 696                 // possible in actual Rust, and hence don't print it
 697                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 698                 if let [_, params @ ..] = &*trait_ref.substitution.0 {
 699                     if is_fn_trait {
 700                         if let Some(args) = params.first().and_then(|it| it.as_tuple()) {
 701                             write!(f, "(")?;
 702                             f.write_joined(&*args.0, ", ")?;
 703                             write!(f, ")")?;
 704                         }
 705                     } else if !params.is_empty() {
 706                         write!(f, "<")?;
 707                         f.write_joined(params, ", ")?;
 708                         // there might be assoc type bindings, so we leave the angle brackets open
 709                         angle_open = true;
 710                     }
 711                 }
 712             }
 713             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 714                 is_fn_trait = false;
 715                 write!(f, " -> ")?;
 716                 alias_eq.ty.hir_fmt(f)?;
 717             }
 718             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 719                 // in types in actual Rust, these will always come
 720                 // after the corresponding Implemented predicate
 721                 if angle_open {
 722                     write!(f, ", ")?;
 723                 } else {
 724                     write!(f, "<")?;
 725                     angle_open = true;
 726                 }
 727                 if let AliasTy::Projection(proj) = alias {
 728                     let type_alias =
 729                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 730                     write!(f, "{} = ", type_alias.name)?;
 731                 }
 732                 ty.hir_fmt(f)?;
 733             }
 734         }
 735         first = false;
 736     }
 737     if angle_open {
 738         write!(f, ">")?;
 739     }
 740     Ok(())
 741 }
 742
 743 impl TraitRef {
 744     fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 745         if f.should_truncate() {
 746             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 747         }
 748
 749         self.substitution[0].hir_fmt(f)?;
 750         if use_as {
 751             write!(f, " as ")?;
 752         } else {
 753             write!(f, ": ")?;
 754         }
 755         write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
 756         if self.substitution.len() > 1 {
 757             write!(f, "<")?;
 758             f.write_joined(&self.substitution[1..], ", ")?;
 759             write!(f, ">")?;
 760         }
 761         Ok(())
 762     }
 763 }
 764
 765 impl HirDisplay for TraitRef {
 766     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 767         self.hir_fmt_ext(f, false)
 768     }
 769 }
 770
 771 impl HirDisplay for WhereClause {
 772     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 773         if f.should_truncate() {
 774             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 775         }
 776
 777         match self {
 778             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 779             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 780                 write!(f, "<")?;
 781                 projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
 782                 write!(
 783                     f,
 784                     ">::{} = ",
 785                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 786                 )?;
 787                 ty.hir_fmt(f)?;
 788             }
 789             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 790         }
 791         Ok(())
 792     }
 793 }
 794
 795 impl HirDisplay for Lifetime {
 796     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 797         match self {
 798             Lifetime::Parameter(id) => {
 799                 let generics = generics(f.db.upcast(), id.parent);
 800                 let param_data = &generics.params.lifetimes[id.local_id];
 801                 write!(f, "{}", &param_data.name)
 802             }
 803             Lifetime::Static => write!(f, "'static"),
 804         }
 805     }
 806 }
 807
 808 impl HirDisplay for DomainGoal {
 809     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 810         match self {
 811             DomainGoal::Holds(wc) => {
 812                 write!(f, "Holds(")?;
 813                 wc.hir_fmt(f)?;
 814                 write!(f, ")")
 815             }
 816         }
 817     }
 818 }
 819
 820 pub fn write_visibility(
 821     module_id: ModuleId,
 822     vis: Visibility,
 823     f: &mut HirFormatter,
 824 ) -> Result<(), HirDisplayError> {
 825     match vis {
 826         Visibility::Public => write!(f, "pub "),
 827         Visibility::Module(vis_id) => {
 828             let def_map = module_id.def_map(f.db.upcast());
 829             let root_module_id = def_map.module_id(def_map.root());
 830             if vis_id == module_id {
 831                 // pub(self) or omitted
 832                 Ok(())
 833             } else if root_module_id == vis_id {
 834                 write!(f, "pub(crate) ")
 835             } else if module_id.containing_module(f.db.upcast()) == Some(vis_id) {
 836                 write!(f, "pub(super) ")
 837             } else {
 838                 write!(f, "pub(in ...) ")
 839             }
 840         }
 841     }
 842 }
 843
 844 impl HirDisplay for TypeRef {
 845     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 846         match self {
 847             TypeRef::Never => write!(f, "!")?,
 848             TypeRef::Placeholder => write!(f, "_")?,
 849             TypeRef::Tuple(elems) => {
 850                 write!(f, "(")?;
 851                 f.write_joined(elems, ", ")?;
 852                 if elems.len() == 1 {
 853                     write!(f, ",")?;
 854                 }
 855                 write!(f, ")")?;
 856             }
 857             TypeRef::Path(path) => path.hir_fmt(f)?,
 858             TypeRef::RawPtr(inner, mutability) => {
 859                 let mutability = match mutability {
 860                     hir_def::type_ref::Mutability::Shared => "*const ",
 861                     hir_def::type_ref::Mutability::Mut => "*mut ",
 862                 };
 863                 write!(f, "{}", mutability)?;
 864                 inner.hir_fmt(f)?;
 865             }
 866             TypeRef::Reference(inner, lifetime, mutability) => {
 867                 let mutability = match mutability {
 868                     hir_def::type_ref::Mutability::Shared => "",
 869                     hir_def::type_ref::Mutability::Mut => "mut ",
 870                 };
 871                 write!(f, "&")?;
 872                 if let Some(lifetime) = lifetime {
 873                     write!(f, "{} ", lifetime.name)?;
 874                 }
 875                 write!(f, "{}", mutability)?;
 876                 inner.hir_fmt(f)?;
 877             }
 878             TypeRef::Array(inner) => {
 879                 write!(f, "[")?;
 880                 inner.hir_fmt(f)?;
 881                 // FIXME: Array length?
 882                 write!(f, "; _]")?;
 883             }
 884             TypeRef::Slice(inner) => {
 885                 write!(f, "[")?;
 886                 inner.hir_fmt(f)?;
 887                 write!(f, "]")?;
 888             }
 889             TypeRef::Fn(tys, is_varargs) => {
 890                 // FIXME: Function pointer qualifiers.
 891                 write!(f, "fn(")?;
 892                 f.write_joined(&tys[..tys.len() - 1], ", ")?;
 893                 if *is_varargs {
 894                     write!(f, "{}...", if tys.len() == 1 { "" } else { ", " })?;
 895                 }
 896                 write!(f, ")")?;
 897                 let ret_ty = tys.last().unwrap();
 898                 match ret_ty {
 899                     TypeRef::Tuple(tup) if tup.is_empty() => {}
 900                     _ => {
 901                         write!(f, " -> ")?;
 902                         ret_ty.hir_fmt(f)?;
 903                     }
 904                 }
 905             }
 906             TypeRef::ImplTrait(bounds) => {
 907                 write!(f, "impl ")?;
 908                 f.write_joined(bounds, " + ")?;
 909             }
 910             TypeRef::DynTrait(bounds) => {
 911                 write!(f, "dyn ")?;
 912                 f.write_joined(bounds, " + ")?;
 913             }
 914             TypeRef::Error => write!(f, "{{error}}")?,
 915         }
 916         Ok(())
 917     }
 918 }
 919
 920 impl HirDisplay for TypeBound {
 921     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 922         match self {
 923             TypeBound::Path(path) => path.hir_fmt(f),
 924             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
 925             TypeBound::Error => write!(f, "{{error}}"),
 926         }
 927     }
 928 }
 929
 930 impl HirDisplay for Path {
 931     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 932         match (self.type_anchor(), self.kind()) {
 933             (Some(anchor), _) => {
 934                 write!(f, "<")?;
 935                 anchor.hir_fmt(f)?;
 936                 write!(f, ">")?;
 937             }
 938             (_, PathKind::Plain) => {}
 939             (_, PathKind::Abs) => write!(f, "::")?,
 940             (_, PathKind::Crate) => write!(f, "crate")?,
 941             (_, PathKind::Super(0)) => write!(f, "self")?,
 942             (_, PathKind::Super(n)) => {
 943                 write!(f, "super")?;
 944                 for _ in 0..*n {
 945                     write!(f, "::super")?;
 946                 }
 947             }
 948             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
 949         }
 950
 951         for (seg_idx, segment) in self.segments().iter().enumerate() {
 952             if seg_idx != 0 {
 953                 write!(f, "::")?;
 954             }
 955             write!(f, "{}", segment.name)?;
 956             if let Some(generic_args) = segment.args_and_bindings {
 957                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
 958                 // Do we actually format expressions?
 959                 write!(f, "<")?;
 960                 let mut first = true;
 961                 for arg in &generic_args.args {
 962                     if first {
 963                         first = false;
 964                         if generic_args.has_self_type {
 965                             // FIXME: Convert to `<Ty as Trait>` form.
 966                             write!(f, "Self = ")?;
 967                         }
 968                     } else {
 969                         write!(f, ", ")?;
 970                     }
 971                     arg.hir_fmt(f)?;
 972                 }
 973                 for binding in &generic_args.bindings {
 974                     if first {
 975                         first = false;
 976                     } else {
 977                         write!(f, ", ")?;
 978                     }
 979                     write!(f, "{}", binding.name)?;
 980                     match &binding.type_ref {
 981                         Some(ty) => {
 982                             write!(f, " = ")?;
 983                             ty.hir_fmt(f)?
 984                         }
 985                         None => {
 986                             write!(f, ": ")?;
 987                             f.write_joined(&binding.bounds, " + ")?;
 988                         }
 989                     }
 990                 }
 991                 write!(f, ">")?;
 992             }
 993         }
 994         Ok(())
 995     }
 996 }
 997
 998 impl HirDisplay for GenericArg {
 999     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1000         match self {
1001             GenericArg::Type(ty) => ty.hir_fmt(f),
1002             GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1003         }
1004     }
1005 }