crates/hir_ty/src/display.rs

   1 //! The `HirDisplay` trait, which serves two purposes: Turning various bits from
   2 //! HIR back into source code, and just displaying them for debugging/testing
   3 //! purposes.
   4
   5 use std::fmt::{self, Debug};
   6
   7 use base_db::CrateId;
   8 use chalk_ir::BoundVar;
   9 use hir_def::{
  10     body,
  11     db::DefDatabase,
  12     find_path,
  13     generics::TypeParamProvenance,
  14     intern::{Internable, Interned},
  15     item_scope::ItemInNs,
  16     path::{Path, PathKind},
  17     type_ref::{TraitBoundModifier, TypeBound, TypeRef},
  18     visibility::Visibility,
  19     HasModule, ItemContainerId, Lookup, ModuleId, TraitId,
  20 };
  21 use hir_expand::{hygiene::Hygiene, name::Name};
  22 use itertools::Itertools;
  23 use syntax::SmolStr;
  24
  25 use crate::{
  26     const_from_placeholder_idx,
  27     db::HirDatabase,
  28     from_assoc_type_id, from_foreign_def_id, from_placeholder_idx, lt_from_placeholder_idx,
  29     mapping::from_chalk,
  30     primitive, subst_prefix, to_assoc_type_id,
  31     utils::{self, generics},
  32     AdtId, AliasEq, AliasTy, CallableDefId, CallableSig, Const, ConstValue, DomainGoal, GenericArg,
  33     ImplTraitId, Interner, Lifetime, LifetimeData, LifetimeOutlives, Mutability, OpaqueTy,
  34     ProjectionTy, ProjectionTyExt, QuantifiedWhereClause, Scalar, TraitRef, TraitRefExt, Ty, TyExt,
  35     TyKind, WhereClause,
  36 };
  37
  38 pub struct HirFormatter<'a> {
  39     pub db: &'a dyn HirDatabase,
  40     fmt: &'a mut dyn fmt::Write,
  41     buf: String,
  42     curr_size: usize,
  43     pub(crate) max_size: Option<usize>,
  44     omit_verbose_types: bool,
  45     display_target: DisplayTarget,
  46 }
  47
  48 pub trait HirDisplay {
  49     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError>;
  50
  51     /// Returns a `Display`able type that is human-readable.
  52     fn into_displayable<'a>(
  53         &'a self,
  54         db: &'a dyn HirDatabase,
  55         max_size: Option<usize>,
  56         omit_verbose_types: bool,
  57         display_target: DisplayTarget,
  58     ) -> HirDisplayWrapper<'a, Self>
  59     where
  60         Self: Sized,
  61     {
  62         assert!(
  63             !matches!(display_target, DisplayTarget::SourceCode { .. }),
  64             "HirDisplayWrapper cannot fail with DisplaySourceCodeError, use HirDisplay::hir_fmt directly instead"
  65         );
  66         HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
  67     }
  68
  69     /// Returns a `Display`able type that is human-readable.
  70     /// Use this for showing types to the user (e.g. diagnostics)
  71     fn display<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
  72     where
  73         Self: Sized,
  74     {
  75         HirDisplayWrapper {
  76             db,
  77             t: self,
  78             max_size: None,
  79             omit_verbose_types: false,
  80             display_target: DisplayTarget::Diagnostics,
  81         }
  82     }
  83
  84     /// Returns a `Display`able type that is human-readable and tries to be succinct.
  85     /// Use this for showing types to the user where space is constrained (e.g. doc popups)
  86     fn display_truncated<'a>(
  87         &'a self,
  88         db: &'a dyn HirDatabase,
  89         max_size: Option<usize>,
  90     ) -> HirDisplayWrapper<'a, Self>
  91     where
  92         Self: Sized,
  93     {
  94         HirDisplayWrapper {
  95             db,
  96             t: self,
  97             max_size,
  98             omit_verbose_types: true,
  99             display_target: DisplayTarget::Diagnostics,
 100         }
 101     }
 102
 103     /// Returns a String representation of `self` that can be inserted into the given module.
 104     /// Use this when generating code (e.g. assists)
 105     fn display_source_code<'a>(
 106         &'a self,
 107         db: &'a dyn HirDatabase,
 108         module_id: ModuleId,
 109     ) -> Result<String, DisplaySourceCodeError> {
 110         let mut result = String::new();
 111         match self.hir_fmt(&mut HirFormatter {
 112             db,
 113             fmt: &mut result,
 114             buf: String::with_capacity(20),
 115             curr_size: 0,
 116             max_size: None,
 117             omit_verbose_types: false,
 118             display_target: DisplayTarget::SourceCode { module_id },
 119         }) {
 120             Ok(()) => {}
 121             Err(HirDisplayError::FmtError) => panic!("Writing to String can't fail!"),
 122             Err(HirDisplayError::DisplaySourceCodeError(e)) => return Err(e),
 123         };
 124         Ok(result)
 125     }
 126
 127     /// Returns a String representation of `self` for test purposes
 128     fn display_test<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
 129     where
 130         Self: Sized,
 131     {
 132         HirDisplayWrapper {
 133             db,
 134             t: self,
 135             max_size: None,
 136             omit_verbose_types: false,
 137             display_target: DisplayTarget::Test,
 138         }
 139     }
 140 }
 141
 142 impl<'a> HirFormatter<'a> {
 143     pub fn write_joined<T: HirDisplay>(
 144         &mut self,
 145         iter: impl IntoIterator<Item = T>,
 146         sep: &str,
 147     ) -> Result<(), HirDisplayError> {
 148         let mut first = true;
 149         for e in iter {
 150             if !first {
 151                 write!(self, "{}", sep)?;
 152             }
 153             first = false;
 154
 155             // Abbreviate multiple omitted types with a single ellipsis.
 156             if self.should_truncate() {
 157                 return write!(self, "{}", TYPE_HINT_TRUNCATION);
 158             }
 159
 160             e.hir_fmt(self)?;
 161         }
 162         Ok(())
 163     }
 164
 165     /// This allows using the `write!` macro directly with a `HirFormatter`.
 166     pub fn write_fmt(&mut self, args: fmt::Arguments) -> Result<(), HirDisplayError> {
 167         // We write to a buffer first to track output size
 168         self.buf.clear();
 169         fmt::write(&mut self.buf, args)?;
 170         self.curr_size += self.buf.len();
 171
 172         // Then we write to the internal formatter from the buffer
 173         self.fmt.write_str(&self.buf).map_err(HirDisplayError::from)
 174     }
 175
 176     pub fn should_truncate(&self) -> bool {
 177         match self.max_size {
 178             Some(max_size) => self.curr_size >= max_size,
 179             None => false,
 180         }
 181     }
 182
 183     pub fn omit_verbose_types(&self) -> bool {
 184         self.omit_verbose_types
 185     }
 186 }
 187
 188 #[derive(Clone, Copy)]
 189 pub enum DisplayTarget {
 190     /// Display types for inlays, doc popups, autocompletion, etc...
 191     /// Showing `{unknown}` or not qualifying paths is fine here.
 192     /// There's no reason for this to fail.
 193     Diagnostics,
 194     /// Display types for inserting them in source files.
 195     /// The generated code should compile, so paths need to be qualified.
 196     SourceCode { module_id: ModuleId },
 197     /// Only for test purpose to keep real types
 198     Test,
 199 }
 200
 201 impl DisplayTarget {
 202     fn is_source_code(&self) -> bool {
 203         matches!(self, Self::SourceCode { .. })
 204     }
 205     fn is_test(&self) -> bool {
 206         matches!(self, Self::Test)
 207     }
 208 }
 209
 210 #[derive(Debug)]
 211 pub enum DisplaySourceCodeError {
 212     PathNotFound,
 213     UnknownType,
 214     Closure,
 215 }
 216
 217 pub enum HirDisplayError {
 218     /// Errors that can occur when generating source code
 219     DisplaySourceCodeError(DisplaySourceCodeError),
 220     /// `FmtError` is required to be compatible with std::fmt::Display
 221     FmtError,
 222 }
 223 impl From<fmt::Error> for HirDisplayError {
 224     fn from(_: fmt::Error) -> Self {
 225         Self::FmtError
 226     }
 227 }
 228
 229 pub struct HirDisplayWrapper<'a, T> {
 230     db: &'a dyn HirDatabase,
 231     t: &'a T,
 232     max_size: Option<usize>,
 233     omit_verbose_types: bool,
 234     display_target: DisplayTarget,
 235 }
 236
 237 impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
 238 where
 239     T: HirDisplay,
 240 {
 241     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 242         println!("formatting..");
 243         match self.t.hir_fmt(&mut HirFormatter {
 244             db: self.db,
 245             fmt: f,
 246             buf: String::with_capacity(20),
 247             curr_size: 0,
 248             max_size: self.max_size,
 249             omit_verbose_types: self.omit_verbose_types,
 250             display_target: self.display_target,
 251         }) {
 252             Ok(()) => Ok(()),
 253             Err(HirDisplayError::FmtError) => Err(fmt::Error),
 254             Err(HirDisplayError::DisplaySourceCodeError(_)) => {
 255                 // This should never happen
 256                 panic!("HirDisplay::hir_fmt failed with DisplaySourceCodeError when calling Display::fmt!")
 257             }
 258         }
 259     }
 260 }
 261
 262 const TYPE_HINT_TRUNCATION: &str = "…";
 263
 264 impl<T: HirDisplay> HirDisplay for &'_ T {
 265     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 266         HirDisplay::hir_fmt(*self, f)
 267     }
 268 }
 269
 270 impl<T: HirDisplay + Internable> HirDisplay for Interned<T> {
 271     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 272         HirDisplay::hir_fmt(self.as_ref(), f)
 273     }
 274 }
 275
 276 impl HirDisplay for ProjectionTy {
 277     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 278         if f.should_truncate() {
 279             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 280         }
 281
 282         let trait_ = f.db.trait_data(self.trait_(f.db));
 283         write!(f, "<")?;
 284         self.self_type_parameter(Interner).hir_fmt(f)?;
 285         write!(f, " as {}", trait_.name)?;
 286         if self.substitution.len(Interner) > 1 {
 287             write!(f, "<")?;
 288             f.write_joined(&self.substitution.as_slice(Interner)[1..], ", ")?;
 289             write!(f, ">")?;
 290         }
 291         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
 292         Ok(())
 293     }
 294 }
 295
 296 impl HirDisplay for OpaqueTy {
 297     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 298         if f.should_truncate() {
 299             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 300         }
 301
 302         self.substitution.at(Interner, 0).hir_fmt(f)
 303     }
 304 }
 305
 306 impl HirDisplay for GenericArg {
 307     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 308         match self.interned() {
 309             crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
 310             crate::GenericArgData::Lifetime(lt) => lt.hir_fmt(f),
 311             crate::GenericArgData::Const(c) => c.hir_fmt(f),
 312         }
 313     }
 314 }
 315
 316 impl HirDisplay for Const {
 317     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 318         let data = self.interned();
 319         match data.value {
 320             ConstValue::BoundVar(idx) => idx.hir_fmt(f),
 321             ConstValue::InferenceVar(..) => write!(f, "_"),
 322             ConstValue::Placeholder(idx) => {
 323                 let id = const_from_placeholder_idx(f.db, idx);
 324                 let generics = generics(f.db.upcast(), id.parent);
 325                 let param_data = &generics.params.consts[id.local_id];
 326                 write!(f, "{}", param_data.name)
 327             }
 328             ConstValue::Concrete(c) => write!(f, "{}", c.interned),
 329         }
 330     }
 331 }
 332
 333 impl HirDisplay for BoundVar {
 334     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 335         write!(f, "?{}.{}", self.debruijn.depth(), self.index)
 336     }
 337 }
 338
 339 impl HirDisplay for Ty {
 340     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 341         if f.should_truncate() {
 342             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 343         }
 344
 345         let interner_kind = self.kind(Interner);
 346         println!("interner kind: {interner_kind:?}");
 347
 348         match self.kind(Interner) {
 349             TyKind::Never => write!(f, "!")?,
 350             TyKind::Str => write!(f, "str")?,
 351             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
 352             TyKind::Scalar(Scalar::Char) => write!(f, "char")?,
 353             &TyKind::Scalar(Scalar::Float(t)) => write!(f, "{}", primitive::float_ty_to_string(t))?,
 354             &TyKind::Scalar(Scalar::Int(t)) => write!(f, "{}", primitive::int_ty_to_string(t))?,
 355             &TyKind::Scalar(Scalar::Uint(t)) => write!(f, "{}", primitive::uint_ty_to_string(t))?,
 356             TyKind::Slice(t) => {
 357                 write!(f, "[")?;
 358                 t.hir_fmt(f)?;
 359                 write!(f, "]")?;
 360             }
 361             TyKind::Array(t, c) => {
 362                 write!(f, "[")?;
 363                 t.hir_fmt(f)?;
 364                 write!(f, "; ")?;
 365                 c.hir_fmt(f)?;
 366                 write!(f, "]")?;
 367             }
 368             TyKind::Raw(m, t) | TyKind::Ref(m, _, t) => {
 369                 if matches!(self.kind(Interner), TyKind::Raw(..)) {
 370                     write!(
 371                         f,
 372                         "*{}",
 373                         match m {
 374                             Mutability::Not => "const ",
 375                             Mutability::Mut => "mut ",
 376                         }
 377                     )?;
 378                 } else {
 379                     write!(
 380                         f,
 381                         "&{}",
 382                         match m {
 383                             Mutability::Not => "",
 384                             Mutability::Mut => "mut ",
 385                         }
 386                     )?;
 387                 }
 388
 389                 // FIXME: all this just to decide whether to use parentheses...
 390                 let contains_impl_fn = |bounds: &[QuantifiedWhereClause]| {
 391                     bounds.iter().any(|bound| {
 392                         if let WhereClause::Implemented(trait_ref) = bound.skip_binders() {
 393                             let trait_ = trait_ref.hir_trait_id();
 394                             fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
 395                         } else {
 396                             false
 397                         }
 398                     })
 399                 };
 400                 let (preds_to_print, has_impl_fn_pred) = match t.kind(Interner) {
 401                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
 402                         let bounds = dyn_ty.bounds.skip_binders().interned();
 403                         (bounds.len(), contains_impl_fn(bounds))
 404                     }
 405                     TyKind::Alias(AliasTy::Opaque(OpaqueTy {
 406                         opaque_ty_id,
 407                         substitution: parameters,
 408                     }))
 409                     | TyKind::OpaqueType(opaque_ty_id, parameters) => {
 410                         let impl_trait_id =
 411                             f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 412                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
 413                             let datas =
 414                                 f.db.return_type_impl_traits(func)
 415                                     .expect("impl trait id without data");
 416                             let data = (*datas)
 417                                 .as_ref()
 418                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 419                             let bounds = data.substitute(Interner, parameters);
 420                             let mut len = bounds.skip_binders().len();
 421
 422                             // Don't count Sized but count when it absent
 423                             // (i.e. when explicit ?Sized bound is set).
 424                             let default_sized = SizedByDefault::Sized {
 425                                 anchor: func.lookup(f.db.upcast()).module(f.db.upcast()).krate(),
 426                             };
 427                             let sized_bounds = bounds
 428                                 .skip_binders()
 429                                 .iter()
 430                                 .filter(|b| {
 431                                     matches!(
 432                                         b.skip_binders(),
 433                                         WhereClause::Implemented(trait_ref)
 434                                             if default_sized.is_sized_trait(
 435                                                 trait_ref.hir_trait_id(),
 436                                                 f.db.upcast(),
 437                                             ),
 438                                     )
 439                                 })
 440                                 .count();
 441                             match sized_bounds {
 442                                 0 => len += 1,
 443                                 _ => {
 444                                     len = len.saturating_sub(sized_bounds);
 445                                 }
 446                             }
 447
 448                             (len, contains_impl_fn(bounds.skip_binders()))
 449                         } else {
 450                             (0, false)
 451                         }
 452                     }
 453                     _ => (0, false),
 454                 };
 455
 456                 if has_impl_fn_pred && preds_to_print <= 2 {
 457                     return t.hir_fmt(f);
 458                 }
 459
 460                 if preds_to_print > 1 {
 461                     write!(f, "(")?;
 462                     t.hir_fmt(f)?;
 463                     write!(f, ")")?;
 464                 } else {
 465                     t.hir_fmt(f)?;
 466                 }
 467             }
 468             TyKind::Tuple(_, substs) => {
 469                 if substs.len(Interner) == 1 {
 470                     write!(f, "(")?;
 471                     substs.at(Interner, 0).hir_fmt(f)?;
 472                     write!(f, ",)")?;
 473                 } else {
 474                     write!(f, "(")?;
 475                     f.write_joined(&*substs.as_slice(Interner), ", ")?;
 476                     write!(f, ")")?;
 477                 }
 478             }
 479             TyKind::Function(fn_ptr) => {
 480                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 481                 sig.hir_fmt(f)?;
 482             }
 483             TyKind::FnDef(def, parameters) => {
 484                 let def = from_chalk(f.db, *def);
 485                 let sig = f.db.callable_item_signature(def).substitute(Interner, parameters);
 486                 match def {
 487                     CallableDefId::FunctionId(ff) => {
 488                         write!(f, "fn {}", f.db.function_data(ff).name)?
 489                     }
 490                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 491                     CallableDefId::EnumVariantId(e) => {
 492                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 493                     }
 494                 };
 495                 if parameters.len(Interner) > 0 {
 496                     let generics = generics(f.db.upcast(), def.into());
 497                     let (parent_params, self_param, type_params, _impl_trait_params) =
 498                         generics.provenance_split();
 499                     let total_len = parent_params + self_param + type_params;
 500                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 501                     if total_len > 0 {
 502                         write!(f, "<")?;
 503                         f.write_joined(&parameters.as_slice(Interner)[..total_len], ", ")?;
 504                         write!(f, ">")?;
 505                     }
 506                 }
 507                 write!(f, "(")?;
 508                 f.write_joined(sig.params(), ", ")?;
 509                 write!(f, ")")?;
 510                 let ret = sig.ret();
 511                 if !ret.is_unit() {
 512                     write!(f, " -> ")?;
 513                     ret.hir_fmt(f)?;
 514                 }
 515             }
 516             TyKind::Adt(AdtId(def_id), parameters) => {
 517                 match f.display_target {
 518                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 519                         let name = match *def_id {
 520                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 521                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 522                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 523                         };
 524                         write!(f, "{}", name)?;
 525                     }
 526                     DisplayTarget::SourceCode { module_id } => {
 527                         if let Some(path) = find_path::find_path(
 528                             f.db.upcast(),
 529                             ItemInNs::Types((*def_id).into()),
 530                             module_id,
 531                         ) {
 532                             write!(f, "{}", path)?;
 533                         } else {
 534                             return Err(HirDisplayError::DisplaySourceCodeError(
 535                                 DisplaySourceCodeError::PathNotFound,
 536                             ));
 537                         }
 538                     }
 539                 }
 540
 541                 if parameters.len(Interner) > 0 {
 542                     let parameters_to_write = if f.display_target.is_source_code()
 543                         || f.omit_verbose_types()
 544                     {
 545                         match self
 546                             .as_generic_def(f.db)
 547                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 548                             .filter(|defaults| !defaults.is_empty())
 549                         {
 550                             None => parameters.as_slice(Interner),
 551                             Some(default_parameters) => {
 552                                 let mut default_from = 0;
 553                                 for (i, parameter) in parameters.iter(Interner).enumerate() {
 554                                     match (
 555                                         parameter.assert_ty_ref(Interner).kind(Interner),
 556                                         default_parameters.get(i),
 557                                     ) {
 558                                         (&TyKind::Error, _) | (_, None) => {
 559                                             default_from = i + 1;
 560                                         }
 561                                         (_, Some(default_parameter)) => {
 562                                             let actual_default = default_parameter
 563                                                 .clone()
 564                                                 .substitute(Interner, &subst_prefix(parameters, i));
 565                                             if parameter.assert_ty_ref(Interner) != &actual_default
 566                                             {
 567                                                 default_from = i + 1;
 568                                             }
 569                                         }
 570                                     }
 571                                 }
 572                                 &parameters.as_slice(Interner)[0..default_from]
 573                             }
 574                         }
 575                     } else {
 576                         parameters.as_slice(Interner)
 577                     };
 578                     if !parameters_to_write.is_empty() {
 579                         write!(f, "<")?;
 580
 581                         if f.display_target.is_source_code() {
 582                             let mut first = true;
 583                             for generic_arg in parameters_to_write {
 584                                 if !first {
 585                                     write!(f, ", ")?;
 586                                 }
 587                                 first = false;
 588
 589                                 if generic_arg.ty(Interner).map(|ty| ty.kind(Interner))
 590                                     == Some(&TyKind::Error)
 591                                 {
 592                                     write!(f, "_")?;
 593                                 } else {
 594                                     generic_arg.hir_fmt(f)?;
 595                                 }
 596                             }
 597                         } else {
 598                             f.write_joined(parameters_to_write, ", ")?;
 599                         }
 600
 601                         write!(f, ">")?;
 602                     }
 603                 }
 604             }
 605             TyKind::AssociatedType(assoc_type_id, parameters) => {
 606                 let type_alias = from_assoc_type_id(*assoc_type_id);
 607                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 608                     ItemContainerId::TraitId(it) => it,
 609                     _ => panic!("not an associated type"),
 610                 };
 611                 let trait_ = f.db.trait_data(trait_);
 612                 let type_alias_data = f.db.type_alias_data(type_alias);
 613
 614                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 615                 if f.display_target.is_test() {
 616                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 617                     if parameters.len(Interner) > 0 {
 618                         write!(f, "<")?;
 619                         f.write_joined(&*parameters.as_slice(Interner), ", ")?;
 620                         write!(f, ">")?;
 621                     }
 622                 } else {
 623                     let projection_ty = ProjectionTy {
 624                         associated_ty_id: to_assoc_type_id(type_alias),
 625                         substitution: parameters.clone(),
 626                     };
 627
 628                     projection_ty.hir_fmt(f)?;
 629                 }
 630             }
 631             TyKind::Foreign(type_alias) => {
 632                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 633                 write!(f, "{}", type_alias.name)?;
 634             }
 635             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 636                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 637                 match impl_trait_id {
 638                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 639                         let datas =
 640                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 641                         let data = (*datas)
 642                             .as_ref()
 643                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 644                         let bounds = data.substitute(Interner, &parameters);
 645                         let krate = func.lookup(f.db.upcast()).module(f.db.upcast()).krate();
 646                         write_bounds_like_dyn_trait_with_prefix(
 647                             "impl",
 648                             bounds.skip_binders(),
 649                             SizedByDefault::Sized { anchor: krate },
 650                             f,
 651                         )?;
 652                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 653                     }
 654                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 655                         write!(f, "impl Future<Output = ")?;
 656                         parameters.at(Interner, 0).hir_fmt(f)?;
 657                         write!(f, ">")?;
 658                     }
 659                 }
 660             }
 661             TyKind::Closure(.., substs) => {
 662                 if f.display_target.is_source_code() {
 663                     return Err(HirDisplayError::DisplaySourceCodeError(
 664                         DisplaySourceCodeError::Closure,
 665                     ));
 666                 }
 667                 let sig = substs.at(Interner, 0).assert_ty_ref(Interner).callable_sig(f.db);
 668                 if let Some(sig) = sig {
 669                     if sig.params().is_empty() {
 670                         write!(f, "||")?;
 671                     } else if f.should_truncate() {
 672                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 673                     } else {
 674                         write!(f, "|")?;
 675                         f.write_joined(sig.params(), ", ")?;
 676                         write!(f, "|")?;
 677                     };
 678
 679                     write!(f, " -> ")?;
 680                     sig.ret().hir_fmt(f)?;
 681                 } else {
 682                     write!(f, "{{closure}}")?;
 683                 }
 684             }
 685             TyKind::Placeholder(idx) => {
 686                 let id = from_placeholder_idx(f.db, *idx);
 687                 let generics = generics(f.db.upcast(), id.parent);
 688                 let param_data = &generics.params.types[id.local_id];
 689                 match param_data.provenance {
 690                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 691                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 692                     }
 693                     TypeParamProvenance::ArgumentImplTrait => {
 694                         let substs = generics.type_params_subst(f.db);
 695                         let bounds =
 696                             f.db.generic_predicates(id.parent)
 697                                 .iter()
 698                                 .map(|pred| pred.clone().substitute(Interner, &substs))
 699                                 .filter(|wc| match &wc.skip_binders() {
 700                                     WhereClause::Implemented(tr) => {
 701                                         &tr.self_type_parameter(Interner) == self
 702                                     }
 703                                     WhereClause::AliasEq(AliasEq {
 704                                         alias: AliasTy::Projection(proj),
 705                                         ty: _,
 706                                     }) => &proj.self_type_parameter(Interner) == self,
 707                                     _ => false,
 708                                 })
 709                                 .collect::<Vec<_>>();
 710                         let krate = id.parent.module(f.db.upcast()).krate();
 711                         write_bounds_like_dyn_trait_with_prefix(
 712                             "impl",
 713                             &bounds,
 714                             SizedByDefault::Sized { anchor: krate },
 715                             f,
 716                         )?;
 717                     }
 718                 }
 719             }
 720             TyKind::BoundVar(idx) => idx.hir_fmt(f)?,
 721             TyKind::Dyn(dyn_ty) => {
 722                 write_bounds_like_dyn_trait_with_prefix(
 723                     "dyn",
 724                     dyn_ty.bounds.skip_binders().interned(),
 725                     SizedByDefault::NotSized,
 726                     f,
 727                 )?;
 728             }
 729             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 730             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 731                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 732                 match impl_trait_id {
 733                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 734                         let datas =
 735                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 736                         let data = (*datas)
 737                             .as_ref()
 738                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 739                         let bounds = data.substitute(Interner, &opaque_ty.substitution);
 740                         let krate = func.lookup(f.db.upcast()).module(f.db.upcast()).krate();
 741                         write_bounds_like_dyn_trait_with_prefix(
 742                             "impl",
 743                             bounds.skip_binders(),
 744                             SizedByDefault::Sized { anchor: krate },
 745                             f,
 746                         )?;
 747                     }
 748                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 749                         write!(f, "{{async block}}")?;
 750                     }
 751                 };
 752             }
 753             TyKind::Error => {
 754                 if f.display_target.is_source_code() {
 755                     return Err(HirDisplayError::DisplaySourceCodeError(
 756                         DisplaySourceCodeError::UnknownType,
 757                     ));
 758                 }
 759                 write!(f, "{{unknown}}")?;
 760             }
 761             TyKind::InferenceVar(..) => write!(f, "_")?,
 762             TyKind::Generator(..) => write!(f, "{{generator}}")?,
 763             TyKind::GeneratorWitness(..) => write!(f, "{{generator witness}}")?,
 764         }
 765         Ok(())
 766     }
 767 }
 768
 769 impl HirDisplay for CallableSig {
 770     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 771         write!(f, "fn(")?;
 772         f.write_joined(self.params(), ", ")?;
 773         if self.is_varargs {
 774             if self.params().is_empty() {
 775                 write!(f, "...")?;
 776             } else {
 777                 write!(f, ", ...")?;
 778             }
 779         }
 780         write!(f, ")")?;
 781         let ret = self.ret();
 782         if !ret.is_unit() {
 783             write!(f, " -> ")?;
 784             ret.hir_fmt(f)?;
 785         }
 786         Ok(())
 787     }
 788 }
 789
 790 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 791     let krate = trait_.lookup(db).container.krate();
 792     utils::fn_traits(db, krate)
 793 }
 794
 795 #[derive(Clone, Copy, PartialEq, Eq)]
 796 pub enum SizedByDefault {
 797     NotSized,
 798     Sized { anchor: CrateId },
 799 }
 800
 801 impl SizedByDefault {
 802     fn is_sized_trait(self, trait_: TraitId, db: &dyn DefDatabase) -> bool {
 803         match self {
 804             Self::NotSized => false,
 805             Self::Sized { anchor } => {
 806                 let sized_trait = db
 807                     .lang_item(anchor, SmolStr::new_inline("sized"))
 808                     .and_then(|lang_item| lang_item.as_trait());
 809                 Some(trait_) == sized_trait
 810             }
 811         }
 812     }
 813 }
 814
 815 pub fn write_bounds_like_dyn_trait_with_prefix(
 816     prefix: &str,
 817     predicates: &[QuantifiedWhereClause],
 818     default_sized: SizedByDefault,
 819     f: &mut HirFormatter,
 820 ) -> Result<(), HirDisplayError> {
 821     write!(f, "{}", prefix)?;
 822     if !predicates.is_empty()
 823         || predicates.is_empty() && matches!(default_sized, SizedByDefault::Sized { .. })
 824     {
 825         write!(f, " ")?;
 826         write_bounds_like_dyn_trait(predicates, default_sized, f)
 827     } else {
 828         Ok(())
 829     }
 830 }
 831
 832 fn write_bounds_like_dyn_trait(
 833     predicates: &[QuantifiedWhereClause],
 834     default_sized: SizedByDefault,
 835     f: &mut HirFormatter,
 836 ) -> Result<(), HirDisplayError> {
 837     // Note: This code is written to produce nice results (i.e.
 838     // corresponding to surface Rust) for types that can occur in
 839     // actual Rust. It will have weird results if the predicates
 840     // aren't as expected (i.e. self types = $0, projection
 841     // predicates for a certain trait come after the Implemented
 842     // predicate for that trait).
 843     let mut first = true;
 844     let mut angle_open = false;
 845     let mut is_fn_trait = false;
 846     let mut is_sized = false;
 847     for p in predicates.iter() {
 848         match p.skip_binders() {
 849             WhereClause::Implemented(trait_ref) => {
 850                 let trait_ = trait_ref.hir_trait_id();
 851                 if default_sized.is_sized_trait(trait_, f.db.upcast()) {
 852                     is_sized = true;
 853                     if matches!(default_sized, SizedByDefault::Sized { .. }) {
 854                         // Don't print +Sized, but rather +?Sized if absent.
 855                         continue;
 856                     }
 857                 }
 858                 if !is_fn_trait {
 859                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 860                 }
 861                 if !is_fn_trait && angle_open {
 862                     write!(f, ">")?;
 863                     angle_open = false;
 864                 }
 865                 if !first {
 866                     write!(f, " + ")?;
 867                 }
 868                 // We assume that the self type is ^0.0 (i.e. the
 869                 // existential) here, which is the only thing that's
 870                 // possible in actual Rust, and hence don't print it
 871                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 872                 if let [_, params @ ..] = &*trait_ref.substitution.as_slice(Interner) {
 873                     if is_fn_trait {
 874                         if let Some(args) =
 875                             params.first().and_then(|it| it.assert_ty_ref(Interner).as_tuple())
 876                         {
 877                             write!(f, "(")?;
 878                             f.write_joined(args.as_slice(Interner), ", ")?;
 879                             write!(f, ")")?;
 880                         }
 881                     } else if !params.is_empty() {
 882                         write!(f, "<")?;
 883                         f.write_joined(params, ", ")?;
 884                         // there might be assoc type bindings, so we leave the angle brackets open
 885                         angle_open = true;
 886                     }
 887                 }
 888             }
 889             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 890                 is_fn_trait = false;
 891                 if !alias_eq.ty.is_unit() {
 892                     write!(f, " -> ")?;
 893                     alias_eq.ty.hir_fmt(f)?;
 894                 }
 895             }
 896             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 897                 // in types in actual Rust, these will always come
 898                 // after the corresponding Implemented predicate
 899                 if angle_open {
 900                     write!(f, ", ")?;
 901                 } else {
 902                     write!(f, "<")?;
 903                     angle_open = true;
 904                 }
 905                 if let AliasTy::Projection(proj) = alias {
 906                     let type_alias =
 907                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 908                     write!(f, "{} = ", type_alias.name)?;
 909                 }
 910                 ty.hir_fmt(f)?;
 911             }
 912
 913             // FIXME implement these
 914             WhereClause::LifetimeOutlives(_) => {}
 915             WhereClause::TypeOutlives(_) => {}
 916         }
 917         first = false;
 918     }
 919     if angle_open {
 920         write!(f, ">")?;
 921     }
 922     if matches!(default_sized, SizedByDefault::Sized { .. }) {
 923         if !is_sized {
 924             write!(f, "{}?Sized", if first { "" } else { " + " })?;
 925         } else if first {
 926             write!(f, "Sized")?;
 927         }
 928     }
 929     Ok(())
 930 }
 931
 932 fn fmt_trait_ref(tr: &TraitRef, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 933     if f.should_truncate() {
 934         return write!(f, "{}", TYPE_HINT_TRUNCATION);
 935     }
 936
 937     tr.self_type_parameter(Interner).hir_fmt(f)?;
 938     if use_as {
 939         write!(f, " as ")?;
 940     } else {
 941         write!(f, ": ")?;
 942     }
 943     write!(f, "{}", f.db.trait_data(tr.hir_trait_id()).name)?;
 944     if tr.substitution.len(Interner) > 1 {
 945         write!(f, "<")?;
 946         f.write_joined(&tr.substitution.as_slice(Interner)[1..], ", ")?;
 947         write!(f, ">")?;
 948     }
 949     Ok(())
 950 }
 951
 952 impl HirDisplay for TraitRef {
 953     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 954         fmt_trait_ref(self, f, false)
 955     }
 956 }
 957
 958 impl HirDisplay for WhereClause {
 959     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 960         if f.should_truncate() {
 961             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 962         }
 963
 964         match self {
 965             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 966             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 967                 write!(f, "<")?;
 968                 fmt_trait_ref(&projection_ty.trait_ref(f.db), f, true)?;
 969                 write!(
 970                     f,
 971                     ">::{} = ",
 972                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 973                 )?;
 974                 ty.hir_fmt(f)?;
 975             }
 976             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 977
 978             // FIXME implement these
 979             WhereClause::TypeOutlives(..) => {}
 980             WhereClause::LifetimeOutlives(..) => {}
 981         }
 982         Ok(())
 983     }
 984 }
 985
 986 impl HirDisplay for LifetimeOutlives {
 987     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 988         self.a.hir_fmt(f)?;
 989         write!(f, ": ")?;
 990         self.b.hir_fmt(f)
 991     }
 992 }
 993
 994 impl HirDisplay for Lifetime {
 995     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 996         self.interned().hir_fmt(f)
 997     }
 998 }
 999
1000 impl HirDisplay for LifetimeData {
1001     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1002         match self {
1003             LifetimeData::BoundVar(idx) => idx.hir_fmt(f),
1004             LifetimeData::InferenceVar(_) => write!(f, "_"),
1005             LifetimeData::Placeholder(idx) => {
1006                 let id = lt_from_placeholder_idx(f.db, *idx);
1007                 let generics = generics(f.db.upcast(), id.parent);
1008                 let param_data = &generics.params.lifetimes[id.local_id];
1009                 write!(f, "{}", param_data.name)
1010             }
1011             LifetimeData::Static => write!(f, "'static"),
1012             LifetimeData::Empty(_) => Ok(()),
1013             LifetimeData::Erased => Ok(()),
1014             LifetimeData::Phantom(_, _) => Ok(()),
1015         }
1016     }
1017 }
1018
1019 impl HirDisplay for DomainGoal {
1020     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1021         match self {
1022             DomainGoal::Holds(wc) => {
1023                 write!(f, "Holds(")?;
1024                 wc.hir_fmt(f)?;
1025                 write!(f, ")")?;
1026             }
1027             _ => write!(f, "?")?,
1028         }
1029         Ok(())
1030     }
1031 }
1032
1033 pub fn write_visibility(
1034     module_id: ModuleId,
1035     vis: Visibility,
1036     f: &mut HirFormatter,
1037 ) -> Result<(), HirDisplayError> {
1038     match vis {
1039         Visibility::Public => write!(f, "pub "),
1040         Visibility::Module(vis_id) => {
1041             let def_map = module_id.def_map(f.db.upcast());
1042             let root_module_id = def_map.module_id(def_map.root());
1043             if vis_id == module_id {
1044                 // pub(self) or omitted
1045                 Ok(())
1046             } else if root_module_id == vis_id {
1047                 write!(f, "pub(crate) ")
1048             } else if module_id.containing_module(f.db.upcast()) == Some(vis_id) {
1049                 write!(f, "pub(super) ")
1050             } else {
1051                 write!(f, "pub(in ...) ")
1052             }
1053         }
1054     }
1055 }
1056
1057 impl HirDisplay for TypeRef {
1058     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1059         match self {
1060             TypeRef::Never => write!(f, "!")?,
1061             TypeRef::Placeholder => write!(f, "_")?,
1062             TypeRef::Tuple(elems) => {
1063                 write!(f, "(")?;
1064                 f.write_joined(elems, ", ")?;
1065                 if elems.len() == 1 {
1066                     write!(f, ",")?;
1067                 }
1068                 write!(f, ")")?;
1069             }
1070             TypeRef::Path(path) => path.hir_fmt(f)?,
1071             TypeRef::RawPtr(inner, mutability) => {
1072                 let mutability = match mutability {
1073                     hir_def::type_ref::Mutability::Shared => "*const ",
1074                     hir_def::type_ref::Mutability::Mut => "*mut ",
1075                 };
1076                 write!(f, "{}", mutability)?;
1077                 inner.hir_fmt(f)?;
1078             }
1079             TypeRef::Reference(inner, lifetime, mutability) => {
1080                 let mutability = match mutability {
1081                     hir_def::type_ref::Mutability::Shared => "",
1082                     hir_def::type_ref::Mutability::Mut => "mut ",
1083                 };
1084                 write!(f, "&")?;
1085                 if let Some(lifetime) = lifetime {
1086                     write!(f, "{} ", lifetime.name)?;
1087                 }
1088                 write!(f, "{}", mutability)?;
1089                 inner.hir_fmt(f)?;
1090             }
1091             TypeRef::Array(inner, len) => {
1092                 write!(f, "[")?;
1093                 inner.hir_fmt(f)?;
1094                 write!(f, "; {}]", len)?;
1095             }
1096             TypeRef::Slice(inner) => {
1097                 write!(f, "[")?;
1098                 inner.hir_fmt(f)?;
1099                 write!(f, "]")?;
1100             }
1101             TypeRef::Fn(parameters, is_varargs) => {
1102                 write!(f, "fn(")?;
1103                 for index in 0..parameters.len() - 1 {
1104                     let (param_name,param_type) = &parameters[index];
1105                     match param_name {
1106                         Some(name) => {
1107                             write!(f, "{}: ", name)?;
1108                             param_type.hir_fmt(f)?;
1109                         },
1110                         None => write!(f, " : {:?}", param_type)?,
1111                     };
1112
1113                     if index != parameters.len() - 2 {
1114                         write!(f, ", ")?;
1115                     }
1116                 }
1117                 if *is_varargs {
1118                     write!(f, "{}...", if parameters.len() == 1 { "" } else { ", " })?;
1119                 }
1120                 write!(f, ")")?;
1121                 let ret_ty = &parameters.last().unwrap().1;
1122                 match ret_ty {
1123                     TypeRef::Tuple(tup) if tup.is_empty() => {}
1124                     _ => {
1125                         write!(f, " -> ")?;
1126                         ret_ty.hir_fmt(f)?;
1127                     }
1128                 }
1129             }
1130             TypeRef::ImplTrait(bounds) => {
1131                 write!(f, "impl ")?;
1132                 f.write_joined(bounds, " + ")?;
1133             }
1134             TypeRef::DynTrait(bounds) => {
1135                 write!(f, "dyn ")?;
1136                 f.write_joined(bounds, " + ")?;
1137             }
1138             TypeRef::Macro(macro_call) => {
1139                 let macro_call = macro_call.to_node(f.db.upcast());
1140                 let ctx = body::LowerCtx::with_hygiene(f.db.upcast(), &Hygiene::new_unhygienic());
1141                 match macro_call.path() {
1142                     Some(path) => match Path::from_src(path, &ctx) {
1143                         Some(path) => path.hir_fmt(f)?,
1144                         None => write!(f, "{{macro}}")?,
1145                     },
1146                     None => write!(f, "{{macro}}")?,
1147                 }
1148                 write!(f, "!(..)")?;
1149             }
1150             TypeRef::Error => write!(f, "{{error}}")?,
1151         }
1152         Ok(())
1153     }
1154 }
1155
1156 impl HirDisplay for TypeBound {
1157     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1158         match self {
1159             TypeBound::Path(path, modifier) => {
1160                 match modifier {
1161                     TraitBoundModifier::None => (),
1162                     TraitBoundModifier::Maybe => write!(f, "?")?,
1163                 }
1164                 path.hir_fmt(f)
1165             }
1166             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1167             TypeBound::ForLifetime(lifetimes, path) => {
1168                 write!(f, "for<{}> ", lifetimes.iter().format(", "))?;
1169                 path.hir_fmt(f)
1170             }
1171             TypeBound::Error => write!(f, "{{error}}"),
1172         }
1173     }
1174 }
1175
1176 impl HirDisplay for Path {
1177     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1178         match (self.type_anchor(), self.kind()) {
1179             (Some(anchor), _) => {
1180                 write!(f, "<")?;
1181                 anchor.hir_fmt(f)?;
1182                 write!(f, ">")?;
1183             }
1184             (_, PathKind::Plain) => {}
1185             (_, PathKind::Abs) => {}
1186             (_, PathKind::Crate) => write!(f, "crate")?,
1187             (_, PathKind::Super(0)) => write!(f, "self")?,
1188             (_, PathKind::Super(n)) => {
1189                 for i in 0..*n {
1190                     if i > 0 {
1191                         write!(f, "::")?;
1192                     }
1193                     write!(f, "super")?;
1194                 }
1195             }
1196             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
1197         }
1198
1199         for (seg_idx, segment) in self.segments().iter().enumerate() {
1200             if !matches!(self.kind(), PathKind::Plain) || seg_idx > 0 {
1201                 write!(f, "::")?;
1202             }
1203             write!(f, "{}", segment.name)?;
1204             if let Some(generic_args) = segment.args_and_bindings {
1205                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
1206                 // Do we actually format expressions?
1207                 if generic_args.desugared_from_fn {
1208                     // First argument will be a tuple, which already includes the parentheses.
1209                     // If the tuple only contains 1 item, write it manually to avoid the trailing `,`.
1210                     if let hir_def::path::GenericArg::Type(TypeRef::Tuple(v)) =
1211                         &generic_args.args[0]
1212                     {
1213                         if v.len() == 1 {
1214                             write!(f, "(")?;
1215                             v[0].hir_fmt(f)?;
1216                             write!(f, ")")?;
1217                         } else {
1218                             generic_args.args[0].hir_fmt(f)?;
1219                         }
1220                     }
1221                     if let Some(ret) = &generic_args.bindings[0].type_ref {
1222                         if !matches!(ret, TypeRef::Tuple(v) if v.is_empty()) {
1223                             write!(f, " -> ")?;
1224                             ret.hir_fmt(f)?;
1225                         }
1226                     }
1227                     return Ok(());
1228                 }
1229
1230                 write!(f, "<")?;
1231                 let mut first = true;
1232                 for arg in &generic_args.args {
1233                     if first {
1234                         first = false;
1235                         if generic_args.has_self_type {
1236                             // FIXME: Convert to `<Ty as Trait>` form.
1237                             write!(f, "Self = ")?;
1238                         }
1239                     } else {
1240                         write!(f, ", ")?;
1241                     }
1242                     arg.hir_fmt(f)?;
1243                 }
1244                 for binding in &generic_args.bindings {
1245                     if first {
1246                         first = false;
1247                     } else {
1248                         write!(f, ", ")?;
1249                     }
1250                     write!(f, "{}", binding.name)?;
1251                     match &binding.type_ref {
1252                         Some(ty) => {
1253                             write!(f, " = ")?;
1254                             ty.hir_fmt(f)?
1255                         }
1256                         None => {
1257                             write!(f, ": ")?;
1258                             f.write_joined(&binding.bounds, " + ")?;
1259                         }
1260                     }
1261                 }
1262                 write!(f, ">")?;
1263             }
1264         }
1265         Ok(())
1266     }
1267 }
1268
1269 impl HirDisplay for hir_def::path::GenericArg {
1270     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1271         match self {
1272             hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
1273             hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1274         }
1275     }
1276 }