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