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