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