crates/hir_ty/src/display.rs

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