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         let first_parameter = self.self_type_parameter(&Interner).into_displayable(
 260             f.db,
 261             f.max_size,
 262             f.omit_verbose_types,
 263             f.display_target,
 264         );
 265         write!(f, "<{} as {}", first_parameter, trait_.name)?;
 266         if self.substitution.len(&Interner) > 1 {
 267             write!(f, "<")?;
 268             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 269             write!(f, ">")?;
 270         }
 271         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
 272         Ok(())
 273     }
 274 }
 275
 276 impl HirDisplay for OpaqueTy {
 277     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 278         if f.should_truncate() {
 279             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 280         }
 281
 282         self.substitution.at(&Interner, 0).hir_fmt(f)
 283     }
 284 }
 285
 286 impl HirDisplay for GenericArg {
 287     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 288         match self.interned() {
 289             crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
 290         }
 291     }
 292 }
 293
 294 impl HirDisplay for Const {
 295     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 296         let data = self.interned();
 297         match data.value {
 298             ConstValue::BoundVar(idx) => idx.hir_fmt(f),
 299             ConstValue::InferenceVar(..) => write!(f, "_"),
 300             ConstValue::Placeholder(idx) => {
 301                 let id = const_from_placeholder_idx(f.db, idx);
 302                 let generics = generics(f.db.upcast(), id.parent);
 303                 let param_data = &generics.params.consts[id.local_id];
 304                 write!(f, "{}", param_data.name)
 305             }
 306             ConstValue::Concrete(_) => write!(f, "_"),
 307         }
 308     }
 309 }
 310
 311 impl HirDisplay for BoundVar {
 312     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 313         write!(f, "?{}.{}", self.debruijn.depth(), self.index)
 314     }
 315 }
 316
 317 impl HirDisplay for Ty {
 318     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 319         if f.should_truncate() {
 320             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 321         }
 322
 323         match self.kind(&Interner) {
 324             TyKind::Never => write!(f, "!")?,
 325             TyKind::Str => write!(f, "str")?,
 326             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
 327             TyKind::Scalar(Scalar::Char) => write!(f, "char")?,
 328             &TyKind::Scalar(Scalar::Float(t)) => write!(f, "{}", primitive::float_ty_to_string(t))?,
 329             &TyKind::Scalar(Scalar::Int(t)) => write!(f, "{}", primitive::int_ty_to_string(t))?,
 330             &TyKind::Scalar(Scalar::Uint(t)) => write!(f, "{}", primitive::uint_ty_to_string(t))?,
 331             TyKind::Slice(t) => {
 332                 write!(f, "[")?;
 333                 t.hir_fmt(f)?;
 334                 write!(f, "]")?;
 335             }
 336             TyKind::Array(t, c) => {
 337                 write!(f, "[")?;
 338                 t.hir_fmt(f)?;
 339                 write!(f, "; ")?;
 340                 c.hir_fmt(f)?;
 341                 write!(f, "]")?;
 342             }
 343             TyKind::Raw(m, t) | TyKind::Ref(m, _, t) => {
 344                 let ty_display =
 345                     t.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 346
 347                 if matches!(self.kind(&Interner), TyKind::Raw(..)) {
 348                     write!(
 349                         f,
 350                         "*{}",
 351                         match m {
 352                             Mutability::Not => "const ",
 353                             Mutability::Mut => "mut ",
 354                         }
 355                     )?;
 356                 } else {
 357                     write!(
 358                         f,
 359                         "&{}",
 360                         match m {
 361                             Mutability::Not => "",
 362                             Mutability::Mut => "mut ",
 363                         }
 364                     )?;
 365                 }
 366
 367                 // FIXME: all this just to decide whether to use parentheses...
 368                 let datas;
 369                 let predicates: Vec<_> = match t.kind(&Interner) {
 370                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
 371                         dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
 372                     }
 373                     &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
 374                         opaque_ty_id,
 375                         substitution: ref parameters,
 376                     })) => {
 377                         let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty_id.into());
 378                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
 379                             datas =
 380                                 f.db.return_type_impl_traits(func)
 381                                     .expect("impl trait id without data");
 382                             let data = (*datas)
 383                                 .as_ref()
 384                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 385                             let bounds = data.substitute(&Interner, parameters);
 386                             bounds.into_value_and_skipped_binders().0
 387                         } else {
 388                             Vec::new()
 389                         }
 390                     }
 391                     _ => Vec::new(),
 392                 };
 393
 394                 if let Some(WhereClause::Implemented(trait_ref)) =
 395                     predicates.get(0).map(|b| b.skip_binders())
 396                 {
 397                     let trait_ = trait_ref.hir_trait_id();
 398                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
 399                         && predicates.len() <= 2
 400                     {
 401                         return write!(f, "{}", ty_display);
 402                     }
 403                 }
 404
 405                 if predicates.len() > 1 {
 406                     write!(f, "(")?;
 407                     write!(f, "{}", ty_display)?;
 408                     write!(f, ")")?;
 409                 } else {
 410                     write!(f, "{}", ty_display)?;
 411                 }
 412             }
 413             TyKind::Tuple(_, substs) => {
 414                 if substs.len(&Interner) == 1 {
 415                     write!(f, "(")?;
 416                     substs.at(&Interner, 0).hir_fmt(f)?;
 417                     write!(f, ",)")?;
 418                 } else {
 419                     write!(f, "(")?;
 420                     f.write_joined(&*substs.interned(), ", ")?;
 421                     write!(f, ")")?;
 422                 }
 423             }
 424             TyKind::Function(fn_ptr) => {
 425                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 426                 sig.hir_fmt(f)?;
 427             }
 428             TyKind::FnDef(def, parameters) => {
 429                 let def = from_chalk(f.db, *def);
 430                 let sig = f.db.callable_item_signature(def).substitute(&Interner, parameters);
 431                 match def {
 432                     CallableDefId::FunctionId(ff) => {
 433                         write!(f, "fn {}", f.db.function_data(ff).name)?
 434                     }
 435                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 436                     CallableDefId::EnumVariantId(e) => {
 437                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 438                     }
 439                 };
 440                 if parameters.len(&Interner) > 0 {
 441                     let generics = generics(f.db.upcast(), def.into());
 442                     let (parent_params, self_param, type_params, _impl_trait_params) =
 443                         generics.provenance_split();
 444                     let total_len = parent_params + self_param + type_params;
 445                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 446                     if total_len > 0 {
 447                         write!(f, "<")?;
 448                         f.write_joined(&parameters.interned()[..total_len], ", ")?;
 449                         write!(f, ">")?;
 450                     }
 451                 }
 452                 write!(f, "(")?;
 453                 f.write_joined(sig.params(), ", ")?;
 454                 write!(f, ")")?;
 455                 let ret = sig.ret();
 456                 if !ret.is_unit() {
 457                     let ret_display = ret.into_displayable(
 458                         f.db,
 459                         f.max_size,
 460                         f.omit_verbose_types,
 461                         f.display_target,
 462                     );
 463
 464                     write!(f, " -> {}", ret_display)?;
 465                 }
 466             }
 467             TyKind::Adt(AdtId(def_id), parameters) => {
 468                 match f.display_target {
 469                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 470                         let name = match *def_id {
 471                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 472                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 473                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 474                         };
 475                         write!(f, "{}", name)?;
 476                     }
 477                     DisplayTarget::SourceCode { module_id } => {
 478                         if let Some(path) = find_path::find_path(
 479                             f.db.upcast(),
 480                             ItemInNs::Types((*def_id).into()),
 481                             module_id,
 482                         ) {
 483                             write!(f, "{}", path)?;
 484                         } else {
 485                             return Err(HirDisplayError::DisplaySourceCodeError(
 486                                 DisplaySourceCodeError::PathNotFound,
 487                             ));
 488                         }
 489                     }
 490                 }
 491
 492                 if parameters.len(&Interner) > 0 {
 493                     let parameters_to_write = if f.display_target.is_source_code()
 494                         || f.omit_verbose_types()
 495                     {
 496                         match self
 497                             .as_generic_def(f.db)
 498                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 499                             .filter(|defaults| !defaults.is_empty())
 500                         {
 501                             None => parameters.interned().as_ref(),
 502                             Some(default_parameters) => {
 503                                 let mut default_from = 0;
 504                                 for (i, parameter) in parameters.iter(&Interner).enumerate() {
 505                                     match (
 506                                         parameter.assert_ty_ref(&Interner).kind(&Interner),
 507                                         default_parameters.get(i),
 508                                     ) {
 509                                         (&TyKind::Error, _) | (_, None) => {
 510                                             default_from = i + 1;
 511                                         }
 512                                         (_, Some(default_parameter)) => {
 513                                             let actual_default =
 514                                                 default_parameter.clone().substitute(
 515                                                     &Interner,
 516                                                     &subst_prefix(parameters, i),
 517                                                 );
 518                                             if parameter.assert_ty_ref(&Interner) != &actual_default
 519                                             {
 520                                                 default_from = i + 1;
 521                                             }
 522                                         }
 523                                     }
 524                                 }
 525                                 &parameters.interned()[0..default_from]
 526                             }
 527                         }
 528                     } else {
 529                         parameters.interned().as_ref()
 530                     };
 531                     if !parameters_to_write.is_empty() {
 532                         write!(f, "<")?;
 533                         f.write_joined(parameters_to_write, ", ")?;
 534                         write!(f, ">")?;
 535                     }
 536                 }
 537             }
 538             TyKind::AssociatedType(assoc_type_id, parameters) => {
 539                 let type_alias = from_assoc_type_id(*assoc_type_id);
 540                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 541                     AssocContainerId::TraitId(it) => it,
 542                     _ => panic!("not an associated type"),
 543                 };
 544                 let trait_ = f.db.trait_data(trait_);
 545                 let type_alias_data = f.db.type_alias_data(type_alias);
 546
 547                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 548                 if f.display_target.is_test() {
 549                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 550                     if parameters.len(&Interner) > 0 {
 551                         write!(f, "<")?;
 552                         f.write_joined(&*parameters.interned(), ", ")?;
 553                         write!(f, ">")?;
 554                     }
 555                 } else {
 556                     let projection_ty = ProjectionTy {
 557                         associated_ty_id: to_assoc_type_id(type_alias),
 558                         substitution: parameters.clone(),
 559                     };
 560
 561                     projection_ty.hir_fmt(f)?;
 562                 }
 563             }
 564             TyKind::Foreign(type_alias) => {
 565                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 566                 write!(f, "{}", type_alias.name)?;
 567             }
 568             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 569                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 570                 match impl_trait_id {
 571                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 572                         let datas =
 573                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 574                         let data = (*datas)
 575                             .as_ref()
 576                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 577                         let bounds = data.substitute(&Interner, &parameters);
 578                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 579                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 580                     }
 581                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 582                         write!(f, "impl Future<Output = ")?;
 583                         parameters.at(&Interner, 0).hir_fmt(f)?;
 584                         write!(f, ">")?;
 585                     }
 586                 }
 587             }
 588             TyKind::Closure(.., substs) => {
 589                 if f.display_target.is_source_code() {
 590                     return Err(HirDisplayError::DisplaySourceCodeError(
 591                         DisplaySourceCodeError::Closure,
 592                     ));
 593                 }
 594                 let sig = substs.at(&Interner, 0).assert_ty_ref(&Interner).callable_sig(f.db);
 595                 if let Some(sig) = sig {
 596                     if sig.params().is_empty() {
 597                         write!(f, "||")?;
 598                     } else if f.omit_verbose_types() {
 599                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 600                     } else {
 601                         write!(f, "|")?;
 602                         f.write_joined(sig.params(), ", ")?;
 603                         write!(f, "|")?;
 604                     };
 605
 606                     let ret_display = sig.ret().into_displayable(
 607                         f.db,
 608                         f.max_size,
 609                         f.omit_verbose_types,
 610                         f.display_target,
 611                     );
 612                     write!(f, " -> {}", ret_display)?;
 613                 } else {
 614                     write!(f, "{{closure}}")?;
 615                 }
 616             }
 617             TyKind::Placeholder(idx) => {
 618                 let id = from_placeholder_idx(f.db, *idx);
 619                 let generics = generics(f.db.upcast(), id.parent);
 620                 let param_data = &generics.params.types[id.local_id];
 621                 match param_data.provenance {
 622                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 623                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 624                     }
 625                     TypeParamProvenance::ArgumentImplTrait => {
 626                         let substs = generics.type_params_subst(f.db);
 627                         let bounds =
 628                             f.db.generic_predicates(id.parent)
 629                                 .into_iter()
 630                                 .map(|pred| pred.clone().substitute(&Interner, &substs))
 631                                 .filter(|wc| match &wc.skip_binders() {
 632                                     WhereClause::Implemented(tr) => {
 633                                         tr.self_type_parameter(&Interner) == self
 634                                     }
 635                                     WhereClause::AliasEq(AliasEq {
 636                                         alias: AliasTy::Projection(proj),
 637                                         ty: _,
 638                                     }) => proj.self_type_parameter(&Interner) == self,
 639                                     _ => false,
 640                                 })
 641                                 .collect::<Vec<_>>();
 642                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds, f)?;
 643                     }
 644                 }
 645             }
 646             TyKind::BoundVar(idx) => idx.hir_fmt(f)?,
 647             TyKind::Dyn(dyn_ty) => {
 648                 write_bounds_like_dyn_trait_with_prefix(
 649                     "dyn",
 650                     dyn_ty.bounds.skip_binders().interned(),
 651                     f,
 652                 )?;
 653             }
 654             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 655             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 656                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 657                 match impl_trait_id {
 658                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 659                         let datas =
 660                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 661                         let data = (*datas)
 662                             .as_ref()
 663                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 664                         let bounds = data.substitute(&Interner, &opaque_ty.substitution);
 665                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 666                     }
 667                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 668                         write!(f, "{{async block}}")?;
 669                     }
 670                 };
 671             }
 672             TyKind::Error => {
 673                 if f.display_target.is_source_code() {
 674                     return Err(HirDisplayError::DisplaySourceCodeError(
 675                         DisplaySourceCodeError::UnknownType,
 676                     ));
 677                 }
 678                 write!(f, "{{unknown}}")?;
 679             }
 680             TyKind::InferenceVar(..) => write!(f, "_")?,
 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             let ret_display =
 701                 ret.into_displayable(f.db, f.max_size, f.omit_verbose_types, f.display_target);
 702             write!(f, " -> {}", ret_display)?;
 703         }
 704         Ok(())
 705     }
 706 }
 707
 708 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 709     let krate = trait_.lookup(db).container.krate();
 710     let fn_traits = [
 711         db.lang_item(krate, "fn".into()),
 712         db.lang_item(krate, "fn_mut".into()),
 713         db.lang_item(krate, "fn_once".into()),
 714     ];
 715     array::IntoIter::new(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 716 }
 717
 718 pub fn write_bounds_like_dyn_trait_with_prefix(
 719     prefix: &str,
 720     predicates: &[QuantifiedWhereClause],
 721     f: &mut HirFormatter,
 722 ) -> Result<(), HirDisplayError> {
 723     write!(f, "{}", prefix)?;
 724     if !predicates.is_empty() {
 725         write!(f, " ")?;
 726         write_bounds_like_dyn_trait(predicates, f)
 727     } else {
 728         Ok(())
 729     }
 730 }
 731
 732 fn write_bounds_like_dyn_trait(
 733     predicates: &[QuantifiedWhereClause],
 734     f: &mut HirFormatter,
 735 ) -> Result<(), HirDisplayError> {
 736     // Note: This code is written to produce nice results (i.e.
 737     // corresponding to surface Rust) for types that can occur in
 738     // actual Rust. It will have weird results if the predicates
 739     // aren't as expected (i.e. self types = $0, projection
 740     // predicates for a certain trait come after the Implemented
 741     // predicate for that trait).
 742     let mut first = true;
 743     let mut angle_open = false;
 744     let mut is_fn_trait = false;
 745     for p in predicates.iter() {
 746         match p.skip_binders() {
 747             WhereClause::Implemented(trait_ref) => {
 748                 let trait_ = trait_ref.hir_trait_id();
 749                 if !is_fn_trait {
 750                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 751                 }
 752                 if !is_fn_trait && angle_open {
 753                     write!(f, ">")?;
 754                     angle_open = false;
 755                 }
 756                 if !first {
 757                     write!(f, " + ")?;
 758                 }
 759                 // We assume that the self type is $0 (i.e. the
 760                 // existential) here, which is the only thing that's
 761                 // possible in actual Rust, and hence don't print it
 762                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 763                 if let [_, params @ ..] = &*trait_ref.substitution.interned() {
 764                     if is_fn_trait {
 765                         if let Some(args) =
 766                             params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
 767                         {
 768                             write!(f, "(")?;
 769                             f.write_joined(&*args.interned(), ", ")?;
 770                             write!(f, ")")?;
 771                         }
 772                     } else if !params.is_empty() {
 773                         write!(f, "<")?;
 774                         f.write_joined(params, ", ")?;
 775                         // there might be assoc type bindings, so we leave the angle brackets open
 776                         angle_open = true;
 777                     }
 778                 }
 779             }
 780             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 781                 is_fn_trait = false;
 782                 write!(f, " -> ")?;
 783                 alias_eq.ty.hir_fmt(f)?;
 784             }
 785             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 786                 // in types in actual Rust, these will always come
 787                 // after the corresponding Implemented predicate
 788                 if angle_open {
 789                     write!(f, ", ")?;
 790                 } else {
 791                     write!(f, "<")?;
 792                     angle_open = true;
 793                 }
 794                 if let AliasTy::Projection(proj) = alias {
 795                     let type_alias =
 796                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 797                     write!(f, "{} = ", type_alias.name)?;
 798                 }
 799                 ty.hir_fmt(f)?;
 800             }
 801         }
 802         first = false;
 803     }
 804     if angle_open {
 805         write!(f, ">")?;
 806     }
 807     Ok(())
 808 }
 809
 810 impl TraitRef {
 811     fn hir_fmt_ext(&self, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 812         if f.should_truncate() {
 813             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 814         }
 815
 816         self.self_type_parameter(&Interner).hir_fmt(f)?;
 817         if use_as {
 818             write!(f, " as ")?;
 819         } else {
 820             write!(f, ": ")?;
 821         }
 822         write!(f, "{}", f.db.trait_data(self.hir_trait_id()).name)?;
 823         if self.substitution.len(&Interner) > 1 {
 824             write!(f, "<")?;
 825             f.write_joined(&self.substitution.interned()[1..], ", ")?;
 826             write!(f, ">")?;
 827         }
 828         Ok(())
 829     }
 830 }
 831
 832 impl HirDisplay for TraitRef {
 833     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 834         self.hir_fmt_ext(f, false)
 835     }
 836 }
 837
 838 impl HirDisplay for WhereClause {
 839     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 840         if f.should_truncate() {
 841             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 842         }
 843
 844         match self {
 845             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 846             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 847                 write!(f, "<")?;
 848                 projection_ty.trait_ref(f.db).hir_fmt_ext(f, true)?;
 849                 write!(
 850                     f,
 851                     ">::{} = ",
 852                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 853                 )?;
 854                 ty.hir_fmt(f)?;
 855             }
 856             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 857         }
 858         Ok(())
 859     }
 860 }
 861
 862 impl HirDisplay for LifetimeOutlives {
 863     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 864         self.a.hir_fmt(f)?;
 865         write!(f, ": ")?;
 866         self.b.hir_fmt(f)
 867     }
 868 }
 869
 870 impl HirDisplay for Lifetime {
 871     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 872         self.interned().hir_fmt(f)
 873     }
 874 }
 875
 876 impl HirDisplay for LifetimeData {
 877     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 878         match self {
 879             LifetimeData::BoundVar(idx) => idx.hir_fmt(f),
 880             LifetimeData::InferenceVar(_) => write!(f, "_"),
 881             LifetimeData::Placeholder(idx) => {
 882                 let id = lt_from_placeholder_idx(f.db, *idx);
 883                 let generics = generics(f.db.upcast(), id.parent);
 884                 let param_data = &generics.params.lifetimes[id.local_id];
 885                 write!(f, "{}", param_data.name)
 886             }
 887             LifetimeData::Static => write!(f, "'static"),
 888             LifetimeData::Empty(_) => Ok(()),
 889             LifetimeData::Erased => Ok(()),
 890             LifetimeData::Phantom(_, _) => Ok(()),
 891         }
 892     }
 893 }
 894
 895 impl HirDisplay for DomainGoal {
 896     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 897         match self {
 898             DomainGoal::Holds(wc) => {
 899                 write!(f, "Holds(")?;
 900                 wc.hir_fmt(f)?;
 901                 write!(f, ")")
 902             }
 903         }
 904     }
 905 }
 906
 907 pub fn write_visibility(
 908     module_id: ModuleId,
 909     vis: Visibility,
 910     f: &mut HirFormatter,
 911 ) -> Result<(), HirDisplayError> {
 912     match vis {
 913         Visibility::Public => write!(f, "pub "),
 914         Visibility::Module(vis_id) => {
 915             let def_map = module_id.def_map(f.db.upcast());
 916             let root_module_id = def_map.module_id(def_map.root());
 917             if vis_id == module_id {
 918                 // pub(self) or omitted
 919                 Ok(())
 920             } else if root_module_id == vis_id {
 921                 write!(f, "pub(crate) ")
 922             } else if module_id.containing_module(f.db.upcast()) == Some(vis_id) {
 923                 write!(f, "pub(super) ")
 924             } else {
 925                 write!(f, "pub(in ...) ")
 926             }
 927         }
 928     }
 929 }
 930
 931 impl HirDisplay for TypeRef {
 932     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 933         match self {
 934             TypeRef::Never => write!(f, "!")?,
 935             TypeRef::Placeholder => write!(f, "_")?,
 936             TypeRef::Tuple(elems) => {
 937                 write!(f, "(")?;
 938                 f.write_joined(elems, ", ")?;
 939                 if elems.len() == 1 {
 940                     write!(f, ",")?;
 941                 }
 942                 write!(f, ")")?;
 943             }
 944             TypeRef::Path(path) => path.hir_fmt(f)?,
 945             TypeRef::RawPtr(inner, mutability) => {
 946                 let mutability = match mutability {
 947                     hir_def::type_ref::Mutability::Shared => "*const ",
 948                     hir_def::type_ref::Mutability::Mut => "*mut ",
 949                 };
 950                 write!(f, "{}", mutability)?;
 951                 inner.hir_fmt(f)?;
 952             }
 953             TypeRef::Reference(inner, lifetime, mutability) => {
 954                 let mutability = match mutability {
 955                     hir_def::type_ref::Mutability::Shared => "",
 956                     hir_def::type_ref::Mutability::Mut => "mut ",
 957                 };
 958                 write!(f, "&")?;
 959                 if let Some(lifetime) = lifetime {
 960                     write!(f, "{} ", lifetime.name)?;
 961                 }
 962                 write!(f, "{}", mutability)?;
 963                 inner.hir_fmt(f)?;
 964             }
 965             TypeRef::Array(inner) => {
 966                 write!(f, "[")?;
 967                 inner.hir_fmt(f)?;
 968                 // FIXME: Array length?
 969                 write!(f, "; _]")?;
 970             }
 971             TypeRef::Slice(inner) => {
 972                 write!(f, "[")?;
 973                 inner.hir_fmt(f)?;
 974                 write!(f, "]")?;
 975             }
 976             TypeRef::Fn(tys, is_varargs) => {
 977                 // FIXME: Function pointer qualifiers.
 978                 write!(f, "fn(")?;
 979                 f.write_joined(&tys[..tys.len() - 1], ", ")?;
 980                 if *is_varargs {
 981                     write!(f, "{}...", if tys.len() == 1 { "" } else { ", " })?;
 982                 }
 983                 write!(f, ")")?;
 984                 let ret_ty = tys.last().unwrap();
 985                 match ret_ty {
 986                     TypeRef::Tuple(tup) if tup.is_empty() => {}
 987                     _ => {
 988                         write!(f, " -> ")?;
 989                         ret_ty.hir_fmt(f)?;
 990                     }
 991                 }
 992             }
 993             TypeRef::ImplTrait(bounds) => {
 994                 write!(f, "impl ")?;
 995                 f.write_joined(bounds, " + ")?;
 996             }
 997             TypeRef::DynTrait(bounds) => {
 998                 write!(f, "dyn ")?;
 999                 f.write_joined(bounds, " + ")?;
1000             }
1001             TypeRef::Error => write!(f, "{{error}}")?,
1002         }
1003         Ok(())
1004     }
1005 }
1006
1007 impl HirDisplay for TypeBound {
1008     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1009         match self {
1010             TypeBound::Path(path) => path.hir_fmt(f),
1011             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1012             TypeBound::Error => write!(f, "{{error}}"),
1013         }
1014     }
1015 }
1016
1017 impl HirDisplay for Path {
1018     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1019         match (self.type_anchor(), self.kind()) {
1020             (Some(anchor), _) => {
1021                 write!(f, "<")?;
1022                 anchor.hir_fmt(f)?;
1023                 write!(f, ">")?;
1024             }
1025             (_, PathKind::Plain) => {}
1026             (_, PathKind::Abs) => write!(f, "::")?,
1027             (_, PathKind::Crate) => write!(f, "crate")?,
1028             (_, PathKind::Super(0)) => write!(f, "self")?,
1029             (_, PathKind::Super(n)) => {
1030                 write!(f, "super")?;
1031                 for _ in 0..*n {
1032                     write!(f, "::super")?;
1033                 }
1034             }
1035             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
1036         }
1037
1038         for (seg_idx, segment) in self.segments().iter().enumerate() {
1039             if seg_idx != 0 {
1040                 write!(f, "::")?;
1041             }
1042             write!(f, "{}", segment.name)?;
1043             if let Some(generic_args) = segment.args_and_bindings {
1044                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
1045                 // Do we actually format expressions?
1046                 write!(f, "<")?;
1047                 let mut first = true;
1048                 for arg in &generic_args.args {
1049                     if first {
1050                         first = false;
1051                         if generic_args.has_self_type {
1052                             // FIXME: Convert to `<Ty as Trait>` form.
1053                             write!(f, "Self = ")?;
1054                         }
1055                     } else {
1056                         write!(f, ", ")?;
1057                     }
1058                     arg.hir_fmt(f)?;
1059                 }
1060                 for binding in &generic_args.bindings {
1061                     if first {
1062                         first = false;
1063                     } else {
1064                         write!(f, ", ")?;
1065                     }
1066                     write!(f, "{}", binding.name)?;
1067                     match &binding.type_ref {
1068                         Some(ty) => {
1069                             write!(f, " = ")?;
1070                             ty.hir_fmt(f)?
1071                         }
1072                         None => {
1073                             write!(f, ": ")?;
1074                             f.write_joined(&binding.bounds, " + ")?;
1075                         }
1076                     }
1077                 }
1078                 write!(f, ">")?;
1079             }
1080         }
1081         Ok(())
1082     }
1083 }
1084
1085 impl HirDisplay for hir_def::path::GenericArg {
1086     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1087         match self {
1088             hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
1089             hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1090         }
1091     }
1092 }