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