crates/hir_ty/src/display.rs

   1 //! The `HirDisplay` trait, which serves two purposes: Turning various bits from
   2 //! HIR back into source code, and just displaying them for debugging/testing
   3 //! purposes.
   4
   5 use std::{
   6     array,
   7     fmt::{self, Debug},
   8 };
   9
  10 use chalk_ir::BoundVar;
  11 use hir_def::{
  12     body,
  13     db::DefDatabase,
  14     find_path,
  15     generics::TypeParamProvenance,
  16     item_scope::ItemInNs,
  17     path::{Path, PathKind},
  18     type_ref::{TypeBound, TypeRef},
  19     visibility::Visibility,
  20     AssocContainerId, Lookup, ModuleId, TraitId,
  21 };
  22 use hir_expand::{hygiene::Hygiene, name::Name};
  23
  24 use crate::{
  25     const_from_placeholder_idx, db::HirDatabase, from_assoc_type_id, from_foreign_def_id,
  26     from_placeholder_idx, lt_from_placeholder_idx, mapping::from_chalk, primitive, subst_prefix,
  27     to_assoc_type_id, utils::generics, AdtId, AliasEq, AliasTy, CallableDefId, CallableSig, Const,
  28     ConstValue, DomainGoal, GenericArg, ImplTraitId, Interner, Lifetime, LifetimeData,
  29     LifetimeOutlives, Mutability, OpaqueTy, ProjectionTy, ProjectionTyExt, QuantifiedWhereClause,
  30     Scalar, TraitRef, TraitRefExt, Ty, TyExt, TyKind, WhereClause,
  31 };
  32
  33 pub struct HirFormatter<'a> {
  34     pub db: &'a dyn HirDatabase,
  35     fmt: &'a mut dyn fmt::Write,
  36     buf: String,
  37     curr_size: usize,
  38     pub(crate) max_size: Option<usize>,
  39     omit_verbose_types: bool,
  40     display_target: DisplayTarget,
  41 }
  42
  43 pub trait HirDisplay {
  44     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError>;
  45
  46     /// Returns a `Display`able type that is human-readable.
  47     fn into_displayable<'a>(
  48         &'a self,
  49         db: &'a dyn HirDatabase,
  50         max_size: Option<usize>,
  51         omit_verbose_types: bool,
  52         display_target: DisplayTarget,
  53     ) -> HirDisplayWrapper<'a, Self>
  54     where
  55         Self: Sized,
  56     {
  57         assert!(
  58             !matches!(display_target, DisplayTarget::SourceCode { .. }),
  59             "HirDisplayWrapper cannot fail with DisplaySourceCodeError, use HirDisplay::hir_fmt directly instead"
  60         );
  61         HirDisplayWrapper { db, t: self, max_size, omit_verbose_types, display_target }
  62     }
  63
  64     /// Returns a `Display`able type that is human-readable.
  65     /// Use this for showing types to the user (e.g. diagnostics)
  66     fn display<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
  67     where
  68         Self: Sized,
  69     {
  70         HirDisplayWrapper {
  71             db,
  72             t: self,
  73             max_size: None,
  74             omit_verbose_types: false,
  75             display_target: DisplayTarget::Diagnostics,
  76         }
  77     }
  78
  79     /// Returns a `Display`able type that is human-readable and tries to be succinct.
  80     /// Use this for showing types to the user where space is constrained (e.g. doc popups)
  81     fn display_truncated<'a>(
  82         &'a self,
  83         db: &'a dyn HirDatabase,
  84         max_size: Option<usize>,
  85     ) -> HirDisplayWrapper<'a, Self>
  86     where
  87         Self: Sized,
  88     {
  89         HirDisplayWrapper {
  90             db,
  91             t: self,
  92             max_size,
  93             omit_verbose_types: true,
  94             display_target: DisplayTarget::Diagnostics,
  95         }
  96     }
  97
  98     /// Returns a String representation of `self` that can be inserted into the given module.
  99     /// Use this when generating code (e.g. assists)
 100     fn display_source_code<'a>(
 101         &'a self,
 102         db: &'a dyn HirDatabase,
 103         module_id: ModuleId,
 104     ) -> Result<String, DisplaySourceCodeError> {
 105         let mut result = String::new();
 106         match self.hir_fmt(&mut HirFormatter {
 107             db,
 108             fmt: &mut result,
 109             buf: String::with_capacity(20),
 110             curr_size: 0,
 111             max_size: None,
 112             omit_verbose_types: false,
 113             display_target: DisplayTarget::SourceCode { module_id },
 114         }) {
 115             Ok(()) => {}
 116             Err(HirDisplayError::FmtError) => panic!("Writing to String can't fail!"),
 117             Err(HirDisplayError::DisplaySourceCodeError(e)) => return Err(e),
 118         };
 119         Ok(result)
 120     }
 121
 122     /// Returns a String representation of `self` for test purposes
 123     fn display_test<'a>(&'a self, db: &'a dyn HirDatabase) -> HirDisplayWrapper<'a, Self>
 124     where
 125         Self: Sized,
 126     {
 127         HirDisplayWrapper {
 128             db,
 129             t: self,
 130             max_size: None,
 131             omit_verbose_types: false,
 132             display_target: DisplayTarget::Test,
 133         }
 134     }
 135 }
 136
 137 impl<'a> HirFormatter<'a> {
 138     pub fn write_joined<T: HirDisplay>(
 139         &mut self,
 140         iter: impl IntoIterator<Item = T>,
 141         sep: &str,
 142     ) -> Result<(), HirDisplayError> {
 143         let mut first = true;
 144         for e in iter {
 145             if !first {
 146                 write!(self, "{}", sep)?;
 147             }
 148             first = false;
 149             e.hir_fmt(self)?;
 150         }
 151         Ok(())
 152     }
 153
 154     /// This allows using the `write!` macro directly with a `HirFormatter`.
 155     pub fn write_fmt(&mut self, args: fmt::Arguments) -> Result<(), HirDisplayError> {
 156         // We write to a buffer first to track output size
 157         self.buf.clear();
 158         fmt::write(&mut self.buf, args)?;
 159         self.curr_size += self.buf.len();
 160
 161         // Then we write to the internal formatter from the buffer
 162         self.fmt.write_str(&self.buf).map_err(HirDisplayError::from)
 163     }
 164
 165     pub fn should_truncate(&self) -> bool {
 166         if let Some(max_size) = self.max_size {
 167             self.curr_size >= max_size
 168         } else {
 169             false
 170         }
 171     }
 172
 173     pub fn omit_verbose_types(&self) -> bool {
 174         self.omit_verbose_types
 175     }
 176 }
 177
 178 #[derive(Clone, Copy)]
 179 pub enum DisplayTarget {
 180     /// Display types for inlays, doc popups, autocompletion, etc...
 181     /// Showing `{unknown}` or not qualifying paths is fine here.
 182     /// There's no reason for this to fail.
 183     Diagnostics,
 184     /// Display types for inserting them in source files.
 185     /// The generated code should compile, so paths need to be qualified.
 186     SourceCode { module_id: ModuleId },
 187     /// Only for test purpose to keep real types
 188     Test,
 189 }
 190
 191 impl DisplayTarget {
 192     fn is_source_code(&self) -> bool {
 193         matches!(self, Self::SourceCode { .. })
 194     }
 195     fn is_test(&self) -> bool {
 196         matches!(self, Self::Test)
 197     }
 198 }
 199
 200 #[derive(Debug)]
 201 pub enum DisplaySourceCodeError {
 202     PathNotFound,
 203     UnknownType,
 204     Closure,
 205 }
 206
 207 pub enum HirDisplayError {
 208     /// Errors that can occur when generating source code
 209     DisplaySourceCodeError(DisplaySourceCodeError),
 210     /// `FmtError` is required to be compatible with std::fmt::Display
 211     FmtError,
 212 }
 213 impl From<fmt::Error> for HirDisplayError {
 214     fn from(_: fmt::Error) -> Self {
 215         Self::FmtError
 216     }
 217 }
 218
 219 pub struct HirDisplayWrapper<'a, T> {
 220     db: &'a dyn HirDatabase,
 221     t: &'a T,
 222     max_size: Option<usize>,
 223     omit_verbose_types: bool,
 224     display_target: DisplayTarget,
 225 }
 226
 227 impl<'a, T> fmt::Display for HirDisplayWrapper<'a, T>
 228 where
 229     T: HirDisplay,
 230 {
 231     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 232         match self.t.hir_fmt(&mut HirFormatter {
 233             db: self.db,
 234             fmt: f,
 235             buf: String::with_capacity(20),
 236             curr_size: 0,
 237             max_size: self.max_size,
 238             omit_verbose_types: self.omit_verbose_types,
 239             display_target: self.display_target,
 240         }) {
 241             Ok(()) => Ok(()),
 242             Err(HirDisplayError::FmtError) => Err(fmt::Error),
 243             Err(HirDisplayError::DisplaySourceCodeError(_)) => {
 244                 // This should never happen
 245                 panic!("HirDisplay::hir_fmt failed with DisplaySourceCodeError when calling Display::fmt!")
 246             }
 247         }
 248     }
 249 }
 250
 251 const TYPE_HINT_TRUNCATION: &str = "…";
 252
 253 impl<T: HirDisplay> HirDisplay for &'_ T {
 254     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 255         HirDisplay::hir_fmt(*self, f)
 256     }
 257 }
 258
 259 impl HirDisplay for ProjectionTy {
 260     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 261         if f.should_truncate() {
 262             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 263         }
 264
 265         let trait_ = f.db.trait_data(self.trait_(f.db));
 266         write!(f, "<")?;
 267         self.self_type_parameter(&Interner).hir_fmt(f)?;
 268         write!(f, " as {}", trait_.name)?;
 269         if self.substitution.len(&Interner) > 1 {
 270             write!(f, "<")?;
 271             f.write_joined(&self.substitution.as_slice(&Interner)[1..], ", ")?;
 272             write!(f, ">")?;
 273         }
 274         write!(f, ">::{}", f.db.type_alias_data(from_assoc_type_id(self.associated_ty_id)).name)?;
 275         Ok(())
 276     }
 277 }
 278
 279 impl HirDisplay for OpaqueTy {
 280     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 281         if f.should_truncate() {
 282             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 283         }
 284
 285         self.substitution.at(&Interner, 0).hir_fmt(f)
 286     }
 287 }
 288
 289 impl HirDisplay for GenericArg {
 290     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 291         match self.interned() {
 292             crate::GenericArgData::Ty(ty) => ty.hir_fmt(f),
 293             crate::GenericArgData::Lifetime(lt) => lt.hir_fmt(f),
 294             crate::GenericArgData::Const(c) => c.hir_fmt(f),
 295         }
 296     }
 297 }
 298
 299 impl HirDisplay for Const {
 300     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 301         let data = self.interned();
 302         match data.value {
 303             ConstValue::BoundVar(idx) => idx.hir_fmt(f),
 304             ConstValue::InferenceVar(..) => write!(f, "_"),
 305             ConstValue::Placeholder(idx) => {
 306                 let id = const_from_placeholder_idx(f.db, idx);
 307                 let generics = generics(f.db.upcast(), id.parent);
 308                 let param_data = &generics.params.consts[id.local_id];
 309                 write!(f, "{}", param_data.name)
 310             }
 311             ConstValue::Concrete(c) => write!(f, "{}", c.interned),
 312         }
 313     }
 314 }
 315
 316 impl HirDisplay for BoundVar {
 317     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 318         write!(f, "?{}.{}", self.debruijn.depth(), self.index)
 319     }
 320 }
 321
 322 impl HirDisplay for Ty {
 323     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 324         if f.should_truncate() {
 325             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 326         }
 327
 328         match self.kind(&Interner) {
 329             TyKind::Never => write!(f, "!")?,
 330             TyKind::Str => write!(f, "str")?,
 331             TyKind::Scalar(Scalar::Bool) => write!(f, "bool")?,
 332             TyKind::Scalar(Scalar::Char) => write!(f, "char")?,
 333             &TyKind::Scalar(Scalar::Float(t)) => write!(f, "{}", primitive::float_ty_to_string(t))?,
 334             &TyKind::Scalar(Scalar::Int(t)) => write!(f, "{}", primitive::int_ty_to_string(t))?,
 335             &TyKind::Scalar(Scalar::Uint(t)) => write!(f, "{}", primitive::uint_ty_to_string(t))?,
 336             TyKind::Slice(t) => {
 337                 write!(f, "[")?;
 338                 t.hir_fmt(f)?;
 339                 write!(f, "]")?;
 340             }
 341             TyKind::Array(t, c) => {
 342                 write!(f, "[")?;
 343                 t.hir_fmt(f)?;
 344                 write!(f, "; ")?;
 345                 c.hir_fmt(f)?;
 346                 write!(f, "]")?;
 347             }
 348             TyKind::Raw(m, t) | TyKind::Ref(m, _, t) => {
 349                 if matches!(self.kind(&Interner), TyKind::Raw(..)) {
 350                     write!(
 351                         f,
 352                         "*{}",
 353                         match m {
 354                             Mutability::Not => "const ",
 355                             Mutability::Mut => "mut ",
 356                         }
 357                     )?;
 358                 } else {
 359                     write!(
 360                         f,
 361                         "&{}",
 362                         match m {
 363                             Mutability::Not => "",
 364                             Mutability::Mut => "mut ",
 365                         }
 366                     )?;
 367                 }
 368
 369                 // FIXME: all this just to decide whether to use parentheses...
 370                 let datas;
 371                 let predicates: Vec<_> = match t.kind(&Interner) {
 372                     TyKind::Dyn(dyn_ty) if dyn_ty.bounds.skip_binders().interned().len() > 1 => {
 373                         dyn_ty.bounds.skip_binders().interned().iter().cloned().collect()
 374                     }
 375                     &TyKind::Alias(AliasTy::Opaque(OpaqueTy {
 376                         opaque_ty_id,
 377                         substitution: ref parameters,
 378                     })) => {
 379                         let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty_id.into());
 380                         if let ImplTraitId::ReturnTypeImplTrait(func, idx) = impl_trait_id {
 381                             datas =
 382                                 f.db.return_type_impl_traits(func)
 383                                     .expect("impl trait id without data");
 384                             let data = (*datas)
 385                                 .as_ref()
 386                                 .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 387                             let bounds = data.substitute(&Interner, parameters);
 388                             bounds.into_value_and_skipped_binders().0
 389                         } else {
 390                             Vec::new()
 391                         }
 392                     }
 393                     _ => Vec::new(),
 394                 };
 395
 396                 if let Some(WhereClause::Implemented(trait_ref)) =
 397                     predicates.get(0).map(|b| b.skip_binders())
 398                 {
 399                     let trait_ = trait_ref.hir_trait_id();
 400                     if fn_traits(f.db.upcast(), trait_).any(|it| it == trait_)
 401                         && predicates.len() <= 2
 402                     {
 403                         return t.hir_fmt(f);
 404                     }
 405                 }
 406
 407                 if predicates.len() > 1 {
 408                     write!(f, "(")?;
 409                     t.hir_fmt(f)?;
 410                     write!(f, ")")?;
 411                 } else {
 412                     t.hir_fmt(f)?;
 413                 }
 414             }
 415             TyKind::Tuple(_, substs) => {
 416                 if substs.len(&Interner) == 1 {
 417                     write!(f, "(")?;
 418                     substs.at(&Interner, 0).hir_fmt(f)?;
 419                     write!(f, ",)")?;
 420                 } else {
 421                     write!(f, "(")?;
 422                     f.write_joined(&*substs.as_slice(&Interner), ", ")?;
 423                     write!(f, ")")?;
 424                 }
 425             }
 426             TyKind::Function(fn_ptr) => {
 427                 let sig = CallableSig::from_fn_ptr(fn_ptr);
 428                 sig.hir_fmt(f)?;
 429             }
 430             TyKind::FnDef(def, parameters) => {
 431                 let def = from_chalk(f.db, *def);
 432                 let sig = f.db.callable_item_signature(def).substitute(&Interner, parameters);
 433                 match def {
 434                     CallableDefId::FunctionId(ff) => {
 435                         write!(f, "fn {}", f.db.function_data(ff).name)?
 436                     }
 437                     CallableDefId::StructId(s) => write!(f, "{}", f.db.struct_data(s).name)?,
 438                     CallableDefId::EnumVariantId(e) => {
 439                         write!(f, "{}", f.db.enum_data(e.parent).variants[e.local_id].name)?
 440                     }
 441                 };
 442                 if parameters.len(&Interner) > 0 {
 443                     let generics = generics(f.db.upcast(), def.into());
 444                     let (parent_params, self_param, type_params, _impl_trait_params) =
 445                         generics.provenance_split();
 446                     let total_len = parent_params + self_param + type_params;
 447                     // We print all params except implicit impl Trait params. Still a bit weird; should we leave out parent and self?
 448                     if total_len > 0 {
 449                         write!(f, "<")?;
 450                         f.write_joined(&parameters.as_slice(&Interner)[..total_len], ", ")?;
 451                         write!(f, ">")?;
 452                     }
 453                 }
 454                 write!(f, "(")?;
 455                 f.write_joined(sig.params(), ", ")?;
 456                 write!(f, ")")?;
 457                 let ret = sig.ret();
 458                 if !ret.is_unit() {
 459                     write!(f, " -> ")?;
 460                     ret.hir_fmt(f)?;
 461                 }
 462             }
 463             TyKind::Adt(AdtId(def_id), parameters) => {
 464                 match f.display_target {
 465                     DisplayTarget::Diagnostics | DisplayTarget::Test => {
 466                         let name = match *def_id {
 467                             hir_def::AdtId::StructId(it) => f.db.struct_data(it).name.clone(),
 468                             hir_def::AdtId::UnionId(it) => f.db.union_data(it).name.clone(),
 469                             hir_def::AdtId::EnumId(it) => f.db.enum_data(it).name.clone(),
 470                         };
 471                         write!(f, "{}", name)?;
 472                     }
 473                     DisplayTarget::SourceCode { module_id } => {
 474                         if let Some(path) = find_path::find_path(
 475                             f.db.upcast(),
 476                             ItemInNs::Types((*def_id).into()),
 477                             module_id,
 478                         ) {
 479                             write!(f, "{}", path)?;
 480                         } else {
 481                             return Err(HirDisplayError::DisplaySourceCodeError(
 482                                 DisplaySourceCodeError::PathNotFound,
 483                             ));
 484                         }
 485                     }
 486                 }
 487
 488                 if parameters.len(&Interner) > 0 {
 489                     let parameters_to_write = if f.display_target.is_source_code()
 490                         || f.omit_verbose_types()
 491                     {
 492                         match self
 493                             .as_generic_def(f.db)
 494                             .map(|generic_def_id| f.db.generic_defaults(generic_def_id))
 495                             .filter(|defaults| !defaults.is_empty())
 496                         {
 497                             None => parameters.as_slice(&Interner),
 498                             Some(default_parameters) => {
 499                                 let mut default_from = 0;
 500                                 for (i, parameter) in parameters.iter(&Interner).enumerate() {
 501                                     match (
 502                                         parameter.assert_ty_ref(&Interner).kind(&Interner),
 503                                         default_parameters.get(i),
 504                                     ) {
 505                                         (&TyKind::Error, _) | (_, None) => {
 506                                             default_from = i + 1;
 507                                         }
 508                                         (_, Some(default_parameter)) => {
 509                                             let actual_default =
 510                                                 default_parameter.clone().substitute(
 511                                                     &Interner,
 512                                                     &subst_prefix(parameters, i),
 513                                                 );
 514                                             if parameter.assert_ty_ref(&Interner) != &actual_default
 515                                             {
 516                                                 default_from = i + 1;
 517                                             }
 518                                         }
 519                                     }
 520                                 }
 521                                 &parameters.as_slice(&Interner)[0..default_from]
 522                             }
 523                         }
 524                     } else {
 525                         parameters.as_slice(&Interner)
 526                     };
 527                     if !parameters_to_write.is_empty() {
 528                         write!(f, "<")?;
 529                         f.write_joined(parameters_to_write, ", ")?;
 530                         write!(f, ">")?;
 531                     }
 532                 }
 533             }
 534             TyKind::AssociatedType(assoc_type_id, parameters) => {
 535                 let type_alias = from_assoc_type_id(*assoc_type_id);
 536                 let trait_ = match type_alias.lookup(f.db.upcast()).container {
 537                     AssocContainerId::TraitId(it) => it,
 538                     _ => panic!("not an associated type"),
 539                 };
 540                 let trait_ = f.db.trait_data(trait_);
 541                 let type_alias_data = f.db.type_alias_data(type_alias);
 542
 543                 // Use placeholder associated types when the target is test (https://rust-lang.github.io/chalk/book/clauses/type_equality.html#placeholder-associated-types)
 544                 if f.display_target.is_test() {
 545                     write!(f, "{}::{}", trait_.name, type_alias_data.name)?;
 546                     if parameters.len(&Interner) > 0 {
 547                         write!(f, "<")?;
 548                         f.write_joined(&*parameters.as_slice(&Interner), ", ")?;
 549                         write!(f, ">")?;
 550                     }
 551                 } else {
 552                     let projection_ty = ProjectionTy {
 553                         associated_ty_id: to_assoc_type_id(type_alias),
 554                         substitution: parameters.clone(),
 555                     };
 556
 557                     projection_ty.hir_fmt(f)?;
 558                 }
 559             }
 560             TyKind::Foreign(type_alias) => {
 561                 let type_alias = f.db.type_alias_data(from_foreign_def_id(*type_alias));
 562                 write!(f, "{}", type_alias.name)?;
 563             }
 564             TyKind::OpaqueType(opaque_ty_id, parameters) => {
 565                 let impl_trait_id = f.db.lookup_intern_impl_trait_id((*opaque_ty_id).into());
 566                 match impl_trait_id {
 567                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 568                         let datas =
 569                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 570                         let data = (*datas)
 571                             .as_ref()
 572                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 573                         let bounds = data.substitute(&Interner, &parameters);
 574                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 575                         // FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
 576                     }
 577                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 578                         write!(f, "impl Future<Output = ")?;
 579                         parameters.at(&Interner, 0).hir_fmt(f)?;
 580                         write!(f, ">")?;
 581                     }
 582                 }
 583             }
 584             TyKind::Closure(.., substs) => {
 585                 if f.display_target.is_source_code() {
 586                     return Err(HirDisplayError::DisplaySourceCodeError(
 587                         DisplaySourceCodeError::Closure,
 588                     ));
 589                 }
 590                 let sig = substs.at(&Interner, 0).assert_ty_ref(&Interner).callable_sig(f.db);
 591                 if let Some(sig) = sig {
 592                     if sig.params().is_empty() {
 593                         write!(f, "||")?;
 594                     } else if f.omit_verbose_types() {
 595                         write!(f, "|{}|", TYPE_HINT_TRUNCATION)?;
 596                     } else {
 597                         write!(f, "|")?;
 598                         f.write_joined(sig.params(), ", ")?;
 599                         write!(f, "|")?;
 600                     };
 601
 602                     write!(f, " -> ")?;
 603                     sig.ret().hir_fmt(f)?;
 604                 } else {
 605                     write!(f, "{{closure}}")?;
 606                 }
 607             }
 608             TyKind::Placeholder(idx) => {
 609                 let id = from_placeholder_idx(f.db, *idx);
 610                 let generics = generics(f.db.upcast(), id.parent);
 611                 let param_data = &generics.params.types[id.local_id];
 612                 match param_data.provenance {
 613                     TypeParamProvenance::TypeParamList | TypeParamProvenance::TraitSelf => {
 614                         write!(f, "{}", param_data.name.clone().unwrap_or_else(Name::missing))?
 615                     }
 616                     TypeParamProvenance::ArgumentImplTrait => {
 617                         let substs = generics.type_params_subst(f.db);
 618                         let bounds =
 619                             f.db.generic_predicates(id.parent)
 620                                 .into_iter()
 621                                 .map(|pred| pred.clone().substitute(&Interner, &substs))
 622                                 .filter(|wc| match &wc.skip_binders() {
 623                                     WhereClause::Implemented(tr) => {
 624                                         &tr.self_type_parameter(&Interner) == self
 625                                     }
 626                                     WhereClause::AliasEq(AliasEq {
 627                                         alias: AliasTy::Projection(proj),
 628                                         ty: _,
 629                                     }) => &proj.self_type_parameter(&Interner) == self,
 630                                     _ => false,
 631                                 })
 632                                 .collect::<Vec<_>>();
 633                         write_bounds_like_dyn_trait_with_prefix("impl", &bounds, f)?;
 634                     }
 635                 }
 636             }
 637             TyKind::BoundVar(idx) => idx.hir_fmt(f)?,
 638             TyKind::Dyn(dyn_ty) => {
 639                 write_bounds_like_dyn_trait_with_prefix(
 640                     "dyn",
 641                     dyn_ty.bounds.skip_binders().interned(),
 642                     f,
 643                 )?;
 644             }
 645             TyKind::Alias(AliasTy::Projection(p_ty)) => p_ty.hir_fmt(f)?,
 646             TyKind::Alias(AliasTy::Opaque(opaque_ty)) => {
 647                 let impl_trait_id = f.db.lookup_intern_impl_trait_id(opaque_ty.opaque_ty_id.into());
 648                 match impl_trait_id {
 649                     ImplTraitId::ReturnTypeImplTrait(func, idx) => {
 650                         let datas =
 651                             f.db.return_type_impl_traits(func).expect("impl trait id without data");
 652                         let data = (*datas)
 653                             .as_ref()
 654                             .map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
 655                         let bounds = data.substitute(&Interner, &opaque_ty.substitution);
 656                         write_bounds_like_dyn_trait_with_prefix("impl", bounds.skip_binders(), f)?;
 657                     }
 658                     ImplTraitId::AsyncBlockTypeImplTrait(..) => {
 659                         write!(f, "{{async block}}")?;
 660                     }
 661                 };
 662             }
 663             TyKind::Error => {
 664                 if f.display_target.is_source_code() {
 665                     return Err(HirDisplayError::DisplaySourceCodeError(
 666                         DisplaySourceCodeError::UnknownType,
 667                     ));
 668                 }
 669                 write!(f, "{{unknown}}")?;
 670             }
 671             TyKind::InferenceVar(..) => write!(f, "_")?,
 672             TyKind::Generator(..) => write!(f, "{{generator}}")?,
 673             TyKind::GeneratorWitness(..) => write!(f, "{{generator witness}}")?,
 674         }
 675         Ok(())
 676     }
 677 }
 678
 679 impl HirDisplay for CallableSig {
 680     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 681         write!(f, "fn(")?;
 682         f.write_joined(self.params(), ", ")?;
 683         if self.is_varargs {
 684             if self.params().is_empty() {
 685                 write!(f, "...")?;
 686             } else {
 687                 write!(f, ", ...")?;
 688             }
 689         }
 690         write!(f, ")")?;
 691         let ret = self.ret();
 692         if !ret.is_unit() {
 693             write!(f, " -> ")?;
 694             ret.hir_fmt(f)?;
 695         }
 696         Ok(())
 697     }
 698 }
 699
 700 fn fn_traits(db: &dyn DefDatabase, trait_: TraitId) -> impl Iterator<Item = TraitId> {
 701     let krate = trait_.lookup(db).container.krate();
 702     let fn_traits = [
 703         db.lang_item(krate, "fn".into()),
 704         db.lang_item(krate, "fn_mut".into()),
 705         db.lang_item(krate, "fn_once".into()),
 706     ];
 707     array::IntoIter::new(fn_traits).into_iter().flatten().flat_map(|it| it.as_trait())
 708 }
 709
 710 pub fn write_bounds_like_dyn_trait_with_prefix(
 711     prefix: &str,
 712     predicates: &[QuantifiedWhereClause],
 713     f: &mut HirFormatter,
 714 ) -> Result<(), HirDisplayError> {
 715     write!(f, "{}", prefix)?;
 716     if !predicates.is_empty() {
 717         write!(f, " ")?;
 718         write_bounds_like_dyn_trait(predicates, f)
 719     } else {
 720         Ok(())
 721     }
 722 }
 723
 724 fn write_bounds_like_dyn_trait(
 725     predicates: &[QuantifiedWhereClause],
 726     f: &mut HirFormatter,
 727 ) -> Result<(), HirDisplayError> {
 728     // Note: This code is written to produce nice results (i.e.
 729     // corresponding to surface Rust) for types that can occur in
 730     // actual Rust. It will have weird results if the predicates
 731     // aren't as expected (i.e. self types = $0, projection
 732     // predicates for a certain trait come after the Implemented
 733     // predicate for that trait).
 734     let mut first = true;
 735     let mut angle_open = false;
 736     let mut is_fn_trait = false;
 737     for p in predicates.iter() {
 738         match p.skip_binders() {
 739             WhereClause::Implemented(trait_ref) => {
 740                 let trait_ = trait_ref.hir_trait_id();
 741                 if !is_fn_trait {
 742                     is_fn_trait = fn_traits(f.db.upcast(), trait_).any(|it| it == trait_);
 743                 }
 744                 if !is_fn_trait && angle_open {
 745                     write!(f, ">")?;
 746                     angle_open = false;
 747                 }
 748                 if !first {
 749                     write!(f, " + ")?;
 750                 }
 751                 // We assume that the self type is ^0.0 (i.e. the
 752                 // existential) here, which is the only thing that's
 753                 // possible in actual Rust, and hence don't print it
 754                 write!(f, "{}", f.db.trait_data(trait_).name)?;
 755                 if let [_, params @ ..] = &*trait_ref.substitution.as_slice(&Interner) {
 756                     if is_fn_trait {
 757                         if let Some(args) =
 758                             params.first().and_then(|it| it.assert_ty_ref(&Interner).as_tuple())
 759                         {
 760                             write!(f, "(")?;
 761                             f.write_joined(args.as_slice(&Interner), ", ")?;
 762                             write!(f, ")")?;
 763                         }
 764                     } else if !params.is_empty() {
 765                         write!(f, "<")?;
 766                         f.write_joined(params, ", ")?;
 767                         // there might be assoc type bindings, so we leave the angle brackets open
 768                         angle_open = true;
 769                     }
 770                 }
 771             }
 772             WhereClause::AliasEq(alias_eq) if is_fn_trait => {
 773                 is_fn_trait = false;
 774                 write!(f, " -> ")?;
 775                 alias_eq.ty.hir_fmt(f)?;
 776             }
 777             WhereClause::AliasEq(AliasEq { ty, alias }) => {
 778                 // in types in actual Rust, these will always come
 779                 // after the corresponding Implemented predicate
 780                 if angle_open {
 781                     write!(f, ", ")?;
 782                 } else {
 783                     write!(f, "<")?;
 784                     angle_open = true;
 785                 }
 786                 if let AliasTy::Projection(proj) = alias {
 787                     let type_alias =
 788                         f.db.type_alias_data(from_assoc_type_id(proj.associated_ty_id));
 789                     write!(f, "{} = ", type_alias.name)?;
 790                 }
 791                 ty.hir_fmt(f)?;
 792             }
 793
 794             // FIXME implement these
 795             WhereClause::LifetimeOutlives(_) => {}
 796             WhereClause::TypeOutlives(_) => {}
 797         }
 798         first = false;
 799     }
 800     if angle_open {
 801         write!(f, ">")?;
 802     }
 803     Ok(())
 804 }
 805
 806 fn fmt_trait_ref(tr: &TraitRef, f: &mut HirFormatter, use_as: bool) -> Result<(), HirDisplayError> {
 807     if f.should_truncate() {
 808         return write!(f, "{}", TYPE_HINT_TRUNCATION);
 809     }
 810
 811     tr.self_type_parameter(&Interner).hir_fmt(f)?;
 812     if use_as {
 813         write!(f, " as ")?;
 814     } else {
 815         write!(f, ": ")?;
 816     }
 817     write!(f, "{}", f.db.trait_data(tr.hir_trait_id()).name)?;
 818     if tr.substitution.len(&Interner) > 1 {
 819         write!(f, "<")?;
 820         f.write_joined(&tr.substitution.as_slice(&Interner)[1..], ", ")?;
 821         write!(f, ">")?;
 822     }
 823     Ok(())
 824 }
 825
 826 impl HirDisplay for TraitRef {
 827     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 828         fmt_trait_ref(self, f, false)
 829     }
 830 }
 831
 832 impl HirDisplay for WhereClause {
 833     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 834         if f.should_truncate() {
 835             return write!(f, "{}", TYPE_HINT_TRUNCATION);
 836         }
 837
 838         match self {
 839             WhereClause::Implemented(trait_ref) => trait_ref.hir_fmt(f)?,
 840             WhereClause::AliasEq(AliasEq { alias: AliasTy::Projection(projection_ty), ty }) => {
 841                 write!(f, "<")?;
 842                 fmt_trait_ref(&projection_ty.trait_ref(f.db), f, true)?;
 843                 write!(
 844                     f,
 845                     ">::{} = ",
 846                     f.db.type_alias_data(from_assoc_type_id(projection_ty.associated_ty_id)).name,
 847                 )?;
 848                 ty.hir_fmt(f)?;
 849             }
 850             WhereClause::AliasEq(_) => write!(f, "{{error}}")?,
 851
 852             // FIXME implement these
 853             WhereClause::TypeOutlives(..) => {}
 854             WhereClause::LifetimeOutlives(..) => {}
 855         }
 856         Ok(())
 857     }
 858 }
 859
 860 impl HirDisplay for LifetimeOutlives {
 861     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 862         self.a.hir_fmt(f)?;
 863         write!(f, ": ")?;
 864         self.b.hir_fmt(f)
 865     }
 866 }
 867
 868 impl HirDisplay for Lifetime {
 869     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 870         self.interned().hir_fmt(f)
 871     }
 872 }
 873
 874 impl HirDisplay for LifetimeData {
 875     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 876         match self {
 877             LifetimeData::BoundVar(idx) => idx.hir_fmt(f),
 878             LifetimeData::InferenceVar(_) => write!(f, "_"),
 879             LifetimeData::Placeholder(idx) => {
 880                 let id = lt_from_placeholder_idx(f.db, *idx);
 881                 let generics = generics(f.db.upcast(), id.parent);
 882                 let param_data = &generics.params.lifetimes[id.local_id];
 883                 write!(f, "{}", param_data.name)
 884             }
 885             LifetimeData::Static => write!(f, "'static"),
 886             LifetimeData::Empty(_) => Ok(()),
 887             LifetimeData::Erased => Ok(()),
 888             LifetimeData::Phantom(_, _) => Ok(()),
 889         }
 890     }
 891 }
 892
 893 impl HirDisplay for DomainGoal {
 894     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
 895         match self {
 896             DomainGoal::Holds(wc) => {
 897                 write!(f, "Holds(")?;
 898                 wc.hir_fmt(f)?;
 899                 write!(f, ")")?;
 900             }
 901             _ => write!(f, "?")?,
 902         }
 903         Ok(())
 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, len) => {
 966                 write!(f, "[")?;
 967                 inner.hir_fmt(f)?;
 968                 write!(f, "; {}]", len)?;
 969             }
 970             TypeRef::Slice(inner) => {
 971                 write!(f, "[")?;
 972                 inner.hir_fmt(f)?;
 973                 write!(f, "]")?;
 974             }
 975             TypeRef::Fn(tys, is_varargs) => {
 976                 // FIXME: Function pointer qualifiers.
 977                 write!(f, "fn(")?;
 978                 f.write_joined(&tys[..tys.len() - 1], ", ")?;
 979                 if *is_varargs {
 980                     write!(f, "{}...", if tys.len() == 1 { "" } else { ", " })?;
 981                 }
 982                 write!(f, ")")?;
 983                 let ret_ty = tys.last().unwrap();
 984                 match ret_ty {
 985                     TypeRef::Tuple(tup) if tup.is_empty() => {}
 986                     _ => {
 987                         write!(f, " -> ")?;
 988                         ret_ty.hir_fmt(f)?;
 989                     }
 990                 }
 991             }
 992             TypeRef::ImplTrait(bounds) => {
 993                 write!(f, "impl ")?;
 994                 f.write_joined(bounds, " + ")?;
 995             }
 996             TypeRef::DynTrait(bounds) => {
 997                 write!(f, "dyn ")?;
 998                 f.write_joined(bounds, " + ")?;
 999             }
1000             TypeRef::Macro(macro_call) => {
1001                 let macro_call = macro_call.to_node(f.db.upcast());
1002                 let ctx = body::LowerCtx::with_hygiene(f.db.upcast(), &Hygiene::new_unhygienic());
1003                 match macro_call.path() {
1004                     Some(path) => match Path::from_src(path, &ctx) {
1005                         Some(path) => path.hir_fmt(f)?,
1006                         None => write!(f, "{{macro}}")?,
1007                     },
1008                     None => write!(f, "{{macro}}")?,
1009                 }
1010                 write!(f, "!(..)")?;
1011             }
1012             TypeRef::Error => write!(f, "{{error}}")?,
1013         }
1014         Ok(())
1015     }
1016 }
1017
1018 impl HirDisplay for TypeBound {
1019     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1020         match self {
1021             TypeBound::Path(path) => path.hir_fmt(f),
1022             TypeBound::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1023             TypeBound::Error => write!(f, "{{error}}"),
1024         }
1025     }
1026 }
1027
1028 impl HirDisplay for Path {
1029     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1030         match (self.type_anchor(), self.kind()) {
1031             (Some(anchor), _) => {
1032                 write!(f, "<")?;
1033                 anchor.hir_fmt(f)?;
1034                 write!(f, ">")?;
1035             }
1036             (_, PathKind::Plain) => {}
1037             (_, PathKind::Abs) => write!(f, "::")?,
1038             (_, PathKind::Crate) => write!(f, "crate")?,
1039             (_, PathKind::Super(0)) => write!(f, "self")?,
1040             (_, PathKind::Super(n)) => {
1041                 write!(f, "super")?;
1042                 for _ in 0..*n {
1043                     write!(f, "::super")?;
1044                 }
1045             }
1046             (_, PathKind::DollarCrate(_)) => write!(f, "{{extern_crate}}")?,
1047         }
1048
1049         for (seg_idx, segment) in self.segments().iter().enumerate() {
1050             if seg_idx != 0 {
1051                 write!(f, "::")?;
1052             }
1053             write!(f, "{}", segment.name)?;
1054             if let Some(generic_args) = segment.args_and_bindings {
1055                 // We should be in type context, so format as `Foo<Bar>` instead of `Foo::<Bar>`.
1056                 // Do we actually format expressions?
1057                 write!(f, "<")?;
1058                 let mut first = true;
1059                 for arg in &generic_args.args {
1060                     if first {
1061                         first = false;
1062                         if generic_args.has_self_type {
1063                             // FIXME: Convert to `<Ty as Trait>` form.
1064                             write!(f, "Self = ")?;
1065                         }
1066                     } else {
1067                         write!(f, ", ")?;
1068                     }
1069                     arg.hir_fmt(f)?;
1070                 }
1071                 for binding in &generic_args.bindings {
1072                     if first {
1073                         first = false;
1074                     } else {
1075                         write!(f, ", ")?;
1076                     }
1077                     write!(f, "{}", binding.name)?;
1078                     match &binding.type_ref {
1079                         Some(ty) => {
1080                             write!(f, " = ")?;
1081                             ty.hir_fmt(f)?
1082                         }
1083                         None => {
1084                             write!(f, ": ")?;
1085                             f.write_joined(&binding.bounds, " + ")?;
1086                         }
1087                     }
1088                 }
1089                 write!(f, ">")?;
1090             }
1091         }
1092         Ok(())
1093     }
1094 }
1095
1096 impl HirDisplay for hir_def::path::GenericArg {
1097     fn hir_fmt(&self, f: &mut HirFormatter) -> Result<(), HirDisplayError> {
1098         match self {
1099             hir_def::path::GenericArg::Type(ty) => ty.hir_fmt(f),
1100             hir_def::path::GenericArg::Lifetime(lifetime) => write!(f, "{}", lifetime.name),
1101         }
1102     }
1103 }