src/librustc_trans/trans_item.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Walks the crate looking for items/impl-items/trait-items that have
  12 //! either a `rustc_symbol_name` or `rustc_item_path` attribute and
  13 //! generates an error giving, respectively, the symbol name or
  14 //! item-path. This is used for unit testing the code that generates
  15 //! paths etc in all kinds of annoying scenarios.
  16
  17 use asm;
  18 use attributes;
  19 use base;
  20 use consts;
  21 use context::CrateContext;
  22 use common;
  23 use declare;
  24 use llvm;
  25 use monomorphize::Instance;
  26 use rustc::hir;
  27 use rustc::hir::def_id::DefId;
  28 use rustc::middle::trans::{Linkage, Visibility};
  29 use rustc::session::config::OptLevel;
  30 use rustc::traits;
  31 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
  32 use rustc::ty::subst::{Subst, Substs};
  33 use syntax::ast;
  34 use syntax::attr;
  35 use syntax_pos::Span;
  36 use syntax_pos::symbol::Symbol;
  37 use type_of;
  38 use std::fmt::{self, Write};
  39 use std::iter;
  40
  41 pub use rustc::middle::trans::TransItem;
  42
  43 /// Describes how a translation item will be instantiated in object files.
  44 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
  45 pub enum InstantiationMode {
  46     /// There will be exactly one instance of the given TransItem. It will have
  47     /// external linkage so that it can be linked to from other codegen units.
  48     GloballyShared {
  49         /// In some compilation scenarios we may decide to take functions that
  50         /// are typically `LocalCopy` and instead move them to `GloballyShared`
  51         /// to avoid translating them a bunch of times. In this situation,
  52         /// however, our local copy may conflict with other crates also
  53         /// inlining the same function.
  54         ///
  55         /// This flag indicates that this situation is occuring, and informs
  56         /// symbol name calculation that some extra mangling is needed to
  57         /// avoid conflicts. Note that this may eventually go away entirely if
  58         /// ThinLTO enables us to *always* have a globally shared instance of a
  59         /// function within one crate's compilation.
  60         may_conflict: bool,
  61     },
  62
  63     /// Each codegen unit containing a reference to the given TransItem will
  64     /// have its own private copy of the function (with internal linkage).
  65     LocalCopy,
  66 }
  67
  68 pub trait TransItemExt<'a, 'tcx>: fmt::Debug {
  69     fn as_trans_item(&self) -> &TransItem<'tcx>;
  70
  71     fn define(&self, ccx: &CrateContext<'a, 'tcx>) {
  72         debug!("BEGIN IMPLEMENTING '{} ({})' in cgu {}",
  73                self.to_string(ccx.tcx()),
  74                self.to_raw_string(),
  75                ccx.codegen_unit().name());
  76
  77         match *self.as_trans_item() {
  78             TransItem::Static(node_id) => {
  79                 let tcx = ccx.tcx();
  80                 let item = tcx.hir.expect_item(node_id);
  81                 if let hir::ItemStatic(_, m, _) = item.node {
  82                     match consts::trans_static(&ccx, m, item.id, &item.attrs) {
  83                         Ok(_) => { /* Cool, everything's alright. */ },
  84                         Err(err) => {
  85                             err.report(tcx, item.span, "static");
  86                         }
  87                     };
  88                 } else {
  89                     span_bug!(item.span, "Mismatch between hir::Item type and TransItem type")
  90                 }
  91             }
  92             TransItem::GlobalAsm(node_id) => {
  93                 let item = ccx.tcx().hir.expect_item(node_id);
  94                 if let hir::ItemGlobalAsm(ref ga) = item.node {
  95                     asm::trans_global_asm(ccx, ga);
  96                 } else {
  97                     span_bug!(item.span, "Mismatch between hir::Item type and TransItem type")
  98                 }
  99             }
 100             TransItem::Fn(instance) => {
 101                 base::trans_instance(&ccx, instance);
 102             }
 103         }
 104
 105         debug!("END IMPLEMENTING '{} ({})' in cgu {}",
 106                self.to_string(ccx.tcx()),
 107                self.to_raw_string(),
 108                ccx.codegen_unit().name());
 109     }
 110
 111     fn predefine(&self,
 112                  ccx: &CrateContext<'a, 'tcx>,
 113                  linkage: Linkage,
 114                  visibility: Visibility) {
 115         debug!("BEGIN PREDEFINING '{} ({})' in cgu {}",
 116                self.to_string(ccx.tcx()),
 117                self.to_raw_string(),
 118                ccx.codegen_unit().name());
 119
 120         let symbol_name = self.symbol_name(ccx.tcx());
 121
 122         debug!("symbol {}", &symbol_name);
 123
 124         match *self.as_trans_item() {
 125             TransItem::Static(node_id) => {
 126                 predefine_static(ccx, node_id, linkage, visibility, &symbol_name);
 127             }
 128             TransItem::Fn(instance) => {
 129                 predefine_fn(ccx, instance, linkage, visibility, &symbol_name);
 130             }
 131             TransItem::GlobalAsm(..) => {}
 132         }
 133
 134         debug!("END PREDEFINING '{} ({})' in cgu {}",
 135                self.to_string(ccx.tcx()),
 136                self.to_raw_string(),
 137                ccx.codegen_unit().name());
 138     }
 139
 140     fn symbol_name(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::SymbolName {
 141         match *self.as_trans_item() {
 142             TransItem::Fn(instance) => tcx.symbol_name(instance),
 143             TransItem::Static(node_id) => {
 144                 let def_id = tcx.hir.local_def_id(node_id);
 145                 tcx.symbol_name(Instance::mono(tcx, def_id))
 146             }
 147             TransItem::GlobalAsm(node_id) => {
 148                 let def_id = tcx.hir.local_def_id(node_id);
 149                 ty::SymbolName {
 150                     name: Symbol::intern(&format!("global_asm_{:?}", def_id)).as_str()
 151                 }
 152             }
 153         }
 154     }
 155
 156     fn local_span(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Span> {
 157         match *self.as_trans_item() {
 158             TransItem::Fn(Instance { def, .. }) => {
 159                 tcx.hir.as_local_node_id(def.def_id())
 160             }
 161             TransItem::Static(node_id) |
 162             TransItem::GlobalAsm(node_id) => {
 163                 Some(node_id)
 164             }
 165         }.map(|node_id| tcx.hir.span(node_id))
 166     }
 167
 168     fn instantiation_mode(&self,
 169                           tcx: TyCtxt<'a, 'tcx, 'tcx>)
 170                           -> InstantiationMode {
 171         let inline_in_all_cgus =
 172             tcx.sess.opts.debugging_opts.inline_in_all_cgus.unwrap_or_else(|| {
 173                 tcx.sess.opts.optimize != OptLevel::No
 174             });
 175
 176         match *self.as_trans_item() {
 177             TransItem::Fn(ref instance) => {
 178                 if self.explicit_linkage(tcx).is_none() &&
 179                     common::requests_inline(tcx, instance)
 180                 {
 181                     if inline_in_all_cgus {
 182                         InstantiationMode::LocalCopy
 183                     } else {
 184                         InstantiationMode::GloballyShared  { may_conflict: true }
 185                     }
 186                 } else {
 187                     InstantiationMode::GloballyShared  { may_conflict: false }
 188                 }
 189             }
 190             TransItem::Static(..) => {
 191                 InstantiationMode::GloballyShared { may_conflict: false }
 192             }
 193             TransItem::GlobalAsm(..) => {
 194                 InstantiationMode::GloballyShared { may_conflict: false }
 195             }
 196         }
 197     }
 198
 199     fn is_generic_fn(&self) -> bool {
 200         match *self.as_trans_item() {
 201             TransItem::Fn(ref instance) => {
 202                 instance.substs.types().next().is_some()
 203             }
 204             TransItem::Static(..) |
 205             TransItem::GlobalAsm(..) => false,
 206         }
 207     }
 208
 209     fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Linkage> {
 210         let def_id = match *self.as_trans_item() {
 211             TransItem::Fn(ref instance) => instance.def_id(),
 212             TransItem::Static(node_id) => tcx.hir.local_def_id(node_id),
 213             TransItem::GlobalAsm(..) => return None,
 214         };
 215
 216         let attributes = tcx.get_attrs(def_id);
 217         if let Some(name) = attr::first_attr_value_str_by_name(&attributes, "linkage") {
 218             if let Some(linkage) = base::linkage_by_name(&name.as_str()) {
 219                 Some(linkage)
 220             } else {
 221                 let span = tcx.hir.span_if_local(def_id);
 222                 if let Some(span) = span {
 223                     tcx.sess.span_fatal(span, "invalid linkage specified")
 224                 } else {
 225                     tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
 226                 }
 227             }
 228         } else {
 229             None
 230         }
 231     }
 232
 233     /// Returns whether this instance is instantiable - whether it has no unsatisfied
 234     /// predicates.
 235     ///
 236     /// In order to translate an item, all of its predicates must hold, because
 237     /// otherwise the item does not make sense. Type-checking ensures that
 238     /// the predicates of every item that is *used by* a valid item *do*
 239     /// hold, so we can rely on that.
 240     ///
 241     /// However, we translate collector roots (reachable items) and functions
 242     /// in vtables when they are seen, even if they are not used, and so they
 243     /// might not be instantiable. For example, a programmer can define this
 244     /// public function:
 245     ///
 246     ///     pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
 247     ///         <&mut () as Clone>::clone(&s);
 248     ///     }
 249     ///
 250     /// That function can't be translated, because the method `<&mut () as Clone>::clone`
 251     /// does not exist. Luckily for us, that function can't ever be used,
 252     /// because that would require for `&'a mut (): Clone` to hold, so we
 253     /// can just not emit any code, or even a linker reference for it.
 254     ///
 255     /// Similarly, if a vtable method has such a signature, and therefore can't
 256     /// be used, we can just not emit it and have a placeholder (a null pointer,
 257     /// which will never be accessed) in its place.
 258     fn is_instantiable(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
 259         debug!("is_instantiable({:?})", self);
 260         let (def_id, substs) = match *self.as_trans_item() {
 261             TransItem::Fn(ref instance) => (instance.def_id(), instance.substs),
 262             TransItem::Static(node_id) => (tcx.hir.local_def_id(node_id), Substs::empty()),
 263             // global asm never has predicates
 264             TransItem::GlobalAsm(..) => return true
 265         };
 266
 267         let predicates = tcx.predicates_of(def_id).predicates.subst(tcx, substs);
 268         traits::normalize_and_test_predicates(tcx, predicates)
 269     }
 270
 271     fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> String {
 272         let hir_map = &tcx.hir;
 273
 274         return match *self.as_trans_item() {
 275             TransItem::Fn(instance) => {
 276                 to_string_internal(tcx, "fn ", instance)
 277             },
 278             TransItem::Static(node_id) => {
 279                 let def_id = hir_map.local_def_id(node_id);
 280                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 281                 to_string_internal(tcx, "static ", instance)
 282             },
 283             TransItem::GlobalAsm(..) => {
 284                 "global_asm".to_string()
 285             }
 286         };
 287
 288         fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 289                                         prefix: &str,
 290                                         instance: Instance<'tcx>)
 291                                         -> String {
 292             let mut result = String::with_capacity(32);
 293             result.push_str(prefix);
 294             let printer = DefPathBasedNames::new(tcx, false, false);
 295             printer.push_instance_as_string(instance, &mut result);
 296             result
 297         }
 298     }
 299
 300     fn to_raw_string(&self) -> String {
 301         match *self.as_trans_item() {
 302             TransItem::Fn(instance) => {
 303                 format!("Fn({:?}, {})",
 304                          instance.def,
 305                          instance.substs.as_ptr() as usize)
 306             }
 307             TransItem::Static(id) => {
 308                 format!("Static({:?})", id)
 309             }
 310             TransItem::GlobalAsm(id) => {
 311                 format!("GlobalAsm({:?})", id)
 312             }
 313         }
 314     }
 315 }
 316
 317 impl<'a, 'tcx> TransItemExt<'a, 'tcx> for TransItem<'tcx> {
 318     fn as_trans_item(&self) -> &TransItem<'tcx> {
 319         self
 320     }
 321 }
 322
 323 fn predefine_static<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 324                               node_id: ast::NodeId,
 325                               linkage: Linkage,
 326                               visibility: Visibility,
 327                               symbol_name: &str) {
 328     let def_id = ccx.tcx().hir.local_def_id(node_id);
 329     let instance = Instance::mono(ccx.tcx(), def_id);
 330     let ty = common::instance_ty(ccx.tcx(), &instance);
 331     let llty = type_of::type_of(ccx, ty);
 332
 333     let g = declare::define_global(ccx, symbol_name, llty).unwrap_or_else(|| {
 334         ccx.sess().span_fatal(ccx.tcx().hir.span(node_id),
 335             &format!("symbol `{}` is already defined", symbol_name))
 336     });
 337
 338     unsafe {
 339         llvm::LLVMRustSetLinkage(g, base::linkage_to_llvm(linkage));
 340         llvm::LLVMRustSetVisibility(g, base::visibility_to_llvm(visibility));
 341     }
 342
 343     ccx.instances().borrow_mut().insert(instance, g);
 344     ccx.statics().borrow_mut().insert(g, def_id);
 345 }
 346
 347 fn predefine_fn<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 348                           instance: Instance<'tcx>,
 349                           linkage: Linkage,
 350                           visibility: Visibility,
 351                           symbol_name: &str) {
 352     assert!(!instance.substs.needs_infer() &&
 353             !instance.substs.has_param_types());
 354
 355     let mono_ty = common::instance_ty(ccx.tcx(), &instance);
 356     let attrs = instance.def.attrs(ccx.tcx());
 357     let lldecl = declare::declare_fn(ccx, symbol_name, mono_ty);
 358     unsafe { llvm::LLVMRustSetLinkage(lldecl, base::linkage_to_llvm(linkage)) };
 359     base::set_link_section(ccx, lldecl, &attrs);
 360     if linkage == Linkage::LinkOnceODR ||
 361         linkage == Linkage::WeakODR {
 362         llvm::SetUniqueComdat(ccx.llmod(), lldecl);
 363     }
 364
 365     // If we're compiling the compiler-builtins crate, e.g. the equivalent of
 366     // compiler-rt, then we want to implicitly compile everything with hidden
 367     // visibility as we're going to link this object all over the place but
 368     // don't want the symbols to get exported.
 369     if linkage != Linkage::Internal && linkage != Linkage::Private &&
 370        attr::contains_name(ccx.tcx().hir.krate_attrs(), "compiler_builtins") {
 371         unsafe {
 372             llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden);
 373         }
 374     } else {
 375         unsafe {
 376             llvm::LLVMRustSetVisibility(lldecl, base::visibility_to_llvm(visibility));
 377         }
 378     }
 379
 380     debug!("predefine_fn: mono_ty = {:?} instance = {:?}", mono_ty, instance);
 381     if common::is_inline_instance(ccx.tcx(), &instance) {
 382         attributes::inline(lldecl, attributes::InlineAttr::Hint);
 383     }
 384     attributes::from_fn_attrs(ccx, &attrs, lldecl);
 385
 386     ccx.instances().borrow_mut().insert(instance, lldecl);
 387 }
 388
 389 //=-----------------------------------------------------------------------------
 390 // TransItem String Keys
 391 //=-----------------------------------------------------------------------------
 392
 393 // The code below allows for producing a unique string key for a trans item.
 394 // These keys are used by the handwritten auto-tests, so they need to be
 395 // predictable and human-readable.
 396 //
 397 // Note: A lot of this could looks very similar to what's already in the
 398 //       ppaux module. It would be good to refactor things so we only have one
 399 //       parameterizable implementation for printing types.
 400
 401 /// Same as `unique_type_name()` but with the result pushed onto the given
 402 /// `output` parameter.
 403 pub struct DefPathBasedNames<'a, 'tcx: 'a> {
 404     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 405     omit_disambiguators: bool,
 406     omit_local_crate_name: bool,
 407 }
 408
 409 impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
 410     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 411                omit_disambiguators: bool,
 412                omit_local_crate_name: bool)
 413                -> Self {
 414         DefPathBasedNames {
 415             tcx,
 416             omit_disambiguators,
 417             omit_local_crate_name,
 418         }
 419     }
 420
 421     pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String) {
 422         match t.sty {
 423             ty::TyBool              => output.push_str("bool"),
 424             ty::TyChar              => output.push_str("char"),
 425             ty::TyStr               => output.push_str("str"),
 426             ty::TyNever             => output.push_str("!"),
 427             ty::TyInt(ast::IntTy::Is)    => output.push_str("isize"),
 428             ty::TyInt(ast::IntTy::I8)    => output.push_str("i8"),
 429             ty::TyInt(ast::IntTy::I16)   => output.push_str("i16"),
 430             ty::TyInt(ast::IntTy::I32)   => output.push_str("i32"),
 431             ty::TyInt(ast::IntTy::I64)   => output.push_str("i64"),
 432             ty::TyInt(ast::IntTy::I128)   => output.push_str("i128"),
 433             ty::TyUint(ast::UintTy::Us)   => output.push_str("usize"),
 434             ty::TyUint(ast::UintTy::U8)   => output.push_str("u8"),
 435             ty::TyUint(ast::UintTy::U16)  => output.push_str("u16"),
 436             ty::TyUint(ast::UintTy::U32)  => output.push_str("u32"),
 437             ty::TyUint(ast::UintTy::U64)  => output.push_str("u64"),
 438             ty::TyUint(ast::UintTy::U128)  => output.push_str("u128"),
 439             ty::TyFloat(ast::FloatTy::F32) => output.push_str("f32"),
 440             ty::TyFloat(ast::FloatTy::F64) => output.push_str("f64"),
 441             ty::TyAdt(adt_def, substs) => {
 442                 self.push_def_path(adt_def.did, output);
 443                 self.push_type_params(substs, iter::empty(), output);
 444             },
 445             ty::TyTuple(component_types, _) => {
 446                 output.push('(');
 447                 for &component_type in component_types {
 448                     self.push_type_name(component_type, output);
 449                     output.push_str(", ");
 450                 }
 451                 if !component_types.is_empty() {
 452                     output.pop();
 453                     output.pop();
 454                 }
 455                 output.push(')');
 456             },
 457             ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
 458                 output.push('*');
 459                 match mutbl {
 460                     hir::MutImmutable => output.push_str("const "),
 461                     hir::MutMutable => output.push_str("mut "),
 462                 }
 463
 464                 self.push_type_name(inner_type, output);
 465             },
 466             ty::TyRef(_, ty::TypeAndMut { ty: inner_type, mutbl }) => {
 467                 output.push('&');
 468                 if mutbl == hir::MutMutable {
 469                     output.push_str("mut ");
 470                 }
 471
 472                 self.push_type_name(inner_type, output);
 473             },
 474             ty::TyArray(inner_type, len) => {
 475                 output.push('[');
 476                 self.push_type_name(inner_type, output);
 477                 write!(output, "; {}",
 478                     len.val.to_const_int().unwrap().to_u64().unwrap()).unwrap();
 479                 output.push(']');
 480             },
 481             ty::TySlice(inner_type) => {
 482                 output.push('[');
 483                 self.push_type_name(inner_type, output);
 484                 output.push(']');
 485             },
 486             ty::TyDynamic(ref trait_data, ..) => {
 487                 if let Some(principal) = trait_data.principal() {
 488                     self.push_def_path(principal.def_id(), output);
 489                     self.push_type_params(principal.skip_binder().substs,
 490                         trait_data.projection_bounds(),
 491                         output);
 492                 }
 493             },
 494             ty::TyFnDef(..) |
 495             ty::TyFnPtr(_) => {
 496                 let sig = t.fn_sig(self.tcx);
 497                 if sig.unsafety() == hir::Unsafety::Unsafe {
 498                     output.push_str("unsafe ");
 499                 }
 500
 501                 let abi = sig.abi();
 502                 if abi != ::abi::Abi::Rust {
 503                     output.push_str("extern \"");
 504                     output.push_str(abi.name());
 505                     output.push_str("\" ");
 506                 }
 507
 508                 output.push_str("fn(");
 509
 510                 let sig = self.tcx.erase_late_bound_regions_and_normalize(&sig);
 511
 512                 if !sig.inputs().is_empty() {
 513                     for &parameter_type in sig.inputs() {
 514                         self.push_type_name(parameter_type, output);
 515                         output.push_str(", ");
 516                     }
 517                     output.pop();
 518                     output.pop();
 519                 }
 520
 521                 if sig.variadic {
 522                     if !sig.inputs().is_empty() {
 523                         output.push_str(", ...");
 524                     } else {
 525                         output.push_str("...");
 526                     }
 527                 }
 528
 529                 output.push(')');
 530
 531                 if !sig.output().is_nil() {
 532                     output.push_str(" -> ");
 533                     self.push_type_name(sig.output(), output);
 534                 }
 535             },
 536             ty::TyGenerator(def_id, ref closure_substs, _) |
 537             ty::TyClosure(def_id, ref closure_substs) => {
 538                 self.push_def_path(def_id, output);
 539                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
 540                 let substs = closure_substs.substs.truncate_to(self.tcx, generics);
 541                 self.push_type_params(substs, iter::empty(), output);
 542             }
 543             ty::TyError |
 544             ty::TyInfer(_) |
 545             ty::TyProjection(..) |
 546             ty::TyParam(_) |
 547             ty::TyAnon(..) => {
 548                 bug!("DefPathBasedNames: Trying to create type name for \
 549                                          unexpected type: {:?}", t);
 550             }
 551         }
 552     }
 553
 554     pub fn push_def_path(&self,
 555                          def_id: DefId,
 556                          output: &mut String) {
 557         let def_path = self.tcx.def_path(def_id);
 558
 559         // some_crate::
 560         if !(self.omit_local_crate_name && def_id.is_local()) {
 561             output.push_str(&self.tcx.crate_name(def_path.krate).as_str());
 562             output.push_str("::");
 563         }
 564
 565         // foo::bar::ItemName::
 566         for part in self.tcx.def_path(def_id).data {
 567             if self.omit_disambiguators {
 568                 write!(output, "{}::", part.data.as_interned_str()).unwrap();
 569             } else {
 570                 write!(output, "{}[{}]::",
 571                        part.data.as_interned_str(),
 572                        part.disambiguator).unwrap();
 573             }
 574         }
 575
 576         // remove final "::"
 577         output.pop();
 578         output.pop();
 579     }
 580
 581     fn push_type_params<I>(&self,
 582                             substs: &Substs<'tcx>,
 583                             projections: I,
 584                             output: &mut String)
 585         where I: Iterator<Item=ty::PolyExistentialProjection<'tcx>>
 586     {
 587         let mut projections = projections.peekable();
 588         if substs.types().next().is_none() && projections.peek().is_none() {
 589             return;
 590         }
 591
 592         output.push('<');
 593
 594         for type_parameter in substs.types() {
 595             self.push_type_name(type_parameter, output);
 596             output.push_str(", ");
 597         }
 598
 599         for projection in projections {
 600             let projection = projection.skip_binder();
 601             let name = &self.tcx.associated_item(projection.item_def_id).name.as_str();
 602             output.push_str(name);
 603             output.push_str("=");
 604             self.push_type_name(projection.ty, output);
 605             output.push_str(", ");
 606         }
 607
 608         output.pop();
 609         output.pop();
 610
 611         output.push('>');
 612     }
 613
 614     pub fn push_instance_as_string(&self,
 615                                    instance: Instance<'tcx>,
 616                                    output: &mut String) {
 617         self.push_def_path(instance.def_id(), output);
 618         self.push_type_params(instance.substs, iter::empty(), output);
 619     }
 620 }