Give RPITITs real names with -Zlower-impl-trait-in-trait-to-assoc-ty

Author: compiler-errors

compiler/rustc_hir/src/definitions.rs

@@ -281,7 +281,7 @@ pub enum DefPathData {
     /// An `impl Trait` type node.
     ImplTrait,
     /// `impl Trait` generated associated type node.
-    ImplTraitAssocTy,
+    ImplTraitAssocTy(Symbol),
 }
 
 impl Definitions {
@@ -402,11 +402,11 @@ impl DefPathData {
     pub fn get_opt_name(&self) -> Option<Symbol> {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => Some(name),
-
-            // We use this name when collecting `ModChild`s.
-            // FIXME this could probably be removed with some refactoring to the name resolver.
-            ImplTraitAssocTy => Some(kw::Empty),
+            TypeNs(name)
+            | ValueNs(name)
+            | MacroNs(name)
+            | LifetimeNs(name)
+            | ImplTraitAssocTy(name) => Some(name),
 
             Impl | ForeignMod | CrateRoot | Use | GlobalAsm | ClosureExpr | Ctor | AnonConst
             | ImplTrait => None,
@@ -416,9 +416,11 @@ impl DefPathData {
     pub fn name(&self) -> DefPathDataName {
         use self::DefPathData::*;
         match *self {
-            TypeNs(name) | ValueNs(name) | MacroNs(name) | LifetimeNs(name) => {
-                DefPathDataName::Named(name)
-            }
+            TypeNs(name)
+            | ValueNs(name)
+            | MacroNs(name)
+            | LifetimeNs(name)
+            | ImplTraitAssocTy(name) => DefPathDataName::Named(name),
             // Note that this does not show up in user print-outs.
             CrateRoot => DefPathDataName::Anon { namespace: kw::Crate },
             Impl => DefPathDataName::Anon { namespace: kw::Impl },
@@ -428,7 +430,7 @@ impl DefPathData {
             ClosureExpr => DefPathDataName::Anon { namespace: sym::closure },
             Ctor => DefPathDataName::Anon { namespace: sym::constructor },
             AnonConst => DefPathDataName::Anon { namespace: sym::constant },
-            ImplTrait | ImplTraitAssocTy => DefPathDataName::Anon { namespace: sym::opaque },
+            ImplTrait => DefPathDataName::Anon { namespace: sym::opaque },
         }
     }
 }

compiler/rustc_symbol_mangling/src/typeid/typeid_itanium_cxx_abi.rs

@@ -396,7 +396,7 @@ fn encode_ty_name(tcx: TyCtxt<'_>, def_id: DefId) -> String {
             hir::definitions::DefPathData::CrateRoot
             | hir::definitions::DefPathData::Use
             | hir::definitions::DefPathData::GlobalAsm
-            | hir::definitions::DefPathData::ImplTraitAssocTy
+            | hir::definitions::DefPathData::ImplTraitAssocTy(_)
             | hir::definitions::DefPathData::MacroNs(..)
             | hir::definitions::DefPathData::LifetimeNs(..) => {
                 bug!("encode_ty_name: unexpected `{:?}`", disambiguated_data.data);

compiler/rustc_symbol_mangling/src/v0.rs

@@ -792,7 +792,7 @@ impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
             | DefPathData::Use
             | DefPathData::GlobalAsm
             | DefPathData::Impl
-            | DefPathData::ImplTraitAssocTy
+            | DefPathData::ImplTraitAssocTy(_)
             | DefPathData::MacroNs(_)
             | DefPathData::LifetimeNs(_) => {
                 bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)

compiler/rustc_ty_utils/src/assoc.rs

@@ -5,7 +5,7 @@ use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
 use rustc_hir::definitions::DefPathData;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::ty::{self, ImplTraitInTraitData, InternalSubsts, TyCtxt};
-use rustc_span::symbol::kw;
+use rustc_span::Symbol;
 
 pub fn provide(providers: &mut ty::query::Providers) {
     *providers = ty::query::Providers {
@@ -266,7 +266,8 @@ fn associated_type_for_impl_trait_in_trait(
     assert_eq!(tcx.def_kind(trait_def_id), DefKind::Trait);
 
     let span = tcx.def_span(opaque_ty_def_id);
-    let trait_assoc_ty = tcx.at(span).create_def(trait_def_id, DefPathData::ImplTraitAssocTy);
+    let name = name_for_impl_trait_in_trait(tcx, opaque_ty_def_id, trait_def_id);
+    let trait_assoc_ty = tcx.at(span).create_def(trait_def_id, DefPathData::ImplTraitAssocTy(name));
 
     let local_def_id = trait_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
@@ -281,7 +282,7 @@ fn associated_type_for_impl_trait_in_trait(
     trait_assoc_ty.def_ident_span(Some(span));
 
     trait_assoc_ty.associated_item(ty::AssocItem {
-        name: kw::Empty,
+        name,
         kind: ty::AssocKind::Type,
         def_id,
         trait_item_def_id: None,
@@ -351,6 +352,24 @@ fn associated_type_for_impl_trait_in_trait(
     local_def_id
 }
 
+/// Create a stable path name for an associated type for an impl trait in trait
+/// by appending the opaque type's path segments starting from the function name.
+fn name_for_impl_trait_in_trait(
+    tcx: TyCtxt<'_>,
+    opaque_ty_def_id: LocalDefId,
+    trait_def_id: LocalDefId,
+) -> Symbol {
+    let mut name = vec![];
+    let mut def_id = opaque_ty_def_id;
+    while def_id != trait_def_id {
+        name.push(tcx.def_key(def_id.to_def_id()).disambiguated_data.to_string());
+        def_id = tcx.local_parent(def_id);
+    }
+    name.reverse();
+    let name = Symbol::intern(&name.join("::"));
+    name
+}
+
 /// Given an `trait_assoc_def_id` corresponding to an associated item synthesized
 /// from an `impl Trait` in an associated function from a trait, and an
 /// `impl_fn_def_id` that represents an implementation of the associated function
@@ -364,9 +383,11 @@ fn associated_type_for_impl_trait_in_impl(
     let impl_local_def_id = tcx.local_parent(impl_fn_def_id);
     let impl_def_id = impl_local_def_id.to_def_id();
 
+    let name = tcx.item_name(trait_assoc_def_id);
     // FIXME fix the span, we probably want the def_id of the return type of the function
     let span = tcx.def_span(impl_fn_def_id);
-    let impl_assoc_ty = tcx.at(span).create_def(impl_local_def_id, DefPathData::ImplTraitAssocTy);
+    let impl_assoc_ty =
+        tcx.at(span).create_def(impl_local_def_id, DefPathData::ImplTraitAssocTy(name));
 
     let local_def_id = impl_assoc_ty.def_id();
     let def_id = local_def_id.to_def_id();
@@ -381,7 +402,7 @@ fn associated_type_for_impl_trait_in_impl(
     impl_assoc_ty.def_ident_span(Some(span));
 
     impl_assoc_ty.associated_item(ty::AssocItem {
-        name: kw::Empty,
+        name,
         kind: ty::AssocKind::Type,
         def_id,
         trait_item_def_id: Some(trait_assoc_def_id),

tests/ui/impl-trait/in-trait/doesnt-satisfy.next.stderr

@@ -6,11 +6,11 @@ LL |     fn bar() -> () {}
    |
    = help: the trait `std::fmt::Display` is not implemented for `()`
    = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead
-note: required by a bound in `Foo::{opaque#0}`
+note: required by a bound in `Foo::bar::{opaque#0}`
   --> $DIR/doesnt-satisfy.rs:8:22
    |
 LL |     fn bar() -> impl std::fmt::Display;
-   |                      ^^^^^^^^^^^^^^^^^ required by this bound in `Foo::`
+   |                      ^^^^^^^^^^^^^^^^^ required by this bound in `Foo::bar::{opaque#0}`
 
 error: aborting due to previous error