typecheck: Add basic handling for applying auto trait bounds

gcc/rust/ChangeLog:

	* hir/rust-ast-lower-item.cc (ASTLoweringItem::visit): Register auto traits in mappings.
	* util/rust-hir-map.cc (Mappings::insert_auto_trait): New.
	(Mappings::get_auto_traits): New.
	* util/rust-hir-map.h: Declare them.
	* typecheck/rust-tyty-bounds.cc (TypeBoundsProbe::scan): Add auto trait bounds when
	scanning.

gcc/testsuite/ChangeLog:

	* rust/compile/nr2/exclude: Some parts of nr2.0 can't handle auto traits yet.
	* rust/compile/auto_traits3.rs: Removed in favor of...
	* rust/compile/auto_traits2.rs: ...this one.
	* rust/compile/auto_traits4.rs: New test.

gcc/rust/hir/rust-ast-lower-item.cc

@@ -606,17 +606,18 @@ ASTLoweringItem::visit (AST::Trait &trait)
 				 mappings.get_next_hir_id (crate_num),
 				 mappings.get_next_localdef_id (crate_num));
 
-  auto trait_unsafety = Unsafety::Normal;
-  if (trait.is_unsafe ())
-    {
-      trait_unsafety = Unsafety::Unsafe;
-    }
+  auto trait_unsafety
+    = trait.is_unsafe () ? Unsafety::Unsafe : Unsafety::Normal;
 
   HIR::Trait *hir_trait
     = new HIR::Trait (mapping, trait.get_identifier (), trait_unsafety,
 		      std::move (generic_params), std::move (type_param_bounds),
 		      where_clause, std::move (trait_items), vis,
 		      trait.get_outer_attrs (), trait.get_locus ());
+
+  if (trait.is_auto ())
+    mappings.insert_auto_trait (hir_trait);
+
   translated = hir_trait;
 
   for (auto trait_item_id : trait_item_ids)

gcc/rust/typecheck/rust-tyty-bounds.cc

@@ -97,6 +97,10 @@ TypeBoundsProbe::scan ()
 
   // marker traits...
   assemble_sized_builtin ();
+
+  // add auto trait bounds
+  for (auto *auto_trait : mappings.get_auto_traits ())
+    add_trait_bound (auto_trait);
 }
 
 void

gcc/rust/util/rust-hir-map.cc

@@ -1309,5 +1309,17 @@ Mappings::get_lang_item_node (LangItem::Kind item_type)
 		    LangItem::ToString (item_type).c_str ());
 }
 
+void
+Mappings::insert_auto_trait (HIR::Trait *trait)
+{
+  auto_traits.emplace_back (trait);
+}
+
+std::vector<HIR::Trait *> &
+Mappings::get_auto_traits ()
+{
+  return auto_traits;
+}
+
 } // namespace Analysis
 } // namespace Rust

gcc/rust/util/rust-hir-map.h

@@ -342,6 +342,9 @@ class Mappings
   tl::optional<HIR::TraitItem *>
   lookup_trait_item_lang_item (LangItem::Kind item, location_t locus);
 
+  void insert_auto_trait (HIR::Trait *trait);
+  std::vector<HIR::Trait *> &get_auto_traits ();
+
 private:
   Mappings ();
 
@@ -380,6 +383,9 @@ class Mappings
   std::map<HirId, HIR::Trait *> hirTraitItemsToTraitMappings;
   std::map<HirId, HIR::Pattern *> hirPatternMappings;
 
+  // FIXME: Add documentation
+  std::vector<HIR::Trait *> auto_traits;
+
   // We need to have two maps here, as lang-items need to be used for both AST
   // passes and HIR passes. Thus those two maps are created at different times.
   std::map<LangItem::Kind, DefId> lang_item_mappings;

gcc/testsuite/rust/compile/auto_traits2.rs

@@ -15,12 +15,11 @@ fn foo(a: &(dyn A + Send + Sync)) {
 struct S;
 
 impl A for S {
-    fn a_method(&self) {}
+    fn a_method(&self) {} // { dg-warning "unused name" }
 }
 
 fn main() {
     let s = S;
 
-    foo(&s); // { dg-error "bounds not satisfied" }
-             // { dg-error "mismatched type" "" { target *-*-* } .-1 }
+    foo(&s);
 }

gcc/testsuite/rust/compile/auto_traits4.rs

@@ -0,0 +1,14 @@
+#![feature(optin_builtin_traits)]
+
+unsafe auto trait Send {}
+unsafe auto trait Sync {}
+
+fn take_send(_: &dyn Send) {}
+fn take_sync(_: &dyn Sync) {}
+
+fn main() {
+    let a = i32;
+
+    take_send(&a);
+    take_sync(&a);
+}

gcc/testsuite/rust/compile/nr2/exclude

@@ -140,7 +140,8 @@ issue-2907.rs
 issue-2423.rs
 issue-266.rs
 additional-trait-bounds2.rs
-auto_traits3.rs
+auto_traits2.rs
+auto_traits4.rs
 issue-3140.rs
 cmp1.rs
 derive_clone_enum1.rs