Make gccrs recognize negative_impls

gcc/rust/checks/errors/rust-feature-gate.cc

@@ -19,6 +19,7 @@
 #include "rust-feature-gate.h"
 #include "rust-abi.h"
 #include "rust-ast-visitor.h"
+#include "rust-feature.h"
 
 namespace Rust {
 
@@ -144,4 +145,12 @@ FeatureGate::visit (AST::ExternalTypeItem &item)
 	"extern types are experimental");
 }
 
+void
+FeatureGate::visit (AST::TraitImpl &impl)
+{
+  if (impl.is_exclam ())
+    gate (Feature::Name::NEGATIVE_IMPLS, impl.get_locus (),
+	  "negative_impls are not yet implemented");
+};
+
 } // namespace Rust

gcc/rust/checks/errors/rust-feature-gate.h

@@ -127,6 +127,7 @@ class FeatureGate : public AST::DefaultASTVisitor
   void visit (AST::StaticItem &static_item) override {}
   void visit (AST::TraitItemConst &item) override {}
   void visit (AST::TraitItemType &item) override {}
+  void visit (AST::TraitImpl &impl) override;
   void visit (AST::Trait &trait) override {}
   void visit (AST::ExternalTypeItem &item) override;
   void visit (AST::ExternalStaticItem &item) override {}

gcc/rust/checks/errors/rust-feature.cc

@@ -42,6 +42,9 @@ Feature::create (Feature::Name name)
     case Feature::Name::EXTERN_TYPES:
       return Feature (Feature::Name::EXTERN_TYPES, Feature::State::ACTIVE,
 		      "extern_types", "1.23.0", 43467, tl::nullopt, "");
+    case Feature::Name::NEGATIVE_IMPLS:
+      return Feature (Feature::Name::NEGATIVE_IMPLS, Feature::State::ACTIVE,
+		      "negative_impls", "1.0.0", 68318, tl::nullopt, "");
     default:
       rust_unreachable ();
     }
@@ -52,6 +55,7 @@ const std::map<std::string, Feature::Name> Feature::name_hash_map = {
   {"intrinsics", Feature::Name::INTRINSICS},
   {"rustc_attrs", Feature::Name::RUSTC_ATTRS},
   {"decl_macro", Feature::Name::DECL_MACRO},
+  {"negative_impls", Feature::Name::NEGATIVE_IMPLS},
   // TODO: Rename to "auto_traits" when supporting
   // later Rust versions
   {"optin_builtin_traits", Feature::Name::AUTO_TRAITS},

gcc/rust/checks/errors/rust-feature.h

@@ -39,6 +39,7 @@ class Feature
   {
     ASSOCIATED_TYPE_BOUNDS,
     INTRINSICS,
+    NEGATIVE_IMPLS,
     RUSTC_ATTRS,
     DECL_MACRO,
     AUTO_TRAITS,

gcc/testsuite/rust/compile/negative_impls.rs

@@ -0,0 +1,8 @@
+#![feature(negative_impls)]
+
+trait ExampleTrait {}
+
+impl !ExampleTrait for i32 {}
+
+
+fn main() {}

gcc/testsuite/rust/compile/negative_impls_2.rs

@@ -0,0 +1,16 @@
+// This test case should error out since we haven't included the negative_impls feature
+// Output from  online rust compiler 2021 ver
+// Compiling playground v0.0.1 (/playground)
+// error[E0658]: negative trait bounds are not yet fully implemented; use marker types for now
+//  --> src/main.rs:8:6
+//   |
+// 8 | impl !ExampleTrait for i32 {}//
+//   |      ^^^^^^^^^^^^^
+//   |
+//   = note: see issue #68318 <https://github.com/rust-lang/rust/issues/68318> for more information
+
+// For more information about this error, try `rustc --explain E0658`.
+// error: could not compile `playground` (bin "playground") due to 1 previous error
+trait ExampleTrait {}
+
+impl !ExampleTrait for i32 {} // { dg-error "negative_impls are not yet implemented" }