Fix NR2.0 compiler ICE caused by Generics in Enums

gcc/rust/ChangeLog:
	* resolve/rust-late-name-resolver-2.0.cc:
	Change the late name resolver to enter proper lexical scope during typechecking
	* resolve/rust-late-name-resolver-2.0.h:
	Add needed prototype to header
	* resolve/rust-toplevel-name-resolver-2.0.cc:
	Add generic parameters to enum's scoped RIB to allow for proper name resolution on types.

gcc/testsuite/ChangeLog:
	* rust/compile/issue-3304.rs:
	Add small test for generics+enums combination for NR2.0

Signed-off-by: Liam Naddell <liam.naddell@mail.utoronto.ca>

Author: liamnaddell

gcc/rust/resolve/rust-late-name-resolver-2.0.cc

@@ -295,6 +295,13 @@ Late::visit (AST::StructStruct &s)
   ctx.scoped (Rib::Kind::Item, s.get_node_id (), s_vis);
 }
 
+void
+Late::visit (AST::Enum &s)
+{
+  auto s_vis = [this, &s] () { AST::DefaultASTVisitor::visit (s); };
+  ctx.scoped (Rib::Kind::Item, s.get_node_id (), s_vis);
+}
+
 void
 Late::visit (AST::StructExprStruct &s)
 {

gcc/rust/resolve/rust-late-name-resolver-2.0.h

@@ -52,6 +52,7 @@ class Late : public DefaultResolver
   void visit (AST::StructExprStructBase &) override;
   void visit (AST::StructExprStructFields &) override;
   void visit (AST::StructStruct &) override;
+  void visit (AST::Enum &) override;
   void visit (AST::GenericArgs &) override;
   void visit (AST::GenericArg &);
 

gcc/rust/resolve/rust-toplevel-name-resolver-2.0.cc

@@ -332,6 +332,15 @@ TopLevel::visit (AST::EnumItemDiscriminant &variant)
 void
 TopLevel::visit (AST::Enum &enum_item)
 {
+  auto generic_vis = [this, &enum_item] () {
+    for (auto &g : enum_item.get_generic_params ())
+      {
+	g->accept_vis (*this);
+      }
+  };
+
+  ctx.scoped (Rib::Kind::Item, enum_item.get_node_id (), generic_vis);
+
   insert_or_error_out (enum_item.get_identifier (), enum_item,
 		       Namespace::Types);
 

gcc/testsuite/rust/compile/issue-3304.rs

@@ -0,0 +1,10 @@
+// { dg-additional-options "-frust-name-resolution-2.0" }
+#[lang = "sized"]
+trait Sized {}
+
+pub enum ROption<T> {
+    RSome(T),
+    RNone,
+}
+
+fn main() {}