gccrs: Fix const checking of enum discriminants

gcc/rust/ChangeLog:

	* checks/errors/rust-const-checker.cc
	(ConstChecker::visit): Visit the enum items of enums.
	* resolve/rust-ast-resolve-item.cc
	(ResolveItem::visit): Resolve enum discriminants during nr1.0.

gcc/testsuite/ChangeLog:

	* rust/compile/enum_discriminant2.rs: New test.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>

gcc/rust/checks/errors/rust-const-checker.cc

@@ -646,6 +646,9 @@ ConstChecker::visit (Enum &enum_item)
 {
   check_default_const_generics (enum_item.get_generic_params (),
 				ConstGenericCtx::Enum);
+
+  for (auto &item : enum_item.get_variants ())
+    item->accept_vis (*this);
 }
 
 void

gcc/rust/resolve/rust-ast-resolve-item.cc

@@ -356,6 +356,8 @@ ResolveItem::visit (AST::EnumItemDiscriminant &item)
   auto cpath = canonical_prefix.append (decl);
 
   mappings.insert_canonical_path (item.get_node_id (), cpath);
+
+  ResolveExpr::go (item.get_expr (), path, cpath);
 }
 
 void

gcc/testsuite/rust/compile/enum_discriminant2.rs

@@ -0,0 +1,9 @@
+fn test() -> isize {
+    1
+}
+
+enum Foo {
+    Bar = test() // { dg-error "only functions marked as .const." }
+}
+
+fn main() {}