Add name resolution processing for discriminant values

gcc/rust/ChangeLog:

	* resolve/rust-ast-resolve-stmt.h:
	Add name resolution processing for discriminant values.
gcc/testsuite/ChangeLog:

	* rust/compile/enum_discriminant3.rs: New test.

Signed-off-by: Ryutaro Okada <1015ryu88@gmail.com>

Author: sakupan102

gcc/rust/resolve/rust-ast-resolve-stmt.h

@@ -235,6 +235,7 @@ class ResolveStmt : public ResolverBase
 	redefined_error (r);
       });
 
+    ResolveExpr::go (item.get_expr (), path, cpath);
     // Done, no fields.
   }
 

gcc/testsuite/rust/compile/enum_discriminant3.rs

@@ -0,0 +1,8 @@
+const x: isize = 1;
+// { dg-warning "unused name" "" { target *-*-* } .-1 }
+
+fn main() {
+    enum Foo {
+        Bar = x,
+    }
+}