Update code from OSX merge to be consistent with the rest of the code

Remove some dead code whilst I was here too :P

src/check_stmt.c

@@ -723,8 +723,7 @@ void check_stmt_internal(Checker *c, AstNode *node, u32 flags) {
 			}
 		}
 
-	skip_expr:
-		;		// again, declaring a variable immediately after a label... weird.
+	skip_expr:; // NOTE(zhiayang): again, declaring a variable immediately after a label... weird.
 		AstNode *lhs[2] = {rs->value, rs->index};
 		Type *   rhs[2] = {val, idx};
 
@@ -1209,10 +1208,6 @@ void check_stmt_internal(Checker *c, AstNode *node, u32 flags) {
 				error(us->token, "`using` cannot be applied to a procedure");
 				break;
 
-			case Entity_ImplicitValue:
-				error(us->token, "`using` cannot be applied to an implicit value");
-				break;
-
 			case Entity_Nil:
 				error(us->token, "`using` cannot be applied to `nil`");
 				break;