Fix not x for optional values

compile.c

@@ -1865,7 +1865,7 @@ CORD compile(env_t *env, ast_t *ast)
     }
     case Not: {
         ast_t *value = Match(ast, Not)->value;
-        type_t *t = get_type(env, ast);
+        type_t *t = get_type(env, value);
 
         binding_t *b = get_namespace_binding(env, value, "negated");
         if (b && b->type->tag == FunctionType) {

test/optionals.tm

@@ -315,3 +315,9 @@ func main():
             >> opt
         else:
             >> opt
+
+    >> not 5?
+    = no
+
+    >> not !Int
+    = yes