impl validation for variables

compiler.h

@@ -1596,6 +1596,9 @@ struct resolver_entity *
 resolver_result_entity_root(struct resolver_result *result);
 struct resolver_entity *resolver_entity_next(struct resolver_entity *entity);
 struct resolver_entity *resolver_result_entity(struct resolver_result *result);
+struct resolver_entity *
+resolver_get_variable_from_local_scope(struct resolver_process *process,
+                                       const char *var_name);
 
 int codegen(struct compile_process *process);
 struct code_generator *codegenerator_new(struct compile_process *process);

resolver.c

@@ -590,6 +590,14 @@ struct resolver_entity *resolver_get_variable(struct resolver_result *result,
                                       RESOLVER_ENTITY_TYPE_VARIABLE);
 }
 
+struct resolver_entity *
+resolver_get_variable_from_local_scope(struct resolver_process *process,
+                                       const char *var_name) {
+  struct resolver_result *result = resolver_new_result(process);
+  return resolver_get_entity_in_scope(
+      result, process, resolver_scope_current(process), var_name);
+}
+
 struct resolver_entity *resolver_get_function_in_scope(
     struct resolver_result *result, struct resolver_process *process,
     const char *func_name, struct resolver_scope *scope) {

test.c

@@ -1,3 +1 @@
-int test() {}
-
-int test() { return 0; }
+int test(int x, int x) { return 0; }

validator.c

@@ -48,8 +48,20 @@ void validate_body(struct body *body) {
 
 void validate_function_body(struct node *node) { validate_body(&node->body); }
 
+void validate_variable(struct node *var_node) {
+  struct resolver_entity *entity = resolver_get_variable_from_local_scope(
+      validator_current_compile_process->resolver, var_node->var.name);
+  if (entity) {
+    compiler_node_error(var_node, "variable %s already defined",
+                        var_node->var.name);
+  }
+
+  resolver_default_new_scope_entity(validator_current_compile_process->resolver,
+                                    var_node, 0, 0);
+}
+
 void validate_function_arg(struct node *func_arg_var_node) {
-  // validate_variable
+  validate_variable(func_arg_var_node);
 }
 
 void validate_function_args(struct function_args *func_args) {