Improve the evaluate requests (#2583)

Currently it evaluates the given expression in the context of the top most stack frame.
The expression should access to any variables and arguments that are in the scope chain.
Implement the eval_at request with the level of the scope chain as a further argument.

JerryScript-DCO-1.0-Signed-off-by: Robert Sipka rsipka.uszeged@partner.samsung.com

jerry-core/vm/vm.c

@@ -252,6 +252,26 @@ vm_run_eval (ecma_compiled_code_t *bytecode_data_p, /**< byte-code data */
   {
     this_binding = ecma_copy_value (JERRY_CONTEXT (vm_top_context_p)->this_binding);
     lex_env_p = JERRY_CONTEXT (vm_top_context_p)->lex_env_p;
+
+#ifdef JERRY_DEBUGGER
+    uint32_t chain_index = parse_opts >> ECMA_PARSE_CHAIN_INDEX_SHIFT;
+
+    while (chain_index != 0)
+    {
+      lex_env_p = ecma_get_lex_env_outer_reference (lex_env_p);
+
+      if (JERRY_UNLIKELY (lex_env_p == NULL))
+      {
+        return ecma_raise_range_error (ECMA_ERR_MSG ("Invalid scope chain index for eval"));
+      }
+
+      if ((ecma_get_lex_env_type (lex_env_p) == ECMA_LEXICAL_ENVIRONMENT_THIS_OBJECT_BOUND)
+          || (ecma_get_lex_env_type (lex_env_p) == ECMA_LEXICAL_ENVIRONMENT_DECLARATIVE))
+      {
+        chain_index--;
+      }
+    }
+#endif
   }
   else
   {