Fix lexical scoping between scripts (#3558)

This change fixes the handling of lexical blocks when executing multiple
scripts, and also fixes a few issues with module environments.

After this change, all script files will run in the same context and
will have access to lexically scoped global variables of previous
scripts, and module environments will no longer have a bound global
'this' value.

The REPL implementation in main-unix is also fixed to correctly handle
lexically scoped variables.

Fixes #3561.

JerryScript-DCO-1.0-Signed-off-by: Dániel Bátyai dbatyai@inf.u-szeged.hu

jerry-core/api/jerry-snapshot.c

@@ -989,7 +989,14 @@ jerry_snapshot_result (const uint32_t *snapshot_p, /**< snapshot */
 
   if (as_function)
   {
-    ecma_object_t *lex_env_p = ecma_get_global_environment ();
+#if ENABLED (JERRY_ES2015)
+    if (bytecode_p->status_flags & CBC_CODE_FLAGS_LEXICAL_BLOCK_NEEDED)
+    {
+      ecma_create_global_lexical_block ();
+    }
+#endif /* ENABLED (JERRY_ES2015) */
+
+    ecma_object_t *lex_env_p = ecma_get_global_scope ();
     ecma_object_t *func_obj_p = ecma_op_create_simple_function_object (lex_env_p, bytecode_p);
 
     if (!(bytecode_p->status_flags & CBC_CODE_FLAGS_STATIC_FUNCTION))

jerry-core/ecma/base/ecma-init-finalize.c

@@ -44,7 +44,7 @@ ecma_init (void)
   JERRY_CONTEXT (ecma_gc_mark_recursion_limit) = JERRY_GC_MARK_LIMIT;
 #endif /* (JERRY_GC_MARK_LIMIT != 0) */
 
-  ecma_init_global_lex_env ();
+  ecma_init_global_environment ();
 
 #if ENABLED (JERRY_PROPRETY_HASHMAP)
   JERRY_CONTEXT (ecma_prop_hashmap_alloc_state) = ECMA_PROP_HASHMAP_ALLOC_ON;
@@ -77,7 +77,7 @@ ecma_finalize (void)
   JERRY_ASSERT (JERRY_CONTEXT (current_function_obj_p) == NULL);
 #endif /* ENABLED (JERRY_ES2015) */
 
-  ecma_finalize_global_lex_env ();
+  ecma_finalize_global_environment ();
   uint8_t runs = 0;
   do
   {

jerry-core/ecma/base/ecma-module.c

@@ -660,7 +660,7 @@ ecma_module_evaluate (ecma_module_t *module_p) /**< module */
  * @return ECMA_VALUE_ERROR - if an error occured
  *         ECMA_VALUE_EMPTY - otherwise
  */
-ecma_value_t
+static ecma_value_t
 ecma_module_connect_imports (void)
 {
   ecma_module_context_t *current_context_p = JERRY_CONTEXT (module_top_context_p);
@@ -669,6 +669,39 @@ ecma_module_connect_imports (void)
   JERRY_ASSERT (ecma_is_lexical_environment (local_env_p));
 
   ecma_module_node_t *import_node_p = current_context_p->imports_p;
+
+  /* Check that the imported bindings don't exist yet. */
+  while (import_node_p != NULL)
+  {
+    ecma_module_names_t *import_names_p = import_node_p->module_names_p;
+
+    while (import_names_p != NULL)
+    {
+      ecma_object_t *lex_env_p = local_env_p;
+      ecma_property_t *binding_p = NULL;
+
+      if (lex_env_p->type_flags_refs & ECMA_OBJECT_FLAG_BLOCK)
+      {
+        binding_p = ecma_find_named_property (lex_env_p, import_names_p->local_name_p);
+
+        JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
+        lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);
+      }
+
+      if (binding_p != NULL || ecma_op_has_binding (lex_env_p, import_names_p->local_name_p))
+      {
+        return ecma_raise_syntax_error (ECMA_ERR_MSG ("Imported binding shadows local variable."));
+      }
+
+      import_names_p = import_names_p->next_p;
+    }
+
+    import_node_p = import_node_p->next_p;
+  }
+
+  import_node_p = current_context_p->imports_p;
+
+  /* Resolve imports and create local bindings. */
   while (import_node_p != NULL)
   {
     ecma_value_t result = ecma_module_evaluate (import_node_p->module_request_p);
@@ -761,6 +794,26 @@ ecma_module_connect_imports (void)
   return ECMA_VALUE_EMPTY;
 } /* ecma_module_connect_imports */
 
+/**
+ * Initialize the current module by creating the local binding for the imported variables
+ * and verifying indirect exports.
+ *
+ * @return ECMA_VALUE_ERROR - if an error occured
+ *         ECMA_VALUE_EMPTY - otherwise
+ */
+ecma_value_t
+ecma_module_initialize_current (void)
+{
+  ecma_value_t ret_value = ecma_module_connect_imports ();
+
+  if (ecma_is_value_empty (ret_value))
+  {
+    ret_value = ecma_module_check_indirect_exports ();
+  }
+
+  return ret_value;
+} /* ecma_module_initialize_current */
+
 /**
  * Parses an EcmaScript module.
  *
@@ -975,7 +1028,8 @@ ecma_module_release_module (ecma_module_t *module_p) /**< module */
     ecma_module_release_module_context (module_p->context_p);
   }
 
-  if (module_p->state >= ECMA_MODULE_STATE_EVALUATING)
+  if (module_p->state >= ECMA_MODULE_STATE_EVALUATING
+      && module_p->scope_p != NULL)
   {
     ecma_deref_object (module_p->scope_p);
   }
@@ -996,11 +1050,6 @@ finished:
 void
 ecma_module_cleanup (void)
 {
-  if (JERRY_CONTEXT (module_top_context_p)->parent_p != NULL)
-  {
-    return;
-  }
-
   ecma_module_t *current_p = JERRY_CONTEXT (ecma_modules_p);
   while (current_p != NULL)
   {
@@ -1009,6 +1058,7 @@ ecma_module_cleanup (void)
     current_p = next_p;
   }
 
+  JERRY_CONTEXT (ecma_modules_p) = NULL;
   JERRY_CONTEXT (module_top_context_p) = NULL;
 } /* ecma_module_cleanup */
 

jerry-core/ecma/base/ecma-module.h

@@ -133,7 +133,7 @@ ecma_module_t *ecma_module_create_native_module (ecma_string_t *const path_p,
                                                  ecma_object_t *const namespace_p);
 ecma_module_t *ecma_module_find_or_create_module (ecma_string_t *const path_p);
 
-ecma_value_t ecma_module_connect_imports (void);
+ecma_value_t ecma_module_initialize_current (void);
 ecma_value_t ecma_module_parse_modules (void);
 ecma_value_t ecma_module_check_indirect_exports (void);
 

jerry-core/ecma/operations/ecma-lex-env.c

@@ -37,25 +37,35 @@
  * Initialize Global environment
  */
 void
-ecma_init_global_lex_env (void)
+ecma_init_global_environment (void)
 {
   ecma_object_t *glob_obj_p = ecma_builtin_get (ECMA_BUILTIN_ID_GLOBAL);
 
   ecma_object_t *global_lex_env_p = ecma_create_object_lex_env (NULL,
                                                                 glob_obj_p,
                                                                 ECMA_LEXICAL_ENVIRONMENT_THIS_OBJECT_BOUND);
-  ECMA_SET_NON_NULL_POINTER (JERRY_CONTEXT (ecma_global_lex_env_cp), global_lex_env_p);
+  ECMA_SET_NON_NULL_POINTER (JERRY_CONTEXT (ecma_global_env_cp), global_lex_env_p);
-} /* ecma_init_global_lex_env */
+#if ENABLED (JERRY_ES2015)
+  ECMA_SET_NON_NULL_POINTER (JERRY_CONTEXT (ecma_global_scope_cp), global_lex_env_p);
+#endif /* ENABLED (JERRY_ES2015) */
+} /* ecma_init_global_environment */
 
 /**
  * Finalize Global environment
  */
 void
-ecma_finalize_global_lex_env (void)
+ecma_finalize_global_environment (void)
 {
-  ecma_deref_object (ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_lex_env_cp)));
+#if ENABLED (JERRY_ES2015)
-  JERRY_CONTEXT (ecma_global_lex_env_cp) = JMEM_CP_NULL;
+  if (JERRY_CONTEXT (ecma_global_scope_cp) != JERRY_CONTEXT (ecma_global_env_cp))
-} /* ecma_finalize_global_lex_env */
+  {
+    ecma_deref_object (ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_scope_cp)));
+  }
+  JERRY_CONTEXT (ecma_global_scope_cp) = JMEM_CP_NULL;
+#endif /* ENABLED (JERRY_ES2015) */
+  ecma_deref_object (ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_env_cp)));
+  JERRY_CONTEXT (ecma_global_env_cp) = JMEM_CP_NULL;
+} /* ecma_finalize_global_environment */
 
 /**
  * Get reference to Global lexical environment
@@ -66,10 +76,43 @@ ecma_finalize_global_lex_env (void)
 ecma_object_t *
 ecma_get_global_environment (void)
 {
-  JERRY_ASSERT (JERRY_CONTEXT (ecma_global_lex_env_cp) != JMEM_CP_NULL);
+  JERRY_ASSERT (JERRY_CONTEXT (ecma_global_env_cp) != JMEM_CP_NULL);
-  return ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_lex_env_cp));
+  return ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_env_cp));
 } /* ecma_get_global_environment */
 
+#if ENABLED (JERRY_ES2015)
+/**
+ * Create the global lexical block on top of the global environment.
+ */
+void
+ecma_create_global_lexical_block (void)
+{
+  if (JERRY_CONTEXT (ecma_global_scope_cp) == JERRY_CONTEXT (ecma_global_env_cp))
+  {
+    ecma_object_t *global_scope_p = ecma_create_decl_lex_env (ecma_get_global_environment ());
+    global_scope_p->type_flags_refs |= (uint16_t) ECMA_OBJECT_FLAG_BLOCK;
+    ECMA_SET_NON_NULL_POINTER (JERRY_CONTEXT (ecma_global_scope_cp), global_scope_p);
+  }
+} /* ecma_create_global_lexical_block */
+#endif /* ENABLED (JERRY_ES2015) */
+
+/**
+ * Get reference to Global lexical scope
+ * without increasing its reference count.
+ *
+ * @return pointer to the object's instance
+ */
+ecma_object_t *
+ecma_get_global_scope (void)
+{
+#if ENABLED (JERRY_ES2015)
+  JERRY_ASSERT (JERRY_CONTEXT (ecma_global_scope_cp) != JMEM_CP_NULL);
+  return ECMA_GET_NON_NULL_POINTER (ecma_object_t, JERRY_CONTEXT (ecma_global_scope_cp));
+#else /* !ENABLED (JERRY_ES2015) */
+  return ecma_get_global_environment ();
+#endif /* !ENABLED (JERRY_ES2015) */
+} /* ecma_get_global_scope */
+
 /**
  * @}
  */

jerry-core/ecma/operations/ecma-lex-env.h

@@ -30,9 +30,13 @@
  * @{
  */
 
-void ecma_init_global_lex_env (void);
+void ecma_init_global_environment (void);
-void ecma_finalize_global_lex_env (void);
+void ecma_finalize_global_environment (void);
 ecma_object_t *ecma_get_global_environment (void);
+ecma_object_t *ecma_get_global_scope (void);
+#if ENABLED (JERRY_ES2015)
+void ecma_create_global_lexical_block (void);
+#endif /* ENABLED (JERRY_ES2015) */
 
 #if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
 void ecma_module_add_lex_env (ecma_object_t *lex_env_p);

jerry-core/ecma/operations/ecma-reference.c

@@ -106,7 +106,7 @@ ecma_value_t
 ecma_op_is_prop_unscopable (ecma_object_t *lex_env_p, /**< lexical environment */
                             ecma_string_t *prop_name_p) /**< property's name */
 {
-  if (lex_env_p == ecma_get_global_environment ())
+  if (lex_env_p == ecma_get_global_scope ())
   {
     return ECMA_VALUE_FALSE;
   }

jerry-core/include/jerryscript-snapshot.h

@@ -30,7 +30,7 @@ extern "C"
 /**
  * Jerry snapshot format version.
  */
-#define JERRY_SNAPSHOT_VERSION (38u)
+#define JERRY_SNAPSHOT_VERSION (39u)
 
 /**
  * Flags for jerry_generate_snapshot and jerry_generate_function_snapshot.

jerry-core/jcontext/jcontext.h

@@ -142,7 +142,10 @@ struct jerry_context_t
   jmem_cpointer_t symbol_list_first_cp; /**< first item of the global symbol list */
 #endif /* ENABLED (JERRY_ES2015) */
   jmem_cpointer_t number_list_first_cp; /**< first item of the literal number list */
-  jmem_cpointer_t ecma_global_lex_env_cp; /**< global lexical environment */
+  jmem_cpointer_t ecma_global_env_cp; /**< global lexical environment */
+#if ENABLED (JERRY_ES2015)
+  jmem_cpointer_t ecma_global_scope_cp; /**< global lexical scope */
+#endif /* ENABLED (JERRY_ES2015) */
 
 #if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
   ecma_module_t *ecma_modules_p; /**< list of referenced modules */

jerry-core/parser/js/byte-code.h

@@ -302,6 +302,10 @@
               VM_OC_NEW | VM_OC_PUT_STACK) \
   CBC_OPCODE (CBC_EVAL, CBC_NO_FLAG, 0, \
               VM_OC_EVAL) \
+  CBC_OPCODE (CBC_CHECK_VAR, CBC_HAS_LITERAL_ARG, 0, \
+              VM_OC_CHECK_VAR) \
+  CBC_OPCODE (CBC_CHECK_LET, CBC_HAS_LITERAL_ARG, 0, \
+              VM_OC_CHECK_LET) \
   CBC_OPCODE (CBC_CREATE_VAR, CBC_HAS_LITERAL_ARG, 0, \
               VM_OC_CREATE_BINDING) \
   CBC_OPCODE (CBC_CREATE_LET, CBC_HAS_LITERAL_ARG, 0, \
@@ -780,6 +784,7 @@ typedef enum
   CBC_CODE_FLAGS_GENERATOR = (1u << 11), /**< this function is a generator */
   CBC_CODE_FLAGS_REST_PARAMETER = (1u << 12), /**< this function has rest parameter */
   CBC_CODE_FLAG_HAS_TAGGED_LITERALS = (1u << 13), /**< this function has tagged template literal list */
+  CBC_CODE_FLAGS_LEXICAL_BLOCK_NEEDED = (1u << 14), /**< compiled code needs a lexical block */
 } cbc_code_flags;
 
 /**

jerry-core/parser/js/js-parser-internal.h

@@ -58,7 +58,7 @@ typedef enum
   PARSER_DEBUGGER_BREAKPOINT_APPENDED = (1u << 11), /**< pending (unsent) breakpoint
                                                      *   info is available */
 #if ENABLED (JERRY_ES2015)
-  PARSER_INSIDE_BLOCK = (1u << 12),           /**< script has a lexical environment for let and const */
+  PARSER_LEXICAL_BLOCK_NEEDED = (1u << 12),   /**< script needs a lexical environment for let and const */
   PARSER_IS_ARROW_FUNCTION = (1u << 13),      /**< an arrow function is parsed */
   PARSER_IS_GENERATOR_FUNCTION = (1u << 14),  /**< a generator function is parsed */
   PARSER_IS_ASYNC_FUNCTION = (1u << 15),      /**< an async function is parsed */
@@ -726,6 +726,7 @@ bool scanner_is_context_needed (parser_context_t *context_p);
 bool scanner_is_global_context_needed (parser_context_t *context_p);
 bool scanner_scope_find_let_declaration (parser_context_t *context_p, lexer_lit_location_t *literal_p);
 bool scanner_try_scan_new_target (parser_context_t *context_p);
+void scanner_check_variables (parser_context_t *context_p);
 #endif /* ENABLED (JERRY_ES2015) */
 void scanner_create_variables (parser_context_t *context_p, uint32_t option_flags);
 

jerry-core/parser/js/js-parser-module.c

@@ -325,8 +325,8 @@ parser_module_context_init (void)
     ecma_module_t *module_p = ecma_module_find_or_create_module (path_p);
 
     module_p->state = ECMA_MODULE_STATE_EVALUATED;
-    module_p->scope_p = ecma_get_global_environment ();
+    /* The lexical scope of the root module does not exist yet. */
-    ecma_ref_object (module_p->scope_p);
+    module_p->scope_p = NULL;
 
     module_p->context_p = module_context_p;
     module_context_p->module_p = module_p;

jerry-core/parser/js/js-parser-statm.c

@@ -125,21 +125,7 @@ static const uint8_t parser_statement_flags[] =
   PARSER_STATM_CONTEXT_BREAK
 };
 
-#if !ENABLED (JERRY_ES2015)
+#if ENABLED (JERRY_ES2015)
-
-/**
- * Get the expected depth of a function call.
- */
-#define JERRY_GET_EXPECTED_DEPTH(context_p) 0
-
-#else /* ENABLED (JERRY_ES2015) */
-
-/**
- * Get the expected depth of a function call.
- */
-#define JERRY_GET_EXPECTED_DEPTH(context_p) \
-  (((context_p)->status_flags & PARSER_INSIDE_BLOCK) ? PARSER_BLOCK_CONTEXT_STACK_ALLOCATION : 0)
-
 /**
  * Block statement.
  */
@@ -2637,7 +2623,7 @@ parser_parse_statements (parser_context_t *context_p) /**< context */
     lexer_lit_location_t lit_location;
     bool is_use_strict = false;
 
-    JERRY_ASSERT (context_p->stack_depth == JERRY_GET_EXPECTED_DEPTH (context_p));
+    JERRY_ASSERT (context_p->stack_depth == 0);
 #ifndef JERRY_NDEBUG
     JERRY_ASSERT (context_p->context_stack_depth == context_p->stack_depth);
 #endif /* !JERRY_NDEBUG */
@@ -3348,7 +3334,7 @@ consume_last_statement:
     }
   }
 
-  JERRY_ASSERT (context_p->stack_depth == JERRY_GET_EXPECTED_DEPTH (context_p));
+  JERRY_ASSERT (context_p->stack_depth == 0);
 #ifndef JERRY_NDEBUG
   JERRY_ASSERT (context_p->context_stack_depth == context_p->stack_depth);
 #endif /* !JERRY_NDEBUG */

jerry-core/parser/js/js-parser.c

@@ -1311,6 +1311,11 @@ parser_post_processing (parser_context_t *context_p) /**< context */
   {
     compiled_code_p->status_flags |= CBC_CODE_FLAG_HAS_TAGGED_LITERALS;
   }
+
+  if (context_p->status_flags & PARSER_LEXICAL_BLOCK_NEEDED)
+  {
+    compiled_code_p->status_flags |= CBC_CODE_FLAGS_LEXICAL_BLOCK_NEEDED;
+  }
 #endif /* ENABLED (JERRY_ES2015) */
 
   literal_pool_p = ((ecma_value_t *) byte_code_p) - context_p->register_count;
@@ -2093,18 +2098,12 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
 #if ENABLED (JERRY_ES2015)
       if (scanner_is_global_context_needed (&context))
       {
-        parser_branch_t branch;
+        context.status_flags |= PARSER_LEXICAL_BLOCK_NEEDED;
+      }
 
-#ifndef JERRY_NDEBUG
+      if ((parse_opts & ECMA_PARSE_EVAL) == 0)
-        PARSER_PLUS_EQUAL_U16 (context.context_stack_depth, PARSER_BLOCK_CONTEXT_STACK_ALLOCATION);
+      {
-#endif /* !JERRY_NDEBUG */
+        scanner_check_variables (&context);
-
-        parser_emit_cbc_forward_branch (&context,
-                                        CBC_BLOCK_CREATE_CONTEXT,
-                                        &branch);
-
-        parser_stack_push (&context, &branch, sizeof (parser_branch_t));
-        context.status_flags |= PARSER_INSIDE_BLOCK;
       }
 #endif /* ENABLED (JERRY_ES2015) */
 
@@ -2113,18 +2112,6 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
 
     parser_parse_statements (&context);
 
-#if ENABLED (JERRY_ES2015)
-    if (context.status_flags & PARSER_INSIDE_BLOCK)
-    {
-      parser_branch_t branch;
-      parser_stack_pop (&context, &branch, sizeof (parser_branch_t));
-
-      parser_emit_cbc (&context, CBC_CONTEXT_END);
-      parser_set_branch_to_current_position (&context, &branch);
-      parser_flush_cbc (&context);
-    }
-#endif /* ENABLED (JERRY_ES2015) */
-
     /* When the parsing is successful, only the
      * dummy value can be remained on the stack. */
     JERRY_ASSERT (context.stack_top_uint8 == CBC_MAXIMUM_BYTE_VALUE

jerry-core/parser/js/js-scanner-internal.h

@@ -257,9 +257,6 @@ typedef enum
   SCANNER_LITERAL_POOL_BLOCK = (1 << 1), /**< literal pool represents a code block */
   SCANNER_LITERAL_POOL_IS_STRICT = (1 << 2), /**< literal pool represents a strict mode code block */
   SCANNER_LITERAL_POOL_NO_REG = (1 << 3), /**< variable declarations cannot be kept in registers */
-#if ENABLED (JERRY_ES2015)
-  SCANNER_LITERAL_POOL_NO_VAR_REG = (1 << 4), /**< non let/const declarations cannot be kept in registers */
-#endif /* ENABLED (JERRY_ES2015) */
   SCANNER_LITERAL_POOL_NO_ARGUMENTS = (1 << 5), /**< arguments object must not be constructed */
 #if ENABLED (JERRY_ES2015)
   SCANNER_LITERAL_POOL_ARGUMENTS_UNMAPPED = (1 << 6), /**< arguments object should be unmapped */

jerry-core/parser/js/js-scanner-util.c

@@ -470,21 +470,14 @@ scanner_pop_literal_pool (parser_context_t *context_p, /**< context */
   bool no_reg = (literal_pool_p->status_flags & SCANNER_LITERAL_POOL_NO_REG) != 0;
   bool search_arguments = (literal_pool_p->status_flags & SCANNER_LITERAL_POOL_NO_ARGUMENTS) == 0;
   bool arguments_required = (no_reg && search_arguments);
+
+  uint8_t no_reg_types = 0;
 #if ENABLED (JERRY_ES2015)
-  uint8_t no_var_flags = 0;
+  if (!(context_p->status_flags & PARSER_IS_DIRECT_EVAL))
-
-  if (literal_pool_p->status_flags & SCANNER_LITERAL_POOL_NO_VAR_REG)
   {
-    no_var_flags = SCANNER_LITERAL_IS_VAR;
+    no_reg_types |= SCANNER_LITERAL_IS_FUNC;
-
-    if (!(context_p->status_flags & PARSER_IS_DIRECT_EVAL))
-    {
-      no_var_flags |= SCANNER_LITERAL_IS_FUNC;
-    }
   }
-#else /* !ENABLED (JERRY_ES2015) */
+#endif /* !ENABLED (JERRY_ES2015) */
-  uint8_t no_var_flags = 0;
-#endif /* ENABLED (JERRY_ES2015) */
 
   if (no_reg && prev_literal_pool_p != NULL)
   {
@@ -565,7 +558,7 @@ scanner_pop_literal_pool (parser_context_t *context_p, /**< context */
         no_declarations++;
       }
 
-      if (no_reg || (type & no_var_flags))
+      if (no_reg || (type & no_reg_types))
       {
         type |= SCANNER_LITERAL_NO_REG;
         literal_p->type = type;
@@ -1738,6 +1731,90 @@ scanner_create_unused_literal (parser_context_t *context_p, /**< context */
   context_p->literal_count++;
 } /* scanner_create_unused_literal */
 
+#if ENABLED (JERRY_ES2015)
+/**
+ * Emit checks for redeclared bindings in the global lexical scope.
+ */
+void
+scanner_check_variables (parser_context_t *context_p) /**< context */
+{
+  scanner_info_t *info_p = context_p->next_scanner_info_p;
+  const uint8_t *next_data_p = (const uint8_t *) (info_p + 1);
+  lexer_lit_location_t literal;
+
+  JERRY_ASSERT (info_p->type == SCANNER_TYPE_FUNCTION);
+
+  literal.char_p = info_p->source_p - 1;
+
+  while (next_data_p[0] != SCANNER_STREAM_TYPE_END)
+  {
+    uint32_t type = next_data_p[0] & SCANNER_STREAM_TYPE_MASK;
+    const uint8_t *data_p = next_data_p;
+
+    JERRY_ASSERT (type != SCANNER_STREAM_TYPE_HOLE
+                  && !SCANNER_STREAM_TYPE_IS_ARG (type)
+                  && !SCANNER_STREAM_TYPE_IS_ARG_FUNC (type));
+    JERRY_ASSERT (data_p[0] & SCANNER_STREAM_NO_REG);
+
+    if (!(data_p[0] & SCANNER_STREAM_UINT16_DIFF))
+    {
+      if (data_p[2] != 0)
+      {
+        literal.char_p += data_p[2];
+        next_data_p += 2 + 1;
+      }
+      else
+      {
+        memcpy (&literal.char_p, data_p + 2 + 1, sizeof (const uint8_t *));
+        next_data_p += 2 + 1 + sizeof (const uint8_t *);
+      }
+    }
+    else
+    {
+      int32_t diff = ((int32_t) data_p[2]) | ((int32_t) data_p[3]) << 8;
+
+      if (diff <= UINT8_MAX)
+      {
+        diff = -diff;
+      }
+
+      literal.char_p += diff;
+      next_data_p += 2 + 2;
+    }
+
+    literal.length = data_p[1];
+    literal.type = LEXER_IDENT_LITERAL;
+    literal.has_escape = (data_p[0] & SCANNER_STREAM_HAS_ESCAPE) ? 1 : 0;
+
+    lexer_construct_literal_object (context_p, &literal, LEXER_NEW_IDENT_LITERAL);
+    literal.char_p += data_p[1];
+
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+    if (type == SCANNER_STREAM_TYPE_IMPORT)
+    {
+      continue;
+    }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
+    context_p->lit_object.literal_p->status_flags |= LEXER_FLAG_USED;
+
+    uint16_t opcode;
+    if (type == SCANNER_STREAM_TYPE_VAR || type == SCANNER_STREAM_TYPE_FUNC)
+    {
+      opcode = CBC_CHECK_VAR;
+    }
+    else
+    {
+      opcode = CBC_CHECK_LET;
+    }
+
+    parser_emit_cbc_literal (context_p, opcode, context_p->lit_object.index);
+  }
+
+  parser_flush_cbc (context_p);
+} /* scanner_check_variables */
+#endif /* ENABLED (JERRY_ES2015) */
+
 /**
  * Create and/or initialize var/let/const/function/etc. variables.
  */

jerry-core/parser/js/js-scanner.c

@@ -2263,11 +2263,7 @@ scanner_scan_all (parser_context_t *context_p, /**< context */
       context_p->source_p = source_p;
       context_p->source_end_p = source_end_p;
 
-#if ENABLED (JERRY_ES2015)
-      uint16_t status_flags = SCANNER_LITERAL_POOL_FUNCTION_WITHOUT_ARGUMENTS | SCANNER_LITERAL_POOL_NO_VAR_REG;
-#else /* !ENABLED (JERRY_DEBUGGER) */
       uint16_t status_flags = SCANNER_LITERAL_POOL_FUNCTION_WITHOUT_ARGUMENTS | SCANNER_LITERAL_POOL_NO_REG;
-#endif /* ENABLED (JERRY_DEBUGGER) */
 
       if (context_p->status_flags & PARSER_IS_STRICT)
       {

jerry-core/vm/vm.c

@@ -260,10 +260,14 @@ ecma_value_t
 vm_run_module (const ecma_compiled_code_t *bytecode_p, /**< pointer to bytecode to run */
                ecma_object_t *lex_env_p) /**< pointer to the specified lexenv to run in */
 {
-  ecma_object_t *glob_obj_p = ecma_builtin_get_global ();
+  const ecma_value_t module_init_result = ecma_module_initialize_current ();
+  if (ECMA_IS_VALUE_ERROR (module_init_result))
+  {
+    return module_init_result;
+  }
 
   return vm_run (bytecode_p,
-                 ecma_make_object_value (glob_obj_p),
+                 ECMA_VALUE_UNDEFINED,
                  lex_env_p,
                  NULL,
                  0);
@@ -283,9 +287,39 @@ vm_run_global (const ecma_compiled_code_t *bytecode_p) /**< pointer to bytecode
 {
   ecma_object_t *glob_obj_p = ecma_builtin_get_global ();
 
+#if ENABLED (JERRY_ES2015)
+  if (bytecode_p->status_flags & CBC_CODE_FLAGS_LEXICAL_BLOCK_NEEDED)
+  {
+    ecma_create_global_lexical_block ();
+  }
+#endif /* ENABLED (JERRY_ES2015) */
+
+  ecma_object_t *const global_scope_p = ecma_get_global_scope ();
+
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+  if (JERRY_CONTEXT (module_top_context_p) != NULL)
+  {
+    JERRY_ASSERT (JERRY_CONTEXT (module_top_context_p)->parent_p == NULL);
+    ecma_module_t *module_p = JERRY_CONTEXT (module_top_context_p)->module_p;
+
+    JERRY_ASSERT (module_p->scope_p == NULL);
+    ecma_ref_object (global_scope_p);
+    module_p->scope_p = global_scope_p;
+
+    const ecma_value_t module_init_result = ecma_module_initialize_current ();
+    ecma_module_cleanup ();
+    JERRY_CONTEXT (module_top_context_p) = NULL;
+
+    if (ECMA_IS_VALUE_ERROR (module_init_result))
+    {
+      return module_init_result;
+    }
+  }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
   return vm_run (bytecode_p,
                  ecma_make_object_value (glob_obj_p),
-                 ecma_get_global_environment (),
+                 global_scope_p,
                  NULL,
                  0);
 } /* vm_run_global */
@@ -333,7 +367,7 @@ vm_run_eval (ecma_compiled_code_t *bytecode_data_p, /**< byte-code data */
     ecma_object_t *global_obj_p = ecma_builtin_get_global ();
     ecma_ref_object (global_obj_p);
     this_binding = ecma_make_object_value (global_obj_p);
-    lex_env_p = ecma_get_global_environment ();
+    lex_env_p = ecma_get_global_scope ();
   }
 
   ecma_ref_object (lex_env_p);
@@ -341,11 +375,20 @@ vm_run_eval (ecma_compiled_code_t *bytecode_data_p, /**< byte-code data */
   if ((bytecode_data_p->status_flags & CBC_CODE_FLAGS_STRICT_MODE) != 0)
   {
     ecma_object_t *strict_lex_env_p = ecma_create_decl_lex_env (lex_env_p);
-    ecma_deref_object (lex_env_p);
 
+    ecma_deref_object (lex_env_p);
     lex_env_p = strict_lex_env_p;
   }
 
+  if ((bytecode_data_p->status_flags & CBC_CODE_FLAGS_LEXICAL_BLOCK_NEEDED) != 0)
+  {
+    ecma_object_t *lex_block_p = ecma_create_decl_lex_env (lex_env_p);
+    lex_block_p->type_flags_refs |= (uint16_t) ECMA_OBJECT_FLAG_BLOCK;
+
+    ecma_deref_object (lex_env_p);
+    lex_env_p = lex_block_p;
+  }
+
   ecma_value_t completion_value = vm_run (bytecode_data_p,
                                           this_binding,
                                           lex_env_p,
@@ -1337,6 +1380,56 @@ vm_loop (vm_frame_ctx_t *frame_ctx_p) /**< frame context */
           continue;
         }
 #if ENABLED (JERRY_ES2015)
+        case VM_OC_CHECK_VAR:
+        {
+          JERRY_ASSERT (ecma_get_global_scope () == frame_ctx_p->lex_env_p);
+
+          uint32_t literal_index;
+          READ_LITERAL_INDEX (literal_index);
+
+          if ((frame_ctx_p->lex_env_p->type_flags_refs & ECMA_OBJECT_FLAG_BLOCK) == 0)
+          {
+            continue;
+          }
+
+          ecma_string_t *const literal_name_p = ecma_get_string_from_value (literal_start_p[literal_index]);
+          ecma_property_t *const binding_p = ecma_find_named_property (frame_ctx_p->lex_env_p, literal_name_p);
+
+          if (binding_p != NULL)
+          {
+            result = ecma_raise_syntax_error (ECMA_ERR_MSG ("Local variable is redeclared."));
+            goto error;
+          }
+
+          continue;
+        }
+        case VM_OC_CHECK_LET:
+        {
+          JERRY_ASSERT (ecma_get_global_scope () == frame_ctx_p->lex_env_p);
+
+          uint32_t literal_index;
+          READ_LITERAL_INDEX (literal_index);
+
+          ecma_string_t *literal_name_p = ecma_get_string_from_value (literal_start_p[literal_index]);
+          ecma_object_t *lex_env_p = frame_ctx_p->lex_env_p;
+          ecma_property_t *binding_p = NULL;
+
+          if (lex_env_p->type_flags_refs & ECMA_OBJECT_FLAG_BLOCK)
+          {
+            binding_p = ecma_find_named_property (lex_env_p, literal_name_p);
+
+            JERRY_ASSERT (lex_env_p->u2.outer_reference_cp != JMEM_CP_NULL);
+            lex_env_p = ECMA_GET_NON_NULL_POINTER (ecma_object_t, lex_env_p->u2.outer_reference_cp);
+          }
+
+          if (binding_p != NULL || ecma_op_has_binding (lex_env_p, literal_name_p))
+          {
+            result = ecma_raise_syntax_error (ECMA_ERR_MSG ("Local variable is redeclared."));
+            goto error;
+          }
+
+          continue;
+        }
         case VM_OC_ASSIGN_LET_CONST:
         {
           uint32_t literal_index;
@@ -4181,27 +4274,6 @@ vm_run (const ecma_compiled_code_t *bytecode_header_p, /**< byte-code data heade
   vm_frame_ctx_t *frame_ctx_p;
   size_t frame_size;
 
-#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
-  if (JERRY_CONTEXT (module_top_context_p) != NULL)
-  {
-    ecma_value_t ret_value = ecma_module_connect_imports ();
-
-    if (ecma_is_value_empty (ret_value))
-    {
-      ret_value = ecma_module_check_indirect_exports ();
-    }
-
-    ecma_module_cleanup ();
-
-    if (!ecma_is_value_empty (ret_value))
-    {
-      return ret_value;
-    }
-
-    JERRY_CONTEXT (module_top_context_p) = NULL;
-  }
-#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
-
   if (bytecode_header_p->status_flags & CBC_CODE_FLAGS_UINT16_ARGUMENTS)
   {
     cbc_uint16_arguments_t *args_p = (cbc_uint16_arguments_t *) bytecode_header_p;

jerry-core/vm/vm.h

@@ -229,6 +229,8 @@ typedef enum
   VM_OC_LINE,                    /**< line number of the next statement */
 #endif /* ENABLED (JERRY_LINE_INFO) */
 #if ENABLED (JERRY_ES2015)
+  VM_OC_CHECK_VAR,               /**< check redeclared vars in the global scope */
+  VM_OC_CHECK_LET,               /**< check redeclared lets in the global scope */
   VM_OC_ASSIGN_LET_CONST,        /**< assign values to let/const declarations */
   VM_OC_COPY_TO_GLOBAL,          /**< copy value to global lex env */
   VM_OC_CLONE_CONTEXT,           /**< clone lexical environment with let/const declarations */
@@ -286,6 +288,8 @@ typedef enum
   VM_OC_LINE = VM_OC_NONE,                    /**< line number of the next statement is unused */
 #endif /* !ENABLED (JERRY_LINE_INFO) */
 #if !ENABLED (JERRY_ES2015)
+  VM_OC_CHECK_VAR = VM_OC_NONE,               /**< check redeclared vars in the global scope */
+  VM_OC_CHECK_LET = VM_OC_NONE,               /**< check redeclared lets in the global scope */
   VM_OC_ASSIGN_LET_CONST = VM_OC_NONE,        /**< assign values to let/const declarations */
   VM_OC_COPY_TO_GLOBAL = VM_OC_NONE,          /**< copy value to global lex env */
   VM_OC_CLONE_CONTEXT = VM_OC_NONE,           /**< clone lexical environment with let/const declarations */

jerry-main/main-unix.c

@@ -889,33 +889,44 @@ main (int argc,
         }
 
         /* Evaluate the line */
-        jerry_value_t ret_val_eval = jerry_eval (buffer, len, JERRY_PARSE_NO_OPTS);
+        jerry_value_t ret_val = jerry_parse (NULL,
+                                             0,
+                                             buffer,
+                                             len,
+                                             JERRY_PARSE_NO_OPTS);
 
-        if (!jerry_value_is_error (ret_val_eval))
+        if (!jerry_value_is_error (ret_val))
+        {
+          jerry_value_t func_val = ret_val;
+          ret_val = jerry_run (func_val);
+          jerry_release_value (func_val);
+        }
+
+        if (!jerry_value_is_error (ret_val))
         {
           /* Print return value */
-          const jerry_value_t args[] = { ret_val_eval };
+          const jerry_value_t args[] = { ret_val };
           jerry_value_t ret_val_print = jerryx_handler_print (jerry_create_undefined (),
                                                               jerry_create_undefined (),
                                                               args,
                                                               1);
           jerry_release_value (ret_val_print);
-          jerry_release_value (ret_val_eval);
+          jerry_release_value (ret_val);
-          ret_val_eval = jerry_run_all_enqueued_jobs ();
+          ret_val = jerry_run_all_enqueued_jobs ();
 
-          if (jerry_value_is_error (ret_val_eval))
+          if (jerry_value_is_error (ret_val))
           {
-            ret_val_eval = jerry_get_value_from_error (ret_val_eval, true);
+            ret_val = jerry_get_value_from_error (ret_val, true);
-            print_unhandled_exception (ret_val_eval);
+            print_unhandled_exception (ret_val);
           }
         }
         else
         {
-          ret_val_eval = jerry_get_value_from_error (ret_val_eval, true);
+          ret_val = jerry_get_value_from_error (ret_val, true);
-          print_unhandled_exception (ret_val_eval);
+          print_unhandled_exception (ret_val);
         }
 
-        jerry_release_value (ret_val_eval);
+        jerry_release_value (ret_val);
       }
     }
   }

tests/unit-core/test-api.c

@@ -811,6 +811,47 @@ main (void)
     jerry_cleanup ();
   }
 
+  /* Test parsing/executing scripts with lexically scoped global variables multiple times. */
+  if (jerry_is_feature_enabled (JERRY_FEATURE_SYMBOL))
+  {
+    jerry_init (JERRY_INIT_EMPTY);
+    const jerry_char_t scoped_src_p[] = "let a;";
+    jerry_value_t parse_result = jerry_parse (NULL,
+                                              0,
+                                              scoped_src_p,
+                                              sizeof (scoped_src_p) - 1,
+                                              JERRY_PARSE_NO_OPTS);
+    TEST_ASSERT (!jerry_value_is_error (parse_result));
+    jerry_release_value (parse_result);
+
+    parse_result = jerry_parse (NULL,
+                                0,
+                                scoped_src_p,
+                                sizeof (scoped_src_p) - 1,
+                                JERRY_PARSE_NO_OPTS);
+    TEST_ASSERT (!jerry_value_is_error (parse_result));
+
+    jerry_value_t run_result = jerry_run (parse_result);
+    TEST_ASSERT (!jerry_value_is_error (run_result));
+    jerry_release_value (run_result);
+
+    /* Should be a syntax error due to redeclaration. */
+    run_result = jerry_run (parse_result);
+    TEST_ASSERT (jerry_value_is_error (run_result));
+    jerry_release_value (run_result);
+    jerry_release_value (parse_result);
+
+    /* The variable should have no effect on parsing. */
+    parse_result = jerry_parse (NULL,
+                                0,
+                                scoped_src_p,
+                                sizeof (scoped_src_p) - 1,
+                                JERRY_PARSE_NO_OPTS);
+    TEST_ASSERT (!jerry_value_is_error (parse_result));
+    jerry_release_value (parse_result);
+    jerry_cleanup ();
+  }
+
   /* Test: parser error location */
   if (jerry_is_feature_enabled (JERRY_FEATURE_ERROR_MESSAGES))
   {

tests/unit-core/test-snapshot.c

@@ -223,15 +223,15 @@ main (void)
     /* Check the snapshot data. Unused bytes should be filled with zeroes */
     const uint8_t expected_data[] =
     {
-      0x4A, 0x52, 0x52, 0x59, 0x26, 0x00, 0x00, 0x00,
+      0x4A, 0x52, 0x52, 0x59, 0x27, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x00, 0x00, 0x48, 0x00, 0x00, 0x00,
       0x01, 0x00, 0x00, 0x00, 0x18, 0x00, 0x00, 0x00,
       0x03, 0x00, 0x01, 0x00, 0x41, 0x00, 0x01, 0x00,
       0x00, 0x00, 0x00, 0x01, 0x18, 0x00, 0x00, 0x00,
-      0x2C, 0x00, 0xC1, 0x4E, 0x00, 0x00, 0x00, 0x00,
+      0x2C, 0x00, 0xC3, 0x50, 0x00, 0x00, 0x00, 0x00,
       0x03, 0x00, 0x01, 0x00, 0x41, 0x00, 0x00, 0x00,
       0x00, 0x00, 0x01, 0x01, 0x07, 0x00, 0x00, 0x00,
-      0x4F, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x51, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
       0x14, 0x00, 0x73, 0x74, 0x72, 0x69, 0x6E, 0x67,
       0x20, 0x66, 0x72, 0x6F, 0x6D, 0x20, 0x73, 0x6E,
       0x61, 0x70, 0x73, 0x68, 0x6F, 0x74,
@@ -416,7 +416,10 @@ main (void)
 
     size_t snapshot_size = (size_t) jerry_get_number_value (generate_result);
     jerry_release_value (generate_result);
-    TEST_ASSERT (snapshot_size == 124);
+
+    /* In ES2015 we emit extra bytecode instructions to check global variable redeclaration. */
+    const size_t expected_size = (jerry_is_feature_enabled (JERRY_FEATURE_SYMBOL)) ? 132 : 124;
+    TEST_ASSERT (snapshot_size == expected_size);
 
     const size_t lit_c_buf_sz = jerry_get_literals_from_snapshot (literal_snapshot_buffer,
                                                                   snapshot_size,