Correctly handle variables imported or exported by modules. (#3270)

Remove var declaration workarounds and correctly create / use variables for modules.

Still missing: create lexical environment for automatic module conversion.
(Or remove this feature overall.)

JerryScript-DCO-1.0-Signed-off-by: Zoltan Herczeg zherczeg.u-szeged@partner.samsung.com

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

@@ -105,6 +105,7 @@ typedef enum
   ECMA_PARSE_HAS_IMPL_SUPER = (1u << 4), /**< the current context has implicit parent class */
   ECMA_PARSE_HAS_STATIC_SUPER = (1u << 5), /**< the current context is a static class method */
   ECMA_PARSE_EVAL = (1u << 6), /**< eval is called */
+  ECMA_PARSE_MODULE = (1u << 7), /**< module is parsed */
 } ecma_parse_opts_t;
 
 /**

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

@@ -818,7 +818,7 @@ ecma_module_parse (ecma_module_t *module_p) /**< module */
                                                 0,
                                                 (jerry_char_t *) source_p,
                                                 source_size,
-                                                JERRY_PARSE_STRICT_MODE,
+                                                ECMA_PARSE_STRICT_MODE | ECMA_PARSE_MODULE,
                                                 &bytecode_data_p);
 
   JERRY_CONTEXT (module_top_context_p) = module_p->context_p->parent_p;

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

@@ -607,11 +607,6 @@ parser_parse_class (parser_context_t *context_p, /**< context */
 {
   JERRY_ASSERT (context_p->token.type == LEXER_KEYW_CLASS);
 
-#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
-  /* FIXME: Remove this hack after module classes are supported. */
-  uint16_t assign_opcode = CBC_ASSIGN_LET_CONST;
-#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
-
   uint16_t class_ident_index = PARSER_MAXIMUM_NUMBER_OF_LITERALS;
 
   if (is_statement)
@@ -632,8 +627,6 @@ parser_parse_class (parser_context_t *context_p, /**< context */
 #if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
     if (context_p->status_flags & PARSER_MODULE_STORE_IDENT)
     {
-      assign_opcode = CBC_ASSIGN_SET_IDENT;
-
       context_p->module_identifier_lit_p = context_p->lit_object.literal_p;
       context_p->status_flags &= (uint32_t) ~(PARSER_MODULE_STORE_IDENT);
     }
@@ -693,7 +686,7 @@ parser_parse_class (parser_context_t *context_p, /**< context */
   if (is_statement)
   {
     parser_emit_cbc_literal (context_p,
-                             class_ident_index >= PARSER_REGISTER_START ? CBC_MOV_IDENT : assign_opcode,
+                             class_ident_index >= PARSER_REGISTER_START ? CBC_MOV_IDENT : CBC_ASSIGN_LET_CONST,
                              class_ident_index);
   }
 

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

@@ -78,8 +78,9 @@ typedef enum
   PARSER_IS_EVAL = (1u << 25),                /**< eval code */
 #endif /* ENABLED (JERRY_ES2015) */
 #if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
-  PARSER_MODULE_DEFAULT_CLASS_OR_FUNC = (1u << 26),  /**< parsing a function or class default export */
+  PARSER_IS_MODULE = (1u << 26),              /**< an export / import keyword is encountered */
-  PARSER_MODULE_STORE_IDENT = (1u << 27),     /**< store identifier of the current export statement */
+  PARSER_MODULE_DEFAULT_CLASS_OR_FUNC = (1u << 27),  /**< parsing a function or class default export */
+  PARSER_MODULE_STORE_IDENT = (1u << 28),     /**< store identifier of the current export statement */
 #endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
 #ifndef JERRY_NDEBUG
   PARSER_SCANNING_SUCCESSFUL = (1u << 30),    /**< scanning process was successful */

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

@@ -435,6 +435,14 @@ parser_module_parse_import_clause (parser_context_t *context_p) /**< parser cont
       parser_raise_error (context_p, PARSER_ERR_IDENTIFIER_EXPECTED);
     }
 
+#if ENABLED (JERRY_ES2015)
+    if (context_p->next_scanner_info_p->source_p == context_p->source_p)
+    {
+      JERRY_ASSERT (context_p->next_scanner_info_p->type == SCANNER_TYPE_ERR_REDECLARED);
+      parser_raise_error (context_p, PARSER_ERR_VARIABLE_REDECLARED);
+    }
+#endif /* ENABLED (JERRY_ES2015) */
+
     ecma_string_t *import_name_p = NULL;
     ecma_string_t *local_name_p = NULL;
 
@@ -454,6 +462,14 @@ parser_module_parse_import_clause (parser_context_t *context_p) /**< parser cont
         parser_raise_error (context_p, PARSER_ERR_IDENTIFIER_EXPECTED);
       }
 
+#if ENABLED (JERRY_ES2015)
+      if (context_p->next_scanner_info_p->source_p == context_p->source_p)
+      {
+        JERRY_ASSERT (context_p->next_scanner_info_p->type == SCANNER_TYPE_ERR_REDECLARED);
+        parser_raise_error (context_p, PARSER_ERR_VARIABLE_REDECLARED);
+      }
+#endif /* ENABLED (JERRY_ES2015) */
+
       lexer_construct_literal_object (context_p, &context_p->token.lit_location, LEXER_NEW_IDENT_LITERAL);
 
       local_name_index = context_p->lit_object.index;

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

@@ -1766,7 +1766,6 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
     context.status_flags = PARSER_IS_FUNCTION;
   }
 
-
 #if ENABLED (JERRY_ES2015)
   context.status_flags |= PARSER_GET_CLASS_PARSER_OPTS (parse_opts);
 #endif /* ENABLED (JERRY_ES2015) */
@@ -1865,6 +1864,7 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
   context.u.allocated_buffer_p = NULL;
   context.line = 1;
   context.column = 1;
+  context.token.flags = 0;
 
   parser_stack_init (&context);
 
@@ -1873,6 +1873,11 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
 #endif /* ENABLED (JERRY_DEBUGGER) */
 
 #if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+  if (context.status_flags & PARSER_IS_MODULE)
+  {
+    context.status_flags |= PARSER_IS_STRICT;
+  }
+
   if (parse_opts & ECMA_PARSE_EVAL)
   {
     /* After this point this flag is set for non-direct evals as well. */
@@ -1906,6 +1911,12 @@ parser_parse_source (const uint8_t *arg_list_p, /**< function argument list */
 
       lexer_next_token (&context);
     }
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+    else if (parse_opts & ECMA_PARSE_MODULE)
+    {
+      scanner_create_variables (&context, SCANNER_CREATE_VARS_NO_OPTS);
+    }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
     else
     {
       JERRY_ASSERT (context.next_scanner_info_p->source_p == source_p

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

@@ -63,7 +63,7 @@ typedef enum
  *
  *  SCANNER_LITERAL_IS_FUNC | SCANNER_LITERAL_IS_LET : function declared in this block, might be let or var
  *  SCANNER_LITERAL_IS_FUNC | SCANNER_LITERAL_IS_CONST : function declared in this block, must be let
- *  SCANNER_LITERAL_IS_LET | SCANNER_LITERAL_IS_CONST : catch block variable
+ *  SCANNER_LITERAL_IS_LET | SCANNER_LITERAL_IS_CONST : module import on global scope, catch block variable otherwise
  */
 
 /**
@@ -105,6 +105,9 @@ typedef enum
 #endif /* ENABLED (JERRY_ES2015) */
   SCANNER_LITERAL_POOL_NO_ARGUMENTS = (1 << 4), /**< arguments object should not be constructed */
   SCANNER_LITERAL_POOL_IN_WITH = (1 << 5), /**< literal pool is in a with statement */
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+  SCANNER_LITERAL_POOL_IN_EXPORT = (1 << 6), /**< the declared variables are exported by the module system */
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
 } scanner_literal_pool_flags_t;
 
 /**
@@ -167,6 +170,7 @@ void scanner_append_argument (parser_context_t *context_p, scanner_context_t *sc
 bool scanner_scope_find_let_declaration (parser_context_t *context_p, lexer_lit_location_t *literal_p);
 void scanner_detect_invalid_var (parser_context_t *context_p, scanner_context_t *scanner_context_p,
                                  lexer_lit_location_t *var_literal_p);
+void scanner_detect_invalid_let (parser_context_t *context_p, lexer_lit_location_t *let_literal_p);
 #endif /* ENABLED (JERRY_ES2015) */
 void scanner_detect_eval_call (parser_context_t *context_p, scanner_context_t *scanner_context_p);
 

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

@@ -120,6 +120,12 @@ scanner_get_stream_size (scanner_info_t *info_p, /**< scanner info block */
       case SCANNER_STREAM_TYPE_ARG:
       case SCANNER_STREAM_TYPE_ARG_FUNC:
       case SCANNER_STREAM_TYPE_FUNC:
+#if ENABLED (JERRY_ES2015)
+      case SCANNER_STREAM_TYPE_FUNC_LOCAL:
+#endif /* ENABLED (JERRY_ES2015) */
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+      case SCANNER_STREAM_TYPE_IMPORT:
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
       {
         break;
       }
@@ -639,6 +645,12 @@ scanner_pop_literal_pool (parser_context_t *context_p, /**< context */
         {
           type = SCANNER_STREAM_TYPE_LET;
         }
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+        else if (prev_literal_pool_p == NULL)
+        {
+          type = SCANNER_STREAM_TYPE_IMPORT;
+        }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
       }
       else if (literal_p->type & SCANNER_LITERAL_IS_CONST)
       {
@@ -1029,7 +1041,7 @@ scanner_scope_find_let_declaration (parser_context_t *context_p, /**< context */
 void
 scanner_detect_invalid_var (parser_context_t *context_p, /**< context */
                             scanner_context_t *scanner_context_p, /**< scanner context */
-                            lexer_lit_location_t *var_literal_p) /**< literal */
+                            lexer_lit_location_t *var_literal_p) /**< var literal */
 {
   if (var_literal_p->type & SCANNER_LITERAL_IS_LOCAL
       && !(var_literal_p->type & SCANNER_LITERAL_IS_FUNC)
@@ -1097,6 +1109,26 @@ scanner_detect_invalid_var (parser_context_t *context_p, /**< context */
   }
 } /* scanner_detect_invalid_var */
 
+/**
+ * Throws an error for invalid let statements.
+ */
+void
+scanner_detect_invalid_let (parser_context_t *context_p, /**< context */
+                            lexer_lit_location_t *let_literal_p) /**< let literal */
+{
+  if (let_literal_p->type & (SCANNER_LITERAL_IS_ARG
+                             | SCANNER_LITERAL_IS_VAR
+                             | SCANNER_LITERAL_IS_LOCAL))
+  {
+    scanner_raise_redeclaration_error (context_p);
+  }
+
+  if (let_literal_p->type & SCANNER_LITERAL_IS_FUNC)
+  {
+    let_literal_p->type &= (uint8_t) ~SCANNER_LITERAL_IS_FUNC;
+  }
+} /* scanner_detect_invalid_let */
+
 #endif /* ENABLED (JERRY_ES2015) */
 
 /**
@@ -1374,11 +1406,14 @@ scanner_is_global_context_needed (parser_context_t *context_p) /**< context */
     uint8_t data = data_p[0];
     uint32_t type = data & SCANNER_STREAM_TYPE_MASK;
 
+    /* FIXME: a private declarative lexical environment should always be present
+     * for modules. Remove SCANNER_STREAM_TYPE_IMPORT after it is implemented. */
     JERRY_ASSERT (type == SCANNER_STREAM_TYPE_VAR
                   || type == SCANNER_STREAM_TYPE_LET
                   || type == SCANNER_STREAM_TYPE_CONST
                   || type == SCANNER_STREAM_TYPE_FUNC
-                  || type == SCANNER_STREAM_TYPE_FUNC_LOCAL);
+                  || type == SCANNER_STREAM_TYPE_FUNC_LOCAL
+                  || type == SCANNER_STREAM_TYPE_IMPORT);
 
     /* Only let/const can be stored in registers */
     JERRY_ASSERT ((data & SCANNER_STREAM_NO_REG)
@@ -1401,7 +1436,9 @@ scanner_is_global_context_needed (parser_context_t *context_p) /**< context */
       data_p += 2 + 2;
     }
 
-    if (type == SCANNER_STREAM_TYPE_VAR || type == SCANNER_STREAM_TYPE_FUNC)
+    if (type == SCANNER_STREAM_TYPE_VAR
+        || type == SCANNER_STREAM_TYPE_FUNC
+        || type == SCANNER_STREAM_TYPE_IMPORT)
     {
       continue;
     }
@@ -1556,10 +1593,17 @@ scanner_create_variables (parser_context_t *context_p, /**< context */
     uint16_t map_to;
     uint16_t func_init_opcode = CBC_INIT_LOCAL;
 
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+    JERRY_ASSERT (type != SCANNER_STREAM_TYPE_IMPORT || (data_p[0] & SCANNER_STREAM_NO_REG));
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
 #if ENABLED (JERRY_ES2015)
     if (info_type == SCANNER_TYPE_FUNCTION)
     {
       if (type != SCANNER_STREAM_TYPE_LET
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+          && type != SCANNER_STREAM_TYPE_IMPORT
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
           && type != SCANNER_STREAM_TYPE_CONST)
       {
         context_p->lit_object.literal_p->status_flags |= LEXER_FLAG_GLOBAL;

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

@@ -681,6 +681,10 @@ scanner_scan_primary_expression_end (parser_context_t *context_p, /**< context *
     case SCAN_STACK_CONST:
 #endif /* ENABLED (JERRY_ES2015) */
     {
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+      scanner_context_p->active_literal_pool_p->status_flags &= (uint16_t) ~SCANNER_LITERAL_POOL_IN_EXPORT;
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
       parser_stack_pop_uint8 (context_p);
       return SCAN_KEEP_TOKEN;
     }
@@ -1291,20 +1295,17 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
 
       lexer_lit_location_t *literal_p = scanner_add_literal (context_p, scanner_context_p);
 
-      if (literal_p->type & (SCANNER_LITERAL_IS_ARG
+      scanner_detect_invalid_let (context_p, literal_p);
-                             | SCANNER_LITERAL_IS_VAR
-                             | SCANNER_LITERAL_IS_LOCAL))
-      {
-        scanner_raise_redeclaration_error (context_p);
-      }
-
-      if (literal_p->type & SCANNER_LITERAL_IS_FUNC)
-      {
-        literal_p->type = (uint8_t) (literal_p->type & ~SCANNER_LITERAL_IS_FUNC);
-      }
-
       literal_p->type |= SCANNER_LITERAL_IS_LET;
 
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+      if (scanner_context_p->active_literal_pool_p->status_flags & SCANNER_LITERAL_POOL_IN_EXPORT)
+      {
+        literal_p->type |= SCANNER_LITERAL_NO_REG;
+        scanner_context_p->active_literal_pool_p->status_flags &= (uint16_t) ~SCANNER_LITERAL_POOL_IN_EXPORT;
+      }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
       scanner_context_p->mode = SCAN_MODE_CLASS_DECLARATION;
       parser_stack_push_uint8 (context_p, SCAN_STACK_CLASS_STATEMENT);
       return SCAN_NEXT_TOKEN;
@@ -1318,6 +1319,8 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
         scanner_raise_error (context_p);
       }
 
+      context_p->status_flags |= PARSER_IS_MODULE;
+
       scanner_context_p->mode = SCAN_MODE_STATEMENT_END;
       lexer_next_token (context_p);
 
@@ -1332,8 +1335,14 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
       if (context_p->token.type == LEXER_LITERAL
           && context_p->token.lit_location.type == LEXER_IDENT_LITERAL)
       {
-        lexer_lit_location_t *location_p = scanner_add_literal (context_p, scanner_context_p);
+        lexer_lit_location_t *literal_p = scanner_add_literal (context_p, scanner_context_p);
-        location_p->type |= SCANNER_LITERAL_IS_VAR;
+
+#if ENABLED (JERRY_ES2015)
+        scanner_detect_invalid_let (context_p, literal_p);
+        literal_p->type |= SCANNER_LITERAL_IS_LOCAL | SCANNER_LITERAL_NO_REG;
+#else /* !ENABLED (JERRY_ES2015) */
+        literal_p->type |= SCANNER_LITERAL_IS_VAR | SCANNER_LITERAL_NO_REG;
+#endif /* ENABLED (JERRY_ES2015) */
 
         lexer_next_token (context_p);
 
@@ -1365,8 +1374,14 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
             scanner_raise_error (context_p);
           }
 
-          lexer_lit_location_t *location_p = scanner_add_literal (context_p, scanner_context_p);
+          lexer_lit_location_t *literal_p = scanner_add_literal (context_p, scanner_context_p);
-          location_p->type |= SCANNER_LITERAL_IS_VAR;
+
+#if ENABLED (JERRY_ES2015)
+          scanner_detect_invalid_let (context_p, literal_p);
+          literal_p->type |= SCANNER_LITERAL_IS_LOCAL | SCANNER_LITERAL_NO_REG;
+#else /* !ENABLED (JERRY_ES2015) */
+          literal_p->type |= SCANNER_LITERAL_IS_VAR | SCANNER_LITERAL_NO_REG;
+#endif /* ENABLED (JERRY_ES2015) */
 
           lexer_next_token (context_p);
         }
@@ -1382,6 +1397,10 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
               scanner_raise_error (context_p);
             }
 
+#if ENABLED (JERRY_ES2015)
+            const uint8_t *source_p = context_p->source_p;
+#endif /* ENABLED (JERRY_ES2015) */
+
             if (lexer_check_next_character (context_p, LIT_CHAR_LOWERCASE_A))
             {
               lexer_next_token (context_p);
@@ -1398,10 +1417,32 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
               {
                 scanner_raise_error (context_p);
               }
+
+#if ENABLED (JERRY_ES2015)
+              source_p = context_p->source_p;
+#endif /* ENABLED (JERRY_ES2015) */
             }
 
-            lexer_lit_location_t *location_p = scanner_add_literal (context_p, scanner_context_p);
+            lexer_lit_location_t *literal_p = scanner_add_literal (context_p, scanner_context_p);
-            location_p->type |= SCANNER_LITERAL_IS_VAR;
+
+#if ENABLED (JERRY_ES2015)
+            if (literal_p->type & (SCANNER_LITERAL_IS_ARG
+                                   | SCANNER_LITERAL_IS_VAR
+                                   | SCANNER_LITERAL_IS_LOCAL))
+            {
+              context_p->source_p = source_p;
+              scanner_raise_redeclaration_error (context_p);
+            }
+
+            if (literal_p->type & SCANNER_LITERAL_IS_FUNC)
+            {
+              literal_p->type &= (uint8_t) ~SCANNER_LITERAL_IS_FUNC;
+            }
+
+            literal_p->type |= SCANNER_LITERAL_IS_LOCAL | SCANNER_LITERAL_NO_REG;
+#else /* !ENABLED (JERRY_ES2015) */
+            literal_p->type |= SCANNER_LITERAL_IS_VAR | SCANNER_LITERAL_NO_REG;
+#endif /* ENABLED (JERRY_ES2015) */
 
             lexer_next_token (context_p);
 
@@ -1446,6 +1487,8 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
         scanner_raise_error (context_p);
       }
 
+      context_p->status_flags |= PARSER_IS_MODULE;
+
       lexer_next_token (context_p);
 
       if (context_p->token.type == LEXER_KEYW_DEFAULT)
@@ -1502,16 +1545,19 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
 
           if (context_p->token.type == LEXER_LITERAL && context_p->token.lit_location.type == LEXER_IDENT_LITERAL)
           {
-            lexer_lit_location_t *location_p = scanner_add_literal (context_p, scanner_context_p);
+            lexer_lit_location_t *literal_p = scanner_add_literal (context_p, scanner_context_p);
-            location_p->type |= SCANNER_LITERAL_IS_VAR;
+
+            scanner_detect_invalid_let (context_p, literal_p);
+
+            literal_p->type |= SCANNER_LITERAL_IS_LET | SCANNER_LITERAL_NO_REG;
             return SCAN_NEXT_TOKEN;
           }
 
-          lexer_lit_location_t *location_p;
+          lexer_lit_location_t *literal_p;
-          location_p = scanner_add_custom_literal (context_p,
+          literal_p = scanner_add_custom_literal (context_p,
-                                                   scanner_context_p->active_literal_pool_p,
+                                                  scanner_context_p->active_literal_pool_p,
-                                                   &lexer_default_literal);
+                                                  &lexer_default_literal);
-          location_p->type |= SCANNER_LITERAL_IS_VAR;
+          literal_p->type |= SCANNER_LITERAL_IS_LET | SCANNER_LITERAL_NO_REG;
           return SCAN_KEEP_TOKEN;
         }
 #endif /* ENABLED (JERRY_ES2015) */
@@ -1612,25 +1658,19 @@ scanner_scan_statement (parser_context_t *context_p, /**< context */
         return SCAN_NEXT_TOKEN;
       }
 
-#if ENABLED (JERRY_ES2015)
+      switch (context_p->token.type)
-      if (context_p->token.type == LEXER_KEYW_CLASS)
       {
-        /* FIXME: classes should be let declarations. */
+#if ENABLED (JERRY_ES2015)
-        scanner_context_p->mode = SCAN_MODE_CLASS_DECLARATION;
+        case LEXER_KEYW_CLASS:
-        parser_stack_push_uint8 (context_p, SCAN_STACK_CLASS_STATEMENT);
+        case LEXER_KEYW_LET:
-
+        case LEXER_KEYW_CONST:
-        lexer_next_token (context_p);
-
-        if (context_p->token.type != LEXER_LITERAL || context_p->token.lit_location.type != LEXER_IDENT_LITERAL)
-        {
-          scanner_raise_error (context_p);
-        }
-
-        lexer_lit_location_t *location_p = scanner_add_literal (context_p, scanner_context_p);
-        location_p->type |= SCANNER_LITERAL_IS_VAR;
-        return SCAN_NEXT_TOKEN;
-      }
 #endif /* ENABLED (JERRY_ES2015) */
+        case LEXER_KEYW_VAR:
+        {
+          scanner_context_p->active_literal_pool_p->status_flags |= SCANNER_LITERAL_POOL_IN_EXPORT;
+          break;
+        }
+      }
 
       scanner_context_p->mode = SCAN_MODE_STATEMENT;
       return SCAN_KEEP_TOKEN;
@@ -2198,17 +2238,7 @@ scanner_scan_all (parser_context_t *context_p, /**< context */
 #if ENABLED (JERRY_ES2015)
           if (stack_top == SCAN_STACK_LET || stack_top == SCAN_STACK_CONST)
           {
-            if (literal_p->type & (SCANNER_LITERAL_IS_ARG
+            scanner_detect_invalid_let (context_p, literal_p);
-                                   | SCANNER_LITERAL_IS_VAR
-                                   | SCANNER_LITERAL_IS_LOCAL))
-            {
-              scanner_raise_redeclaration_error (context_p);
-            }
-
-            if (literal_p->type & SCANNER_LITERAL_IS_FUNC)
-            {
-              literal_p->type = (uint8_t) (literal_p->type & ~SCANNER_LITERAL_IS_FUNC);
-            }
 
             if (stack_top == SCAN_STACK_LET)
             {
@@ -2260,6 +2290,13 @@ scanner_scan_all (parser_context_t *context_p, /**< context */
           lexer_next_token (context_p);
 #endif /* ENABLED (JERRY_ES2015) */
 
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+          if (scanner_context.active_literal_pool_p->status_flags & SCANNER_LITERAL_POOL_IN_EXPORT)
+          {
+            literal_p->type |= SCANNER_LITERAL_NO_REG;
+          }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
           switch (context_p->token.type)
           {
             case LEXER_ASSIGN:
@@ -2276,6 +2313,10 @@ scanner_scan_all (parser_context_t *context_p, /**< context */
 
           if (SCANNER_IS_FOR_START (stack_top))
           {
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+            JERRY_ASSERT (!(scanner_context.active_literal_pool_p->status_flags & SCANNER_LITERAL_POOL_IN_EXPORT));
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
             if (context_p->token.type != LEXER_SEMICOLON
                 && context_p->token.type != LEXER_KEYW_IN
                 && !SCANNER_IDENTIFIER_IS_OF ())
@@ -2293,6 +2334,10 @@ scanner_scan_all (parser_context_t *context_p, /**< context */
           JERRY_ASSERT (stack_top == SCAN_STACK_VAR);
 #endif /* ENABLED (JERRY_ES2015) */
 
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+          scanner_context.active_literal_pool_p->status_flags &= (uint16_t) ~SCANNER_LITERAL_POOL_IN_EXPORT;
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
+
           scanner_context.mode = SCAN_MODE_STATEMENT_END;
           parser_stack_pop_uint8 (context_p);
           continue;
@@ -2646,6 +2691,13 @@ scan_completed:
                 break;
               }
 #endif /* ENABLED (JERRY_ES2015) */
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+              case SCANNER_STREAM_TYPE_IMPORT:
+              {
+                JERRY_DEBUG_MSG ("    IMPORT ");
+                break;
+              }
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
               default:
               {
                 JERRY_ASSERT ((data_p[0] & SCANNER_STREAM_TYPE_MASK) == SCANNER_STREAM_TYPE_HOLE);

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

@@ -145,6 +145,9 @@ typedef enum
   SCANNER_STREAM_TYPE_LET, /**< let declaration */
   SCANNER_STREAM_TYPE_CONST, /**< const declaration */
 #endif /* ENABLED (JERRY_ES2015) */
+#if ENABLED (JERRY_ES2015_MODULE_SYSTEM)
+  SCANNER_STREAM_TYPE_IMPORT, /**< module import */
+#endif /* ENABLED (JERRY_ES2015_MODULE_SYSTEM) */
   SCANNER_STREAM_TYPE_ARG, /**< argument declaration */
   /* Function types should be at the end. See the SCANNER_STREAM_TYPE_IS_FUNCTION macro. */
   SCANNER_STREAM_TYPE_ARG_FUNC, /**< argument declaration which is later initialized with a function */

tests/jerry/es2015/module-export-fail-test.js

@@ -0,0 +1,17 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/* This module is imported by failing tests. */
+export let a;

tests/jerry/fail/module-032.js

@@ -0,0 +1,17 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+let a;
+import { a } from "../es2015/module-export-fail-test.js";

tests/jerry/fail/module-033.js

@@ -0,0 +1,17 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+var a;
+import { a } from "../es2015/module-export-fail-test.js";

tests/jerry/fail/module-034.js

@@ -0,0 +1,17 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { a } from "../es2015/module-export-fail-test.js";
+class a {};

tests/jerry/fail/module-035.js

@@ -0,0 +1,17 @@
+/* Copyright JS Foundation and other contributors, http://js.foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import { a } from "../es2015/module-export-fail-test.js";
+function a() {}