[parser] Forbid \08 in strict strings and in untagged templates

This was never legal; the spec only allows '\0' in strict-mode strings or templates
when not followed by a decimal digit. Previously we were only enforcing that it
not be followed by an _octal_ digit.

This was already fixed for numeric literals, but not for escape sequences in strings.

BUG=v8:6504

Review-Url: https://codereview.chromium.org/2950633002
Cr-Commit-Position: refs/heads/master@{#46046}

src/parsing/scanner.cc

@@ -1045,7 +1045,7 @@ uc32 Scanner::ScanOctalEscape(uc32 c, int length) {
   // can be reported later (in strict mode).
   // We don't report the error immediately, because the octal escape can
   // occur before the "use strict" directive.
-  if (c != '0' || i > 0) {
+  if (c != '0' || i > 0 || c0_ == '8' || c0_ == '9') {
     octal_pos_ = Location(source_pos() - i - 1, source_pos() - 1);
     octal_message_ = MessageTemplate::kStrictOctalEscape;
   }

test/cctest/test-parsing.cc

@@ -5901,6 +5901,33 @@ TEST(UnicodeEscapes) {
   RunParserSyncTest(context_data, data, kSuccess);
 }
 
+TEST(OctalEscapes) {
+  const char* sloppy_context_data[][2] = {{"", ""},    // as a directive
+                                          {"0;", ""},  // as a string literal
+                                          {NULL, NULL}};
+
+  const char* strict_context_data[][2] = {
+      {"'use strict';", ""},     // as a directive before 'use strict'
+      {"", ";'use strict';"},    // as a directive after 'use strict'
+      {"'use strict'; 0;", ""},  // as a string literal
+      {NULL, NULL}};
+
+  // clang-format off
+  const char* data[] = {
+    "'\\1'",
+    "'\\01'",
+    "'\\001'",
+    "'\\08'",
+    "'\\09'",
+    NULL};
+  // clang-format on
+
+  // Permitted in sloppy mode
+  RunParserSyncTest(sloppy_context_data, data, kSuccess);
+
+  // Error in strict mode
+  RunParserSyncTest(strict_context_data, data, kError);
+}
 
 TEST(ScanTemplateLiterals) {
   const char* context_data[][2] = {{"'use strict';", ""},
@@ -7112,6 +7139,7 @@ TEST(TemplateEscapesPositiveTests) {
 
   // clang-format off
   const char* data[] = {
+    "tag`\\08`",
     "tag`\\01`",
     "tag`\\01${0}right`",
     "tag`left${0}\\01`",
@@ -7195,6 +7223,7 @@ TEST(TemplateEscapesNegativeTests) {
 
   // clang-format off
   const char* data[] = {
+    "`\\08`",
     "`\\01`",
     "`\\01${0}right`",
     "`left${0}\\01`",

test/mjsunit/es6/templates.js

@@ -476,7 +476,7 @@ var obj = {
 (function testLegacyOctal() {
   assertEquals('\u0000', `\0`);
   assertEquals('\u0000a', `\0a`);
-  for (var i = 0; i < 8; i++) {
+  for (var i = 0; i < 10; i++) {
     var code = "`\\0" + i + "`";
     assertThrows(code, SyntaxError);
     code = "(function(){})" + code;
@@ -502,8 +502,6 @@ var obj = {
 (function testValidNumericEscapes() {
   assertEquals("8", `\8`);
   assertEquals("9", `\9`);
-  assertEquals("\u00008", `\08`);
-  assertEquals("\u00009", `\09`);
 })();