Disallow \8 and \9 in strict mode and template literals

This reached consensus in the July 2020 TC39:
https://github.com/tc39/ecma262/pull/2054

Bug: v8:10769
Change-Id: Iecea1d9d9c9be5c2fbfb820aed2285719c4e6382
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2333350
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Marja Hölttä <marja@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69206}

src/common/message-template.h

@@ -482,9 +482,11 @@ namespace internal {
     "Decimals with leading zeros are not allowed in strict mode.")             \
   T(StrictOctalEscape,                                                         \
     "Octal escape sequences are not allowed in strict mode.")                  \
+  T(Strict8Or9Escape, "\\8 and \\9 are not allowed in strict mode.")           \
   T(StrictWith, "Strict mode code may not include a with statement")           \
   T(TemplateOctalLiteral,                                                      \
     "Octal escape sequences are not allowed in template strings.")             \
+  T(Template8Or9Escape, "\\8 and \\9 are not allowed in template strings.")    \
   T(ThisFormalParameter, "'this' is not a valid formal parameter name")        \
   T(AwaitBindingIdentifier,                                                    \
     "'await' is not a valid identifier name in an async function")             \

src/parsing/scanner.cc

@@ -403,16 +403,24 @@ bool Scanner::ScanEscape() {
       if (IsInvalid(c)) return false;
       break;
     }
-    case '0':  // Fall through.
-    case '1':  // fall through
-    case '2':  // fall through
-    case '3':  // fall through
-    case '4':  // fall through
-    case '5':  // fall through
-    case '6':  // fall through
+    case '0':
+    case '1':
+    case '2':
+    case '3':
+    case '4':
+    case '5':
+    case '6':
     case '7':
       c = ScanOctalEscape<capture_raw>(c, 2);
       break;
+    case '8':
+    case '9':
+      // '\8' and '\9' are disallowed in strict mode.
+      // Re-use the octal error state to propagate the error.
+      octal_pos_ = Location(source_pos() - 2, source_pos() - 1);
+      octal_message_ = capture_raw ? MessageTemplate::kTemplate8Or9Escape
+                                   : MessageTemplate::kStrict8Or9Escape;
+      break;
   }
 
   // Other escaped characters are interpreted as their non-escaped version.

test/mjsunit/es6/templates.js

@@ -506,9 +506,9 @@ var obj = {
 })();
 
 
-(function testValidNumericEscapes() {
-  assertEquals("8", `\8`);
-  assertEquals("9", `\9`);
+(function testInvalidNumericEscapes() {
+  assertThrows(function() { eval("`\\8`"); }, SyntaxError)
+  assertThrows(function() { eval("`\\9`"); }, SyntaxError)
 })();
 
 

test/test262/test262.status

@@ -554,10 +554,6 @@
   'built-ins/Atomics/xor/bigint/non-shared-bufferdata': [FAIL],
   'built-ins/Atomics/xor/non-shared-bufferdata': [FAIL],
 
-  # https://bugs.chromium.org/p/v8/issues/detail?id=10769
-  'language/expressions/template-literal/invalid-legacy-octal-escape-sequence-8': [FAIL],
-  'language/literals/string/legacy-non-octal-escape-sequence-8-strict': [FAIL],
-
   ######################## NEEDS INVESTIGATION ###########################
 
   # https://bugs.chromium.org/p/v8/issues/detail?id=7833

test/webkit/fast/js/numeric-escapes-in-string-literals-expected.txt

@@ -25,7 +25,6 @@ Test numeric escapes in string literals - https://bugs.webkit.org/show_bug.cgi?i
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
-
 PASS eval(stringLiteral) is nonStrictResult
 PASS eval(stringLiteral) is strictResult
 PASS eval(stringLiteral) is nonStrictResult
@@ -33,9 +32,9 @@ PASS eval(stringLiteral) threw exception SyntaxError: Octal escape sequences are
 PASS eval(stringLiteral) is nonStrictResult
 PASS eval(stringLiteral) threw exception SyntaxError: Octal escape sequences are not allowed in strict mode..
 PASS eval(stringLiteral) is nonStrictResult
-FAIL eval(stringLiteral) should throw an exception. Was 8.
+PASS eval(stringLiteral) threw exception SyntaxError: \8 and \9 are not allowed in strict mode..
 PASS eval(stringLiteral) is nonStrictResult
-FAIL eval(stringLiteral) should throw an exception. Was 9.
+PASS eval(stringLiteral) threw exception SyntaxError: \8 and \9 are not allowed in strict mode..
 PASS eval(stringLiteral) is nonStrictResult
 PASS eval(stringLiteral) threw exception SyntaxError: Octal escape sequences are not allowed in strict mode..
 PASS eval(stringLiteral) is nonStrictResult
@@ -61,7 +60,7 @@ PASS eval(stringLiteral) threw exception SyntaxError: Octal escape sequences are
 PASS eval(stringLiteral) is nonStrictResult
 PASS eval(stringLiteral) threw exception SyntaxError: Octal escape sequences are not allowed in strict mode..
 PASS eval(stringLiteral) is nonStrictResult
-FAIL eval(stringLiteral) should throw an exception. Was 99.
+PASS eval(stringLiteral) threw exception SyntaxError: \8 and \9 are not allowed in strict mode..
 PASS successfullyParsed is true
 
 TEST COMPLETE