Revert of Make Error.prototype.toString spec compliant; and fix various side-effect-free error printing metho…

src/js/messages.js

Index: src/js/messages.js
diff --git a/src/js/messages.js b/src/js/messages.js
index d0305412b74896a7971e4e435032b5f9a8ee3a05..dc845ea97adc855fa7d0847374dad1af99e7551a 100644
--- a/src/js/messages.js
+++ b/src/js/messages.js
@@ -23,7 +23,6 @@
     utils.ImportNow("call_site_position_symbol");
 var callSiteStrictSymbol =
     utils.ImportNow("call_site_strict_symbol");
-var FLAG_harmony_tostring;
 var Float32x4ToString;
 var formattedStackTraceSymbol =
     utils.ImportNow("formatted_stack_trace_symbol");
@@ -42,7 +41,6 @@
 var StringIndexOf;
 var StringSubstring;
 var SymbolToString;
-var toStringTagSymbol = utils.ImportNow("to_string_tag_symbol");
 var Uint16x8ToString;
 var Uint32x4ToString;
 var Uint8x16ToString;
@@ -68,10 +66,6 @@
   Uint8x16ToString = from.Uint8x16ToString;
 });
 
-utils.ImportFromExperimental(function(from) {
-  FLAG_harmony_tostring = from.FLAG_harmony_tostring;
-});
-
 // -------------------------------------------------------------------
 
 var GlobalError;
@@ -86,35 +80,11 @@
 function NoSideEffectsObjectToString() {
   if (IS_UNDEFINED(this)) return "[object Undefined]";
   if (IS_NULL(this)) return "[object Null]";
-  var O = TO_OBJECT(this);
-  var builtinTag = %_ClassOf(O);
-  var tag;
-  if (FLAG_harmony_tostring) {
-    tag = %GetDataProperty(O, toStringTagSymbol);
-    if (!IS_STRING(tag)) {
-      tag = builtinTag;
-    }
-  } else {
-    tag = builtinTag;
-  }
-  return `[object ${tag}]`;
-}
-
-function IsErrorObject(obj) {
-  return HAS_PRIVATE(obj, stackTraceSymbol);
-}
-
-function NoSideEffectsErrorToString() {
-  var name = %GetDataProperty(this, "name");
-  var message = %GetDataProperty(this, "message");
-  name = IS_UNDEFINED(name) ? "Error" : NoSideEffectsToString(name);
-  message = IS_UNDEFINED(message) ? "" : NoSideEffectsToString(message);
-  if (name == "") return message;
-  if (message == "") return name;
-  return `${name}: ${message}`;
-}
-
-function NoSideEffectsToString(obj) {
+  return "[object " + %_ClassOf(TO_OBJECT(this)) + "]";
+}
+
+
+function NoSideEffectToString(obj) {
   if (IS_STRING(obj)) return obj;
   if (IS_NUMBER(obj)) return %_NumberToString(obj);
   if (IS_BOOLEAN(obj)) return obj ? 'true' : 'false';
@@ -143,26 +113,69 @@
       case 'bool8x16':  return %_Call(Bool8x16ToString, obj);
     }
   }
-
-  if (IS_SPEC_OBJECT(obj)) {
-    // When internally formatting error objects, use a side-effects-free version
-    // of Error.prototype.toString independent of the actually installed
-    // toString method.
-    if (IsErrorObject(obj) ||
-        %GetDataProperty(obj, "toString") === ErrorToString) {
-      return %_Call(NoSideEffectsErrorToString, obj);
-    }
-
-    if (%GetDataProperty(obj, "toString") === ObjectToString) {
-      var constructor = %GetDataProperty(obj, "constructor");
-      if (IS_FUNCTION(constructor)) {
-        var constructor_name = %FunctionGetName(constructor);
-        if (constructor_name != "") return `#<${constructor_name}>`;
+  if (IS_OBJECT(obj)
+      && %GetDataProperty(obj, "toString") === ObjectToString) {
+    var constructor = %GetDataProperty(obj, "constructor");
+    if (typeof constructor == "function") {
+      var constructorName = constructor.name;
+      if (IS_STRING(constructorName) && constructorName !== "") {
+        return "#<" + constructorName + ">";
       }
     }
   }
+  if (CanBeSafelyTreatedAsAnErrorObject(obj)) {
+    return %_Call(ErrorToString, obj);
+  }
 
   return %_Call(NoSideEffectsObjectToString, obj);
+}
+
+// To determine whether we can safely stringify an object using ErrorToString
+// without the risk of side-effects, we need to check whether the object is
+// either an instance of a native error type (via '%_ClassOf'), or has Error
+// in its prototype chain and hasn't overwritten 'toString' with something
+// strange and unusual.
+function CanBeSafelyTreatedAsAnErrorObject(obj) {
+  switch (%_ClassOf(obj)) {
+    case 'Error':
+    case 'EvalError':
+    case 'RangeError':
+    case 'ReferenceError':
+    case 'SyntaxError':
+    case 'TypeError':
+    case 'URIError':
+      return true;
+  }
+
+  var objToString = %GetDataProperty(obj, "toString");
+  return obj instanceof GlobalError && objToString === ErrorToString;
+}
+
+
+// When formatting internally created error messages, do not
+// invoke overwritten error toString methods but explicitly use
+// the error to string method. This is to avoid leaking error
+// objects between script tags in a browser setting.
+function ToStringCheckErrorObject(obj) {
+  if (CanBeSafelyTreatedAsAnErrorObject(obj)) {
+    return %_Call(ErrorToString, obj);
+  } else {
+    return TO_STRING(obj);
+  }
+}
+
+
+function ToDetailString(obj) {
+  if (obj != null && IS_OBJECT(obj) && obj.toString === ObjectToString) {
+    var constructor = obj.constructor;
+    if (typeof constructor == "function") {
+      var constructorName = constructor.name;
+      if (IS_STRING(constructorName) && constructorName !== "") {
+        return "#<" + constructorName + ">";
+      }
+    }
+  }
+  return ToStringCheckErrorObject(obj);
 }
 
 
@@ -187,9 +200,9 @@
 
 // Helper functions; called from the runtime system.
 function FormatMessage(type, arg0, arg1, arg2) {
-  var arg0 = NoSideEffectsToString(arg0);
-  var arg1 = NoSideEffectsToString(arg1);
-  var arg2 = NoSideEffectsToString(arg2);
+  var arg0 = NoSideEffectToString(arg0);
+  var arg1 = NoSideEffectToString(arg1);
+  var arg2 = NoSideEffectToString(arg2);
   try {
     return %FormatMessageString(type, arg0, arg1, arg2);
   } catch (e) {
@@ -836,13 +849,20 @@
 
 function GetTypeName(receiver, requireConstructor) {
   if (IS_NULL_OR_UNDEFINED(receiver)) return null;
-  if (%_IsJSProxy(receiver)) return "Proxy";
-
-  var constructor = %GetDataProperty(TO_OBJECT(receiver), "constructor");
-  if (!IS_FUNCTION(constructor)) {
-    return requireConstructor ? null : %_Call(NoSideEffectsToString, receiver);
-  }
-  return %FunctionGetName(constructor);
+  if (%_IsJSProxy(receiver)) {
+    return "Proxy";
+  };
+  var constructor = receiver.constructor;
+  if (!constructor) {
+    return requireConstructor ? null :
+        %_Call(NoSideEffectsObjectToString, receiver);
+  }
+  var constructorName = constructor.name;
+  if (!constructorName) {
+    return requireConstructor ? null :
+        %_Call(NoSideEffectsObjectToString, receiver);
+  }
+  return constructorName;
 }
 
 
@@ -876,7 +896,7 @@
 // If the receiver equals the holder, set the formatted stack trace that the
 // getter returns.
 var StackTraceSetter = function(v) {
-  if (IsErrorObject(this)) {
+  if (HAS_PRIVATE(this, stackTraceSymbol)) {
     SET_PRIVATE(this, stackTraceSymbol, UNDEFINED);
     SET_PRIVATE(this, formattedStackTraceSymbol, v);
   }
@@ -936,15 +956,7 @@
     throw MakeTypeError(kCalledOnNonObject, "Error.prototype.toString");
   }
 
-  var name = this.name;
-  name = IS_UNDEFINED(name) ? "Error" : TO_STRING(name);
-
-  var message = this.message;
-  message = IS_UNDEFINED(message) ? "" : TO_STRING(message);
-
-  if (name == "") return message;
-  if (message == "") return name;
-  return `${name}: ${message}`
+  return %ErrorToStringRT(this);
 }
 
 function MakeError(type, arg0, arg1, arg2) {
@@ -992,8 +1004,9 @@
   "message_get_column_number", GetColumnNumber,
   "message_get_line_number", GetLineNumber,
   "message_get_source_line", GetSourceLine,
-  "no_side_effects_to_string_fun", NoSideEffectsToString,
+  "no_side_effect_to_string_fun", NoSideEffectToString,
   "stack_overflow_boilerplate", StackOverflowBoilerplate,
+  "to_detail_string_fun", ToDetailString,
 ]);
 
 utils.Export(function(to) {