Source/JavaScriptCore/runtime/ExceptionHelpers.cpp - WebKit - Git at Google

 /*
  * Copyright (C) 2008-2019 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
  *     notice, this list of conditions and the following disclaimer in the
  *     documentation and/or other materials provided with the distribution.
  * 3.  Neither the name of Apple Inc. ("Apple") nor the names of
  *     its contributors may be used to endorse or promote products derived
  *     from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */

 #include "config.h"
 #include "ExceptionHelpers.h"

 #include "CallFrame.h"
 #include "CatchScope.h"
 #include "CodeBlock.h"
 #include "ErrorHandlingScope.h"
 #include "Exception.h"
 #include "Interpreter.h"
 #include "JSCInlines.h"
 #include "JSGlobalObjectFunctions.h"
 #include "RuntimeType.h"
 #include <wtf/text/StringBuilder.h>
 #include <wtf/text/StringView.h>

 namespace JSC {

 STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(TerminatedExecutionError);

 const ClassInfo TerminatedExecutionError::s_info = { "TerminatedExecutionError", &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(TerminatedExecutionError) };

 JSValue TerminatedExecutionError::defaultValue(const JSObject*, ExecState* exec, PreferredPrimitiveType hint)
 {
     if (hint == PreferString)
         return jsNontrivialString(exec, String("JavaScript execution terminated."_s));
     return JSValue(PNaN);
 }

 JSObject* createTerminatedExecutionException(VM* vm)
 {
     return TerminatedExecutionError::create(*vm);
 }

 bool isTerminatedExecutionException(VM& vm, Exception* exception)
 {
     if (!exception->value().isObject())
         return false;

     return exception->value().inherits<TerminatedExecutionError>(vm);
 }

 JSObject* createStackOverflowError(ExecState* exec)
 {
     return createStackOverflowError(exec, exec->lexicalGlobalObject());
 }

 JSObject* createStackOverflowError(ExecState* exec, JSGlobalObject* globalObject)
 {
     auto* error = createRangeError(exec, globalObject, "Maximum call stack size exceeded."_s);
     jsCast<ErrorInstance*>(error)->setStackOverflowError();
     return error;
 }

 JSObject* createUndefinedVariableError(ExecState* exec, const Identifier& ident)
 {
     if (ident.isPrivateName()) {
         String message(makeString("Can't find private variable: PrivateSymbol.", ident.string()));
         return createReferenceError(exec, message);
     }
     String message(makeString("Can't find variable: ", ident.string()));
     return createReferenceError(exec, message);
 }

 String errorDescriptionForValue(ExecState* exec, JSValue v)
 {
     if (v.isString()) {
         String string = asString(v)->value(exec);
         if (!string)
             return string;
         return tryMakeString('"', string, '"');
     }

     if (v.isSymbol())
         return asSymbol(v)->descriptiveString();
     if (v.isObject()) {
         VM& vm = exec->vm();
         CallData callData;
         JSObject* object = asObject(v);
         if (object->methodTable(vm)->getCallData(object, callData) != CallType::None)
             return vm.smallStrings.functionString()->value(exec);
         return JSObject::calculatedClassName(object);
     }
     return v.toString(exec)->value(exec);
 }

 static String defaultApproximateSourceError(const String& originalMessage, const String& sourceText)
 {
     return makeString(originalMessage, " (near '...", sourceText, "...')");
 }

 String defaultSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     if (occurrence == ErrorInstance::FoundApproximateSource)
         return defaultApproximateSourceError(originalMessage, sourceText);

     ASSERT(occurrence == ErrorInstance::FoundExactSource);
     return makeString(originalMessage, " (evaluating '", sourceText, "')");
 }

 static String functionCallBase(const String& sourceText)
 {
     // This function retrieves the 'foo.bar' substring from 'foo.bar(baz)'.
     // FIXME: This function has simple processing of /* */ style comments.
     // It doesn't properly handle embedded comments of string literals that contain
     // parenthesis or comment constructs, e.g. foo.bar("/abc\)*/").
     // https://bugs.webkit.org/show_bug.cgi?id=146304

     unsigned sourceLength = sourceText.length();
     unsigned idx = sourceLength - 1;
     if (sourceLength < 2 || sourceText[idx] != ')') {
         // For function calls that have many new lines in between their open parenthesis
         // and their closing parenthesis, the text range passed into the message appender
         // will not inlcude the text in between these parentheses, it will just be the desired
         // text that precedes the parentheses.
         return String();
     }

     unsigned parenStack = 1;
     bool isInMultiLineComment = false;
     idx -= 1;
     // Note that we're scanning text right to left instead of the more common left to right,
     // so syntax detection is backwards.
     while (parenStack && idx) {
         UChar curChar = sourceText[idx];
         if (isInMultiLineComment) {
             if (curChar == '*' && sourceText[idx - 1] == '/') {
                 isInMultiLineComment = false;
                 --idx;
             }
         } else if (curChar == '(')
             --parenStack;
         else if (curChar == ')')
             ++parenStack;
         else if (curChar == '/' && sourceText[idx - 1] == '*') {
             isInMultiLineComment = true;
             --idx;
         }

         if (idx)
             --idx;
     }

     if (parenStack) {
         // As noted in the FIXME at the top of this function, there are bugs
         // in the above string processing. This algorithm is mostly best effort
         // and it works for most JS text in practice. However, if we determine
         // that the algorithm failed, we should just return the empty value.
         return String();
     }

     return sourceText.left(idx + 1);
 }

 static String notAFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType type, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     ASSERT(type != TypeFunction);

     if (occurrence == ErrorInstance::FoundApproximateSource)
         return defaultApproximateSourceError(originalMessage, sourceText);

     ASSERT(occurrence == ErrorInstance::FoundExactSource);
     auto notAFunctionIndex = originalMessage.reverseFind("is not a function");
     RELEASE_ASSERT(notAFunctionIndex != notFound);
     StringView displayValue;
     if (originalMessage.is8Bit())
         displayValue = StringView(originalMessage.characters8(), notAFunctionIndex - 1);
     else
         displayValue = StringView(originalMessage.characters16(), notAFunctionIndex - 1);

     String base = functionCallBase(sourceText);
     if (!base)
         return defaultApproximateSourceError(originalMessage, sourceText);
     StringBuilder builder(StringBuilder::OverflowHandler::RecordOverflow);
     builder.append(base);
     builder.appendLiteral(" is not a function. (In '");
     builder.append(sourceText);
     builder.appendLiteral("', '");
     builder.append(base);
     builder.appendLiteral("' is ");
     if (type == TypeSymbol)
         builder.appendLiteral("a Symbol");
     else {
         if (type == TypeObject)
             builder.appendLiteral("an instance of ");
         builder.append(displayValue);
     }
     builder.append(')');

     if (builder.hasOverflowed())
         return makeString("object is not a function."_s);

     return builder.toString();
 }

 static String invalidParameterInSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType type, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     ASSERT_UNUSED(type, type != TypeObject);

     if (occurrence == ErrorInstance::FoundApproximateSource)
         return defaultApproximateSourceError(originalMessage, sourceText);

     ASSERT(occurrence == ErrorInstance::FoundExactSource);
     auto inIndex = sourceText.reverseFind("in");
     if (inIndex == notFound) {
         // This should basically never happen, since JS code must use the literal
         // text "in" for the `in` operation. However, if we fail to find "in"
         // for any reason, just fail gracefully.
         return originalMessage;
     }
     if (sourceText.find("in") != inIndex)
         return makeString(originalMessage, " (evaluating '", sourceText, "')");

     static const unsigned inLength = 2;
     String rightHandSide = sourceText.substring(inIndex + inLength).simplifyWhiteSpace();
     return makeString(rightHandSide, " is not an Object. (evaluating '", sourceText, "')");
 }

 inline String invalidParameterInstanceofSourceAppender(const String& content, const String& originalMessage, const String& sourceText, RuntimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     if (occurrence == ErrorInstance::FoundApproximateSource)
         return defaultApproximateSourceError(originalMessage, sourceText);

     ASSERT(occurrence == ErrorInstance::FoundExactSource);
     auto instanceofIndex = sourceText.reverseFind("instanceof");
     RELEASE_ASSERT(instanceofIndex != notFound);
     if (sourceText.find("instanceof") != instanceofIndex)
         return makeString(originalMessage, " (evaluating '", sourceText, "')");

     static const unsigned instanceofLength = 10;
     String rightHandSide = sourceText.substring(instanceofIndex + instanceofLength).simplifyWhiteSpace();
     return makeString(rightHandSide, content, ". (evaluating '", sourceText, "')");
 }

 static String invalidParameterInstanceofNotFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType runtimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     return invalidParameterInstanceofSourceAppender(WTF::makeString(" is not a function"), originalMessage, sourceText, runtimeType, occurrence);
 }

 static String invalidParameterInstanceofhasInstanceValueNotFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType runtimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
 {
     return invalidParameterInstanceofSourceAppender(WTF::makeString("[Symbol.hasInstance] is not a function, undefined, or null"), originalMessage, sourceText, runtimeType, occurrence);
 }

 JSObject* createError(ExecState* exec, JSValue value, const String& message, ErrorInstance::SourceAppender appender)
 {
     VM& vm = exec->vm();
     auto scope = DECLARE_CATCH_SCOPE(vm);

     String valueDescription = errorDescriptionForValue(exec, value);
     ASSERT(scope.exception() || !!valueDescription);
     if (!valueDescription) {
         scope.clearException();
         return createOutOfMemoryError(exec);
     }
     String errorMessage = tryMakeString(valueDescription, ' ', message);
     if (!errorMessage)
         return createOutOfMemoryError(exec);
     scope.assertNoException();
     JSObject* exception = createTypeError(exec, errorMessage, appender, runtimeTypeForValue(vm, value));
     ASSERT(exception->isErrorInstance());

     return exception;
 }

 JSObject* createInvalidFunctionApplyParameterError(ExecState* exec, JSValue value)
 {
     VM& vm = exec->vm();
     JSObject* exception = createTypeError(exec, makeString("second argument to Function.prototype.apply must be an Array-like object"), defaultSourceAppender, runtimeTypeForValue(vm, value));
     ASSERT(exception->isErrorInstance());
     return exception;
 }

 JSObject* createInvalidInParameterError(ExecState* exec, JSValue value)
 {
     return createError(exec, value, makeString("is not an Object."), invalidParameterInSourceAppender);
 }

 JSObject* createInvalidInstanceofParameterErrorNotFunction(ExecState* exec, JSValue value)
 {
     return createError(exec, value, makeString(" is not a function"), invalidParameterInstanceofNotFunctionSourceAppender);
 }

 JSObject* createInvalidInstanceofParameterErrorHasInstanceValueNotFunction(ExecState* exec, JSValue value)
 {
     return createError(exec, value, makeString("[Symbol.hasInstance] is not a function, undefined, or null"), invalidParameterInstanceofhasInstanceValueNotFunctionSourceAppender);
 }

 JSObject* createNotAConstructorError(ExecState* exec, JSValue value)
 {
     return createError(exec, value, "is not a constructor"_s, defaultSourceAppender);
 }

 JSObject* createNotAFunctionError(ExecState* exec, JSValue value)
 {
     return createError(exec, value, "is not a function"_s, notAFunctionSourceAppender);
 }

 JSObject* createNotAnObjectError(ExecState* exec, JSValue value)
 {
     return createError(exec, value, "is not an object"_s, defaultSourceAppender);
 }

 JSObject* createErrorForInvalidGlobalAssignment(ExecState* exec, const String& propertyName)
 {
     return createReferenceError(exec, makeString("Strict mode forbids implicit creation of global property '", propertyName, '\''));
 }

 JSObject* createTDZError(ExecState* exec)
 {
     return createReferenceError(exec, "Cannot access uninitialized variable.");
 }

 Exception* throwOutOfMemoryError(ExecState* exec, ThrowScope& scope)
 {
     return throwException(exec, scope, createOutOfMemoryError(exec));
 }

 Exception* throwStackOverflowError(ExecState* exec, ThrowScope& scope)
 {
     VM& vm = exec->vm();
     ErrorHandlingScope errorScope(vm);
     return throwException(exec, scope, createStackOverflowError(exec));
 }

 Exception* throwTerminatedExecutionException(ExecState* exec, ThrowScope& scope)
 {
     VM& vm = exec->vm();
     ErrorHandlingScope errorScope(vm);
     return throwException(exec, scope, createTerminatedExecutionException(&vm));
 }

 } // namespace JSC
	/*
	* Copyright (C) 2008-2019 Apple Inc. All rights reserved.
	*
	* Redistribution and use in source and binary forms, with or without
	* modification, are permitted provided that the following conditions
	* are met:
	*
	* 1. Redistributions of source code must retain the above copyright
	* notice, this list of conditions and the following disclaimer.
	* 2. Redistributions in binary form must reproduce the above copyright
	* notice, this list of conditions and the following disclaimer in the
	* documentation and/or other materials provided with the distribution.
	* 3. Neither the name of Apple Inc. ("Apple") nor the names of
	* its contributors may be used to endorse or promote products derived
	* from this software without specific prior written permission.
	*
	* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
	* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
	* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
	* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
	* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
	* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
	* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
	* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	*/

	#include "config.h"
	#include "ExceptionHelpers.h"

	#include "CallFrame.h"
	#include "CatchScope.h"
	#include "CodeBlock.h"
	#include "ErrorHandlingScope.h"
	#include "Exception.h"
	#include "Interpreter.h"
	#include "JSCInlines.h"
	#include "JSGlobalObjectFunctions.h"
	#include "RuntimeType.h"
	#include <wtf/text/StringBuilder.h>
	#include <wtf/text/StringView.h>

	namespace JSC {

	STATIC_ASSERT_IS_TRIVIALLY_DESTRUCTIBLE(TerminatedExecutionError);

	const ClassInfo TerminatedExecutionError::s_info = { "TerminatedExecutionError", &Base::s_info, nullptr, nullptr, CREATE_METHOD_TABLE(TerminatedExecutionError) };

	JSValue TerminatedExecutionError::defaultValue(const JSObject, ExecState exec, PreferredPrimitiveType hint)
	{
	if (hint == PreferString)
	return jsNontrivialString(exec, String("JavaScript execution terminated."_s));
	return JSValue(PNaN);
	}

	JSObject* createTerminatedExecutionException(VM* vm)
	{
	return TerminatedExecutionError::create(*vm);
	}

	bool isTerminatedExecutionException(VM& vm, Exception* exception)
	{
	if (!exception->value().isObject())
	return false;

	return exception->value().inherits<TerminatedExecutionError>(vm);
	}

	JSObject* createStackOverflowError(ExecState* exec)
	{
	return createStackOverflowError(exec, exec->lexicalGlobalObject());
	}

	JSObject* createStackOverflowError(ExecState* exec, JSGlobalObject* globalObject)
	{
	auto* error = createRangeError(exec, globalObject, "Maximum call stack size exceeded."_s);
	jsCast<ErrorInstance*>(error)->setStackOverflowError();
	return error;
	}

	JSObject* createUndefinedVariableError(ExecState* exec, const Identifier& ident)
	{
	if (ident.isPrivateName()) {
	String message(makeString("Can't find private variable: PrivateSymbol.", ident.string()));
	return createReferenceError(exec, message);
	}
	String message(makeString("Can't find variable: ", ident.string()));
	return createReferenceError(exec, message);
	}

	String errorDescriptionForValue(ExecState* exec, JSValue v)
	{
	if (v.isString()) {
	String string = asString(v)->value(exec);
	if (!string)
	return string;
	return tryMakeString('"', string, '"');
	}

	if (v.isSymbol())
	return asSymbol(v)->descriptiveString();
	if (v.isObject()) {
	VM& vm = exec->vm();
	CallData callData;
	JSObject* object = asObject(v);
	if (object->methodTable(vm)->getCallData(object, callData) != CallType::None)
	return vm.smallStrings.functionString()->value(exec);
	return JSObject::calculatedClassName(object);
	}
	return v.toString(exec)->value(exec);
	}

	static String defaultApproximateSourceError(const String& originalMessage, const String& sourceText)
	{
	return makeString(originalMessage, " (near '...", sourceText, "...')");
	}

	String defaultSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	if (occurrence == ErrorInstance::FoundApproximateSource)
	return defaultApproximateSourceError(originalMessage, sourceText);

	ASSERT(occurrence == ErrorInstance::FoundExactSource);
	return makeString(originalMessage, " (evaluating '", sourceText, "')");
	}

	static String functionCallBase(const String& sourceText)
	{
	// This function retrieves the 'foo.bar' substring from 'foo.bar(baz)'.
	// FIXME: This function has simple processing of /* */ style comments.
	// It doesn't properly handle embedded comments of string literals that contain
	// parenthesis or comment constructs, e.g. foo.bar("/abc\)*/").
	// https://bugs.webkit.org/show_bug.cgi?id=146304

	unsigned sourceLength = sourceText.length();
	unsigned idx = sourceLength - 1;
	if (sourceLength < 2 \|\| sourceText[idx] != ')') {
	// For function calls that have many new lines in between their open parenthesis
	// and their closing parenthesis, the text range passed into the message appender
	// will not inlcude the text in between these parentheses, it will just be the desired
	// text that precedes the parentheses.
	return String();
	}

	unsigned parenStack = 1;
	bool isInMultiLineComment = false;
	idx -= 1;
	// Note that we're scanning text right to left instead of the more common left to right,
	// so syntax detection is backwards.
	while (parenStack && idx) {
	UChar curChar = sourceText[idx];
	if (isInMultiLineComment) {
	if (curChar == '*' && sourceText[idx - 1] == '/') {
	isInMultiLineComment = false;
	--idx;
	}
	} else if (curChar == '(')
	--parenStack;
	else if (curChar == ')')
	++parenStack;
	else if (curChar == '/' && sourceText[idx - 1] == '*') {
	isInMultiLineComment = true;
	--idx;
	}

	if (idx)
	--idx;
	}

	if (parenStack) {
	// As noted in the FIXME at the top of this function, there are bugs
	// in the above string processing. This algorithm is mostly best effort
	// and it works for most JS text in practice. However, if we determine
	// that the algorithm failed, we should just return the empty value.
	return String();
	}

	return sourceText.left(idx + 1);
	}

	static String notAFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType type, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	ASSERT(type != TypeFunction);

	if (occurrence == ErrorInstance::FoundApproximateSource)
	return defaultApproximateSourceError(originalMessage, sourceText);

	ASSERT(occurrence == ErrorInstance::FoundExactSource);
	auto notAFunctionIndex = originalMessage.reverseFind("is not a function");
	RELEASE_ASSERT(notAFunctionIndex != notFound);
	StringView displayValue;
	if (originalMessage.is8Bit())
	displayValue = StringView(originalMessage.characters8(), notAFunctionIndex - 1);
	else
	displayValue = StringView(originalMessage.characters16(), notAFunctionIndex - 1);

	String base = functionCallBase(sourceText);
	if (!base)
	return defaultApproximateSourceError(originalMessage, sourceText);
	StringBuilder builder(StringBuilder::OverflowHandler::RecordOverflow);
	builder.append(base);
	builder.appendLiteral(" is not a function. (In '");
	builder.append(sourceText);
	builder.appendLiteral("', '");
	builder.append(base);
	builder.appendLiteral("' is ");
	if (type == TypeSymbol)
	builder.appendLiteral("a Symbol");
	else {
	if (type == TypeObject)
	builder.appendLiteral("an instance of ");
	builder.append(displayValue);
	}
	builder.append(')');

	if (builder.hasOverflowed())
	return makeString("object is not a function."_s);

	return builder.toString();
	}

	static String invalidParameterInSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType type, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	ASSERT_UNUSED(type, type != TypeObject);

	if (occurrence == ErrorInstance::FoundApproximateSource)
	return defaultApproximateSourceError(originalMessage, sourceText);

	ASSERT(occurrence == ErrorInstance::FoundExactSource);
	auto inIndex = sourceText.reverseFind("in");
	if (inIndex == notFound) {
	// This should basically never happen, since JS code must use the literal
	// text "in" for the `in` operation. However, if we fail to find "in"
	// for any reason, just fail gracefully.
	return originalMessage;
	}
	if (sourceText.find("in") != inIndex)
	return makeString(originalMessage, " (evaluating '", sourceText, "')");

	static const unsigned inLength = 2;
	String rightHandSide = sourceText.substring(inIndex + inLength).simplifyWhiteSpace();
	return makeString(rightHandSide, " is not an Object. (evaluating '", sourceText, "')");
	}

	inline String invalidParameterInstanceofSourceAppender(const String& content, const String& originalMessage, const String& sourceText, RuntimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	if (occurrence == ErrorInstance::FoundApproximateSource)
	return defaultApproximateSourceError(originalMessage, sourceText);

	ASSERT(occurrence == ErrorInstance::FoundExactSource);
	auto instanceofIndex = sourceText.reverseFind("instanceof");
	RELEASE_ASSERT(instanceofIndex != notFound);
	if (sourceText.find("instanceof") != instanceofIndex)
	return makeString(originalMessage, " (evaluating '", sourceText, "')");

	static const unsigned instanceofLength = 10;
	String rightHandSide = sourceText.substring(instanceofIndex + instanceofLength).simplifyWhiteSpace();
	return makeString(rightHandSide, content, ". (evaluating '", sourceText, "')");
	}

	static String invalidParameterInstanceofNotFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType runtimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	return invalidParameterInstanceofSourceAppender(WTF::makeString(" is not a function"), originalMessage, sourceText, runtimeType, occurrence);
	}

	static String invalidParameterInstanceofhasInstanceValueNotFunctionSourceAppender(const String& originalMessage, const String& sourceText, RuntimeType runtimeType, ErrorInstance::SourceTextWhereErrorOccurred occurrence)
	{
	return invalidParameterInstanceofSourceAppender(WTF::makeString("[Symbol.hasInstance] is not a function, undefined, or null"), originalMessage, sourceText, runtimeType, occurrence);
	}

	JSObject* createError(ExecState* exec, JSValue value, const String& message, ErrorInstance::SourceAppender appender)
	{
	VM& vm = exec->vm();
	auto scope = DECLARE_CATCH_SCOPE(vm);

	String valueDescription = errorDescriptionForValue(exec, value);
	ASSERT(scope.exception() \|\| !!valueDescription);
	if (!valueDescription) {
	scope.clearException();
	return createOutOfMemoryError(exec);
	}
	String errorMessage = tryMakeString(valueDescription, ' ', message);
	if (!errorMessage)
	return createOutOfMemoryError(exec);
	scope.assertNoException();
	JSObject* exception = createTypeError(exec, errorMessage, appender, runtimeTypeForValue(vm, value));
	ASSERT(exception->isErrorInstance());

	return exception;
	}

	JSObject* createInvalidFunctionApplyParameterError(ExecState* exec, JSValue value)
	{
	VM& vm = exec->vm();
	JSObject* exception = createTypeError(exec, makeString("second argument to Function.prototype.apply must be an Array-like object"), defaultSourceAppender, runtimeTypeForValue(vm, value));
	ASSERT(exception->isErrorInstance());
	return exception;
	}

	JSObject* createInvalidInParameterError(ExecState* exec, JSValue value)
	{
	return createError(exec, value, makeString("is not an Object."), invalidParameterInSourceAppender);
	}

	JSObject* createInvalidInstanceofParameterErrorNotFunction(ExecState* exec, JSValue value)
	{
	return createError(exec, value, makeString(" is not a function"), invalidParameterInstanceofNotFunctionSourceAppender);
	}

	JSObject* createInvalidInstanceofParameterErrorHasInstanceValueNotFunction(ExecState* exec, JSValue value)
	{
	return createError(exec, value, makeString("[Symbol.hasInstance] is not a function, undefined, or null"), invalidParameterInstanceofhasInstanceValueNotFunctionSourceAppender);
	}

	JSObject* createNotAConstructorError(ExecState* exec, JSValue value)
	{
	return createError(exec, value, "is not a constructor"_s, defaultSourceAppender);
	}

	JSObject* createNotAFunctionError(ExecState* exec, JSValue value)
	{
	return createError(exec, value, "is not a function"_s, notAFunctionSourceAppender);
	}

	JSObject* createNotAnObjectError(ExecState* exec, JSValue value)
	{
	return createError(exec, value, "is not an object"_s, defaultSourceAppender);
	}

	JSObject* createErrorForInvalidGlobalAssignment(ExecState* exec, const String& propertyName)
	{
	return createReferenceError(exec, makeString("Strict mode forbids implicit creation of global property '", propertyName, '\''));
	}

	JSObject* createTDZError(ExecState* exec)
	{
	return createReferenceError(exec, "Cannot access uninitialized variable.");
	}

	Exception* throwOutOfMemoryError(ExecState* exec, ThrowScope& scope)
	{
	return throwException(exec, scope, createOutOfMemoryError(exec));
	}

	Exception* throwStackOverflowError(ExecState* exec, ThrowScope& scope)
	{
	VM& vm = exec->vm();
	ErrorHandlingScope errorScope(vm);
	return throwException(exec, scope, createStackOverflowError(exec));
	}

	Exception* throwTerminatedExecutionException(ExecState* exec, ThrowScope& scope)
	{
	VM& vm = exec->vm();
	ErrorHandlingScope errorScope(vm);
	return throwException(exec, scope, createTerminatedExecutionException(&vm));
	}

	} // namespace JSC