Implement Function.name and Function#toString for ES6 class.
https://bugs.webkit.org/show_bug.cgi?id=155336
Reviewed by Geoffrey Garen.
Source/JavaScriptCore:
The only thing that the ES6 spec says about toString with regards to class
objects is:
"The string representation must have the syntax of a FunctionDeclaration,
FunctionExpression, GeneratorDeclaration, GeneratorExpression, ClassDeclaration,
ClassExpression, ArrowFunction, MethodDefinition, or GeneratorMethod depending
upon the actual characteristics of the object."
Previously, invoking toString() on a class object will return the function
source string of the class' constructor function. This does not conform to the
spec in that the toString string for a class does not have the syntax of a
ClassDeclaration or ClassExpression.
This is now fixed by doing the following:
- Added "m_classSource" to FunctionExecutable (and correspondingly to
UnlinkedFunctionExecutable, FunctionMetadataNode, and ClassExprNode).
m_classSource is the SourceCode for the code range "class ... { ... }".
Since the class constructor function is the in memory representation of the
class object, only class constructor functions will have its m_classSource
set. m_classSource will be "null" (by default) for all other functions.
This is how we know if a FunctionExecutable is for a class.
Note: FunctionExecutable does not have its own m_classSource. It always gets
it from its UnlinkedFunctionExecutable. This is ok to do because our CodeCache
currently does not cache UnlinkedFunctionExecutables for class constructors.
- The ClassExprNode now tracks the SourceCode range for the class expression.
This is used to set m_classSource in the UnlinkedFunctionExecutable at
bytecode generation time, and the FunctionExecutable later at bytecode
linking time.
- Function.prototype.toString() now checks if the function is for a class.
If so, it returns the string for the class source instead of just the
function source for the class constructor.
Note: the class source is static from the time the class was parsed. This
can introduces some weirdness at runtime. Consider the following:
var v1 = class {}
v1.toString(); yields "class {}".
class c2 extends v1 {}
c2.proto === v1; yields true i.e. c2 extends v1.
c2.toString(); yields "class c2 extends v1 {}" which is fine.
v1 = {}; point v1 to something else now.
c2.proto === v1; now yields false i.e. c2 no longer extends v1.
c2 actually extends the class that v1 used to
point to, but ...
c2.toString(); still yields "class c2 extends v1 {}" which is no longer true.
It is unclear how we can best implement toString() to avoid this issue.
The above behavior is how Chrome (Version 51.0.2671.0 canary (64-bit))
currently implements toString() of a class, and we do the same in this patch.
In Firefox (45.0), toString() of a class will yield the function source of it
constructor function, which is not better.
In this patch, we also added ES6 compliance for Function.name on class objects:
- The ClassExprNode now has a m_ecmaName string for tracking the inferred
name of a class according to the ES6 spec. The ASTBuilder now mirrors its
handling of FuncExprNodes to ClassExprNodes in setting the nodes' m_ecmaName
where relevant.
The m_ecmaName is later used to set the m_ecmaName of the FunctionExecutable
of the class constructor, which in turn is used to populate the initial value
of the Function.name property.
- Also renamed some variable names (/m_metadata/metadata/) to be consistent with
webkit naming convention.
- bytecode/UnlinkedFunctionExecutable.cpp:
(JSC::UnlinkedFunctionExecutable::UnlinkedFunctionExecutable):
- bytecode/UnlinkedFunctionExecutable.h:
- bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::emitNewArrowFunctionExpression):
(JSC::BytecodeGenerator::emitNewDefaultConstructor):
- bytecompiler/BytecodeGenerator.h:
- bytecompiler/NodesCodegen.cpp:
(JSC::ClassExprNode::emitBytecode):
(JSC::ASTBuilder::createAssignResolve):
(JSC::ASTBuilder::createYield):
(JSC::ASTBuilder::createClassExpr):
(JSC::ASTBuilder::createFunctionExpr):
(JSC::ASTBuilder::createProperty):
(JSC::ASTBuilder::makeAssignNode):
- parser/NodeConstructors.h:
(JSC::FunctionParameters::FunctionParameters):
(JSC::BaseFuncExprNode::BaseFuncExprNode):
(JSC::FuncExprNode::FuncExprNode):
(JSC::FuncDeclNode::FuncDeclNode):
(JSC::ArrowFuncExprNode::ArrowFuncExprNode):
(JSC::ClassDeclNode::ClassDeclNode):
(JSC::ClassExprNode::ClassExprNode):
(JSC::ExpressionNode::isDestructuringNode):
(JSC::ExpressionNode::isFuncExprNode):
(JSC::ExpressionNode::isArrowFuncExprNode):
(JSC::ExpressionNode::isClassExprNode):
(JSC::ExpressionNode::isCommaNode):
(JSC::ExpressionNode::isSimpleArray):
(JSC::ExpressionNode::isAdd):
(JSC::stringForFunctionMode):
(JSC::Parser<LexerType>::parseFunctionInfo):
(JSC::Parser<LexerType>::parseClass):
- parser/ParserFunctionInfo.h:
- parser/SyntaxChecker.h:
(JSC::SyntaxChecker::createEmptyLetExpression):
(JSC::SyntaxChecker::createYield):
(JSC::SyntaxChecker::createClassExpr):
(JSC::SyntaxChecker::createFunctionExpr):
(JSC::SyntaxChecker::createFunctionMetadata):
(JSC::SyntaxChecker::createArrowFunctionExpr):
(JSC::FunctionExecutable::FunctionExecutable):
(JSC::FunctionExecutable::finishCreation):
- runtime/Executable.h:
- runtime/FunctionPrototype.cpp:
(JSC::functionProtoFuncToString):
LayoutTests:
- js/class-syntax-name-expected.txt:
- js/script-tests/class-syntax-name.js:
(shouldBe):
(shouldBeTrue):
- js/function-toString-vs-name.html:
- js/script-tests/function-toString-vs-name.js:
- Added new tests for class.
- platform/mac/inspector/model/remote-object-expected.txt:
- Rebased expected result.
