update a class extending null w.r.t the ES7 spec
https://bugs.webkit.org/show_bug.cgi?id=160417
Reviewed by Keith Miller.
Source/JavaScriptCore:
When a class extends null, it should not be marked as a derived class.
This was changed in the ES2016 spec, and this patch makes the needed
changes in JSC to follow the spec. This allows classes to extend
null and have their default constructor invoked without throwing an exception.
This also prevents |this| from being under TDZ at the start of the constructor.
Because ES6 allows arbitrary expressions in the class <ident> extends <expr>
syntax, we don't know statically if a constructor is extending null or not.
Therefore, we don't always know statically if it's a base or derived constructor.
I solved this by putting a boolean on the constructor function under a private
symbol named isDerivedConstructor when doing class construction. We only need
to put this boolean on constructors that may extend null. Constructors that are
declared in a class with no extends syntax can tell statically that they are a base constructor.
I've also renamed the ConstructorKind::Derived enum value to be
ConstructorKind::Extends to better indicate that we can't answer
the "am I a derived constructor?" question statically.
- builtins/BuiltinExecutables.cpp:
(JSC::BuiltinExecutables::createDefaultConstructor):
- builtins/BuiltinNames.h:
- bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::initializeArrowFunctionContextScopeIfNeeded):
(JSC::BytecodeGenerator::emitReturn):
(JSC::BytecodeGenerator::emitLoadArrowFunctionLexicalEnvironment):
(JSC::BytecodeGenerator::ensureThis):
(JSC::BytecodeGenerator::emitPutDerivedConstructorToArrowFunctionContextScope):
- bytecompiler/BytecodeGenerator.h:
(JSC::BytecodeGenerator::makeFunction):
- bytecompiler/NodesCodegen.cpp:
(JSC::EvalFunctionCallNode::emitBytecode):
(JSC::FunctionCallValueNode::emitBytecode):
(JSC::FunctionNode::emitBytecode):
(JSC::ClassExprNode::emitBytecode):
(JSC::Parser<LexerType>::Parser):
(JSC::Parser<LexerType>::parseFunctionInfo):
(JSC::Parser<LexerType>::parseClass):
(JSC::Parser<LexerType>::parseMemberExpression):
LayoutTests:
- js/class-syntax-extends-expected.txt:
- js/class-syntax-super-expected.txt:
- js/script-tests/class-syntax-extends.js:
- js/script-tests/class-syntax-super.js:
