Initial implementation of annex b.3.3 behavior was incorrect
https://bugs.webkit.org/show_bug.cgi?id=156276
Reviewed by Keith Miller.
Source/JavaScriptCore:
I almost got annex B.3.3 correct in my first implementation.
There is a subtlety here I got wrong. We always create a local binding for
a function at the very beginning of execution of a block scope. So we
hoist function declarations to their local binding within a given
block scope. When we actually evaluate the function declaration statement
itself, we must lookup the binding in the current scope, and bind the
value to the binding in the "var" scope. We perform the following
abstract operations when executing a function declaration statement.
f = lookupBindingInCurrentScope("func")
store(varScope, "func", f)
I got this wrong by performing the store to the var binding at the beginning
of the block scope instead of when we evaluate the function declaration statement.
This behavior is observable. For example, a program could change the value
of "func" before the actual function declaration statement executes.
Consider the following two functions:
function foo1() {
func === undefined
{
typeof func === "function"
function func() { } Executing this statement binds the local "func" binding to the implicit "func" var binding.
func = 20 This sets the local "func" binding to 20.
}
typeof func === "function"
}
function foo2() {
func === undefined
{
typeof func === "function"
func = 20 This sets the local "func" binding to 20.
function func() { } Executing this statement binds the local "func" binding to the implicit "func" var binding.
}
func === 20
}
- bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::initializeBlockScopedFunctions):
(JSC::BytecodeGenerator::hoistSloppyModeFunctionIfNecessary):
- bytecompiler/BytecodeGenerator.h:
(JSC::BytecodeGenerator::emitNodeForLeftHandSide):
- bytecompiler/NodesCodegen.cpp:
(JSC::FuncDeclNode::emitBytecode):
- tests/stress/sloppy-mode-function-hoisting.js:
(test.foo):
(test):
(test.):
(test.bar):
(test.switch.case.0):
(test.capFoo1):
(test.switch.capFoo2):
(test.outer):
(foo):
LayoutTests:
- js/function-declarations-in-switch-statement-expected.txt:
- js/script-tests/function-declarations-in-switch-statement.js:
