Branch: refs/heads/main
Home: https://github.com/WebKit/WebKit
Commit: 29265f95211bfd7902bcd648b87a863509a3c50f
https://github.com/WebKit/WebKit/commit/29265f95211bfd7902bcd648b87a863509a3c50f
Author: Yijia Huang <[email protected]>
Date: 2022-11-18 (Fri, 18 Nov 2022)
Changed paths:
A JSTests/stress/catch-rest-parameter.js
M Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp
M Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h
Log Message:
-----------
Fix TypeError in parameter destructuring in async function should be a
rejected promise
https://bugs.webkit.org/show_bug.cgi?id=247785
rdar://102325201
Reviewed by Yusuke Suzuki.
Rest parameter should be caught in async function. So, running this
JavaScript program should print "caught".
```
async function f(...[[]]) { }
f().catch(e => print("caught"));
```
V8 (used console.log)
```
$ node input.js
caught
```
GraalJS
```
$ js input.js
caught
```
https://tc39.es/ecma262/#sec-async-function-definitions
...
AsyncFunctionDeclaration[Yield, Await, Default] :
async [no LineTerminator here] function BindingIdentifier[?Yield, ?Await] (
FormalParameters[~Yield, +Await] ) { AsyncFunctionBody }
[+Default] async [no LineTerminator here] function (
FormalParameters[~Yield, +Await] ) { AsyncFunctionBody }
AsyncFunctionExpression :
async [no LineTerminator here] function BindingIdentifier[~Yield,
+Await]opt ( FormalParameters[~Yield, +Await] ) { AsyncFunctionBody }
...
According to the spec, it indicates `FormalParameters` is used for Async
Function, where `FormalParameters` can be converted to `FunctionRestParameter`.
https://tc39.es/ecma262/#sec-parameter-lists
...
FormalParameters[Yield, Await] :
[empty]
FunctionRestParameter[?Yield, ?Await]
FormalParameterList[?Yield, ?Await]
FormalParameterList[?Yield, ?Await] ,
FormalParameterList[?Yield, ?Await] , FunctionRestParameter[?Yield, ?Await]
...
And based on RS: EvaluateAsyncFunctionBody, it will invoke the promise.reject
callback function with abrupt value ([[value]] of non-normal completion record).
https://tc39.es/ecma262/#sec-runtime-semantics-evaluateasyncfunctionbody
...
2. Let declResult be
Completion(FunctionDeclarationInstantiation(functionObject, argumentsList)).
3. If declResult is an abrupt completion, then
a. Perform ! Call(promiseCapability.[[Reject]], undefined, «
declResult.[[Value]] »).
...
In that case, any non-normal results of evaluating rest parameters should be
caught and passed to the reject callback function.
To resolve this problem, we should allow the emitted RestParameterNode be
wrapped
by the catch handler for promise. However, we should remove `m_restParameter`
and
emit rest parameter byte code in
`initializeDefaultParameterValuesAndSetupFunctionScopeStack`
if we can prove that change has no side effect. In that case, we can only use
one
exception handler.
Current fix is to add another exception handler. And move the handler byte
codes to
the bottom of code block in order to make other byte codes as much compact as
possible.
Input:
```
async function f(arg0, ...[[]]) { }
f();
```
Dumped Byte Codes:
```
...
bb#2
Predecessors: [ #1 ]
[ 20] mov dst:loc9, src:<JSValue()>(const0)
...
bb#3
Predecessors: [ #2 ]
[ 29] get_rest_length dst:loc11, numParametersToSkip:1
...
bb#12
Predecessors: [ #8 #9 #10 ]
[ 138] new_func_exp dst:loc10, scope:loc4, functionDecl:0
...
bb#13
Predecessors: [ ]
[ 170] catch exception:loc10, thrownValue:loc8
[ 174] jmp targetLabel:8(->182)
Successors: [ #15 ]
bb#14
Predecessors: [ #7 #11 ]
[ 176] catch exception:loc10, thrownValue:loc8
[ 180] jmp targetLabel:2(->182)
Successors: [ #15 ]
bb#15
Predecessors: [ #13 #14 ]
[ 182] mov dst:loc12, src:Undefined(const1)
...
Exception Handlers:
1: { start: [ 20] end: [ 29] target: [ 170] } synthesized catch
2: { start: [ 29] end: [ 138] target: [ 176] } synthesized catch
```
* JSTests/stress/catch-rest-parameter.js: Added.
(throwError):
(shouldThrow):
(async f):
(throwError.async f):
(throwError.async let):
(async let):
(x.async f):
(x):
(async shouldThrow):
* Source/JavaScriptCore/bytecompiler/BytecodeGenerator.cpp:
(JSC::BytecodeGenerator::BytecodeGenerator):
(JSC::BytecodeGenerator::initializeDefaultParameterValuesAndSetupFunctionScopeStack):
* Source/JavaScriptCore/bytecompiler/BytecodeGenerator.h:
Canonical link: https://commits.webkit.org/256864@main
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