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remove built-in async function infrastructure from this proposal (#245)
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michaelficarra committed Oct 24, 2022
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Expand Up @@ -127,105 +127,6 @@ <h1>Well-Known Intrinsic Objects</h1>
</emu-table>
</emu-clause>

<emu-clause id="sec-built-in-function-objects">
<h1>Built-in Function Objects</h1>

<p>
<del>If a built-in function object is not implemented as an ECMAScript function it must provide [[Call]] and [[Construct]] internal methods that conform to the following definitions:</del>
<ins>Unless otherwise specified, a built-in function object must provide [[Call]] and [[Construct]] internal methods that conform to the following definitions:</ins>
</p>

<emu-clause id="sec-createbuiltinfunction" type="abstract operation">
<h1>
CreateBuiltinFunction (
_behaviour_: an Abstract Closure, a set of algorithm steps, or some other definition of a function's behaviour provided in this specification,
_length_: a non-negative integer or +&infin;,
_name_: a property key or a Private Name,
_additionalInternalSlotsList_: a List of names of internal slots,
optional _realm_: a Realm Record,
optional _prototype_: an Object or *null*,
optional _prefix_: a String,
): a function object
</h1>
<dl class="header">
<dt>description</dt>
<dd>_additionalInternalSlotsList_ contains the names of additional internal slots that must be defined as part of the object. This operation creates a built-in function object.</dd>
</dl>
<emu-alg>
1. If _realm_ is not present, set _realm_ to the current Realm Record.
1. If _prototype_ is not present, set _prototype_ to _realm_.[[Intrinsics]].[[%Function.prototype%]].
1. Let _internalSlotsList_ be a List containing the names of all the internal slots that <emu-xref href="#sec-built-in-function-objects"></emu-xref> requires for the built-in function object that is about to be created.
1. Append to _internalSlotsList_ the elements of _additionalInternalSlotsList_.
1. <ins>If _behaviour_ is described as async, then</ins>
1. <ins>Let _func_ be a new built-in async function object that, when called, performs the action described by _behaviour_ using the provided arguments as the values of the corresponding parameters specified by _behaviour_. The new function object has internal slots whose names are the elements of _internalSlotsList_, and an [[InitialName]] internal slot.</ins>
1. <ins>Else,</ins>
1. Let _func_ be a new built-in function object that, when called, performs the action described by _behaviour_ using the provided arguments as the values of the corresponding parameters specified by _behaviour_. The new function object has internal slots whose names are the elements of _internalSlotsList_, and an [[InitialName]] internal slot.
1. Set _func_.[[Prototype]] to _prototype_.
1. Set _func_.[[Extensible]] to *true*.
1. Set _func_.[[Realm]] to _realm_.
1. Set _func_.[[InitialName]] to *null*.
1. Perform SetFunctionLength(_func_, _length_).
1. If _prefix_ is not present, then
1. Perform SetFunctionName(_func_, _name_).
1. Else,
1. Perform SetFunctionName(_func_, _name_, _prefix_).
1. Return _func_.
</emu-alg>
<p>Each built-in function defined in this specification is created by calling the CreateBuiltinFunction abstract operation.</p>
</emu-clause>
</emu-clause>

<emu-clause id="sec-built-in-async-function-objects">
<h1>Built-in Async Function Objects</h1>
<p><dfn variants="built-in async function object,built-in async function objects">Built-in async function objects</dfn> are built-in function objects that provide alternative [[Call]] and [[Construct]] internal methods that conform to the following definitions:</p>

<emu-clause id="sec-built-in-function-objects-call-thisargument-argumentslist" type="internal method">
<h1>
[[Call]] (
_thisArgument_: an ECMAScript language value,
_argumentsList_: a List of ECMAScript language values,
): a normal completion containing an ECMAScript language value
</h1>
<dl class="header">
<dt>for</dt>
<dd>a built-in async function object _F_</dd>
</dl>
<emu-alg>
1. Let _callerContext_ be the running execution context.
1. If _callerContext_ is not already suspended, suspend _callerContext_.
1. Let _calleeContext_ be a new execution context.
1. Set the Function of _calleeContext_ to _F_.
1. Let _calleeRealm_ be _F_.[[Realm]].
1. Set the Realm of _calleeContext_ to _calleeRealm_.
1. Set the ScriptOrModule of _calleeContext_ to *null*.
1. Perform any necessary implementation-defined initialization of _calleeContext_.
1. Push _calleeContext_ onto the execution context stack; _calleeContext_ is now the running execution context.
1. Let _promiseCapability_ be ! NewPromiseCapability(%Promise%).
1. Let _resultsClosure_ be a new Abstract Closure that captures _F_, _thisArgument_, and _argumentsList_ and performs the following steps when called:
1. Return the result of evaluating _F_ in a manner that conforms to the specification of _F_. _thisArgument_ is the *this* value, _argumentsList_ provides the named parameters, and the NewTarget value is *undefined*.
1. Perform AsyncFunctionStart(_promiseCapability_, _resultsClosure_).
1. Remove _calleeContext_ from the execution context stack and restore _callerContext_ as the running execution context.
1. Return _promiseCapability_.
</emu-alg>
</emu-clause>

<emu-clause id="sec-built-in-function-objects-construct-argumentslist-newtarget" type="internal method">
<h1>
[[Construct]] (
_argumentsList_: a List of ECMAScript language values,
_newTarget_: a constructor,
): either a normal completion containing an Object or a throw completion
</h1>
<dl class="header">
<dt>for</dt>
<dd>a built-in async function object _F_</dd>
</dl>
<emu-alg>
1. Throw a *TypeError* exception.
</emu-alg>
</emu-clause>
</emu-clause>

<emu-clause id="sec-abstract-operations">
<h1>Abstract Operations</h1>

Expand Down Expand Up @@ -1118,72 +1019,6 @@ <h1>AsyncIterator.prototype [ @@toStringTag ]</h1>
</emu-clause>
</emu-clause>
</emu-clause>

<emu-clause id="sec-async-function-objects">
<h1>AsyncFunction Objects</h1>

<emu-clause id="sec-async-functions-abstract-operations">
<h1>Async Functions Abstract Operations</h1>

<emu-clause id="sec-async-functions-abstract-operations-async-function-start" type="abstract operation">
<h1>
AsyncFunctionStart (
_promiseCapability_: a PromiseCapability Record,
_asyncFunctionBody_: a |FunctionBody| Parse Node or an |ExpressionBody| Parse Node <ins>or an Abstract Closure with no parameters</ins>,
): ~unused~
</h1>
<dl class="header">
</dl>
<emu-alg>
1. Let _runningContext_ be the running execution context.
1. Let _asyncContext_ be a copy of _runningContext_.
1. NOTE: Copying the execution state is required for AsyncBlockStart to resume its execution. It is ill-defined to resume a currently executing context.
1. Perform AsyncBlockStart(_promiseCapability_, _asyncFunctionBody_, _asyncContext_).
1. Return ~unused~.
</emu-alg>
</emu-clause>

<emu-clause id="sec-asyncblockstart" type="abstract operation">
<h1>
AsyncBlockStart (
_promiseCapability_: a PromiseCapability Record,
_asyncBody_: a Parse Node <ins>or an Abstract Closure with no parameters</ins>,
_asyncContext_: an execution context,
)
</h1>
<dl class="header">
</dl>
<emu-alg>
1. Assert: _promiseCapability_ is a PromiseCapability Record.
1. Let _runningContext_ be the running execution context.
1. [fence-effects="user-code"] Set the code evaluation state of _asyncContext_ such that when evaluation is resumed for that execution context the following steps will be performed:
1. <ins>If _asyncBody_ is a Parse Node, then</ins>
1. <ins>Let _result_ be the result of evaluating _asyncBody_.</ins>
1. <ins>Else,</ins>
1. <ins>Assert: _asyncBody_ is an Abstract Closure with no parameters.</ins>
1. <ins>Let _result_ be _asyncBody_().</ins>
1. <ins>If _result_ is a normal completion, then</ins>
1. <ins>Set _result_ to Completion Record { [[Type]]: ~return~, [[Value]]: _result_.[[Value]], [[Target]]: ~empty~ }.</ins>
1. <del>Let _result_ be the result of evaluating _asyncBody_.</del>
1. Assert: If we return here, the async function either threw an exception or performed an implicit or explicit return; all awaiting is done.
1. Remove _asyncContext_ from the execution context stack and restore the execution context that is at the top of the execution context stack as the running execution context.
1. If _result_.[[Type]] is ~normal~, then
1. Perform ! Call(_promiseCapability_.[[Resolve]], *undefined*, « *undefined* »).
1. Else if _result_.[[Type]] is ~return~, then
1. Perform ! Call(_promiseCapability_.[[Resolve]], *undefined*, « _result_.[[Value]] »).
1. Else,
1. Assert: _result_.[[Type]] is ~throw~.
1. Perform ! Call(_promiseCapability_.[[Reject]], *undefined*, « _result_.[[Value]] »).
1. [id="step-asyncblockstart-return-undefined"] Return.
1. Push _asyncContext_ onto the execution context stack; _asyncContext_ is now the running execution context.
1. <emu-meta effects="user-code">Resume the suspended evaluation of _asyncContext_</emu-meta>. Let _result_ be the value returned by the resumed computation.
1. Assert: When we return here, _asyncContext_ has already been removed from the execution context stack and _runningContext_ is the currently running execution context.
1. Assert: _result_ is a normal completion with a value of *undefined*. The possible sources of completion values are Await or, if the async function doesn't await anything, step <emu-xref href="#step-asyncblockstart-return-undefined"></emu-xref> above.
1. Return.
</emu-alg>
</emu-clause>
</emu-clause>
</emu-clause>
</emu-clause>

<emu-clause id="sec-new-asyncgenerator-aos">
Expand Down

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