Allow await in a simple unary expression
#9890
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Please add tests for both of the cases you pointed out. Also, in the future you should consult the bleeding edge spec and spec proposals over any runtimes:
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| @@ -3337,7 +3337,10 @@ namespace ts { | |||
| function parseAwaitExpression() { | |||
| const node = <AwaitExpression>createNode(SyntaxKind.AwaitExpression); | |||
| nextToken(); | |||
| node.expression = parseSimpleUnaryExpression(); | |||
| node.expression = token === SyntaxKind.AwaitKeyword | |||
| // Forbid `await await` | |||
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Why is await await forbidden?
- UnaryExpression
- AwaitExpression
awaitUnaryExpressionawaitAwaitExpressionawaitawaitUnaryExpression
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In the spec it looked like 'await' was specifically exempted from following. Maybe I read that wrong.
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Currently it is not possible for an AwaitExpression and a YieldExpression to be parsed together, so technically passing the ?Yield parameter for UnaryExpression: [+Await]
awaitUnaryExpression[?Yield, Await] is unnecessary. It will probably be useful for AsyncGenerators however.
yield expressions and await expressions can't be mixed because since async generators aren't really a thing at this point, so whether or not it's a valid parse is kind of moot.
Keep in mind, await yield is valid in a plain async function. yield would be parsed as an identifier right there.
If you did have asynchronous generators, yield await 10 would be valid in those contexts, but await yield would not - you'd need to parenthesized the yield keyword.
ghost
assigned | @@ -3386,6 +3386,7 @@ namespace ts { | |||
| * 6) - UnaryExpression[?yield] | |||
| * 7) ~ UnaryExpression[?yield] | |||
| * 8) ! UnaryExpression[?yield] | |||
| * 9) [+Await] await AwaitExpression[?yield] | |||
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It's await UnaryExpression
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Other than fixing up that comment, 👍 |
ghost
merged commit 
Fixes #9877
However, this may not be up to the ES spec. Node.js does not allow
typeof yield foo, so it may be wrong to allowtypeof await foo.On the other hand, babel allows
typeof awaitbut nottypeof yield.