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Invalid code generation for top-level await with newline (expression duplicated) #39186
Description
TypeScript Version: Nightly
Search Terms: top-level await newline duplicate duplicated
Code
export let foo = () => {
console.log('called')
return Promise.resolve(123)
}
export let bar = await
foo()Expected behavior:
The generated code should only call foo() once.
Actual behavior:
The generated code calls foo() twice:
export let foo = () => {
console.log('called');
return Promise.resolve(123);
};
export let bar = await foo();
foo();This may lead to subtle correctness bugs. This only happens when there's a newline between the await keyword and the awaited expression. This also only happens for top-level await. Enclosing the await in an async function makes the bug disappear.
Playground Link: link
Related Issues:
Activity
RyanCavanaugh commentedon Jun 22, 2020
Ron Buckton (@rbuckton) big emit bug here
rbuckton commentedon Jun 22, 2020
Hmm. Not an emit bug, but a bug in the reparse for top-level await due to newline handling probably. I'll investigate.
rbuckton commentedon Jun 22, 2020
Ryan Cavanaugh (@RyanCavanaugh):
There's a "quick solution" and a "good solution":
expression expectederror following theawait. This is undesirable, but is also no worse than the behavior in 3.9.I'm investigating the "good solution" currently, and if it looks like it will take more than the rest of the day to implement I would advise we implement the "quick solution" for the 4.0 beta.
RyanCavanaugh commentedon Jun 23, 2020
If we already shipped this in 3.9 then I'm OK waiting for the "good solution"
rbuckton commentedon Jun 23, 2020
This wasn't in 3.9, its is a bug in the change in 4.0 to reparse
awaitin the top-level of a module.