Repository navigation
Rest declarations in destructured arrays receiving incorrect types from tuples declaring the types in the destructured array #16700
Description
TypeScript Version: 2.3.4
Code
public async action([res, commandName, ...roleNames]: [ResourceLoader, string, string[]]): Promise<void> { ... }Expected behavior:
When destructuring the method parameter (which can be an array of potentially anything after middleware has had its say, but I know exactly what it will be in this case) I've gathered the remaining array values (which I know to be strings) into roleNames and declared the type of the variables in the destructured array via the tuple [ResourceLoader, string, string[]].
I expect roleNames to take on the declared type from the tuple as res and commandName have correctly done.
Actual behavior:
When hovering over the roleNames declaration I get the following:
var roleNames: (string | ResourceLoader | string[])[]Apologies for the convoluted title. Couldn't think of a less verbose description.
Activity
DanielRosenwasser commentedon Mar 22, 2018
The type
[ResourceLoader, string, string[]]probably isn't what you had in mind. What you really want is an open-ended tuple where all of the trailing elements are known to bestrings.Generally related is #5453.
zajrik commentedon Mar 23, 2018
I've actually recently re-engineered the code in question because it allowed me to merge the functionality of two separate things into one, so I'm actually just receiving a string where
...roleNamesused to exist and parsing potentially multiple roles within the function body, but I am still interested in a resolution to this problem.I'm not entirely sure what you mean by open-ended tuple. Given what you've linked is a proposal, is this something that is possible in current TS?
ahejlsberg commentedon Jun 26, 2018
Now implemented in #24897.
zajrik commentedon Jul 22, 2018
I somehow missed seeing this get closed, but I saw this change in the 3.0 RC and thought "Hey, that was my issue!"
Glad to see this resolved. Cheers 🎉