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simple: flag unnecessary assignment to the blank identifier #253
Description
While debugging code, one (at least I do) often temporarily stops using a variable and assigns it to the blank identifier to shut up the compiler. For example:
x1, x2 := fn()
_ = x1
// use(x1)
use(x2)
As debugging continues and code is uncommented, this may result in
x1, x2 := fn()
_ = x1
use(x1)
use(x2)
with a leftover, unnecessary assignment to _. It might be desirable to flag this.
Reacted by Ainar Garipov
Activity
dmitshur commentedon Jan 17, 2018
One thing that immediately comes to mind is that you’ll want to be careful about expressions that may panic. Removing them would change program behavior (potentially significantly, if there’d be no panic otherwise).
There are some false positives to avoid, such as “early bound checks”, e.g.:
https://gotools.org/encoding/binary#binary.go-L68
Otherwise, this seems like a nice
simplecheck. (That said, personally, I don’t often find myself leaving such unnecessary assignments to blank identifier after finishing debugging or development.)dominikh commentedon Jan 18, 2018
We'll limit it to identifiers that are local variables; no function calls or indexing or the like. That should get rid of any false positives.
mvdan commentedon Jan 18, 2018
I have forgotten about these a couple of times myself too. If the decision is about "is this useful", it has my thumbs up.
Perhaps
printandprintlnshould be in the same boat somehow, as in general they should never be used in production code and tend to be u 55F2 sed for debugging. But those tend to be harder to miss, as you are likely to see the debug output.