lambdas are actually a (very mild) code smell
Lambdas alone are not a code smell. That is like saying Objects or Functions or even naming things is a code smell just because you can use them in bad ways. It is just to broad a statement to be useful. At best you might say that large/complex anonymous lambdas are a code smell - just like large/complex and badly named functions are. You need to be specific about code smells, otherwise you are basically saying code is a code smell.
Well, remember, a code smell isn’t something that’s inherently bad, it’s “a hint that something might be wrong”.
I’m not saying that anyone should flag lambdas as a problem in code review, just that when you see one, it’s probably worth taking a second to ask yourself if a named function would make more sense.
It is such a weak smell though you might as well look at any bit of code you have and ask yourself if it is bad code. Lambdas are fine in a lot of places and the existence of them is not an indication of good or bad code. It is just a tool that can be used in lots of situations.
A better smell here is excessive inlineing causing a loss of context. Does not matter if it is a lambda, or a parameter to a function call, or a field in a object creation. None of those are signs of bad code, but if you cannot understand what something anonymous is doing you might want to give it a name. This does not mean creating a named function, but might just be assigning the lambda or parameter to a variable so it is named.
But on the flip side I find it you are struggling to name something then that can also be a smell that maybe it should just be inlined. Giving everything a name can create just as bad code as trying to inline everything. There is a balance in the middle somewhere. And the presence of a lambda does not really hint as to which way you want to go. So its existence is a very poor marker for code quality.
it’s probably worth taking a second to ask yourself
You can extend this to all code, not just lambdas. Any code you can take a second to ask yourself if you could write it better or more readable. If that is the bar then all code has a very weak code smell and singling out lambdas here seems arbitrary.