truthy on nillable types does not produce the correct results

[geekrelief]

https://play.nim-lang.org/#ix=3MaY

elvis/elvis.nim

Line 19 in 09e536d

template truthy*[T](val: T): bool = not compiles(val.isNil())

The implementation uses compile: https://nim-lang.github.io/Nim/system.html#compiles%2Cuntyped, which always returns true if val is a nillable type, but we want to actually check not val.isNil at runtime.

This will produce the expected results for nillable types.

# true if not isNil()
template truthy*[T](val: ref T): bool = not val.isNil
template truthy*[T](val: ptr T): bool = not val.isNil
template truthy*(val: pointer): bool = not val.isNil

[mattaylor]

fixed

[geekrelief]

I think we still need the old version too otherwise the array test won't pass.

elvis/tests.nim

Line 31 in c9e74b3

test "not empty seq": check(?[0])

That should say not empty array since a seq literal needs an @ prefix. Then again doing a truthy check on an array is kinda weird.

But if you put:

template truthy*[T](val: T): bool = not compiles(val.isNil())

Back then array[N, T] can match against it.

[mattaylor]

done - and updated tests

[geekrelief]

cool, created a PR to clean up things based on a forum response from Hlaaftana. https://forum.nim-lang.org/t/8806#57402

[mattaylor]

good stuff - merged and ive added some extra tests and fixes for mutable chains like pop
thanks for your help!

[mattaylor]

I was trying to add condition access support for functions with extra args eg table.get(key), (see commented out tests) but Ive no idea how to capture the relevant args in the template to test. Do you know how this could be done, or do you think this would require a macro?