Wrong code generation/memory errors in generic lambda parameters #4168
Description
In the code below, when I define the lambda argument in filter() as box->A!, it works, but when I define it as this->A! it compiles and runs, but the lambda surprisingly does not get called at all.
use @printf[I32](fmt: Pointer[U8] tag, ...)
class ArrayLike[A: Any #read] // Array-like class with .filter() function
embed _data: Array[A] = []
new fromArray(a: Array[A]) =>
var i = USize(0)
while i < a.size() do
try _data.push(a(i = i + 1)?) end
end
fun apply(i: USize): this->A ? => _data(i)?
// works correctly | with box->A!, but is buggy with this->A!
// v
fun filter(f: {(this->A!): Bool}): FilterClass[A, this->ArrayLike[A]]^ =>
FilterClass[A, this->ArrayLike[A]](this, f)
class FilterClass[A: Any #read, B: ArrayLike[A] #read]
new create(array: B, f: {(B->A!): Bool}) =>
try @printf((f(array(0)?).string() + "\n").cstring()) end
class Thingy
actor Main
new create(env: Env) =>
let a: ArrayLike[I32] = ArrayLike[I32].fromArray([0])
let b: ArrayLike[Thingy] = ArrayLike[Thingy].fromArray([Thingy])
let f1 = a.filter({(x) => true})
let f2 = b.filter({(x) => true})with fun filter(f: {(box->A!): Bool}) .. this outputs
true
true
with fun filter(f: {(this->A!): Bool}) .. this outputs
true
false
The false is likely bug: it means that the lambda is NOT called! It is worth pointing out that in a slightly different version of this, where the lambda was supposed to actually filter, most of the time no output was generated with the this->A! version but sometimes random characters appeared (memory corruption?!)