`val` binding causes unexpected type escape or effect mismatch in presence of `local` effect

[amistozy]

Description:
When I write the following code:

fun test(action)
  var i := 0
  val res = action()
  res

I get the following compiler error:

abstract type(s) escape(s) into the context
term         :   var i := 0
                 val res = action()
                 res
inferred type: () -> <local<$h>|_e> _a
hint         : give a higher-rank type annotation to a function parameter?

So I try to fix it by adding a type annotation:

fun test(action : () -> e a) : e a
  var i := 0
  val res = action()
  res

However, this gives a different error:

effects do not match
context        :   var i := 0
                   val res = action()
                   res
term           :   val res = action()
                   res
inferred effect: $e
expected effect: <local<_h>|_e1>

Surprisingly, if I inline the call to action() without a val binding, the code compiles and runs fine:

fun test(action)
  var i := 0
  action()

This behavior is confusing.

Expected behavior:
The presence or absence of a val binding for the result of action() should not affect whether type or effect inference succeeds. The two forms should be equivalent from the perspective of effects and region scoping.

Environment:

• Koka version: v3.1.3-alpha14
• OS: Windows 11

Minimal reproduction:

fun test(action)
  var i := 0
  val res = action()
  res

Thanks!

[TimWhiting]

Definitely a bug, but a workaround for now is:

fun test(action)
  var i := 0
  val res = mask<local>{action()}
  res

[JanBeh]

I think I ran into a similar or the same issue that boiled down to this:

fun main()
  var a := ()
  fun inner()
    // commenting out either(!) of the following two lines works:
    a := ()
    var b := ()
    ()
  inner()

Using Koka version 3.2.2 (39b4bec), I get:

var-bug.kk(5, 5): type error: abstract type(s) escape(s) into the context
  term         :     a := ()
  inferred type: () -> <local<$h>|_e> ()
  hint         : give a higher-rank type annotation to a function parameter?

Failed to compile var-bug.kk

Not sure if this is the same issue, or a different problem.