Roc crashed: ... does not implement ... without type annotation

[HajagosNorbert]

Source main.roc (same behavior with differently named file)

main! = |_args| {
  # uncommenting this line solves the crash
  # x : Dec
  x = 3
  _a = x.to_u64()
  Ok({})
}

$ roc version
Roc compiler version debug-e19771d2

$ uname -a
Linux desktop-nixos 6.18.15 #1-NixOS SMP PREEMPT_DYNAMIC Fri Feb 27 21:05:10 UTC 2026 x86_64 GNU/Linux

$ roc --no-cache repro.roc
Roc crashed: Builtin.Num.Dec does not implement to_u64

after uncommenting the type annotation:

$ roc repro.roc
-- MISSING METHOD --------------------------------

This to_u64 method is being called on a value whose type doesn't have that method:
   ┌─ /home/ez/code/examples-roc/examples/TowersOfHanoi/repro.roc:11:10
   │
11 │   _a = x.to_u64()
   │          ^^^^^^

The value's type, which does not have a method named to_u64, is:

    Dec

Hint: For this to work, the type would need to have a method named to_u64 associated with it in the type's declaration.