use parsing is weird?

[aryairani]

Describe and demonstrate the bug

scratch/main> builtins.merge

addOne : Nat -> Nat
addOne n1 =
  use Nat +
    n1 + 1

-- parses the same as:

addOne' : Nat -> Nat
addOne' n1 = 
  use Nat + n1 +
  1

-- when it was meant to parse as:

addOne'' : Nat -> Nat
addOne'' n =
  use Nat +
  n + 1


> addOne 5
> addOne' 5
> addOne'' 5

  Loading changes detected in scratch.u.

  I found and typechecked these definitions in scratch.u. If you
  do an `add` or `update`, here's how your codebase would
  change:

    ⍟ These new definitions are ok to `add`:
    
      addOne   : Nat -> Nat
      addOne'  : Nat -> Nat
      addOne'' : Nat -> Nat

  Now evaluating any watch expressions (lines starting with
  `>`)... Ctrl+C cancels.

    17 | > addOne 5
           ⧩
           1

    18 | > addOne' 5
           ⧩
           1

    19 | > addOne'' 5
           ⧩
           6

UCM should at least give an error, not split the use line arbitrarily at the nat literal.

Screenshots
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Environment (please complete the following information):

• 0.5.29

Additional context

[aryairani]

reported by @Ash-the-practical-programmer and @kylegoetz

[kylegoetz]

I also checked

addOne n1 =
  use Nat +
    n1 + 1 |> (_ -> Debug.trace "n1" n1)

to see if n1 was possibly somehow a valid hash for something in Nat, but UCM reports

I couldn't figure out what Nat.n1 refers to here:
  
      4 |     n1 + 1 |> (_ -> Debug.trace "n1" n1)

so it looks like it is just no error on non-existent import