unison/unison-src/transcripts/todo-bug-builtins.output.md

The todo and bug builtin

todo and bug have type a -> b. They take a message or a value of type a and crash during runtime displaying a in ucm.

> todo "implement me later"

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

  💔💥
  
  I've encountered a call to builtin.todo with the following
  value:
  
    "implement me later"
  
  I'm sorry this message doesn't have more detail about the
  location of the failure. My makers plan to fix this in a
  future release. 😢

> bug "there's a bug in my code"

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

  💔💥
  
  I've encountered a call to builtin.bug with the following
  value:
  
    "there's a bug in my code"
  
  I'm sorry this message doesn't have more detail about the
  location of the failure. My makers plan to fix this in a
  future release. 😢

Todo

todo is useful if you want to come back to a piece of code later but you want your project to compile.

complicatedMathStuff x = todo "Come back and to something with x here"

  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`:
    
      complicatedMathStuff : x -> r

Bug

bug is used to indicate that a particular branch is not expected to execute.

test = match true with
    true -> "Yay"
    false -> bug "Wow, that's unexpected"

  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`:
    
      test : Text