[JulianMorrison]

It sounds like nested error handling will be the abnormal case and the "default" error handling will often be normal. That is, all you will notice in common use is that the boilerplate "if" is replaced with a "check".

It also sounds like the nesting does not escape the function itself. It always either returns error, or doesn't.

[floatingsmoke]

Well, How about multiple return values? How will "check" keyword handle return values other than error?

  func ReadFile(path string) (string, error) {
    b, err := ioutil.ReadFile(path)
    s := string(b[:])
    return s, err
  }

How this function would be written regarding to drafts?. I am really confused.

[SaidinWoT]

The draft doesn't include any actual examples with multiple returns on a function that uses check internally, but the behavior is fully specified:

> A check returns from the enclosing function by returning the result of invoking the handler chain with the error value.

> A return statement in a handler causes the enclosing function to return immediately with the given return values. A return without values is only allowed if the enclosing function has no results or uses named results. In the latter case, the function returns with the current values of those results.

> A handler chain function takes an argument of type error and has the same result signature as the function for which it is defined.

> If the enclosing function has result parameters, it is a compile-time error if the handler chain for any check is not guaranteed to execute a return statement.

So any handler defined in ReadFile would be required to return (string, error) or not include a return at all (such that other handlers got their chance to interact with the error).

[secure]

check returns all non-error return values, so the function would be written as:

  func ReadFile(path string) (string, error) {
    b := check ioutil.ReadFile(path)
    return string(b), nil
  }

[bloomer]

A handle block has access to all variables that are in scope. So if you have partial results that you want to return is a check fails you can return them in the handle block if they are already declared/assigned. The easier way to handle this is using named return variables which are always in scope. If no partial results have been assigned then they will be returned as zero values otherwise the partial results can be set.

[JulianMorrison]

What you're thinking of is the default handler (because if you wrote a handler, it would be your code returning things).

The default handler will populate the last element of the return list with the error, and return.

The other elements get zeroes, if not named, or they are unchanged from how they have already been set, if named.