Re: chain of exceptions, next method

[Ali Çehreli via Digitalmars-d-learn]

On 8/13/22 15:59, kdevel wrote:
> Quote from `src/druntime/src`:
>
> ```
>      /**
>       * Returns:
>       * A reference to the _next error in the list. This is used when 
a new
>       * $(D Throwable) is thrown from inside a $(D catch) block. The
> originally
>       * caught $(D Exception) will be chained to the new $(D Throwable)
> via this
>       * field.
>       */
>      @property inout(Throwable) next() @safe inout return scope pure
> nothrow @nogc { return nextInChain; }
>
> ```
This automatic "combining" of exceptions happens for cleanup code like 
scope(exit). (I remember bug(s) for scope(failure).):

import std.stdio;

void foo() {
  // Bug? Should work for scope(failure) as well.
  scope (exit) {
    bar();
  }
  throw new Exception("from foo");
}

void bar() {
  throw new Exception("from bar");
}

void main() {
  try {
    foo();

  } catch (Exception exc) {
    for (Throwable e = exc; e; e = e.next) {
      writeln(e.msg);
    }
  }
}

The output:

from foo
from bar

You can do the same by calling chainTogether(). Here is an excerpt from 
an old experiment of mine:

      try {
        foo();

      } catch (Throwable exc) {
        Throwable.chainTogether(exc, new Exception(" ... "));
        throw exc;
      }

Ali