On: Wrong by Default

[shhsshs]

Java’s `throws` keyword comes to mind. It forces you to handle exceptions or explicitly declare that you expect the exception to be handled by a method higher up the call stack.

Your strongly-typed suggestion seems better. But you’d have to somehow allow for cases where a function opens a file, does something with it, and also expects the file to be closed by a higher function. Perhaps something like:

    PleaseDeferMe<File> BeginWrite() {
      PleaseDeferMe<File> p = File.open(...);
      // unsafe! Make sure to return p to the calling function so this gets called with “defer” at some point 
      File f = unwrapDefer p;
      f.Write(some header)
      return p
    }

[adrianmonk → shhsshs]

Yeah, or I guess you could pass some object in:

   File BeginWrite(DeferTrustee t) {
     PleaseDeferMe<File> p = File.open(...);
     File f = t.defer p;
     f.Write(some header);
     return f;
   }

And then the caller would look something like:

   void WriteWholeFile() {
     DeferTrustee t = defer; // defers to the end of this function
     File f = BeginWrite(t);
     f.Write(the body);
   }

Then you can still defer before anything else and avoid unsafe situations.