Clarification on migration to value types and boxed vs unboxed representations

[John Rose]

On Jan 5, 2015, at 6:02 PM, Vitaly Davidovich <vitalyd at gmail.com> wrote:
> Also, you can just as well get lost writes with immutable objects if you forget to reassign the variable with the result of a mutating operation.

The risks are in some sense complementary.  But IMO this one, unlike the aliasing problem, is easy to check for statically:

class ImmutableComplex { ...
   @Preserve
   ImmutableComplex add(ImmutableComplex that) {
     return new ImmutableComplex(this.re + that.re, this.im + that.im);
   }
}

class String { ...
  @Preserve
  String concat(String str) { ... }
}

void dufus(String s) {
  s.concat(" more!");  // javac says Warning: discarding a preserved value
  return s;
}

— John