[Issue 17379] Mangle voldemort types as if they are defined in the outer scope to avoid exponential symbol name length with templates

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17379

Steven Schveighoffer <schveiguy at yahoo.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|WONTFIX                     |---

--- Comment #7 from Steven Schveighoffer <schveiguy at yahoo.com> ---
Reopening, in case someone wishes to tackle this issue with the hairy problems
it has.

The largest blocking issue to getting this to work is if you have 2 overloads
of the same function template (this is completely made up, but something
similar would cause problems):

auto foo(T)(T t, int x)
{
   static struct Result {T t; int x;}
   return Result(t, x);
}

auto foo(T)(T t, string x)
{
  static struct Result {T t; string x;}
  return Result(t, x);
}

If you refactor this, then the Result struct doesn't get properly mangled -- it
only depends on the template itself. This will produce 2 identical manglings
for the 2 functions.

Note that if you do actually do the refactoring here (move the Result outside
the function), the current compiler simply doesn't redefine the Result struct
-- it considers it fully defined in the first overload.

So a user would not refactor both, he would get errors on his compilation. But
the compiler that was just adjusting the mangling would cause other problems.

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