[Issue 14210] invalid merging of template instances

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=14210

--- Comment #3 from Ketmar Dark <ketmar at ketmar.no-ip.org> ---
it's ok to instantiate the same template (as the function signatures are the
same). but it's not ok to merge them for CTFE. actually, i have code like this:

===
  import std.traits : isSomeFunction;
  Cell opIndexAssign(DT) (DT dg, string name) if (isSomeFunction!DT) {
    import std.traits : ParameterTypeTuple, ParameterDefaultValueTuple,
ReturnType;
    alias args = ParameterTypeTuple!DT;
    alias retType = ReturnType!DT;
    Cell cfn;
    // default args can be taken only from delegate itself, not from the type,
hence this hack
    alias defaultArguments = ParameterDefaultValueTuple!dg;
    cfn new CellFnX!(DT, defaultArguments)(dg);
    this[name] = cfn;
    return cfn;
  }

private class CellFnX(DT, Defs…) : Cell {
  DT dg;

  this (DT adg) { super(aismacro); dg = adg; }

  override Cell execute (Milf eng, CellCons args) {
    …
    ParameterTypeTuple!DT arguments;
    foreach (auto idx, ref arg; arguments) {
      static if (!is(Defs[idx] == void)) {
        arg = Defs[idx];
      } else {
        arg = Cell.from(args.car);
        args = args.cdr;
      }
    }
  }
}
===

this is CTFE wrapper generator, and with merging like now *each* registered
delegate with the same parameter types will get the same default values. this
kills the whole CTFE wrapper generation idea.

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