Always use Map for int64 keys

[zhuscat]

message Foo {
  map<int64, int64> bar = 1;
}

is generated to

export interface Foo {
  bar: { [key: Long]: Long }
}

when --ts_proto_opt=forceLong=long

This is a type error:

An index signature parameter type must be 'string', 'number', 'symbol', or a template literal type.

[stephenh]

Hey @zhuscat ; thanks for the report. That's a good find.

We already have some code that will use a JS map, which is enabled with:

--ts_proto_opt=useMapType=true

It would probably be a good idea to always use the map type for longs, even if useMapType=false.

If you'd like to submit a PR for that fix, that'd be great!

Otherwise just using useMapType=true should unblock you for now, I think.

[stephenh]

This should be fixed by #905 in the next release, thanks @buzap !