this will probably explode if this would reach public API surface, with tslib setup for compat packages this should be removed as WeakMap is part of ts definitions

@Hotell I need to port utility functions with zero changes so that we can't introduce any bugs for partners. I don't expect it to ever be exported. Is the tslib WeakMap the exact same implementation? If not, then I think I need to leave this in here.

I understand what's at play here but we might be forced to do some changes in order to not clash with v9 (not this case). I double-check the .d.ts rolluped bundle emit and it is not exposed so we are good with this one.

is the tslib WeakMap the exact same implementation?

obviously it's not :D it's strongly typed with generics and other jazz

but because it's declared like this declare class it would clash with existing typescript lib definitions

if it would be declared as interface global override ( allowed behaviour in TS ) it dangerous approach as it would affect whole application codebase , that's why I pointed this out.

hope it's more clear now.