User can copy Java code as text and paste into MPS editor as base language.
There are 3 modes of such a paste: paste as class, paste as methods and paste as statements.
If a user selects an appropriate paste mode and all names in the copied piece of code are known then the pasted base language code is fully legal.
If a user selects some statements and pastes as methods or selects several methods and pastes as statements MPS will not break but the result of paste will be strange.
Unresolved names from copied code are pasted as unresolved references with an appropriate resolve info.