Interesting. So, if I'm understanding this correctly - Truffle allows a language designer to specify a certain logical layout for data structures, along with hints for how this will get converted to a physical memory layout. Language implementors also get the full power of Graal for lowering their AST to machine code and other compiler tasks. On cross-language boundaries, it generates automatic accessors for other languages to access that data, using the logical layout to identify how particular fields need to be pulled out and manipulated, but not requiring that the full data structure be converted across the foreign-call boundary. One consequence of this is that nesting & embedding of data structures may require an explicit conversion, since if an object is a hashtable in Javascript but a packed series of fields in C, it's obviously not going to fit.

Sorta like SWIG++? If you could do SWIG but never require that an end-user write a typemap or debug a crash themself, there'd probably be a big market for that.