Hi, I'd support the idea of extending the primitive definition. My addition is, to extend the meaning of the corePrimConv field, perhaps to carry the information about external language the Core interacts with (as much as it may be associated with calling convention). I'd like to have ability to pass "javascript" into this field, even though this may break the existing FFI convention (or would it? - are we limited to only ccall and stdcall?). I'd also like to be able to have a free syntax form for foreign identifier (corePrimExternal) (thus being able to wrap calls to methods of Javascript objects such as "new Date.getTime()": foreign import javascript "new Date.getTime" getTime :: ... This would help developers of backends to detect which primitives imported from standard libraries (where they would be "ccall") are OK, and which need to be substituted using Overlays, e. g. ycr2js could complain if it encounters any primitive that uses "ccall". Thanks. PS Hopefully, it is not too late to add suggestions... -- Dimitry Golubovsky Anywhere on the Web