Ensure that integer values we parse fit inside the declared integer type.

Clones _p making a new copy of it. This does not mutate the called on cell */

Use this instead of assert to break on a condition and still be able to continue in the debugger.

Used by type-checker to and optimizer. If it returns true, sets val to a value that gives the correct True(). Also sets correct scalar values.

fun_idx is 0..N-1 imports followed by N..M-1 defined functions.