Doubly so for building compilers, or compiler-like programs (a long chain of intermediate representations, with lots of little transformations from one to the n

Doubly so for building compilers, or compiler-like programs (a long chain of intermediate representations, with lots of little transformations from one to the next). Adding a new type of node, in a language with ADTs, leads to compile-time breakage I can fix. In a language where exhaustiveness errors are caught at runtime, it's like building on quicksand.