correct-by-construction
/correct-by-construction
For any prompt that presents a class of invalid states, start at the type algebra or public type surface. The type system is the enforcer: compose types so valid states are inhabitable and the class's invalid combinations fail before execution. Then trace the earliest supporting owner and prescribe or implement the structural change that closes the whole class.
"By construction" means the next caller receives a valid value, contract, or route without relying on memory, a final defensive check, or a special workaround. For a class of invalid states, a type composition is the construction fix. A runtime writer, parser, validator, clamp, evaluator, or brand-minting function can be evidence or a residual boundary, never the type-level enforcer or closure proof.