LineNever

LineNever is a programming convention used to designate that a particular line or block of code should never be executed during normal operation. It functions as a metadata cue rather than a runtime instruction, guiding compilers, interpreters, and analysis tools to treat the marked code as unreachable. The term is used across multiple language ecosystems through various forms of annotations, pragmas, or macros.

Common forms include pragmas such as #lineNever or // lineNever preceding a statement, language-specific annotations like [LineNever], or inline macros that expand away at compile time. When a line is marked LineNever, static analyzers can warn if the condition that would make the line reachable becomes possible, and optimizers may drop the code from generated binaries or ignore it during instrumentation. Usage may vary by toolchain, so syntax and exact behavior are implementation-specific.

Usage considerations: LineNever is intended for invariants, exhaustive pattern matching, or API usage guarantees where certain paths are logically impossible. It should not be used to conceal bugs; if surrounding logic changes so the line could become reachable, tooling should surface a warning. It does not universally guarantee runtime removal; some environments preserve code for debugging or portability. Tools that support LineNever may differ in how aggressively they drop code or instrumentation.

LineNever is often discussed alongside concepts like unreachable code and dead-code elimination in language design and tooling discussions. It serves as a targeted aid for developers to express intent about non-reachable paths without altering program semantics.