used pragma

Nim produces a warning for symbols that are not exported and not used either. The used pragma can be attached to a symbol to suppress this warning. This is particularly useful when the symbol was generated by a macro:

template implementArithOps(T) =
  proc echoAdd(a, b: T) {.used.} =
    echo a + b
  proc echoSub(a, b: T) {.used.} =
    echo a - b
# no warning produced for the unused 'echoSub'
implementArithOps(int)
echoAdd 3, 5

used can also be used as a top-level statement to mark a module as “used”. This prevents the “Unused import” warning:

# module: debughelper.nim
when defined(nimHasUsed):
  # 'import debughelper' is so useful for debugging
  # that Nim shouldn't produce a warning for that import,
  # even if currently unused:
  {.used.}