unreachable_code

What it does

Detects code that can never be executed because it appears after control flow statements like return, break, or next, or in branches that cannot be reached.

Why is this bad?

Unreachable code indicates a logic error or dead code that should be removed. It clutters the codebase, confuses readers, and may indicate unintended behavior.

Unreachable code can only be detected in functions.

Example

foo <- function(x) {
  return(x + 1)
  print("hi")  # unreachable
}

foo <- function(x) {
  for (i in 1:10) {
    x <- x + 1
    if (x > 10) {
       break
       print("x is greater than 10") # unreachable
    }
  }
}

foo <- function(x) {
  if (x > 5) {
    return("hi")
  } else {
    return("bye")
  }
  1 + 1 # unreachable
}