org.wartremover.warts.NoNeedImport.scala Maven / Gradle / Ivy
package org.wartremover
package warts
object NoNeedImport extends WartTraverser {
def apply(u: WartUniverse): u.Traverser = {
import u.universe._
def isRename(origName: Name, rename: Name) = {
val maybeRename = Option(rename) // 'rename' can be null
maybeRename.exists(_ != origName)
}
new Traverser {
override def traverse(tree: Tree): Unit = {
tree match {
case t if hasWartAnnotation(u)(t) =>
// Ignore trees marked by SuppressWarnings
case Import(_, iss) =>
iss.foldLeft(ImportTypeContainer.init) {
case (acc, ImportSelector(termNames.WILDCARD, _, _, _)) =>
// If `import aaa.bbb.{ _ => ccc }` or `import aaa.bbb.{ _ => _ }`
// would be written, it should be the same meaning of
// `import aaa.bbb._` so we don't need to care the 3rd parameter of the `ImportSelector`
acc.copy(existsWildCard = true)
case (acc, ImportSelector(_, _, termNames.WILDCARD, _)) =>
acc.copy(existsNameToWildCard = true)
case (acc, ImportSelector(origName, _, rename, _)) if !isRename(origName, rename) =>
// We are avoiding rename imports like `import aaa.bbb.{ ccc => ddd } since these
// are valid in the context of wildcard imports
acc.copy(existsRegular = true)
case (acc, _) =>
acc
} match {
case ImportTypeContainer(true, true, _) =>
// In this case, there are `import aaa.bbb.{ ccc => _, ddd, _ }`.
// It means that all should be imported except `ccc`.
case ImportTypeContainer(true, false, _) =>
// In case `import aaa.bbb.{ ccc => _, ddd }`,
// a programmer could remove `ccc => _`.
error(u)(tree.pos, "Import into the wildcard(`something => _`) is meaningless. Remove it.")
case ImportTypeContainer(false, true, true) =>
// In case there is a wildcard and at least one regular (non-rename) import
// (the case where there is a renamed import and a wildcard is okay)
error(u)(tree.pos, "The wildcard import exists. Remove other explicitly names of the `import`.")
case _ =>
}
case _ =>
super.traverse(tree)
}
}
}
}
}