wartremover.warts.NonUnitStatements.scala Maven / Gradle / Ivy
package org.wartremover
package warts
import scala.annotation.tailrec
object NonUnitStatements extends WartTraverser {
def apply(u: WartUniverse): u.Traverser = {
import u.universe._
import scala.reflect.NameTransformer
val ReadName: TermName = "$read"
val IwName: TermName = "$iw"
val NodeBufferAddName: TermName = NameTransformer.encode("&+")
@tailrec
def isClassConstructor(tree: Tree): Boolean = tree match {
case Select(_, nme.CONSTRUCTOR) => true
case Apply(t, _) => isClassConstructor(t)
case _ => false
}
def isIgnoredStatement(tree: Tree) = tree match {
// scala.xml.NodeBuffer#&+ returns NodeBuffer instead of Unit, so
// val x = 5 desugars to a non-Unit statement; ignore.
case Apply(Select(qual, NodeBufferAddName), _)
if qual.symbol.typeSignature =:= typeOf[scala.xml.NodeBuffer] => true
// Scala creates synthetic blocks with calls on classes.
// The calls return Object so we need to ignore them.
case t @ Apply(_, _) => isClassConstructor(t)
// REPL needs this
case Select(Select(Select(Ident(_), ReadName), IwName), IwName) => true
case _ => false
}
def checkUnitLike(statements: List[Tree]): Unit = {
statements.foreach { stat =>
val unitLike = stat.isEmpty || stat.tpe == null || stat.tpe =:= typeOf[Unit] || stat.isDef || isIgnoredStatement(stat)
if (!unitLike)
error(u)(stat.pos, "Statements must return Unit")
}
}
new u.Traverser {
override def traverse(tree: Tree): Unit = {
tree match {
// Ignore trees marked by SuppressWarnings
case t if hasWartAnnotation(u)(t) =>
case Block(statements, _) =>
checkUnitLike(statements)
super.traverse(tree)
case ClassDef(_, _, _, Template((_, _, statements))) =>
checkUnitLike(statements)
super.traverse(tree)
case ModuleDef(_, _, Template((_, _, statements))) =>
checkUnitLike(statements)
super.traverse(tree)
case _ => super.traverse(tree)
}
}
}
}
}