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-Wnonunit-statement setting for dotty (scala#16936)
`-Wnonunit-statement` warns about discarded values in statement positions (Somewhat a supplement to `-Wvalue-discard` and a stronger version of pure expression warnings)
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198 changes: 198 additions & 0 deletions
198
tests/neg-custom-args/fatal-warnings/nonunit-statement.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,198 @@ | ||
| // scalac: -Wnonunit-statement -Wvalue-discard | ||
| import collection.ArrayOps | ||
| import collection.mutable.{ArrayBuilder, LinkedHashSet, ListBuffer} | ||
| import concurrent._ | ||
| import scala.reflect.ClassTag | ||
|
|
||
| class C { | ||
| import ExecutionContext.Implicits._ | ||
| def c = { | ||
| def improved = Future(42) | ||
| def stale = Future(27) | ||
| improved // error | ||
| stale | ||
| } | ||
| } | ||
| class D { | ||
| def d = { | ||
| class E | ||
| new E().toString // error | ||
| new E().toString * 2 | ||
| } | ||
| } | ||
| class F { | ||
| import ExecutionContext.Implicits._ | ||
| Future(42) // error | ||
| } | ||
| // unused template expression uses synthetic method of class | ||
| case class K(s: String) { | ||
| copy() // error | ||
| } | ||
| // mutations returning this are ok | ||
| class Mutate { | ||
| val b = ListBuffer.empty[Int] | ||
| b += 42 // nowarn, returns this.type | ||
| val xs = List(42) | ||
| 27 +: xs // error | ||
|
|
||
| def f(x: Int): this.type = this | ||
| def g(): Unit = f(42) // nowarn | ||
| } | ||
| // some uninteresting expressions may warn for other reasons | ||
| class WhoCares { | ||
| null // error for purity | ||
| ??? // nowarn for impurity | ||
| } | ||
| // explicit Unit ascription to opt out of warning, even for funky applies | ||
| class Absolution { | ||
| def f(i: Int): Int = i+1 | ||
| import ExecutionContext.Implicits._ | ||
| // Future(42): Unit // nowarn { F(42)(ctx) }: Unit where annot is on F(42) | ||
| // f(42): Unit // nowarn | ||
| } | ||
| // warn uni-branched unless user disables it with -Wnonunit-if:false | ||
| class Boxed[A](a: A) { | ||
| def isEmpty = false | ||
| def foreach[U](f: A => U): Unit = | ||
| if (!isEmpty) f(a) // error (if) | ||
| def forall(f: A => Boolean): Unit = | ||
| if (!isEmpty) { | ||
| println(".") | ||
| f(a) // error (if) | ||
| } | ||
| def take(p: A => Boolean): Option[A] = { | ||
| while (isEmpty || !p(a)) () | ||
| Some(a).filter(p) | ||
| } | ||
| } | ||
| class Unibranch[A, B] { | ||
| def runWith[U](action: B => U): A => Boolean = { x => | ||
| val z = null.asInstanceOf[B] | ||
| val fellback = false | ||
| if (!fellback) action(z) // error (if) | ||
| !fellback | ||
| } | ||
| def f(i: Int): Int = { | ||
| def g = 17 | ||
| if (i < 42) { | ||
| g // error block statement | ||
| println("uh oh") | ||
| g // error (if) | ||
| } | ||
| while (i < 42) { | ||
| g // error | ||
| println("uh oh") | ||
| g // error | ||
| } | ||
| 42 | ||
| } | ||
| } | ||
| class Dibranch { | ||
| def i: Int = ??? | ||
| def j: Int = ??? | ||
| def f(b: Boolean): Int = { | ||
| // if-expr might have an uninteresting LUB | ||
| if (b) { // error, at least one branch looks interesting | ||
| println("true") | ||
| i | ||
| } | ||
| else { | ||
| println("false") | ||
| j | ||
| } | ||
| 42 | ||
| } | ||
| } | ||
| class Next[A] { | ||
| val all = ListBuffer.empty[A] | ||
| def f(it: Iterator[A], g: A => A): Unit = | ||
| while (it.hasNext) | ||
| all += g(it.next()) // nowarn | ||
| } | ||
| class Setting[A] { | ||
| def set = LinkedHashSet.empty[A] | ||
| def f(a: A): Unit = { | ||
| set += a // error because cannot know whether the `set` was supposed to be consumed or assigned | ||
| println(set) | ||
| } | ||
| } | ||
| // neither StringBuilder warns, because either append is Java method or returns this.type | ||
| // while loop looks like if branch with block1(block2, jump to label), where block2 typed as non-unit | ||
| class Strung { | ||
| def iterator = Iterator.empty[String] | ||
| def addString(b: StringBuilder, start: String, sep: String, end: String): StringBuilder = { | ||
| val jsb = b.underlying | ||
| if (start.length != 0) jsb.append(start) // error (value-discard) | ||
| val it = iterator | ||
| if (it.hasNext) { | ||
| jsb.append(it.next()) | ||
| while (it.hasNext) { | ||
| jsb.append(sep) // nowarn (java) | ||
| jsb.append(it.next()) // error (value-discard) | ||
| } | ||
| } | ||
| if (end.length != 0) jsb.append(end) // error (value-discard) | ||
| b | ||
| } | ||
| def f(b: java.lang.StringBuilder, it: Iterator[String]): String = { | ||
| while (it.hasNext) { | ||
| b.append("\n") // nowarn (java) | ||
| b.append(it.next()) // error (value-discard) | ||
| } | ||
| b.toString | ||
| } | ||
| def g(b: java.lang.StringBuilder, it: Iterator[String]): String = { | ||
| while (it.hasNext) it.next() // error | ||
| b.toString | ||
| } | ||
| } | ||
| class J { | ||
| import java.util.Collections | ||
| def xs: java.util.List[Int] = ??? | ||
| def f(): Int = { | ||
| Collections.checkedList[Int](xs, classOf[Int]) | ||
| 42 | ||
| } | ||
| } | ||
| class Variant { | ||
| var bs = ListBuffer.empty[Int] | ||
| val xs = ListBuffer.empty[Int] | ||
| private[this] val ys = ListBuffer.empty[Int] | ||
| private[this] var zs = ListBuffer.empty[Int] | ||
| def f(i: Int): Unit = { | ||
| bs.addOne(i) | ||
| xs.addOne(i) | ||
| ys.addOne(i) | ||
| zs.addOne(i) | ||
| println("done") | ||
| } | ||
| } | ||
| final class ArrayOops[A](private val xs: Array[A]) extends AnyVal { | ||
| def other: ArrayOps[A] = ??? | ||
| def transpose[B](implicit asArray: A => Array[B]): Array[Array[B]] = { | ||
| val aClass = xs.getClass.getComponentType | ||
| val bb = new ArrayBuilder.ofRef[Array[B]]()(ClassTag[Array[B]](aClass)) | ||
| if (xs.length == 0) bb.result() | ||
| else { | ||
| def mkRowBuilder() = ArrayBuilder.make[B](ClassTag[B](aClass.getComponentType)) | ||
| val bs = new ArrayOps(asArray(xs(0))).map((x: B) => mkRowBuilder()) | ||
| for (xs <- other) { | ||
| var i = 0 | ||
| for (x <- new ArrayOps(asArray(xs))) { | ||
| bs(i) += x | ||
| i += 1 | ||
| } | ||
| } | ||
| for (b <- new ArrayOps(bs)) bb += b.result() | ||
| bb.result() | ||
| } | ||
| } | ||
| } | ||
| class Depends { | ||
| def f[A](a: A): a.type = a | ||
| def g() = { | ||
| val d = new Depends | ||
| f(d) | ||
| () | ||
| } | ||
| } |