From a3c7b7753f3955c58df5d0f4b29d7d25c4820e61 Mon Sep 17 00:00:00 2001
From: Szymon Rodziewicz <szymonrodant@gmail.com>
Date: Mon, 2 Oct 2023 15:13:36 +0200
Subject: [PATCH] Add -Wall option

---
 .../tools/dotc/config/ScalaSettings.scala     | 12 ++--
 .../dotty/tools/dotc/config/Settings.scala    | 19 +++++-
 tests/neg/i18559.scala                        | 67 +++++++++++++++++++
 3 files changed, 93 insertions(+), 5 deletions(-)
 create mode 100644 tests/neg/i18559.scala

diff --git a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
index 3dbfbfc6bab9..69bbbda5e8c4 100644
--- a/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
+++ b/compiler/src/dotty/tools/dotc/config/ScalaSettings.scala
@@ -159,10 +159,11 @@ private sealed trait WarningSettings:
   import Setting.ChoiceWithHelp
 
   val Whelp: Setting[Boolean] = BooleanSetting("-W", "Print a synopsis of warning options.")
+  val Wall: Setting[Boolean] = BooleanSetting("-Wall", "Enable all warnings")
   val XfatalWarnings: Setting[Boolean] = BooleanSetting("-Werror", "Fail the compilation if there are any warnings.", aliases = List("-Xfatal-warnings"))
-  val WvalueDiscard: Setting[Boolean] = BooleanSetting("-Wvalue-discard", "Warn when non-Unit expression results are unused.")
-  val WNonUnitStatement = BooleanSetting("-Wnonunit-statement", "Warn when block statements are non-Unit expressions.")
-  val WimplausiblePatterns = BooleanSetting("-Wimplausible-patterns", "Warn if comparison with a pattern value looks like it might always fail.")
+  val WvalueDiscard: Setting[Boolean] = BooleanSetting("-Wvalue-discard", "Warn when non-Unit expression results are unused.").overrideWith(Wall)
+  val WNonUnitStatement = BooleanSetting("-Wnonunit-statement", "Warn when block statements are non-Unit expressions.").overrideWith(Wall)
+  val WimplausiblePatterns = BooleanSetting("-Wimplausible-patterns", "Warn if comparison with a pattern value looks like it might always fail.").overrideWith(Wall)
   val Wunused: Setting[List[ChoiceWithHelp[String]]] = MultiChoiceHelpSetting(
     name = "-Wunused",
     helpArg = "warning",
@@ -194,7 +195,10 @@ private sealed trait WarningSettings:
         )
     ),
     default = Nil
-  )
+  ).overrideWith(Wall, {
+    case true => List(ChoiceWithHelp("all", ""))
+    case false => Nil
+  })
   object WunusedHas:
     def isChoiceSet(s: String)(using Context) = Wunused.value.pipe(us => us.contains(s))
     def allOr(s: String)(using Context) = Wunused.value.pipe(us => us.contains("all") || us.contains(s))
diff --git a/compiler/src/dotty/tools/dotc/config/Settings.scala b/compiler/src/dotty/tools/dotc/config/Settings.scala
index 34e5582e8a91..75981e8c1edd 100644
--- a/compiler/src/dotty/tools/dotc/config/Settings.scala
+++ b/compiler/src/dotty/tools/dotc/config/Settings.scala
@@ -63,10 +63,27 @@ object Settings:
     aliases: List[String] = Nil,
     depends: List[(Setting[?], Any)] = Nil,
     propertyClass: Option[Class[?]] = None)(private[Settings] val idx: Int) {
+    
+    private var overridenBy: Option[Setting[_]] = None
+    private var overridenByMapper: Any => T = _
 
     private var changed: Boolean = false
 
-    def valueIn(state: SettingsState): T = state.value(idx).asInstanceOf[T]
+    def valueIn(state: SettingsState): T =
+      overridenBy.map(_.valueIn(state)).map(overridenByMapper)
+        .getOrElse(state.value(idx).asInstanceOf[T])
+
+    def overrideWith(setting: Setting[T]): Setting[T] = {
+      overridenBy = Some(setting)
+      overridenByMapper = _.asInstanceOf[T]
+      this
+    }
+    
+    def overrideWith[A](setting: Setting[A], mapper: A => T): Setting[T] = {
+      overridenBy = Some(setting)
+      overridenByMapper = mapper.asInstanceOf[Any => T]
+      this
+    }
 
     def updateIn(state: SettingsState, x: Any): SettingsState = x match
       case _: T => state.update(idx, x)
diff --git a/tests/neg/i18559.scala b/tests/neg/i18559.scala
new file mode 100644
index 000000000000..da47fe65d14f
--- /dev/null
+++ b/tests/neg/i18559.scala
@@ -0,0 +1,67 @@
+//> using options -Werror -Wall
+
+val b = // OK
+  var e3 = 2 // error
+  1
+
+object FooUnused:
+  import collection.mutable.Set // error
+  import collection.mutable.{Map => MutMap} // error
+  import collection.mutable._ // error
+
+object FooWildcardUnused:
+  import collection.mutable._ // error
+
+object Foo:
+  import collection.mutable.Set // OK
+  import collection.mutable.{Map => MutMap} // OK
+
+  val bar = Set() // OK
+  val baz = MutMap() // OK
+
+sealed trait Calc
+sealed trait Const extends Calc
+case class Sum(a: Calc, b: Calc) extends Calc
+case class S(pred: Const) extends Const
+case object Z extends Const
+
+val a = Sum(S(S(Z)),Z) match {
+  case Sum(a,Z) => Z // error
+  // case Sum(a @ _,Z) => Z // todo : this should pass in the future
+  case Sum(a@S(_),Z) => Z // error
+  case Sum(a@S(_),Z) => a // OK
+  case Sum(a@S(b@S(_)), Z) => a // error
+  case Sum(a@S(b@S(_)), Z) => a // error
+  case Sum(a@S(b@(S(_))), Z) => Sum(a,b) // OK
+  case Sum(_,_) => Z // OK
+  case _ => Z // OK
+}
+
+import scala.util.{Either, Right, Left}
+import scala.collection.mutable
+
+case class Failed(msg: String)
+
+def firstThing(): Either[Failed, Unit] =
+  Right(())
+
+def secondThing(): Either[Failed, Unit] =
+  Left(Failed("whoops you should have flatMapped me"))
+
+def singleExpr(): Either[Failed, Unit] =
+  firstThing().map(_ => secondThing()) // error
+
+def block(): Either[Failed, Unit] = {
+  firstThing().map(_ => secondThing()) // error 
+}
+
+class C {
+  import concurrent._
+  import ExecutionContext.Implicits._
+  def c = {
+    def improved = Future(42)
+    def stale = Future(27)
+    improved  // error
+    stale
+  }
+}
\ No newline at end of file