Make -Wunused:patvars to unsafe

- Suppress -Wunused:patvars
- Replace by -Wunused:unsafe-warn-patvars

Author: PaulCoral

compiler/src/dotty/tools/dotc/config/ScalaSettings.scala

@@ -171,18 +171,24 @@ private sealed trait WarningSettings:
         name = "imports",
         description = "Warn if an import selector is not referenced.\n" +
         "NOTE : overrided by -Wunused:strict-no-implicit-warn"),
-      ChoiceWithHelp("patvars","Warn if a variable bound in a pattern is unused"),
-      ChoiceWithHelp("privates","Warn if a private member is unused"),
-      ChoiceWithHelp("locals","Warn if a local definition is unused"),
-      ChoiceWithHelp("explicits","Warn if an explicit parameter is unused"),
-      ChoiceWithHelp("implicits","Warn if an implicit parameter is unused"),
-      ChoiceWithHelp("params","Enable -Wunused:explicits,implicits"),
-      ChoiceWithHelp("linted","Enable -Wunused:imports,privates,locals,implicits"),
-      ChoiceWithHelp(
-        name = "strict-no-implicit-warn",
-        description = "Same as -Wunused:import, only for imports of explicit named members.\n" +
-        "NOTE : This overrides -Wunused:imports and NOT set by -Wunused:all"
-      )
+        ChoiceWithHelp("privates","Warn if a private member is unused"),
+        ChoiceWithHelp("locals","Warn if a local definition is unused"),
+        ChoiceWithHelp("explicits","Warn if an explicit parameter is unused"),
+        ChoiceWithHelp("implicits","Warn if an implicit parameter is unused"),
+        ChoiceWithHelp("params","Enable -Wunused:explicits,implicits"),
+        ChoiceWithHelp("linted","Enable -Wunused:imports,privates,locals,implicits"),
+        ChoiceWithHelp(
+          name = "strict-no-implicit-warn",
+          description = "Same as -Wunused:import, only for imports of explicit named members.\n" +
+          "NOTE : This overrides -Wunused:imports and NOT set by -Wunused:all"
+        ),
+        // ChoiceWithHelp("patvars","Warn if a variable bound in a pattern is unused"),
+        ChoiceWithHelp(
+          name = "unsafe-warn-patvars",
+          description = "(UNSAFE) Warn if a variable bound in a pattern is unused.\n" +
+          "This warning can generate false positive, as warning cannot be\n" +
+          "suppressed yet."
+        )
     ),
     default = Nil
   )
@@ -206,7 +212,8 @@ private sealed trait WarningSettings:
     def privates(using Context) =
       allOr("privates") || allOr("linted")
     def patvars(using Context) =
-      allOr("patvars")
+      isChoiceSet("unsafe-warn-patvars") // not with "all"
+      // allOr("patvars") // todo : rename once fixed
     def linted(using Context) =
       allOr("linted")
     def strictNoImplicitWarn(using Context) =

tests/neg-custom-args/fatal-warnings/i15503d.scala

@@ -1,4 +1,5 @@
-// scalac: -Wunused:patvars
+// scalac: -Wunused:unsafe-warn-patvars
+// todo : change to :patvars
 
 sealed trait Calc
 sealed trait Const extends Calc
@@ -8,10 +9,22 @@ 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
 }
+
+// todo : This should pass in the future
+// val b = for {
+//   case Some(x) <- Option(Option(1))
+// } println(s"$x")
+
+// todo : This should *NOT* pass in the future
+// val c = for {
+//   case Some(x) <- Option(Option(1))
+// } println(s"hello world")

tests/neg-custom-args/fatal-warnings/i15503i.scala

@@ -29,10 +29,11 @@ class A {
     def g = 4 // OK
     y + g
 
-  def g(x: Int): Int = x match
-    case x:1 => 0 // error
-    case x:2 => x // OK
-    case _ => 1 // OK
+  // todo : uncomment once patvars is fixed
+  // def g(x: Int): Int = x match
+  //   case x:1 => 0 // ?error
+  //   case x:2 => x // ?OK
+  //   case _ => 1 // ?OK
 }
 
 /* ---- CHECK scala.annotation.unused ---- */