Drop showAlways on UncheckedTypePattern

Author: dwijnand

Diff for: compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -897,7 +897,6 @@ extends Message(PatternMatchExhaustivityID) {
 
 class UncheckedTypePattern(argType: Type, whyNot: String)(using Context)
   extends PatternMatchMsg(UncheckedTypePatternID) {
-  override def showAlways = true
   def msg(using Context) = i"the type test for $argType cannot be checked at runtime because $whyNot"
   def explain(using Context) =
     i"""|Type arguments and type refinements are erased during compile time, thus it's

Diff for: tests/warn/enum-approx2.check

@@ -1,5 +1,5 @@
 -- [E030] Match case Unreachable Warning: tests/warn/enum-approx2.scala:7:12 -------------------------------------------
-7 |    case Fun(x: Exp[Int => String]) => ??? // warn: unreachable            // warn: unchecked
+7 |    case Fun(x: Exp[Int => String]) => ??? // warn: unreachable            // also: unchecked (hidden)
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |         Unreachable case
 -- [E121] Pattern Match Warning: tests/warn/enum-approx2.scala:8:9 -----------------------------------------------------
@@ -12,9 +12,3 @@
   |the type test for Fun[Int, Double] cannot be checked at runtime because its type arguments can't be determined from Exp[Int => Int]
   |
   | longer explanation available when compiling with `-explain`
--- [E092] Pattern Match Unchecked Warning: tests/warn/enum-approx2.scala:7:13 ------------------------------------------
-7 |    case Fun(x: Exp[Int => String]) => ??? // warn: unreachable            // warn: unchecked
-  |             ^
-  |the type test for Exp[Int => String] cannot be checked at runtime because its type arguments can't be determined from Exp[Int => Int]
-  |
-  | longer explanation available when compiling with `-explain`

Diff for: tests/warn/enum-approx2.scala

@@ -4,7 +4,7 @@ case class Fun[A, B](f: Exp[A => B]) extends Exp[A => B]
 class Test {
   def eval(e: Fun[Int, Int]) = e match {
     case Fun(x: Fun[Int, Double]) => ???                                   // warn: unchecked
-    case Fun(x: Exp[Int => String]) => ??? // warn: unreachable            // warn: unchecked
+    case Fun(x: Exp[Int => String]) => ??? // warn: unreachable            // also: unchecked (hidden)
     case _ =>                              // warn: unreachable-only-null
   }
 }

Diff for: tests/warn/i16451.check

@@ -1,9 +1,9 @@
 -- [E030] Match case Unreachable Warning: tests/warn/i16451.scala:14:9 -------------------------------------------------
-14 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
+14 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // also: unchecked (hidden)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         Unreachable case
 -- [E030] Match case Unreachable Warning: tests/warn/i16451.scala:22:9 -------------------------------------------------
-22 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
+22 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // also: unchecked (hidden)
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |         Unreachable case
 -- [E092] Pattern Match Unchecked Warning: tests/warn/i16451.scala:13:9 ------------------------------------------------
@@ -12,24 +12,12 @@
    |the type test for Wrapper[(Color.Red : Color)] cannot be checked at runtime because its type arguments can't be determined from Wrapper[Color]
    |
    | longer explanation available when compiling with `-explain`
--- [E092] Pattern Match Unchecked Warning: tests/warn/i16451.scala:14:9 ------------------------------------------------
-14 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
-   |         ^
-   |the type test for Wrapper[(Color.Green : Color)] cannot be checked at runtime because its type arguments can't be determined from Wrapper[Color]
-   |
-   | longer explanation available when compiling with `-explain`
 -- [E092] Pattern Match Unchecked Warning: tests/warn/i16451.scala:21:9 ------------------------------------------------
 21 |    case x: Wrapper[Color.Red.type]   => Some(x)                      // warn: unchecked
    |         ^
    |the type test for Wrapper[(Color.Red : Color)] cannot be checked at runtime because its type arguments can't be determined from Any
    |
    | longer explanation available when compiling with `-explain`
--- [E092] Pattern Match Unchecked Warning: tests/warn/i16451.scala:22:9 ------------------------------------------------
-22 |    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
-   |         ^
-   |the type test for Wrapper[(Color.Green : Color)] cannot be checked at runtime because its type arguments can't be determined from Any
-   |
-   | longer explanation available when compiling with `-explain`
 -- [E092] Pattern Match Unchecked Warning: tests/warn/i16451.scala:25:9 ------------------------------------------------
 25 |    case x: Wrapper[Color.Red.type] => Some(x) // error: unreachable // error: unchecked
    |         ^

Diff for: tests/warn/i16451.scala

@@ -11,15 +11,15 @@ case class Wrapper[A](value: A)
 object Test:
   def test_correct(x: Wrapper[Color]): Option[Wrapper[Color.Red.type]] = x match
     case x: Wrapper[Color.Red.type]   => Some(x)                      // warn: unchecked
-    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
+    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // also: unchecked (hidden)
 
   def test_different(x: Wrapper[Color]): Option[Wrapper[Color]] = x match
     case x @ Wrapper(_: Color.Red.type)   => Some(x)
     case x @ Wrapper(_: Color.Green.type) => None
 
   def test_any(x: Any): Option[Wrapper[Color.Red.type]] = x match
     case x: Wrapper[Color.Red.type]   => Some(x)                      // warn: unchecked
-    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // warn: unchecked
+    case x: Wrapper[Color.Green.type] => None    // warn: unreachable // also: unchecked (hidden)
 
   def test_wrong(x: Wrapper[Color]): Option[Wrapper[Color.Red.type]] = x match
     case x: Wrapper[Color.Red.type] => Some(x) // error: unreachable // error: unchecked