Reuse & switch to UncheckedTypePattern

compiler/src/dotty/tools/dotc/reporting/messages.scala

@@ -895,9 +895,9 @@ extends Message(PatternMatchExhaustivityID) {
   }
 }
 
-class UncheckedTypePattern(msgFn: => String)(using Context)
+class UncheckedTypePattern(argType: Type, whyNot: String)(using Context)
   extends PatternMatchMsg(UncheckedTypePatternID) {
-  def msg(using Context) = msgFn
+  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
         |impossible to check them at run-time.

compiler/src/dotty/tools/dotc/transform/TypeTestsCasts.scala

@@ -363,7 +363,7 @@ object TypeTestsCasts {
           if !isTrusted && !isUnchecked then
             val whyNot = whyUncheckable(expr.tpe, argType, tree.span)
             if whyNot.nonEmpty then
-              report.uncheckedWarning(em"the type test for $argType cannot be checked at runtime because $whyNot", expr.srcPos)
+              report.uncheckedWarning(UncheckedTypePattern(argType, whyNot), expr.srcPos)
           transformTypeTest(expr, argType,
             flagUnrelated = enclosingInlineds.isEmpty) // if test comes from inlined code, dont't flag it even if it always false
         }

tests/neg/15981.check

@@ -1,4 +1,6 @@
--- Error: tests/neg/15981.scala:4:45 -----------------------------------------------------------------------------------
+-- [E092] Pattern Match Error: tests/neg/15981.scala:4:45 --------------------------------------------------------------
 4 |    override def equals(any: Any): Boolean = any.isInstanceOf[PosInt] // error
   |                                             ^^^
   |                                  the type test for PosInt cannot be checked at runtime because it's a local class
+  |
+  | longer explanation available when compiling with `-explain`

tests/neg/i12253.check

@@ -1,9 +1,13 @@
--- Error: tests/neg/i12253.scala:13:10 ---------------------------------------------------------------------------------
+-- [E092] Pattern Match Error: tests/neg/i12253.scala:13:10 ------------------------------------------------------------
 13 |     case extractors.InlinedLambda(_, Select(_, name)) => Expr(name) // error // error
    |          ^
    |the type test for extractors.q2.reflect.Term cannot be checked at runtime because it refers to an abstract type member or type parameter
--- Error: tests/neg/i12253.scala:13:38 ---------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i12253.scala:13:38 ------------------------------------------------------------
 13 |     case extractors.InlinedLambda(_, Select(_, name)) => Expr(name) // error // error
    |                                      ^
    |the type test for q1.reflect.Select cannot be checked at runtime because it refers to an abstract type member or type parameter
+   |
+   | longer explanation available when compiling with `-explain`
 there was 1 deprecation warning; re-run with -deprecation for details

tests/neg/i16728.check

@@ -1,4 +1,6 @@
--- Error: tests/neg/i16728.scala:18:11 ---------------------------------------------------------------------------------
+-- [E092] Pattern Match Error: tests/neg/i16728.scala:18:11 ------------------------------------------------------------
 18 |      case tx : C[Int]#X => // error
    |           ^
    |     the type test for C[Int] cannot be checked at runtime because its type arguments can't be determined from A
+   |
+   | longer explanation available when compiling with `-explain`

tests/neg/i4812.check

@@ -1,28 +1,42 @@
--- Error: tests/neg/i4812.scala:8:11 -----------------------------------------------------------------------------------
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:8:11 --------------------------------------------------------------
 8 |      case prev: A => // error: the type test for A cannot be checked at runtime
   |           ^
   |           the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:18:11 ----------------------------------------------------------------------------------
+  |
+  | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:18:11 -------------------------------------------------------------
 18 |      case prev: A => // error: the type test for A cannot be checked at runtime
    |           ^
    |           the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:28:11 ----------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:28:11 -------------------------------------------------------------
 28 |      case prev: A => // error: the type test for A cannot be checked at runtime
    |           ^
    |           the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:38:11 ----------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:38:11 -------------------------------------------------------------
 38 |      case prev: A => // error: the type test for A cannot be checked at runtime
    |           ^
    |           the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:50:13 ----------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:50:13 -------------------------------------------------------------
 50 |        case prev: A => // error: the type test for A cannot be checked at runtime
    |             ^
    |             the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:60:11 ----------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:60:11 -------------------------------------------------------------
 60 |      case prev: A => // error: the type test for A cannot be checked at runtime
    |           ^
    |           the type test for A cannot be checked at runtime because it's a local class
--- Error: tests/neg/i4812.scala:96:11 ----------------------------------------------------------------------------------
+   |
+   | longer explanation available when compiling with `-explain`
+-- [E092] Pattern Match Error: tests/neg/i4812.scala:96:11 -------------------------------------------------------------
 96 |      case x: B => // error: the type test for B cannot be checked at runtime
    |           ^
    |           the type test for B cannot be checked at runtime because it's a local class
+   |
+   | longer explanation available when compiling with `-explain`

tests/neg/nowarn.check

@@ -66,10 +66,12 @@ Matching filters for @nowarn or -Wconf:
 49 |def t7c = f             // warning (deprecation)
    |          ^
    |          method f is deprecated
--- Unchecked Warning: tests/neg/nowarn.scala:55:7 ----------------------------------------------------------------------
+-- [E092] Pattern Match Unchecked Warning: tests/neg/nowarn.scala:55:7 -------------------------------------------------
 55 |  case _: List[Int] => 0 // warning (patmat, unchecked)
    |       ^
    |the type test for List[Int] cannot be checked at runtime because its type arguments can't be determined from Any
+   |
+   | longer explanation available when compiling with `-explain`
 -- Error: tests/neg/nowarn.scala:33:1 ----------------------------------------------------------------------------------
 33 |@nowarn("id=1") def t4d = try 1 // error and warning (unused nowarn, wrong id)
    |^^^^^^^^^^^^^^^