Only record in MatchTypeTrace if not previously attempted

`recurseWith` can be called with the same scrutinee (even if match type reduction is cached) if it is an applied match alias

For example, `Tuple.Head[Tuple.Tail[T]]` will attempt to reduce `Tuple.Tail[T]` twice:
- once as an argument of the match alias `Head`, and
- once as a scrutinee in body of `Head` (after the substitution).

Author: EugeneFlesselle

compiler/src/dotty/tools/dotc/core/MatchTypeTrace.scala

@@ -78,7 +78,7 @@ object MatchTypeTrace:
    */
   def recurseWith(scrut: Type)(op: => Type)(using Context): Type =
     ctx.property(MatchTrace) match
-      case Some(trace) =>
+      case Some(trace) if !trace.entries.contains(TryReduce(scrut)) =>
         val prev = trace.entries
         trace.entries = TryReduce(scrut) :: prev
         val res = op

tests/neg/i12049.check

@@ -46,12 +46,6 @@
    |
    |                        case t1 *: t2 *: ts => Tuple.Concat[Reverse[ts], (t2, t1)]
    |                        case EmptyTuple => EmptyTuple
-   |                      trying to reduce  Reverse[A *: EmptyTuple.type]
-   |                      failed since selector A *: EmptyTuple.type
-   |                      matches none of the cases
-   |
-   |                        case t1 *: t2 *: ts => Tuple.Concat[Reverse[ts], (t2, t1)]
-   |                        case EmptyTuple => EmptyTuple
    |
    | longer explanation available when compiling with `-explain`
 -- [E172] Type Error: tests/neg/i12049.scala:24:20 ---------------------------------------------------------------------
@@ -95,12 +89,6 @@
    |
    |                                case t1 *: t2 *: ts => Tuple.Concat[Reverse[ts], (t2, t1)]
    |                                case EmptyTuple => EmptyTuple
-   |                              trying to reduce  Reverse[A *: EmptyTuple.type]
-   |                              failed since selector A *: EmptyTuple.type
-   |                              matches none of the cases
-   |
-   |                                case t1 *: t2 *: ts => Tuple.Concat[Reverse[ts], (t2, t1)]
-   |                                case EmptyTuple => EmptyTuple
 -- [E008] Not Found Error: tests/neg/i12049.scala:28:21 ----------------------------------------------------------------
 28 |val _ = (??? : M[B]).length // error
    |        ^^^^^^^^^^^^^^^^^^^

tests/neg/i17944.check

@@ -14,33 +14,3 @@
    |  Therefore, reduction cannot advance to the remaining case
    |
    |    case _ *: t => test.FindField0[t, ("i" : String), scala.compiletime.ops.int.S[(0 : Int)]]
-   |  trying to reduce  test.FindField[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String)]
-   |  trying to reduce  test.FindField0[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String), (0 : Int)]
-   |  failed since selector (("s" : String) ->> String, ("i" : String) ->> Int)
-   |  does not match  case (("i" : String) ->> f) *: _ => (f, (0 : Int))
-   |  and cannot be shown to be disjoint from it either.
-   |  Therefore, reduction cannot advance to the remaining case
-   |
-   |    case _ *: t => test.FindField0[t, ("i" : String), scala.compiletime.ops.int.S[(0 : Int)]]
-   |  trying to reduce  test.FindField0[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String), (0 : Int)]
-   |  failed since selector (("s" : String) ->> String, ("i" : String) ->> Int)
-   |  does not match  case (("i" : String) ->> f) *: _ => (f, (0 : Int))
-   |  and cannot be shown to be disjoint from it either.
-   |  Therefore, reduction cannot advance to the remaining case
-   |
-   |    case _ *: t => test.FindField0[t, ("i" : String), scala.compiletime.ops.int.S[(0 : Int)]]
-   |  trying to reduce  test.FindField[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String)]
-   |  trying to reduce  test.FindField0[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String), (0 : Int)]
-   |  failed since selector (("s" : String) ->> String, ("i" : String) ->> Int)
-   |  does not match  case (("i" : String) ->> f) *: _ => (f, (0 : Int))
-   |  and cannot be shown to be disjoint from it either.
-   |  Therefore, reduction cannot advance to the remaining case
-   |
-   |    case _ *: t => test.FindField0[t, ("i" : String), scala.compiletime.ops.int.S[(0 : Int)]]
-   |  trying to reduce  test.FindField0[(("s" : String) ->> String, ("i" : String) ->> Int), ("i" : String), (0 : Int)]
-   |  failed since selector (("s" : String) ->> String, ("i" : String) ->> Int)
-   |  does not match  case (("i" : String) ->> f) *: _ => (f, (0 : Int))
-   |  and cannot be shown to be disjoint from it either.
-   |  Therefore, reduction cannot advance to the remaining case
-   |
-   |    case _ *: t => test.FindField0[t, ("i" : String), scala.compiletime.ops.int.S[(0 : Int)]]