Instantiate for wildcards in paramInstances

Author: dwijnand

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

@@ -3095,7 +3095,7 @@ class TrackingTypeComparer(initctx: Context) extends TypeComparer(initctx) {
     def paramInstances(canApprox: Boolean) = new TypeAccumulator[Array[Type]]:
       def apply(insts: Array[Type], t: Type) = t match
         case param @ TypeParamRef(b, n) if b eq caseLambda =>
-          def range1(tp: Type) = if variance == 0 then tp else Range(tp, tp)
+          def range1(tp: Type) = if variance == 0 || param.paramName.is(NameKinds.WildcardParamName) then tp else Range(tp, tp)
           insts(n) =
             if canApprox then
               approximation(param, fromBelow = variance >= 0, Int.MaxValue).simplified

compiler/test/dotty/tools/dotc/interactive/CustomCompletionTests.scala

@@ -36,7 +36,7 @@ class CustomCompletionTests extends DottyTest:
         initialCtx.fresh
           .addMode(Mode.ReadPositions | Mode.Interactive)
           // discard errors - comment out this line to print them in the console
-          .setReporter(new StoreReporter(dotc.reporting.Reporter.NoReporter))
+          .setReporter(new StoreReporter(null))
           .setSetting(initialCtx.settings.YstopAfter, List("typer"))
       )
       val file = SourceFile.virtual("<completions>", allCode, maybeIncomplete = true)

tests/neg/i11982a.check

@@ -7,10 +7,9 @@
   |
   |                                    trying to reduce  Tuple.Tail[X]
   |                                    failed since selector X
-  |                                    does not uniquely determine parameters _, xs in
+  |                                    does not uniquely determine parameter xs in
   |                                      case _ *: xs => xs
-  |                                    The computed bounds for the parameters are:
-  |                                      _ >: Any
+  |                                    The computed bounds for the parameter are:
   |                                      xs >: Any *: EmptyTuple.type <: Tuple
   |
   | longer explanation available when compiling with `-explain`
@@ -23,10 +22,9 @@
    |
    |                                        trying to reduce  Tuple.Tail[X]
    |                                        failed since selector X
-   |                                        does not uniquely determine parameters _, xs in
+   |                                        does not uniquely determine parameter xs in
    |                                          case _ *: xs => xs
-   |                                        The computed bounds for the parameters are:
-   |                                          _ >: Any
+   |                                        The computed bounds for the parameter are:
    |                                          xs >: Any *: EmptyTuple.type <: Tuple
    |
    | longer explanation available when compiling with `-explain`
@@ -39,10 +37,9 @@
    |
    |                           trying to reduce  Tuple.Tail[X]
    |                           failed since selector X
-   |                           does not uniquely determine parameters _, xs in
+   |                           does not uniquely determine parameter xs in
    |                             case _ *: xs => xs
-   |                           The computed bounds for the parameters are:
-   |                             _ >: Any
+   |                           The computed bounds for the parameter are:
    |                             xs >: Any *: EmptyTuple.type <: Tuple
    |
    | longer explanation available when compiling with `-explain`