bugfix: highlight enum cases correctly

[Cherry-picked aca2503]

Author: kasiaMarek

Diff for: presentation-compiler/src/main/dotty/tools/pc/PcCollector.scala

@@ -194,6 +194,13 @@ abstract class PcCollector[T](
       case (df: NamedDefTree) :: _
           if df.nameSpan.contains(pos.span) && !isGeneratedGiven(df) =>
         Some(symbolAlternatives(df.symbol), pos.withSpan(df.nameSpan))
+      /* enum cases with params
+       * enum Foo:
+       *  case B@@ar[A](i: A)
+       */
+      case (df: NamedDefTree) :: Template(_, _, self, _) :: _
+          if (df.name == nme.apply || df.name == nme.unapply) && df.nameSpan.isZeroExtent =>
+        Some(symbolAlternatives(self.tpt.symbol), self.sourcePos)
       /**
        * For traversing annotations:
        * @JsonNo@@tification("")

Diff for: presentation-compiler/test/dotty/tools/pc/tests/highlight/DocumentHighlightSuite.scala

@@ -998,3 +998,23 @@ class DocumentHighlightSuite extends BaseDocumentHighlightSuite:
          |    def double2(ys: List[EF]) = <<xs>> ++ ys
          |end extension""".stripMargin
     )
+
+  @Test def `enum-cases` =
+    check(
+      """|enum MyOption:
+         |  case <<My@@Some>>(value: Int)
+         |  case MyNone
+         |
+         |val alpha = MyOption.<<MySome>>(1)
+         |""".stripMargin
+    )
+
+  @Test def `enum-cases2` =
+    check(
+      """|enum MyOption:
+         |  case <<My@@Some>>[U](value: U)
+         |  case MyNone
+         |
+         |val alpha = MyOption.<<MySome>>(1)
+         |""".stripMargin,
+    )