Remove error that cannot appear anymore

Now that we do not support the old syntax for splicing types it is not
possible to get this error. The code is buggy and fails with another
error that is not worth testing.

Author: nicolasstucki

compiler/src/dotty/tools/dotc/ast/Desugar.scala

@@ -1911,8 +1911,6 @@ object desugar {
         new UntypedTreeTraverser {
           def traverse(tree: untpd.Tree)(using Context): Unit = tree match {
             case Splice(expr) => collect(expr)
-            case TypSplice(expr) =>
-              report.error(TypeSpliceInValPattern(expr), tree.srcPos)
             case _ => traverseChildren(tree)
           }
         }.traverse(expr)

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

@@ -19,8 +19,8 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case TypeMismatchID // errorNumber: 7
   case NotAMemberID // errorNumber: 8
   case EarlyDefinitionsNotSupportedID // errorNumber: 9
-  case TopLevelImplicitClassID extends ErrorMessageID(isActive = false) // errorNumber: 10 
-  case ImplicitCaseClassID // errorNumber: 11 
+  case TopLevelImplicitClassID extends ErrorMessageID(isActive = false) // errorNumber: 10
+  case ImplicitCaseClassID // errorNumber: 11
   case ImplicitClassPrimaryConstructorArityID // errorNumber: 12
   case ObjectMayNotHaveSelfTypeID // errorNumber: 13
   case TupleTooLongID extends ErrorMessageID(isActive = false) // errorNumber: 14
@@ -97,7 +97,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case FunctionTypeNeedsNonEmptyParameterListID // errorNumber: 85
   case WrongNumberOfParametersID // errorNumber: 86
   case DuplicatePrivateProtectedQualifierID // errorNumber: 87
-  case ExpectedStartOfTopLevelDefinitionID // errorNumber: 88 
+  case ExpectedStartOfTopLevelDefinitionID // errorNumber: 88
   case MissingReturnTypeWithReturnStatementID // errorNumber: 89
   case NoReturnFromInlineableID // errorNumber: 90
   case ReturnOutsideMethodDefinitionID // errorNumber: 91
@@ -164,7 +164,7 @@ enum ErrorMessageID(val isActive: Boolean = true) extends java.lang.Enum[ErrorMe
   case ExtensionCanOnlyHaveDefsID // errorNumber: 152
   case UnexpectedPatternForSummonFromID // errorNumber: 153
   case AnonymousInstanceCannotBeEmptyID // errorNumber: 154
-  case TypeSpliceInValPatternID // errorNumber: 155
+  case TypeSpliceInValPatternID extends ErrorMessageID(isActive = false) // errorNumber: 155
   case ModifierNotAllowedForDefinitionID // errorNumber: 156
   case CannotExtendJavaEnumID // errorNumber: 157
   case InvalidReferenceInImplicitNotFoundAnnotationID // errorNumber: 158

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

@@ -2447,15 +2447,6 @@ import transform.SymUtils._
            |""".stripMargin
   }
 
-  class TypeSpliceInValPattern(expr:  untpd.Tree)(using Context)
-    extends SyntaxMsg(TypeSpliceInValPatternID) {
-    def msg = "Type splices cannot be used in val patterns. Consider using `match` instead."
-    def explain =
-      em"""|Type splice: `$$${expr.show}` cannot be used in a `val` pattern. Consider rewriting the `val` pattern
-           |as a `match` with a corresponding `case` to replace the `val`.
-           |""".stripMargin
-  }
-
   class ModifierNotAllowedForDefinition(flag: Flag)(using Context)
     extends SyntaxMsg(ModifierNotAllowedForDefinitionID) {
     def msg = em"Modifier ${hl(flag.flagsString)} is not allowed for this definition"