Make NamedTuples work under new MatchType spec

Author: odersky

library/src/scala/NamedTuple.scala

@@ -15,6 +15,8 @@ object NamedTuple:
   extension [V <: Tuple](x: V)
     inline def withNames[N <: Tuple]: NamedTuple[N, V] = x
 
+  export NamedTupleDecomposition.{Names, DropNames}
+
   extension [N <: Tuple, V <: Tuple](x: NamedTuple[N, V])
 
     /** The underlying tuple without the names */
@@ -103,14 +105,6 @@ object NamedTuple:
 
   end extension
 
-  /** The names of a named tuple, represented as a tuple of literal string values. */
-  type Names[X <: AnyNamedTuple] <: Tuple = X match
-    case NamedTuple[n, _] => n
-
-  /** The value types of a named tuple represented as a regular tuple. */
-  type DropNames[NT <: AnyNamedTuple] <: Tuple = NT match
-    case NamedTuple[_, x] => x
-
   /** The size of a named tuple, represented as a literal constant subtype of Int */
   type Size[X <: AnyNamedTuple] = Tuple.Size[DropNames[X]]
 
@@ -182,3 +176,16 @@ object NamedTuple:
         NamedTuple[Names[X], Tuple.Zip[DropNames[X], DropNames[Y]]]
 
 end NamedTuple
+
+@experimental
+/** Separate from NamedTuple object so that we can match on the opaque type NamedTuple. */
+object NamedTupleDecomposition:
+  import NamedTuple.*
+
+  /** The names of a named tuple, represented as a tuple of literal string values. */
+  type Names[X <: AnyNamedTuple] <: Tuple = X match
+    case NamedTuple[n, _] => n
+
+  /** The value types of a named tuple represented as a regular tuple. */
+  type DropNames[NT <: AnyNamedTuple] <: Tuple = NT match
+    case NamedTuple[_, x] => x

tests/pos/named-tuples-strawman-2.scala

@@ -62,24 +62,29 @@ object TupleOps:
   inline def concatDistinct[X <: Tuple, Y <: Tuple](xs: X, ys: Y): ConcatDistinct[X, Y] =
     (xs ++ ys.filter[Y, [Elem] =>> ![Contains[X, Elem]]]).asInstanceOf[ConcatDistinct[X, Y]]
 
+object NamedTupleDecomposition:
+  import NamedTupleOps.*
+
+  /** The names of the named tuple type `NT` */
+  type Names[NT <: AnyNamedTuple] <: Tuple = NT match
+    case NamedTuple[n, _] => n
+
+  /** The value types of the named tuple type `NT` */
+  type DropNames[NT <: AnyNamedTuple] <: Tuple = NT match
+    case NamedTuple[_, x] => x
+
 object NamedTupleOps:
   import TupleOps.*
 
   opaque type AnyNamedTuple = Any
 
   opaque type NamedTuple[N <: Tuple, +X <: Tuple] >: X <: AnyNamedTuple = X
 
+  export NamedTupleDecomposition.*
+
   object NamedTuple:
     def apply[N <: Tuple, X <: Tuple](x: X): NamedTuple[N, X] = x
 
-  /** The names of the named tuple type `NT` */
-  type Names[NT <: AnyNamedTuple] <: Tuple = NT match
-    case NamedTuple[n, _] => n
-
-  /** The value types of the named tuple type `NT` */
-  type DropNames[NT <: AnyNamedTuple] <: Tuple = NT match
-    case NamedTuple[_, x] => x
-
   extension [NT <: AnyNamedTuple](x: NT)
     inline def toTuple: DropNames[NT] = x.asInstanceOf
     inline def names: Names[NT] = constValueTuple[Names[NT]]

tests/run-tasty-inspector/stdlibExperimentalDefinitions.scala

@@ -94,6 +94,8 @@ val experimentalDefinitionInLibrary = Set(
   // New feature: named tuples
   "scala.NamedTuple",
   "scala.NamedTuple$",
+  "scala.NamedTupleDecomposition",
+  "scala.NamedTupleDecomposition$",
 )