Fix HK quoted pattern type variables

The issue was in the encoding into `{ExprMatchModule,TypeMatchModule}.unapply`.
Specifically with the `TypeBindings` argument. This arguments holds the
list of type variable definitions (`tpd.Bind` trees). We used a `Tuple`
to list all the types inside. The problem is that higher-kinded type
variables do not conform with the upper bounds of the tuple elements.
The solution is to use an HList with any-kinded elements.

Author: nicolasstucki

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

@@ -1502,7 +1502,7 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     }
   }
 
-  /** Creates the tuple type tree repesentation of the type trees in `ts` */
+  /** Creates the tuple type tree representation of the type trees in `ts` */
   def tupleTypeTree(elems: List[Tree])(using Context): Tree = {
     val arity = elems.length
     if arity <= Definitions.MaxTupleArity then
@@ -1513,10 +1513,14 @@ object tpd extends Trees.Instance[Type] with TypedTreeInfo {
     else nestedPairsTypeTree(elems)
   }
 
-  /** Creates the nested pairs type tree repesentation of the type trees in `ts` */
+  /** Creates the nested pairs type tree representation of the type trees in `ts` */
   def nestedPairsTypeTree(ts: List[Tree])(using Context): Tree =
     ts.foldRight[Tree](TypeTree(defn.EmptyTupleModule.termRef))((x, acc) => AppliedTypeTree(TypeTree(defn.PairClass.typeRef), x :: acc :: Nil))
 
+  /** Creates the nested higher-kinded pairs type tree representation of the type trees in `ts` */
+  def hkNestedPairsTypeTree(ts: List[Tree])(using Context): Tree =
+    ts.foldRight[Tree](TypeTree(defn.QuoteMatching_HKNil.typeRef))((x, acc) => AppliedTypeTree(TypeTree(defn.QuoteMatching_HKCons.typeRef), x :: acc :: Nil))
+
   /** Replaces all positions in `tree` with zero-extent positions */
   private def focusPositions(tree: Tree)(using Context): Tree = {
     val transformer = new tpd.TreeMap {

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

@@ -865,6 +865,9 @@ class Definitions {
     @tu lazy val QuoteMatching_ExprMatchModule: Symbol = QuoteMatchingClass.requiredClass("ExprMatchModule")
     @tu lazy val QuoteMatching_TypeMatch: Symbol = QuoteMatchingClass.requiredMethod("TypeMatch")
     @tu lazy val QuoteMatching_TypeMatchModule: Symbol = QuoteMatchingClass.requiredClass("TypeMatchModule")
+  @tu lazy val QuoteMatchingModule: Symbol = requiredModule("scala.quoted.runtime.QuoteMatching")
+    @tu lazy val QuoteMatching_HKNil: Symbol = QuoteMatchingModule.requiredType("HKNil")
+    @tu lazy val QuoteMatching_HKCons: Symbol = QuoteMatchingModule.requiredType("HKCons")
 
   @tu lazy val ToExprModule: Symbol = requiredModule("scala.quoted.ToExpr")
     @tu lazy val ToExprModule_BooleanToExpr: Symbol = ToExprModule.requiredMethod("BooleanToExpr")

compiler/src/dotty/tools/dotc/typer/QuotesAndSplices.scala

@@ -411,7 +411,7 @@ trait QuotesAndSplices {
     val replaceBindings = new ReplaceBindings
     val patType = defn.tupleType(splices.tpes.map(tpe => replaceBindings(tpe.widen)))
 
-    val typeBindingsTuple = tpd.tupleTypeTree(typeBindings.values.toList)
+    val typeBindingsTuple = tpd.hkNestedPairsTypeTree(typeBindings.values.toList)
 
     val replaceBindingsInTree = new TreeMap {
       private var bindMap = Map.empty[Symbol, Symbol]

compiler/src/scala/quoted/runtime/impl/QuoteMatcher.scala

@@ -121,9 +121,9 @@ object QuoteMatcher {
 
   private def withEnv[T](env: Env)(body: Env ?=> T): T = body(using env)
 
-  def treeMatch(scrutineeTerm: Tree, patternTerm: Tree)(using Context): Option[Tuple] =
+  def treeMatch(scrutineeTree: Tree, patternTree: Tree)(using Context): Option[Tuple] =
     given Env = Map.empty
-    scrutineeTerm =?= patternTerm
+    scrutineeTree =?= patternTree
 
   /** Check that all trees match with `mtch` and concatenate the results with &&& */
   private def matchLists[T](l1: List[T], l2: List[T])(mtch: (T, T) => Matching): Matching = (l1, l2) match {

compiler/src/scala/quoted/runtime/impl/QuotesImpl.scala

@@ -3092,14 +3092,14 @@ class QuotesImpl private (using val ctx: Context) extends Quotes, QuoteUnpickler
     new TypeImpl(tree, SpliceScope.getCurrent).asInstanceOf[scala.quoted.Type[T]]
 
   object ExprMatch extends ExprMatchModule:
-    def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: scala.quoted.Expr[Any])(using pattern: scala.quoted.Expr[Any]): Option[Tup] =
+    def unapply[TypeBindings, Tup <: Tuple](scrutinee: scala.quoted.Expr[Any])(using pattern: scala.quoted.Expr[Any]): Option[Tup] =
       val scrutineeTree = reflect.asTerm(scrutinee)
       val patternTree = reflect.asTerm(pattern)
       treeMatch(scrutineeTree, patternTree).asInstanceOf[Option[Tup]]
   end ExprMatch
 
   object TypeMatch extends TypeMatchModule:
-    def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: scala.quoted.Type[?])(using pattern: scala.quoted.Type[?]): Option[Tup] =
+    def unapply[TypeBindings, Tup <: Tuple](scrutinee: scala.quoted.Type[?])(using pattern: scala.quoted.Type[?]): Option[Tup] =
       val scrutineeTree = reflect.TypeTree.of(using scrutinee)
       val patternTree = reflect.TypeTree.of(using pattern)
       treeMatch(scrutineeTree, patternTree).asInstanceOf[Option[Tup]]

library/src/scala/quoted/runtime/QuoteMatching.scala

@@ -1,6 +1,7 @@
 package scala.quoted.runtime
 
 import scala.quoted.{Expr, Type}
+import scala.annotation.experimental
 
 /** Part of the Quotes interface that needs to be implemented by the compiler but is not visible to users */
 trait QuoteMatching:
@@ -17,7 +18,7 @@ trait QuoteMatching:
     *    - `ExprMatch.unapply('{ f(0, myInt) })('{ f(patternHole[Int], patternHole[Int]) }, _)`
     *       will return `Some(Tuple2('{0}, '{ myInt }))`
     *    - `ExprMatch.unapply('{ f(0, "abc") })('{ f(0, patternHole[Int]) }, _)`
-    *       will return `None` due to the missmatch of types in the hole
+    *       will return `None` due to the mismatch of types in the hole
     *
     *  Holes:
     *    - scala.quoted.runtime.Patterns.patternHole[T]: hole that matches an expression `x` of type `Expr[U]`
@@ -27,7 +28,8 @@ trait QuoteMatching:
     *  @param pattern `Expr[Any]` containing the pattern tree
     *  @return None if it did not match, `Some(tup)` if it matched where `tup` contains `Expr[Ti]``
     */
-    def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: Expr[Any])(using pattern: Expr[Any]): Option[Tup]
+    // FIXME: is this change TASTy binary compatible? Or we need to create a new version of the interface?
+    def unapply[TypeBindings, Tup <: Tuple](scrutinee: Expr[Any])(using pattern: Expr[Any]): Option[Tup]
   }
 
   val TypeMatch: TypeMatchModule
@@ -40,5 +42,13 @@ trait QuoteMatching:
      *  @param pattern `Type[?]` containing the pattern tree
      *  @return None if it did not match, `Some(tup)` if it matched where `tup` contains `Type[Ti]``
      */
-    def unapply[TypeBindings <: Tuple, Tup <: Tuple](scrutinee: Type[?])(using pattern: Type[?]): Option[Tup]
+    // FIXME: is this change TASTy binary compatible? Or we need to create a new version of the interface?
+    def unapply[TypeBindings, Tup <: Tuple](scrutinee: Type[?])(using pattern: Type[?]): Option[Tup]
   }
+
+@experimental
+object QuoteMatching:
+  // FIXME: Where should this be defined?
+  type HKHList
+  type HKCons[+H <: AnyKind, +T <: HKHList] <: HKHList
+  type HKNil <: HKHList

tests/pos-macros/hk-quoted-type-patterns/Macro_1.scala

@@ -0,0 +1,17 @@
+import scala.quoted._
+
+private def impl(x: Expr[Any])(using Quotes): Expr[Unit] = {
+  x match
+    case '{ foo[x] } =>
+      assert(Type.show[x] == "scala.Int", Type.show[x])
+    case '{ type f[X]; foo[`f`] } =>
+      assert(Type.show[f] == "[A >: scala.Nothing <: scala.Any] => scala.collection.immutable.List[A]", Type.show[f])
+    case '{ type f <: AnyKind; foo[`f`] } =>
+      assert(Type.show[f] == "[K >: scala.Nothing <: scala.Any, V >: scala.Nothing <: scala.Any] => scala.collection.immutable.Map[K, V]", Type.show[f])
+    case x => throw MatchError(x.show)
+  '{}
+}
+
+inline def test(inline x: Any): Unit = ${ impl('x) }
+
+def foo[T <: AnyKind]: Any = ???

tests/pos-macros/hk-quoted-type-patterns/Test_2.scala

@@ -0,0 +1,5 @@
+@main
+def Test =
+  test(foo[Int])
+  test(foo[List])
+  test(foo[Map])

tests/run-custom-args/tasty-inspector/stdlibExperimentalDefinitions.scala

@@ -66,6 +66,9 @@ val experimentalDefinitionInLibrary = Set(
   "scala.annotation.MacroAnnotation",
 
    //// New APIs: Quotes
+  // Can be stabilized in 3.4.0
+  "scala.quoted.runtime.QuoteMatching",
+  "scala.quoted.runtime.QuoteMatching$",
   // Can be stabilized in 3.3.0 (unsure) or later
   "scala.quoted.Quotes.reflectModule.CompilationInfoModule.XmacroSettings",
   "scala.quoted.Quotes.reflectModule.FlagsModule.JavaAnnotation",