WIP: Pattern match against hoas pattern wtih type vars

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

@@ -288,7 +288,42 @@ class QuoteMatcher(debug: Boolean) {
           val captureEnv = env.filter((k, v) => !capturedSymbols.contains(v))
           withEnv(captureEnv) {
             scrutinee match
-              case ClosedPatternTerm(scrutinee) => matchedOpen(scrutinee, pattern.tpe, capturedIds, args.map(_.tpe), env)
+              case ClosedPatternTerm(scrutinee) => matchedOpen(scrutinee, pattern.tpe, capturedIds, args.map(_.tpe), Nil, env)
+              case _ => notMatched
+          }
+
+        /* Higher order term hole */
+        // Matches an open term and wraps it into a lambda that provides the free variables
+        case Apply(TypeApply(Ident(_), List(TypeTree(), targs)), SeqLiteral(args, _) :: Nil)
+            if pattern.symbol.eq(defn.QuotedRuntimePatterns_higherOrderHoleWithTypes) =>
+
+          /* Some of method symbols in arguments of higher-order term hole are eta-expanded.
+           * e.g.
+           * g: (Int) => Int
+           * => {
+           *   def $anonfun(y: Int): Int = g(y)
+           *   closure($anonfun)
+           * }
+           *
+           * f: (using Int) => Int
+           * => f(using x)
+           * This function restores the symbol of the original method from
+           * the eta-expanded function.
+           */
+          def getCapturedIdent(arg: Tree)(using Context): Ident =
+            arg match
+              case id: Ident => id
+              case Apply(fun, _) => getCapturedIdent(fun)
+              case Block((ddef: DefDef) :: _, _: Closure) => getCapturedIdent(ddef.rhs)
+              case Typed(expr, _) => getCapturedIdent(expr)
+
+          val env = summon[Env]
+          val capturedIds = args.map(getCapturedIdent)
+          val capturedSymbols = capturedIds.map(_.symbol)
+          val captureEnv = env.filter((k, v) => !capturedSymbols.contains(v))
+          withEnv(captureEnv) {
+            scrutinee match
+              case ClosedPatternTerm(scrutinee) => matchedOpen(scrutinee, pattern.tpe, capturedIds, args.map(_.tpe), targs, env)
               case _ => notMatched
           }
 
@@ -558,9 +593,10 @@ class QuoteMatcher(debug: Boolean) {
      *  @param patternTpe Type of the pattern hole (from the pattern)
      *  @param argIds Identifiers of HOAS arguments (from the pattern)
      *  @param argTypes Eta-expanded types of HOAS arguments (from the pattern)
+     *  @param typeArgs type arguments from the pattern
      *  @param env Mapping between scrutinee and pattern variables
      */
-    case OpenTree(tree: Tree, patternTpe: Type, argIds: List[Tree], argTypes: List[Type], env: Env)
+    case OpenTree(tree: Tree, patternTpe: Type, argIds: List[Tree], argTypes: List[Type], typeArgs: List[Type], env: Env)
 
     /** Return the expression that was extracted from a hole.
      *
@@ -573,29 +609,63 @@ class QuoteMatcher(debug: Boolean) {
     def toExpr(mapTypeHoles: Type => Type, spliceScope: Scope)(using Context): Expr[Any] = this match
       case MatchResult.ClosedTree(tree) =>
         new ExprImpl(tree, spliceScope)
-      case MatchResult.OpenTree(tree, patternTpe, argIds, argTypes, env) =>
-        val names: List[TermName] = argIds.map(_.symbol.name.asTermName)
-        val paramTypes = argTypes.map(tpe => mapTypeHoles(tpe.widenTermRefExpr))
-        val methTpe = MethodType(names)(_ => paramTypes, _ => mapTypeHoles(patternTpe))
-        val meth = newAnonFun(ctx.owner, methTpe)
-        def bodyFn(lambdaArgss: List[List[Tree]]): Tree = {
-          val argsMap = argIds.view.map(_.symbol).zip(lambdaArgss.head).toMap
-          val body = new TreeMap {
-            override def transform(tree: Tree)(using Context): Tree =
-              tree match
-                /*
-                 * When matching a method call `f(0)` against a HOAS pattern `p(g)` where
-                 * f has a method type `(x: Int): Int` and  `f` maps to `g`, `p` should hold
-                 * `g.apply(0)` because the type of `g` is `Int => Int` due to eta expansion.
-                 */
-                case Apply(fun, args) if env.contains(tree.symbol) => transform(fun).select(nme.apply).appliedToArgs(args.map(transform))
-                case tree: Ident => env.get(tree.symbol).flatMap(argsMap.get).getOrElse(tree)
-                case tree => super.transform(tree)
-          }.transform(tree)
-          TreeOps(body).changeNonLocalOwners(meth)
-        }
-        val hoasClosure = Closure(meth, bodyFn)
-        new ExprImpl(hoasClosure, spliceScope)
+      case MatchResult.OpenTree(tree, patternTpe, argIds, argTypes, typeArgs, env) =>
+        if typeArgs.isEmpty then
+          val names: List[TermName] = argIds.map(_.symbol.name.asTermName)
+          val paramTypes = argTypes.map(tpe => mapTypeHoles(tpe.widenTermRefExpr))
+          val methTpe = MethodType(names)(_ => paramTypes, _ => mapTypeHoles(patternTpe))
+          val meth = newAnonFun(ctx.owner, methTpe)
+          def bodyFn(lambdaArgss: List[List[Tree]]): Tree = {
+            val argsMap = argIds.view.map(_.symbol).zip(lambdaArgss.head).toMap
+            val body = new TreeMap {
+              override def transform(tree: Tree)(using Context): Tree =
+                tree match
+                  /*
+                  * When matching a method call `f(0)` against a HOAS pattern `p(g)` where
+                  * f has a method type `(x: Int): Int` and  `f` maps to `g`, `p` should hold
+                  * `g.apply(0)` because the type of `g` is `Int => Int` due to eta expansion.
+                  */
+                  case Apply(fun, args) if env.contains(tree.symbol) => transform(fun).select(nme.apply).appliedToArgs(args.map(transform))
+                  case tree: Ident => env.get(tree.symbol).flatMap(argsMap.get).getOrElse(tree)
+                  case tree => super.transform(tree)
+            }.transform(tree)
+            TreeOps(body).changeNonLocalOwners(meth)
+          }
+          val hoasClosure = Closure(meth, bodyFn)
+          new ExprImpl(hoasClosure, spliceScope)
+        else
+          val names: List[TermName] = argIds.map(_.symbol.name.asTermName)
+          val paramTypes = argTypes.map(tpe => mapTypeHoles(tpe.widenTermRefExpr))
+
+          val typeArgs1 = PolyType.syntheticParamNames(typeArgs.length)
+          val bounds = typeArgs map (_ => TypeBounds.empty)
+          val resultTypeExp = (pt: PolyType) => {
+            val fromSymbols = typeArgs.map(_.typeSymbol)
+            val argTypes1 = argTypes.map(_.subst(fromSymbols, pt.paramRefs))
+            val resultType1 = mapTypeHoles(patternTpe).subst(fromSymbols, pt.paramRefs)
+            MethodType(argTypes1, resultType1)
+          }
+          val methTpe = PolyType(typeArgs1)(_ => bounds, resultTypeExp)
+          val meth = newAnonFun(ctx.owner, methTpe)
+          // TODO-18271
+          def bodyFn(lambdaArgss: List[List[Tree]]): Tree = {
+            val argsMap = argIds.view.map(_.symbol).zip(lambdaArgss.head).toMap
+            val body = new TreeMap {
+              override def transform(tree: Tree)(using Context): Tree =
+                tree match
+                  /*
+                  * When matching a method call `f(0)` against a HOAS pattern `p(g)` where
+                  * f has a method type `(x: Int): Int` and  `f` maps to `g`, `p` should hold
+                  * `g.apply(0)` because the type of `g` is `Int => Int` due to eta expansion.
+                  */
+                  case Apply(fun, args) if env.contains(tree.symbol) => transform(fun).select(nme.apply).appliedToArgs(args.map(transform))
+                  case tree: Ident => env.get(tree.symbol).flatMap(argsMap.get).getOrElse(tree)
+                  case tree => super.transform(tree)
+            }.transform(tree)
+            TreeOps(body).changeNonLocalOwners(meth)
+          }
+          val hoasClosure = Closure(meth, bodyFn)
+          new ExprImpl(hoasClosure, spliceScope)
 
   private inline def notMatched[T]: optional[T] =
     optional.break()
@@ -606,8 +676,8 @@ class QuoteMatcher(debug: Boolean) {
   private inline def matched(tree: Tree)(using Context): MatchingExprs =
     Seq(MatchResult.ClosedTree(tree))
 
-  private def matchedOpen(tree: Tree, patternTpe: Type, argIds: List[Tree], argTypes: List[Type], env: Env)(using Context): MatchingExprs =
-    Seq(MatchResult.OpenTree(tree, patternTpe, argIds, argTypes, env))
+  private def matchedOpen(tree: Tree, patternTpe: Type, argIds: List[Tree], argTypes: List[Type], typeArgs: List[Type], env: Env)(using Context): MatchingExprs =
+    Seq(MatchResult.OpenTree(tree, patternTpe, argIds, argTypes, typeArgs, env))
 
   extension (self: MatchingExprs)
       /** Concatenates the contents of two successful matchings */