Merge pull request scala#6949 from dotty-staging/move-quote-beta-redu…

…ction-to-context

 Move quote beta-reduction to QuoteContext

compiler/src/dotty/tools/dotc/core/quoted/PickledQuotes.scala

@@ -47,8 +47,6 @@ object PickledQuotes {
       }
       forceAndCleanArtefacts.transform(unpickled)
     case expr: TastyTreeExpr[Tree] @unchecked => healOwner(expr.tree)
-    case expr: FunctionAppliedTo[_] =>
-      functionAppliedTo(quotedExprToTree(expr.f), expr.args.map(arg => quotedExprToTree(arg(new scala.quoted.QuoteContext(ReflectionImpl(ctx))))).toList)
   }
 
   /** Transform the expression into its fully spliced TypeTree */
@@ -127,33 +125,6 @@ object PickledQuotes {
     tree
   }
 
-  private def functionAppliedTo(fn: Tree, args: List[Tree])(implicit ctx: Context): Tree = {
-    val (argVals, argRefs) = args.map(arg => arg.tpe match {
-      case tpe: SingletonType if isIdempotentExpr(arg) => (Nil, arg)
-      case _ =>
-        val argVal = SyntheticValDef(NameKinds.UniqueName.fresh("x".toTermName), arg).withSpan(arg.span)
-        (argVal :: Nil, ref(argVal.symbol))
-    }).unzip
-    def rec(fn: Tree): Tree = fn match {
-      case Inlined(call, bindings, expansion) =>
-        // this case must go before closureDef to avoid dropping the inline node
-        cpy.Inlined(fn)(call, bindings, rec(expansion))
-      case closureDef(ddef) =>
-        val paramSyms = ddef.vparamss.head.map(param => param.symbol)
-        val paramToVals = paramSyms.zip(argRefs).toMap
-        new TreeTypeMap(
-          oldOwners = ddef.symbol :: Nil,
-          newOwners = ctx.owner :: Nil,
-          treeMap = tree => paramToVals.get(tree.symbol).map(_.withSpan(tree.span)).getOrElse(tree)
-        ).transform(ddef.rhs)
-      case Block(stats, expr) =>
-        seq(stats, rec(expr)).withSpan(fn.span)
-      case _ =>
-        fn.select(nme.apply).appliedToArgs(argRefs).withSpan(fn.span)
-    }
-    seq(argVals.flatten, rec(fn))
-  }
-
   /** Make sure that the owner of this tree is `ctx.owner` */
   private def healOwner(tree: Tree)(implicit ctx: Context): Tree = {
     val getCurrentOwner = new TreeAccumulator[Option[Symbol]] {

compiler/src/dotty/tools/dotc/tastyreflect/KernelImpl.scala

@@ -1,16 +1,16 @@
 package dotty.tools.dotc
 package tastyreflect
 
-import dotty.tools.dotc.ast.Trees.SeqLiteral
-import dotty.tools.dotc.ast.{Trees, tpd, untpd}
-import dotty.tools.dotc.ast.tpd.TreeOps
+import dotty.tools.dotc.ast.Trees._
+import dotty.tools.dotc.ast.{TreeTypeMap, Trees, tpd, untpd}
 import dotty.tools.dotc.typer.{Implicits, Typer}
 import dotty.tools.dotc.core._
 import dotty.tools.dotc.core.Flags._
 import dotty.tools.dotc.core.StdNames.nme
 import dotty.tools.dotc.core.quoted.PickledQuotes
 import dotty.tools.dotc.core.Symbols._
 import dotty.tools.dotc.core.Decorators._
+import dotty.tools.dotc.core.Types.SingletonType
 import dotty.tools.dotc.tastyreflect.FromSymbol.{definitionFromSym, packageDefFromSym}
 import dotty.tools.dotc.parsing.Parsers.Parser
 import dotty.tools.dotc.typer.Implicits.{AmbiguousImplicits, DivergingImplicit, NoMatchingImplicits, SearchFailure, SearchFailureType}
@@ -19,6 +19,7 @@ import dotty.tools.dotc.util.{SourceFile, SourcePosition, Spans}
 import scala.tasty.reflect.Kernel
 
 class KernelImpl(val rootContext: core.Contexts.Context) extends Kernel {
+  import tpd._
 
   private implicit def ctx: core.Contexts.Context = rootContext
 
@@ -1894,6 +1895,35 @@ class KernelImpl(val rootContext: core.Contexts.Context) extends Kernel {
     case _ => None
   }
 
+  def betaReduce(fn: Term, args: List[Term]) given (ctx: Context): Term = {
+    val (argVals0, argRefs0) = args.foldLeft((List.empty[ValDef], List.empty[Tree])) { case ((acc1, acc2), arg) => arg.tpe match {
+      case tpe: SingletonType if isIdempotentExpr(arg) => (acc1, arg :: acc2)
+      case _ =>
+        val argVal = SyntheticValDef(NameKinds.UniqueName.fresh("x".toTermName), arg).withSpan(arg.span)
+        (argVal :: acc1, ref(argVal.symbol) :: acc2)
+    }}
+    val argVals = argVals0.reverse
+    val argRefs = argRefs0.reverse
+    def rec(fn: Tree): Tree = fn match {
+      case Inlined(call, bindings, expansion) =>
+        // this case must go before closureDef to avoid dropping the inline node
+        cpy.Inlined(fn)(call, bindings, rec(expansion))
+      case closureDef(ddef) =>
+        val paramSyms = ddef.vparamss.head.map(param => param.symbol)
+        val paramToVals = paramSyms.zip(argRefs).toMap
+        new TreeTypeMap(
+          oldOwners = ddef.symbol :: Nil,
+          newOwners = ctx.owner :: Nil,
+          treeMap = tree => paramToVals.get(tree.symbol).map(_.withSpan(tree.span)).getOrElse(tree)
+        ).transform(ddef.rhs)
+      case Block(stats, expr) =>
+        seq(stats, rec(expr)).withSpan(fn.span)
+      case _ =>
+        fn.select(nme.apply).appliedToArgs(argRefs).withSpan(fn.span)
+    }
+    seq(argVals, rec(fn))
+  }
+
   //
   // HELPERS
   //

library/src/scala/quoted/Expr.scala

@@ -35,16 +35,20 @@ package quoted {
     /** Converts a tuple `(T1, ..., Tn)` to `(Expr[T1], ..., Expr[Tn])` */
     type TupleOfExpr[Tup <: Tuple] = Tuple.Map[Tup, [X] =>> given QuoteContext => Expr[X]]
 
-    implicit class AsFunction[F, Args <: Tuple, R](f: Expr[F]) given (tf: TupledFunction[F, Args => R]) {
+    implicit class AsFunction[F, Args <: Tuple, R](f: Expr[F]) given (tf: TupledFunction[F, Args => R], qctx: QuoteContext) {
       /** Beta-reduces the function appication. Generates the an expression only containing the body of the function */
-      def apply[G] given (tg: TupledFunction[G, TupleOfExpr[Args] => Expr[R]]): G =
-        tg.untupled(args => new FunctionAppliedTo[R](f, args.toArray.map(_.asInstanceOf[QuoteContext => Expr[_]])))
+      def apply[G] given (tg: TupledFunction[G, TupleOfExpr[Args] => Expr[R]]): G = {
+        import qctx.tasty._
+        tg.untupled(args => qctx.tasty.kernel.betaReduce(f.unseal, args.toArray.toList.map(_.asInstanceOf[QuoteContext => Expr[_]](qctx).unseal)).seal.asInstanceOf[Expr[R]])
+      }
     }
 
-    implicit class AsContextualFunction[F, Args <: Tuple, R](f: Expr[F]) given (tf: TupledFunction[F, given Args => R]) {
+    implicit class AsContextualFunction[F, Args <: Tuple, R](f: Expr[F]) given (tf: TupledFunction[F, given Args => R], qctx: QuoteContext) {
       /** Beta-reduces the function appication. Generates the an expression only containing the body of the function */
-      def apply[G] given (tg: TupledFunction[G, TupleOfExpr[Args] => Expr[R]]): G =
-        tg.untupled(args => new FunctionAppliedTo[R](f, args.toArray.map(_.asInstanceOf[QuoteContext => Expr[_]])))
+      def apply[G] given (tg: TupledFunction[G, TupleOfExpr[Args] => Expr[R]]): G = {
+        import qctx.tasty._
+        tg.untupled(args => qctx.tasty.kernel.betaReduce(f.unseal, args.toArray.toList.map(_.asInstanceOf[QuoteContext => Expr[_]](qctx).unseal)).seal.asInstanceOf[Expr[R]])
+      }
     }
 
     /** Returns a null expresssion equivalent to `'{null}` */
@@ -93,13 +97,5 @@ package internal {
       override def toString: String = s"Expr(<tasty tree>)"
     }
 
-    // TODO Use a List in FunctionAppliedTo(val f: Expr[_], val args: List[Expr[_]])
-    // FIXME: Having the List in the code above trigers an assertion error while testing dotty.tools.dotc.reporting.ErrorMessagesTests.i3187
-    //        This test does redefine `scala.collection`. Further investigation is needed.
-    /** An Expr representing `'{($f).apply($x1, ..., $xn)}` but it is beta-reduced when the closure is known */
-    final class FunctionAppliedTo[+R](val f: Expr[_], val args: Array[QuoteContext => Expr[_]]) extends Expr[R] {
-      override def toString: String = s"Expr($f <applied to> ${args.toList})"
-    }
-
   }
 }

library/src/scala/tasty/reflect/Kernel.scala

@@ -1538,4 +1538,9 @@ trait Kernel {
    */
   def searchImplicit(tpe: Type) given (ctx: Context): ImplicitSearchResult
 
+  /** Inline fn if it is an explicit closure possibly nested inside the expression of a block.
+   *  Otherwise apply the arguments to the closure.
+   */
+  def betaReduce(f: Term, args: List[Term]) given (ctx: Context): Term
+
 }