Merge pull request #9265 from dotty-staging/fix-#9251

Fix #9251: Print applied lambda types directly

Author: nicolasstucki

library/src/scala/tasty/reflect/SourceCodePrinter.scala

@@ -1123,7 +1123,10 @@ class SourceCodePrinter[R <: Reflection & Singleton](val tasty: R)(syntaxHighlig
       case AppliedType(tp, args) =>
         tp match {
           case tp: TypeLambda =>
-            printType(tpe.dealias)
+            this += "("
+            printType(tp)
+            this += ")"
+            inSquare(printTypesOrBounds(args, ", "))
           case tp: TypeRef if tp.typeSymbol == ctx.requiredClass("scala.<repeated>") =>
             this += "_*"
           case _ =>

tests/pos-macros/i9251/Macro_1.scala

@@ -0,0 +1,34 @@
+package cps
+
+import scala.quoted._
+
+trait CpsMonad[F[_]]
+
+trait ComputationBound[T]
+
+implicit object ComputationBoundMonad extends CpsMonad[ComputationBound]
+
+inline def async[F[_]](using am:CpsMonad[F]): Async.InferAsyncArg[F] =
+   new Async.InferAsyncArg[F]
+
+object Async {
+
+  class InferAsyncArg[F[_]](using am:CpsMonad[F]) {
+      inline def apply[T](inline expr: T):Unit = ${ Async.checkPrintTypeImpl[F,T]('expr) }
+  }
+
+
+  def checkPrintTypeImpl[F[_]:Type,T:Type](f: Expr[T])(using qctx: QuoteContext): Expr[Unit] =
+    import qctx.tasty._
+
+    val fu = f.unseal
+    fu match
+      case Inlined(_,_,Block(_,Apply(TypeApply(Select(q,n),tparams),List(param)))) =>
+        param.tpe match
+          case AppliedType(tp,tparams1) =>
+            val fType = summon[quoted.Type[F]]
+            val ptp = tparams1.tail.head
+            val ptpTree = Inferred(AppliedType(fType.unseal.tpe,List(ptp)))
+            '{ println(${Expr(ptpTree.show)}) }
+
+}

tests/pos-macros/i9251/Test_2.scala

@@ -0,0 +1,5 @@
+package cps
+
+val c = async[ComputationBound] {
+  List(1,2,3,4).collectFirst { case x if x > 0 => x > 3 }
+}