fix(compiler): Import abilities with use [LNG-324] (#1077)

* Add IntoApply

* Savepoint

* Add backtrack

* Return ability name

* Add service resolution

* Return import ability

* Add test

* Rewrite toDottedName

* Rewrite ability resolution

* Fix offset

* Add tests

* Add test

* Add comments

* Add test

---------

Co-authored-by: Dima <dmitry.shakhtarin@fluence.ai>

compiler/src/test/scala/aqua/compiler/AquaCompilerSpec.scala

@@ -87,6 +87,25 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers with Inside {
     inside(funcs)(test)
   )
 
+  def through(peer: ValueModel) =
+    MakeRes.hop(peer)
+
+  val relay = VarRaw("-relay-", ScalarType.string)
+
+  def getDataSrv(name: String, varName: String, t: Type) = {
+    CallServiceRes(
+      LiteralModel.quote("getDataSrv"),
+      name,
+      CallRes(Nil, Some(CallModel.Export(varName, t))),
+      LiteralModel.fromRaw(ValueRaw.InitPeerId)
+    ).leaf
+  }
+
+  private val init = LiteralModel.fromRaw(ValueRaw.InitPeerId)
+
+  private def join(vm: VarModel, size: ValueModel) =
+    ResBuilder.join(vm, size, init)
+
   "aqua compiler" should "compile a simple snippet to the right context" in {
 
     val src = Map(
@@ -115,25 +134,6 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers with Inside {
     }
   }
 
-  def through(peer: ValueModel) =
-    MakeRes.hop(peer)
-
-  val relay = VarRaw("-relay-", ScalarType.string)
-
-  def getDataSrv(name: String, varName: String, t: Type) = {
-    CallServiceRes(
-      LiteralModel.quote("getDataSrv"),
-      name,
-      CallRes(Nil, Some(CallModel.Export(varName, t))),
-      LiteralModel.fromRaw(ValueRaw.InitPeerId)
-    ).leaf
-  }
-
-  private val init = LiteralModel.fromRaw(ValueRaw.InitPeerId)
-
-  private def join(vm: VarModel, size: ValueModel) =
-    ResBuilder.join(vm, size, init)
-
   it should "create right topology" in {
     val src = Map(
       "index.aqua" ->
@@ -502,4 +502,385 @@ class AquaCompilerSpec extends AnyFlatSpec with Matchers with Inside {
       main.body.equalsOrShowDiff(expected) should be(true)
     }
   }
+
+  val moduleNames = List("Test", "Imp", "Sub", "Path").inits
+    .takeWhile(_.nonEmpty)
+    .map(_.mkString("."))
+    .toList
+
+  it should "import function with `use`" in {
+    def test(name: String, rename: Option[String]) = {
+      val src = Map(
+        "main.aqua" ->
+          s"""aqua Main
+             |export main
+             |use "import.aqua"${rename.fold("")(" as " + _)}
+             |func main() -> i32:
+             |  <- ${rename.getOrElse(name)}.foo()
+             |""".stripMargin
+      )
+      val imports = Map(
+        "import.aqua" ->
+          s"""aqua $name declares foo
+             |func foo() -> i32:
+             |  <- 42
+             |""".stripMargin
+      )
+
+      val transformCfg = TransformConfig(relayVarName = None)
+
+      insideRes(src, imports, transformCfg)(
+        "main"
+      ) { case main :: _ =>
+        val expected = XorRes.wrap(
+          respCall(transformCfg, LiteralModel.number(42), initPeer),
+          errorCall(transformCfg, 0, initPeer)
+        )
+
+        main.body.equalsOrShowDiff(expected) should be(true)
+      }
+    }
+
+    moduleNames.foreach { name =>
+      val rename = "Imported"
+
+      withClue(s"Testing $name") {
+        test(name, None)
+      }
+      withClue(s"Testing $name as $rename") {
+        test(name, rename.some)
+      }
+    }
+  }
+
+  it should "import service with `use`" in {
+    def test(name: String, rename: Option[String]) = {
+      val srvName = rename.getOrElse(name) + ".Srv"
+      val src = Map(
+        "main.aqua" ->
+          s"""aqua Main
+             |export main
+             |use "import.aqua"${rename.fold("")(" as " + _)}
+             |
+             |func main() -> i32:
+             |  a <- $srvName.call()
+             |  $srvName "res-id"
+             |  b <- $srvName.call()
+             |  <- a + b
+             |""".stripMargin
+      )
+      val imports = Map(
+        "import.aqua" ->
+          s"""aqua $name declares *
+             |service Srv("def-id"):
+             |  call() -> i32
+             |""".stripMargin
+      )
+
+      val transformCfg = TransformConfig(relayVarName = None)
+
+      insideRes(src, imports, transformCfg)(
+        "main"
+      ) { case main :: _ =>
+        def call(id: String, exp: CallModel.Export) =
+          CallServiceRes(
+            LiteralModel.quote(id),
+            "call",
+            CallRes(Nil, Some(exp)),
+            initPeer
+          ).leaf
+
+        val a = CallModel.Export("ret", ScalarType.i32)
+        val b = CallModel.Export("ret-0", ScalarType.i32)
+        val add = CallModel.Export("add", ScalarType.i32)
+        val expected = XorRes.wrap(
+          SeqRes.wrap(
+            call("def-id", a),
+            call("res-id", b),
+            CallServiceRes(
+              LiteralModel.quote("math"),
+              "add",
+              CallRes(List(a.asVar, b.asVar), Some(add)),
+              initPeer
+            ).leaf,
+            respCall(transformCfg, add.asVar, initPeer)
+          ),
+          errorCall(transformCfg, 0, initPeer)
+        )
+
+        main.body.equalsOrShowDiff(expected) should be(true)
+      }
+    }
+
+    moduleNames.foreach { name =>
+      val rename = "Imported"
+
+      withClue(s"Testing $name") {
+        test(name, None)
+      }
+      withClue(s"Testing $name as $rename") {
+        test(name, rename.some)
+      }
+    }
+  }
+
+  it should "import ability with `use`" in {
+    def test(name: String, rename: Option[String]) = {
+      val abName = rename.getOrElse(name) + ".Ab"
+      val src = Map(
+        "main.aqua" ->
+          s"""aqua Main
+             |export main
+             |use "import.aqua"${rename.fold("")(" as " + _)}
+             |func useAb{$abName}() -> i32:
+             |  <- $abName.a
+             |
+             |func main() -> i32:
+             |  ab = $abName(a = 42)
+             |  <- useAb{ab}()
+             |""".stripMargin
+      )
+      val imports = Map(
+        "import.aqua" ->
+          s"""aqua $name declares *
+             |ability Ab:
+             |  a: i32
+             |""".stripMargin
+      )
+
+      val transformCfg = TransformConfig(relayVarName = None)
+
+      insideRes(src, imports, transformCfg)(
+        "main"
+      ) { case main :: _ =>
+        val ap = CallModel.Export("literal_ap", LiteralType.unsigned)
+        val props = ap.copy(name = "literal_props")
+        val expected = XorRes.wrap(
+          SeqRes.wrap(
+            // NOTE: Result of compilation is inefficient
+            ApRes(LiteralModel.number(42), ap).leaf,
+            ApRes(ap.asVar, props).leaf,
+            respCall(transformCfg, props.asVar, initPeer)
+          ),
+          errorCall(transformCfg, 0, initPeer)
+        )
+
+        main.body.equalsOrShowDiff(expected) should be(true)
+      }
+    }
+
+    moduleNames.foreach { name =>
+      val rename = "Imported"
+
+      withClue(s"Testing $name") {
+        test(name, None)
+      }
+      withClue(s"Testing $name as $rename") {
+        test(name, rename.some)
+      }
+    }
+  }
+
+  it should "import ability (nested) with `use`" in {
+    def test(name: String, rename: Option[String]) = {
+      val impName = rename.getOrElse(name)
+      val abName = impName + ".Ab"
+      val src = Map(
+        "main.aqua" ->
+          s"""aqua Main
+             |export main
+             |use "import.aqua"${rename.fold("")(" as " + _)}
+             |func useAb{$abName}() -> i32:
+             |  <- $abName.ab1.ab0.call($abName.ab1.ab0.a)
+             |
+             |func main() -> i32:
+             |  id = (x: i32) -> i32:
+             |    <- x
+             |  ab0 = $impName.Ab0(a = 42, call = id)
+             |  ab1 = $impName.Ab1(ab0 = ab0)
+             |  ab = $abName(ab1 = ab1)
+             |  <- useAb{ab}()
+             |""".stripMargin
+      )
+      val imports = Map(
+        "import.aqua" ->
+          s"""aqua $name declares *
+             |ability Ab0:
+             |  a: i32
+             |  call(x: i32) -> i32
+             |
+             |ability Ab1:
+             |  ab0: Ab0
+             |
+             |ability Ab:
+             |  ab1: Ab1
+             |""".stripMargin
+      )
+
+      val transformCfg = TransformConfig(relayVarName = None)
+
+      insideRes(src, imports, transformCfg)(
+        "main"
+      ) { case main :: _ =>
+        val ap = CallModel.Export("literal_ap", LiteralType.unsigned)
+        val props = ap.copy(name = "literal_props")
+        val expected = XorRes.wrap(
+          SeqRes.wrap(
+            // NOTE: Result of compilation is inefficient
+            ApRes(LiteralModel.number(42), ap).leaf,
+            ApRes(ap.asVar, props).leaf,
+            respCall(transformCfg, props.asVar, initPeer)
+          ),
+          errorCall(transformCfg, 0, initPeer)
+        )
+
+        main.body.equalsOrShowDiff(expected) should be(true)
+      }
+    }
+
+    moduleNames.foreach { name =>
+      val rename = "Imported"
+
+      withClue(s"Testing $name") {
+        test(name, None)
+      }
+      withClue(s"Testing $name as $rename") {
+        test(name, rename.some)
+      }
+    }
+  }
+
+  it should "import abilities in chain of imports" in {
+    case class Imp(header: String, rename: Option[String] = None) {
+      val as = rename.fold("")(" as " + _)
+      val name = rename.getOrElse(header)
+
+      override def toString: String = s"$header$as"
+    }
+
+    def test(hierarchy: List[Imp]) = {
+      hierarchy.nonEmpty should be(true)
+
+      def genImp(header: String, imported: Imp, path: String): String = {
+        s"""aqua ${header} declares *
+           |use "${path}"${imported.as}
+           |
+           |ability Inner:
+           |  ab: ${imported.name}.Outer
+           |
+           |ability Outer:
+           |  ab: Inner
+           |
+           |func create{${imported.name}.Outer}() -> Inner:
+           |  ab = Inner(ab = ${imported.name}.Outer)
+           |  <- ab
+           |""".stripMargin
+      }
+
+      val base = Imp("Base")
+      val basePath = "base.aqua"
+      val baseCode = s"""aqua Base declares *
+                        |
+                        |ability Outer:
+                        |  a: i32
+                        |  call(x: i32) -> i32
+                        |""".stripMargin
+
+      val withPaths = hierarchy.zipWithIndex.map { case (imp, idx) =>
+        imp -> s"import$idx.aqua"
+      }
+      val nexts = withPaths.tail :+ (base -> basePath)
+      val imports = withPaths
+        .zip(nexts)
+        .map { case ((curImp, curPath), (nextImp, nextPath)) =>
+          curPath -> genImp(curImp.header, nextImp, nextPath)
+        }
+        .appended(basePath -> baseCode)
+        .toMap
+
+      val importStmts = withPaths.map { case (imp, path) =>
+        s"use \"${path}\"${imp.as}"
+      }.prepended(s"use \"${basePath}\"")
+      val createStmts = hierarchy.reverse.zipWithIndex.flatMap { case (imp, idx) =>
+        s"abIn${idx + 1} = ${imp.name}.create{abOut$idx}()" ::
+          s"abOut${idx + 1} = ${imp.name}.Outer(ab = abIn${idx + 1})" ::
+          Nil
+      }.prepended("abOut0 = Base.Outer(a = 42, call = id)")
+
+      val lastAb = s"abOut${hierarchy.size}" + ".ab".repeat(hierarchy.size * 2)
+      val main = s"""aqua Main
+                    |export main
+                    |${importStmts.mkString("\n")}
+                    |
+                    |func main() -> i32:
+                    |  id = (x: i32) -> i32:
+                    |    <- x
+                    |  ${createStmts.mkString("\n  ")}
+                    |  <- $lastAb.call($lastAb.a)
+                    |""".stripMargin
+
+      val src = Map(
+        "main.aqua" -> main
+      )
+
+      val transformCfg = TransformConfig(relayVarName = None)
+
+      insideRes(src, imports, transformCfg)(
+        "main"
+      ) { case main :: _ =>
+        val ap = CallModel.Export("literal_ap", LiteralType.unsigned)
+        val props = ap.copy(name = "literal_props")
+        val expected = XorRes.wrap(
+          SeqRes.wrap(
+            // NOTE: Result of compilation is inefficient
+            ApRes(LiteralModel.number(42), ap).leaf,
+            ApRes(ap.asVar, props).leaf,
+            respCall(transformCfg, props.asVar, initPeer)
+          ),
+          errorCall(transformCfg, 0, initPeer)
+        )
+
+        main.body.equalsOrShowDiff(expected) should be(true)
+      }
+    }
+
+    // Simple
+    (1 to 10).map(i => (1 to i).map(n => Imp(s"Imp$n")).toList).foreach { h =>
+      withClue(s"Testing ${h.mkString(" -> ")}") {
+        test(h)
+      }
+    }
+
+    // With renaming
+    (1 to 10)
+      .map(i =>
+        (1 to i)
+          .map(n =>
+            // Rename every second one
+            Imp(s"Imp$n", s"Renamed$n".some.filter(_ => n % 2 == 0))
+          )
+          .toList
+      )
+      .foreach { h =>
+        withClue(s"Testing ${h.mkString(" -> ")}") {
+          test(h)
+        }
+      }
+
+    // With subpath
+    (1 to 10)
+      .map(i =>
+        (1 to i)
+          .map(n => s"Imp$n")
+          .inits
+          .takeWhile(_.nonEmpty)
+          .map(p => Imp(p.mkString(".")))
+          .toList
+      )
+      .foreach { h =>
+        withClue(s"Testing ${h.mkString(" -> ")}") {
+          test(h)
+        }
+      }
+  }
 }

parser/src/main/scala/aqua/parser/lexer/NamedArg.scala

@@ -35,6 +35,11 @@ enum NamedArg[F[_]] extends Token[F] {
       case Full(name, value) => Full(name.mapK(fk), value.mapK(fk))
       case Short(variable) => Short(variable.mapK(fk))
     }
+
+  override def toString: String = this match {
+    case Full(name, value) => s"$name = $value"
+    case Short(variable) => variable.toString
+  }
 }
 
 object NamedArg {

parser/src/main/scala/aqua/parser/lexer/PropertyOp.scala

@@ -1,20 +1,20 @@
 package aqua.parser.lexer
 
+import aqua.parser.lexer.CallArrowToken.CallBraces
+import aqua.parser.lexer.NamedArg.namedArgs
 import aqua.parser.lexer.Token.*
 import aqua.parser.lift.LiftParser
 import aqua.parser.lift.LiftParser.*
 import aqua.parser.lift.Span
 import aqua.parser.lift.Span.{P0ToSpan, PToSpan}
 import aqua.types.LiteralType
-import aqua.parser.lexer.CallArrowToken.CallBraces
-import aqua.parser.lexer.NamedArg.namedArgs
 
-import cats.~>
 import cats.data.{NonEmptyList, NonEmptyMap}
 import cats.parse.{Numbers, Parser as P, Parser0 as P0}
 import cats.syntax.comonad.*
 import cats.syntax.functor.*
 import cats.{Comonad, Functor}
+import cats.~>
 import scala.language.postfixOps
 
 sealed trait PropertyOp[F[_]] extends Token[F] {
@@ -36,7 +36,7 @@ case class IntoField[F[_]: Comonad](name: F[String]) extends PropertyOp[F] {
 
   override def mapK[K[_]: Comonad](fk: F ~> K): PropertyOp[K] = copy(fk(name))
 
-  def value: String = name.extract
+  lazy val value: String = name.extract
 
   override def toString: String = name.extract
 }
@@ -46,6 +46,8 @@ case class IntoIndex[F[_]: Comonad](point: F[Unit], idx: Option[ValueToken[F]])
   override def as[T](v: T): F[T] = point.as(v)
 
   override def mapK[K[_]: Comonad](fk: F ~> K): IntoIndex[K] = copy(fk(point), idx.map(_.mapK(fk)))
+
+  override def toString: String = s"[$idx]"
 }
 
 case class IntoCopy[F[_]: Comonad](
@@ -56,6 +58,27 @@ case class IntoCopy[F[_]: Comonad](
 
   override def mapK[K[_]: Comonad](fk: F ~> K): IntoCopy[K] =
     copy(fk(point), args.map(_.mapK(fk)))
+
+  override def toString: String = s".copy(${args.map(_.toString).toList.mkString(", ")})"
+}
+
+/**
+ * WARNING: This is parsed when we have parens after a name, but `IntoArrow` failed to parse.
+ *          This is a case of imported named type, e.g. `Some.Imported.Module.DefinedAbility(...)`
+ *          It is transformed into `NamedTypeValue` in `ValuesAlgebra`
+ * TODO: Eliminate `IntoArrow`, unify it with this property
+ */
+case class IntoApply[F[_]: Comonad](
+  argsF: F[NonEmptyList[NamedArg[F]]]
+) extends PropertyOp[F] {
+  lazy val args: NonEmptyList[NamedArg[F]] = argsF.extract
+
+  override def as[T](v: T): F[T] = argsF.as(v)
+
+  override def mapK[K[_]: Comonad](fk: F ~> K): IntoApply[K] =
+    copy(fk(argsF.map(_.map(_.mapK(fk)))))
+
+  override def toString: String = s"(${args.map(_.toString).toList.mkString(", ")})"
 }
 
 object PropertyOp {
@@ -87,8 +110,19 @@ object PropertyOp {
       }
     }
 
+  private val parseApply: P[PropertyOp[Span.S]] =
+    namedArgs.lift.map(IntoApply.apply)
+
   private val parseOp: P[PropertyOp[Span.S]] =
-    P.oneOf(parseCopy.backtrack :: parseArrow.backtrack :: parseField :: parseIdx :: Nil)
+    P.oneOf(
+      // NOTE: order is important here
+      // intoApply has lower priority than intoArrow
+      parseCopy.backtrack ::
+        parseArrow.backtrack ::
+        parseField ::
+        parseIdx ::
+        parseApply.backtrack :: Nil
+    )
 
   val ops: P[NonEmptyList[PropertyOp[Span.S]]] =
     parseOp.rep

parser/src/main/scala/aqua/parser/lexer/TypeToken.scala

@@ -121,9 +121,11 @@ case class ArrowTypeToken[S[_]: Comonad](
       args.map { case (n, t) => (n.map(_.mapK(fk)), t.mapK(fk)) },
       res.map(_.mapK(fk)),
       abilities.map(_.mapK(fk))
-  )
+    )
   def argTypes: List[TypeToken[S]] = abilities ++ args.map(_._2)
-  lazy val absWithArgs: List[(Option[Name[S]], TypeToken[S])] = abilities.map(n => Some(n.asName) -> n) ++ args
+
+  lazy val absWithArgs: List[(Option[Name[S]], TypeToken[S])] =
+    abilities.map(n => Some(n.asName) -> n) ++ args
 }
 
 object ArrowTypeToken {
@@ -136,9 +138,9 @@ object ArrowTypeToken {
   ).map(_.toList)
 
   // {SomeAb, SecondAb} for NamedTypeToken
-  def abilities(): P0[List[NamedTypeToken[S]]] =
-    (`{` *> comma(`Class`.surroundedBy(`/s*`).lift.map(NamedTypeToken(_)))
-      .map(_.toList) <* `}`).?.map(_.getOrElse(List.empty))
+  def abilities(): P0[List[NamedTypeToken[S]]] = (
+    `{` *> comma(NamedTypeToken.dotted).map(_.toList) <* `}`
+  ).?.map(_.getOrElse(List.empty))
 
   def `arrowdef`(argTypeP: P[TypeToken[Span.S]]): P[ArrowTypeToken[Span.S]] =
     ((abilities() ~ comma0(argTypeP)).with1 ~ ` -> `.lift ~

parser/src/main/scala/aqua/parser/lexer/ValueToken.scala

@@ -42,112 +42,105 @@ case class PropertyToken[F[_]: Comonad](
     name.forall(c => !c.isLetter || c.isUpper)
 
   /**
-   * This method tries to convert property token to
-   * property token with dotted var name inside value token.
-   *
-   * Next properties pattern is untouched:
-   * Class (field)*
-   *
-   * Next properties pattern is transformed:
-   * (Class)* (CONST | field) ..props..
-   * ^^^^^^^^^^^^^^^^^^^^^^^^
-   * this part is transformed to dotted name.
+   * Try to transform this token to imported ability access
+   * e.g. in `Some.Imported.Module.Ab.innerAb.call(...)`:
+   * - `Some.Imported.Module` is imported module name
+   * - `Ab.innerAb.call(...)` is ability access
+   * so it should be handled as `(Some.Imported.Module.Ab).innerAb.call(...)`
+   *                              ^^^^^^^^^^^^^^^^^^^^^^^
+   *                    ability name inside `VarToken` as one string
+   * but we don't know this in advance, so this method returns
+   * a list of all possible (imported module name, ability access value token) pairs
+   * so calling code can check what prefix is valid imported module name and
+   * handle the corresponding ability access value token.
    */
-  private def toDottedName: Option[ValueToken[F]] = value match {
-    case VarToken(name) =>
-      // Pattern `Class (field)*` is ability access
-      // and should not be transformed
-      val isAbility = isClass(name.value) && properties.forall {
-        case f @ IntoField(_) => isField(f.value)
-        case _ => true
-      }
+  def toAbility: List[(NamedTypeToken[F], ValueToken[F])] =
+    value match {
+      // NOTE: guard against recursion: if dot is alredy in the name, do not transform
+      case VarToken(name) if !name.value.contains(".") =>
+        val fields = properties.toList.takeWhile {
+          case IntoField(_) => true
+          case _ => false
+        }.collect { case f @ IntoField(_) => f.value }.toList
+        val names = name.value +: fields
 
-      if (isAbility) none
-      else {
-        // Gather prefix of properties that are IntoField
-        val props = name.value +: properties.toList.view.map {
-          case IntoField(name) => name.extract.some
-          case _ => none
-        }.takeWhile(_.isDefined).flatten.toList
+        fields.inits
+          // do not use the last field
+          // those cases are handled in `toCallArrow` and `toNamedValue`
+          .drop(1)
+          .map { init =>
+            // Length of the import name
+            val importLength = init.length + 1
+            // Length of the imported name
+            val nameLength = importLength + 1
+            val newProps = NonEmptyList.fromList(
+              properties.toList.drop(importLength)
+            )
+            val newName = name.rename(names.take(nameLength).mkString("."))
+            val importAbility = name.rename(names.take(importLength).mkString(".")).asTypeToken
 
-        val propsWithIndex = props.zipWithIndex
+            val varToken = VarToken(newName)
+            val token = newProps.fold(varToken)(ps => PropertyToken(varToken, ps))
 
-        // Find first property that is not Class
-        val classesTill = propsWithIndex.find { case (name, _) =>
-          !isClass(name)
-        }.collect { case (_, idx) =>
-          idx
-        }.getOrElse(props.length)
-
-        // Find last property after classes
-        // that is CONST or field
-        val lastSuitable = propsWithIndex
-          .take(classesTill)
-          .findLast { case (name, _) =>
-            isConst(name) || isField(name)
+            importAbility -> token
           }
-          .collect { case (_, idx) => idx }
+          .toList
+          // test shorter prefixes first
+          .reverse
+      case _ => Nil
+    }
 
-        lastSuitable.map(last =>
-          val newProps = NonEmptyList.fromList(
-            properties.toList.drop(last + 1)
+  /**
+   * Try to convert this token into `CallArrowToken`
+   * e.g. `Some.Imported.Module.call(...)`
+   *       ^^^^^^^^^^^^^^^^^^^^ ^^^^
+   *       ability name         function name
+   */
+  def toCallArrow: Option[CallArrowToken[F]] = (
+    value,
+    properties.last
+  ) match {
+    case (VarToken(name), IntoArrow(funcName, args)) =>
+      properties.init.traverse {
+        case IntoField(name) => name.extract.some
+        case _ => none
+      }.map { fields =>
+        val imported = name
+          .rename(
+            (name.value +: fields).mkString(".")
           )
-          val newName = props.take(last + 1).mkString(".")
-          val varToken = VarToken(name.rename(newName))
+          .asTypeToken
 
-          newProps.fold(varToken)(props => PropertyToken(varToken, props))
+        CallArrowToken(
+          imported.some,
+          funcName,
+          args
         )
       }
     case _ => none
   }
 
   /**
-   * This method tries to convert property token to
-   * call arrow token.
-   *
-   * Next properties pattern is transformed:
-   * (Class)+ arrow()
-   * ^^^^^^^
-   * this part is transformed to ability name.
+   * Try to convert this token into `NamedValueToken`,
+   * e.g. `Some.Imported.Module.DefinedAbility(...)`
+   *       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   *       type name
    */
-  private def toCallArrow: Option[CallArrowToken[F]] = value match {
-    case VarToken(name) =>
-      val ability = properties.init.traverse {
-        case f @ IntoField(_) => f.value.some
-        case _ => none
-      }.map(
-        name.value +: _
-      ).filter(
-        _.forall(isClass)
-      ).map(props => name.rename(props.mkString(".")))
+  def toNamedValue: Option[NamedValueToken[F]] =
+    (value, properties.last) match {
+      case (v @ VarToken(name), IntoApply(args)) =>
+        properties.init.traverse {
+          case IntoField(name) => name.extract.some
+          case _ => none
+        }.map { props =>
+          val typeName = name
+            .rename(
+              (name.value +: props).mkString(".")
+            )
+            .asTypeToken
 
-      (properties.last, ability) match {
-        case (IntoArrow(funcName, args), Some(ability)) =>
-          CallArrowToken(
-            ability.asTypeToken.some,
-            funcName,
-            args
-          ).some
-        case _ => none
-      }
-    case _ => none
-  }
-
-  /**
-   * This is a hacky method to adjust parsing result
-   * to format that was used previously.
-   * This method tries to convert property token to
-   * call arrow token or property token with
-   * dotted var name inside value token.
-   *
-   * @return Some(token) if token was adjusted, None otherwise
-   */
-  def adjust: Option[ValueToken[F]] =
-    toCallArrow.orElse(toDottedName)
-
-  lazy val leadingName: Option[NamedTypeToken[F]] =
-    value match {
-      case VarToken(name) => name.asTypeToken.some
+          NamedValueToken(typeName, args.extract)
+        }
       case _ => none
     }
 }

semantics/src/main/scala/aqua/semantics/header/HeaderHandler.scala

@@ -72,7 +72,7 @@ class HeaderHandler[S[_]: Comonad, C](using
         .toValidNec(
           error(
             tkn,
-            s"Used module has no `module` header. Please add `module` header or use ... as ModuleName, or switch to import"
+            s"Used module has no `aqua` header. Please add `aqua` header or use ... as ModuleName, or switch to import"
           )
         )
 

semantics/src/main/scala/aqua/semantics/rules/ValuesAlgebra.scala

@@ -1,5 +1,6 @@
 package aqua.semantics.rules
 
+import aqua.errors.Errors.internalError
 import aqua.helpers.syntax.optiont.*
 import aqua.parser.lexer.*
 import aqua.parser.lexer.InfixToken.{BoolOp, CmpOp, EqOp, MathOp, Op as InfOp}
@@ -85,6 +86,8 @@ class ValuesAlgebra[S[_], Alg[_]: Monad](using
           idx <- OptionT(op.idx.fold(LiteralRaw.Zero.some.pure)(valueToRaw))
           valueType <- OptionT(T.resolveIntoIndex(op, rootType, idx.`type`))
         } yield IntoIndexRaw(idx, valueType)).value
+      case op: IntoApply[S] =>
+        internalError("Unexpected. `IntoApply` expected to be transformed into `NamedValueToken`")
     }
 
   def valueToRaw(v: ValueToken[S]): Alg[Option[ValueRaw]] =
@@ -129,14 +132,29 @@ class ValuesAlgebra[S[_], Alg[_]: Monad](using
          * so here we try to differentiate them and adjust property
          * token accordingly.
          */
-        prop.leadingName.fold(default)(name =>
-          A.isDefinedAbility(name)
-            .flatMap(isDefined =>
-              prop.adjust
-                .filter(_ => isDefined)
-                .fold(default)(valueToRaw)
+
+        val callArrow = OptionT
+          .fromOption(prop.toCallArrow)
+          .filterF(ca =>
+            ca.ability.fold(false.pure)(
+              A.isDefinedAbility
             )
-        )
+          )
+          .widen[ValueToken[S]]
+
+        val ability = OptionT(
+          prop.toAbility.findM { case (ab, _) =>
+            // Test if name is an import
+            A.isDefinedAbility(ab)
+          }
+        ).map { case (_, token) => token }
+
+        val namedValue = OptionT
+          .fromOption(prop.toNamedValue)
+          .filterF(nv => T.resolveType(nv.typeName, mustBeDefined = false).map(_.isDefined))
+          .widen[ValueToken[S]]
+
+        callArrow.orElse(ability).orElse(namedValue).foldF(default)(valueToRaw)
 
       case dvt @ NamedValueToken(typeName, fields) =>
         (for {

semantics/src/main/scala/aqua/semantics/rules/types/TypesAlgebra.scala

@@ -19,7 +19,7 @@ trait TypesAlgebra[S[_], Alg[_]] {
 
   def resolveArrowDef(arrowDef: ArrowTypeToken[S]): Alg[Option[ArrowType]]
 
-  def resolveServiceType(name: NamedTypeToken[S]): Alg[Option[ServiceType]]
+  def resolveServiceType(name: NamedTypeToken[S], mustBeDefined: Boolean = true): Alg[Option[ServiceType]]
 
   def defineAbilityType(
     name: NamedTypeToken[S],

semantics/src/main/scala/aqua/semantics/rules/types/TypesInterpreter.scala

@@ -76,14 +76,18 @@ class TypesInterpreter[S[_], X](using
         }.as(none)
     }
 
-  override def resolveServiceType(name: NamedTypeToken[S]): State[X, Option[ServiceType]] =
-    resolveType(name).flatMap {
+  override def resolveServiceType(
+    name: NamedTypeToken[S],
+    mustBeDefined: Boolean = true
+  ): State[X, Option[ServiceType]] =
+    resolveType(name, mustBeDefined).flatMap {
       case Some(serviceType: ServiceType) =>
         serviceType.some.pure
-      case Some(t) =>
+      case Some(t) if mustBeDefined =>
         report.error(name, s"Type `$t` is not a service").as(none)
-      case None =>
+      case None if mustBeDefined =>
         report.error(name, s"Type `${name.value}` is not defined").as(none)
+      case _ => none.pure
     }
 
   override def defineAbilityType(