feat(compiler)!: Make nil option bottom [LNG-279] (#968)

* Make nil option of bottom

* Fix tests

* Make literals of data type

* Add unit tests

* Remove print

integration-tests/aqua/examples/stream.aqua

@@ -1,6 +1,15 @@
+aqua Stream
+
 import "@fluencelabs/aqua-lib/builtin.aqua"
 import "println.aqua"
 
+export Stringer
+export checkStreams, returnStreamFromFunc
+export stringEmpty, returnEmptyLiteral
+export returnNilLength, stringNone
+export streamFunctor, streamAssignment
+export streamIntFunctor, streamJoin
+
 service Stringer("stringer-id"):
     returnString: string -> string
 
@@ -20,16 +29,18 @@ func returnStreamFromFunc() -> *u32:
     nums <- getStream()
     <- nums
 
-func stringNil() -> *string:
+func stringEmpty() -> *string:
     valueNil: *string
     <- valueNil
 
-func returnNil() -> *string:
+func returnEmpty() -> *string:
-    relayNil <- stringNil()
+    relayNil <- stringEmpty()
     <- relayNil
 
-func returnNilLiteral() -> *string:
+func returnEmptyLiteral() -> *string:
-    <- nil
+    empty: *string
+    -- TODO: return *[] here after LNG-280
+    <- empty
 
 func returnNilLength() -> u32:
     arr = nil

integration-tests/src/examples/streamCall.ts

@@ -1,14 +1,14 @@
 import {
-  checkStreams,
   registerStringer,
+  checkStreams,
   returnNilLength,
-  returnNilLiteral,
+  returnEmptyLiteral,
   returnStreamFromFunc,
   streamAssignment,
   streamFunctor,
   streamIntFunctor,
   streamJoin,
-  stringNil,
+  stringEmpty,
   stringNone,
 } from "../compiled/examples/stream.js";
 
@@ -23,7 +23,7 @@ export async function streamCall() {
 }
 
 export async function returnNilCall() {
-  return stringNil();
+  return stringEmpty();
 }
 
 export async function returnNoneCall() {
@@ -47,7 +47,7 @@ export async function streamAssignmentCall() {
 }
 
 export async function nilLiteralCall() {
-  return await returnNilLiteral();
+  return await returnEmptyLiteral();
 }
 
 export async function nilLengthCall() {

model/inline/src/main/scala/aqua/model/inline/raw/ApplyPropertiesRawInliner.scala

@@ -17,8 +17,8 @@ import cats.syntax.applicative.*
 import cats.syntax.bifunctor.*
 import cats.syntax.foldable.*
 import cats.syntax.monoid.*
-import cats.syntax.traverse.*
 import cats.syntax.option.*
+import cats.syntax.traverse.*
 import scribe.Logging
 
 object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Logging {
@@ -33,19 +33,15 @@ object ApplyPropertiesRawInliner extends RawInliner[ApplyPropertyRaw] with Loggi
       apName <- Mangler[S].findAndForbidName("literal_ap")
       resultName <- Mangler[S].findAndForbidName(s"literal_props")
     } yield {
-      val cleanedType = literal.`type` match {
+      val typ = literal.`type`
-        // literals cannot be streams, use it as an array to use properties
+      val apVar = VarModel(apName, typ, properties)
-        case StreamType(el) => ArrayType(el)
-        case tt => tt
-      }
-      val apVar = VarModel(apName, cleanedType, properties)
       val tree = inl |+| Inline.tree(
         SeqModel.wrap(
-          FlattenModel(literal.copy(`type` = cleanedType), apVar.name).leaf,
+          FlattenModel(literal.copy(`type` = typ), apVar.name).leaf,
           FlattenModel(apVar, resultName).leaf
         )
       )
-      VarModel(resultName, properties.lastOption.map(_.`type`).getOrElse(cleanedType)) -> tree
+      VarModel(resultName, properties.lastOption.map(_.`type`).getOrElse(typ)) -> tree
     }
   }
 

model/raw/src/main/scala/aqua/raw/value/ValueRaw.scala

@@ -35,7 +35,7 @@ object ValueRaw {
   val ParticleTtl: LiteralRaw = LiteralRaw("%ttl%", ScalarType.u32)
   val ParticleTimestamp: LiteralRaw = LiteralRaw("%timestamp%", ScalarType.u64)
 
-  val Nil: LiteralRaw = LiteralRaw("[]", StreamType(BottomType))
+  val Nil: LiteralRaw = LiteralRaw("[]", OptionType(BottomType))
 
   /**
    * Type of error value
@@ -125,7 +125,7 @@ case class VarRaw(name: String, baseType: Type) extends ValueRaw {
   override def varNames: Set[String] = Set(name)
 }
 
-case class LiteralRaw(value: String, baseType: Type) extends ValueRaw {
+case class LiteralRaw(value: String, baseType: DataType) extends ValueRaw {
   override def mapValues(f: ValueRaw => ValueRaw): ValueRaw = this
 
   override def toString: String = s"{$value: ${baseType}}"

model/src/main/scala/aqua/model/ValueModel.scala

@@ -6,8 +6,8 @@ import aqua.types.*
 
 import cats.Eq
 import cats.data.{Chain, NonEmptyMap}
-import cats.syntax.option.*
 import cats.syntax.apply.*
+import cats.syntax.option.*
 import scribe.Logging
 
 sealed trait ValueModel {
@@ -75,7 +75,7 @@ object ValueModel {
   }
 }
 
-case class LiteralModel(value: String, `type`: Type) extends ValueModel {
+case class LiteralModel(value: String, `type`: DataType) extends ValueModel {
 
   override def toString: String = s"{$value: ${`type`}}"
 

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

@@ -4,8 +4,8 @@ import aqua.parser.lift.Span.S
 
 import cats.data.NonEmptyList
 import cats.parse.{Accumulator0, Parser as P, Parser0 as P0}
-import cats.{~>, Comonad, Functor}
 import cats.syntax.functor.*
+import cats.{Comonad, Functor, ~>}
 
 trait Token[F[_]] {
   def as[T](v: T): F[T]

semantics/src/test/scala/aqua/semantics/SemanticsSpec.scala

@@ -16,6 +16,7 @@ import cats.data.Validated
 import cats.data.{Chain, EitherNec, NonEmptyChain}
 import cats.free.Cofree
 import cats.syntax.foldable.*
+import cats.syntax.option.*
 import cats.syntax.show.*
 import cats.syntax.traverse.*
 import cats.~>
@@ -49,11 +50,13 @@ class SemanticsSpec extends AnyFlatSpec with Matchers with Inside {
     inside(semantics.process(ast, init).value.run)(test)
   }
 
-  def insideBody(script: String)(test: RawTag.Tree => Any): Unit =
+  def insideBody(script: String, func: Option[String] = None)(test: RawTag.Tree => Any): Unit =
     insideResult(script) { case (_, Right(ctx)) =>
-      inside(ctx.funcs.headOption) { case Some((_, func)) =>
+      inside(
-        test(func.arrow.body)
+        func.fold(
-      }
+          ctx.funcs.headOption.map { case (_, raw) => raw }
+        )(ctx.funcs.get)
+      ) { case Some(func) => test(func.arrow.body) }
     }
 
   def insideSemErrors(script: String)(test: NonEmptyChain[SemanticError[Span.S]] => Any): Unit =
@@ -877,7 +880,6 @@ class SemanticsSpec extends AnyFlatSpec with Matchers with Inside {
                       |""".stripMargin
 
       insideBody(script) { body =>
-        println(body.show)
         matchSubtree(body) { case (CallArrowRawTag(_, ca: CallArrowRaw), _) =>
           inside(ca.arguments) { case (c: CollectionRaw) :: Nil =>
             c.values.exists {
@@ -892,4 +894,62 @@ class SemanticsSpec extends AnyFlatSpec with Matchers with Inside {
     test("[]", "")
     test("?", "?")
   }
+
+  it should "allow `nil` in place of an array or an option" in {
+    def test(p: String) = {
+      val script = s"""
+                      |func length(col: ${p}string) -> u32:
+                      |  <- col.length
+                      |
+                      |func return() -> ${p}string:
+                      |  <- nil
+                      |
+                      |func test() -> u32:
+                      |  l <- length(nil)
+                      |  n <- return()
+                      |  <- l + n.length
+                      |""".stripMargin
+
+      insideBody(script, "test".some) { body =>
+        matchSubtree(body) {
+          case (CallArrowRawTag(_, ca: CallArrowRaw), _) if ca.name == "length" =>
+            ca.arguments.length shouldEqual 1
+        }
+        matchSubtree(body) {
+          case (CallArrowRawTag(_, ca: CallArrowRaw), _) if ca.name == "return" =>
+            ca.arguments.length shouldEqual 0
+        }
+      }
+    }
+
+    test("[]")
+    test("?")
+  }
+
+  it should "forbid `nil` in place of a stream" in {
+    val scriptAccept = s"""
+                          |func length(col: *string) -> u32:
+                          |  <- col.length
+                          |
+                          |func test() -> u32:
+                          |  <- length(nil)
+                          |""".stripMargin
+
+    val scriptReturn = s"""
+                          |func return() -> *string:
+                          |  <- nil
+                          |
+                          |func test() -> u32:
+                          |  n <- return()
+                          |  <- n.length
+                          |""".stripMargin
+
+    insideSemErrors(scriptAccept) { errors =>
+      atLeast(1, errors.toChain.toList) shouldBe a[RulesViolated[Span.S]]
+    }
+
+    insideSemErrors(scriptReturn) { errors =>
+      atLeast(1, errors.toChain.toList) shouldBe a[RulesViolated[Span.S]]
+    }
+  }
 }

semantics/src/test/scala/aqua/semantics/ValuesAlgebraSpec.scala

@@ -1,6 +1,7 @@
 package aqua.semantics
 
 import aqua.parser.lexer.*
+import aqua.raw.ConstantRaw
 import aqua.raw.RawContext
 import aqua.raw.value.*
 import aqua.semantics.rules.ValuesAlgebra
@@ -14,7 +15,7 @@ import aqua.semantics.rules.types.{TypesAlgebra, TypesInterpreter}
 import aqua.types.*
 
 import cats.Id
-import cats.data.{NonEmptyList, NonEmptyMap, State}
+import cats.data.{Chain, NonEmptyList, NonEmptyMap, State}
 import monocle.syntax.all.*
 import org.scalatest.Inside
 import org.scalatest.flatspec.AnyFlatSpec
@@ -66,9 +67,15 @@ class ValuesAlgebraSpec extends AnyFlatSpec with Matchers with Inside {
     b <- list
   } yield (a, b)
 
-  def genState(vars: Map[String, Type] = Map.empty) =
+  def genState(vars: Map[String, Type] = Map.empty) = {
+    val init = RawContext.blank.copy(
+      parts = Chain
+        .fromSeq(ConstantRaw.defaultConstants())
+        .map(const => RawContext.blank -> const)
+    )
+
     CompilerState
-      .init[Id](RawContext.blank)
+      .init[Id](init)
       .focus(_.names)
       .modify(
         _.focus(_.stack).modify(
@@ -78,6 +85,7 @@ class ValuesAlgebraSpec extends AnyFlatSpec with Matchers with Inside {
           ) :: _
         )
       )
+  }
 
   def valueOfType(t: Type)(
     varName: String,
@@ -572,4 +580,19 @@ class ValuesAlgebraSpec extends AnyFlatSpec with Matchers with Inside {
       atLeast(1, st.errors.toList) shouldBe a[RulesViolated[Id]]
     }
   }
+
+  it should "consider `nil` of type `?⊥`" in {
+    val nil = variable("nil")
+
+    val alg = algebra()
+
+    val (st, res) = alg
+      .valueToRaw(nil)
+      .run(genState())
+      .value
+
+    inside(res) { case Some(value) =>
+      value.`type` shouldBe OptionType(BottomType)
+    }
+  }
 }