Optional arguments

.gitignore

@@ -8,3 +8,4 @@ project/Dependencies.scala
 project/metals.sbt
 **.worksheet.sc
 .DS_Store
+.idea/

.vscode/launch.json

@@ -0,0 +1,16 @@
+{
+    // Use IntelliSense to learn about possible attributes.
+    // Hover to view descriptions of existing attributes.
+    // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+    "version": "0.2.0",
+    "configurations": [
+        {
+            "type": "java",
+            "request": "attach",
+            "name": "gqd debugger",
+            // "projectName": "mlscript",
+            "hostName": "localhost",
+            "port": "8000"
+        }
+    ]
+}

.vscode/settings.json

@@ -14,5 +14,5 @@
             "strings": "off"
         }
     },
-    "files.autoSave": "off"
+    "files.autoSave": "afterDelay"
 }

compiler/shared/main/scala/mlscript/compiler/ClassLifter.scala

@@ -120,7 +120,7 @@ class ClassLifter(logDebugMsg: Boolean = false) {
       selPath2Term(l.map(x => genParName(x.name)).updated(0, "this").reverse, v)
     })
   }
-  private def toFldsEle(trm: Term): (Option[Var], Fld) = (None, Fld(FldFlags(false, false, false), trm))
+  private def toFldsEle(trm: Term): (Option[Var], Fld) = (None, Fld(FldFlags(false, false, false, false), trm))
 
   def getSupClsInfoByTerm(parentTerm: Term): (List[TypeName], List[(Var, Fld)]) = parentTerm match{
     case Var(nm) => List(TypeName(nm)) -> Nil
@@ -498,7 +498,7 @@ class ClassLifter(logDebugMsg: Boolean = false) {
   private def liftTypeField(target: Field)(using ctx: LocalContext, cache: ClassCache, globFuncs: Map[Var, (Var, LocalContext)], outer: Option[ClassInfoCache]): (Field, LocalContext) = {
     val (inT, iCtx) = target.in.map(liftType).unzip
     val (outT, oCtx) = liftType(target.out)
-    Field(inT, outT) -> (iCtx.getOrElse(emptyCtx) ++ oCtx)
+    Field(inT, outT, false) -> (iCtx.getOrElse(emptyCtx) ++ oCtx)
   }
 
   private def liftType(target: Type)(using ctx: LocalContext, cache: ClassCache, globFuncs: Map[Var, (Var, LocalContext)], outer: Option[ClassInfoCache]): (Type, LocalContext) = target match{

shared/src/main/scala/mlscript/ConstraintSolver.scala

@@ -99,7 +99,7 @@ class ConstraintSolver extends NormalForms { self: Typer =>
                     Nil)
                 val ty = d.typeSignature
                 S(
-                  if (d.fd.isMut) FieldType(S(ty), ty)(d.prov)
+                  if (d.fd.isMut) FieldType(S(ty), ty, false)(d.prov)
                   else ty.toUpper(d.prov)
                 )
               case S(p: NuParam) =>
@@ -512,6 +512,7 @@ class ConstraintSolver extends NormalForms { self: Typer =>
             case (LhsRefined(S(Without(b, _)), _, _, _), RhsBot) => rec(b, BotType, true)
             case (LhsTop, _) | (LhsRefined(N, empty(), RecordType(Nil), empty()), _) =>
               // TODO ^ actually get rid of LhsTop and RhsBot...? (might make constraint solving slower)
+              println(s"REPORT ERROR 515")
               reportError()
             case (LhsRefined(_, ts, _, trs), RhsBases(pts, _, _)) if ts.exists(pts.contains) => ()
 
@@ -530,6 +531,7 @@ class ConstraintSolver extends NormalForms { self: Typer =>
             case (_, RhsBases(_, _, trs)) if trs.nonEmpty => die
 
             case (_, RhsBot) | (_, RhsBases(Nil, N, _)) =>
+              println("REPORT ERRROR LINE 534")
               reportError()
 
             case (LhsRefined(S(f0@FunctionType(l0, r0)), ts, r, _)
@@ -554,7 +556,10 @@ class ConstraintSolver extends NormalForms { self: Typer =>
               lit match {
                 case _: IntLit |  _: DecLit => rec(fldTy.lb.getOrElse(TopType), DecType, false)
                 case _: StrLit => rec(fldTy.lb.getOrElse(TopType), StrType, false)
-                case _: UnitLit => reportError()
+                case _: UnitLit => {
+                  println(s"REPORT ERROR 560")
+                  reportError()
+                }
               }
 
             // * This deals with the implicit Eql type member for user-defined classes.
@@ -604,7 +609,10 @@ class ConstraintSolver extends NormalForms { self: Typer =>
                     case S(Without(b, ns)) =>
                       if (ns(n)) rec(b, RhsBases(ots, N, trs).toType(), true)
                       else rec(b, done_rs.toType(), true)
-                    case _ => reportError()
+                    case _ => {
+                      println("REPORT ERROR 613")
+                      reportError()
+                    }
                   }
               }
             case (LhsRefined(N, ts, r, trs), RhsBases(pts, N, trs2))  =>
@@ -614,9 +622,15 @@ class ConstraintSolver extends NormalForms { self: Typer =>
                 case _ => Nil
               }.contains(p.id)))
                 println(s"OK $ts <: $pts")
-              else reportError()
+              else {
+                println(s"REPORT ERROR 624")
+                reportError()
+              }
             case (LhsRefined(N, ts, r, _), RhsBases(pts, S(L(_: FunctionType | _: ArrayBase)), _)) =>
-              reportError()
+              {
+                println(s"REPORT ERROR 627")
+                reportError()
+              }
             case (LhsRefined(S(b: TupleType), ts, r, _), RhsBases(pts, S(L(ty: TupleType)), _))
               if b.fields.size === ty.fields.size =>
                 (b.fields.unzip._2 lazyZip ty.fields.unzip._2).foreach { (l, r) =>
@@ -626,7 +640,10 @@ class ConstraintSolver extends NormalForms { self: Typer =>
             case (LhsRefined(S(b: ArrayBase), ts, r, _), RhsBases(pts, S(L(ar: ArrayType)), _)) =>
               recLb(ar.inner, b.inner)
               rec(b.inner.ub, ar.inner.ub, false)
-            case (LhsRefined(S(b: ArrayBase), ts, r, _), _) => reportError()
+            case (LhsRefined(S(b: ArrayBase), ts, r, _), _) => {
+              println(s"REPORTERROR 643") 
+              reportError()
+            }
             case (LhsRefined(S(ov: Overload), ts, r, trs), _) =>
               annoying(Nil, LhsRefined(S(ov.approximatePos), ts, r, trs), Nil, done_rs) // TODO remove approx. with ambiguous constraints
             case (LhsRefined(S(Without(b, ns)), ts, r, _), RhsBases(pts, N | S(L(_)), _)) =>
@@ -879,7 +896,7 @@ class ConstraintSolver extends NormalForms { self: Typer =>
             }
 
 
-          case (TupleType(fs0), TupleType(fs1)) if fs0.size === fs1.size => // TODO generalize (coerce compatible tuples)
+          case (t0 @ TupleType(fs0), t1 @ TupleType(fs1)) if t0.isLengthCompatibleWith(t1) => {
             fs0.lazyZip(fs1).foreach { case ((ln, l), (rn, r)) =>
               ln.foreach { ln => rn.foreach { rn =>
                 if (ln =/= rn) err(
@@ -889,6 +906,7 @@ class ConstraintSolver extends NormalForms { self: Typer =>
               recLb(r, l)
               rec(l.ub, r.ub, false)
             }
+          }
           case (t: ArrayBase, a: ArrayType) =>
             recLb(a.inner, t.inner)
             rec(t.inner.ub, a.inner.ub, false)
@@ -911,7 +929,10 @@ class ConstraintSolver extends NormalForms { self: Typer =>
           case (RecordType(fs0), RecordType(fs1)) =>
             fs1.foreach { case (n1, t1) =>
               fs0.find(_._1 === n1).fold {
-                reportError()
+                {
+                  println(s"REPORTERROR 933") 
+                  reportError()
+                }
               } { case (n0, t0) =>
                 recLb(t1, t0)
                 rec(t0.ub, t1.ub, false)
@@ -967,7 +988,10 @@ class ConstraintSolver extends NormalForms { self: Typer =>
               if (tr1.mayHaveTransitiveSelfType) rec(tr1.expand, tr2.expand, true)
               else (tr1.mkClsTag, tr2.mkClsTag) match {
                 case (S(tag1), S(tag2)) if !(tag1 <:< tag2) =>
-                  reportError()
+                  {
+                    println(s"REPORTERROR 992") 
+                    reportError()
+                  }
                 case _ =>
                   rec(tr1.expand, tr2.expand, true)
               }
@@ -1066,14 +1090,17 @@ class ConstraintSolver extends NormalForms { self: Typer =>
             goToWork(lhs, rhs)
           case (_: ClassTag | _: TraitTag, _: TraitTag) =>
             goToWork(lhs, rhs)
-          case _ => reportError()
+          case _ => {
+              println(s"REPORTERROR 1093") 
+              reportError()
+            }
       }}
     }}()
 
     def reportError(failureOpt: Opt[Message] = N)(implicit cctx: ConCtx, ctx: Ctx): Unit = {
       val lhs = cctx._1.head
       val rhs = cctx._2.head
-      
+
       println(s"CONSTRAINT FAILURE: $lhs <: $rhs")
       // println(s"CTX: ${cctx.map(_.map(lr => s"${lr._1} <: ${lr._2} [${lr._1.prov}] [${lr._2.prov}]"))}")
 
@@ -1236,7 +1263,6 @@ class ConstraintSolver extends NormalForms { self: Typer =>
         case _ => doesntMatch(rhs)
       })
 
-
       val mismatchMessage =
         msg"Type mismatch in ${prov.desc}:" -> show(prov.loco) :: (
           msg"${printProv(lhsProv)} `${lhs.expPos}` $failure"
@@ -1248,6 +1274,8 @@ class ConstraintSolver extends NormalForms { self: Typer =>
           msg"but it flows into ${l.prov.desc}$expTyMsg" -> show(l.prov.loco) :: Nil
         }.toList.flatten
 
+      println(s"dbg [ConstraintSolver]: ${flowHint}")
+
       val constraintProvenanceHints = mk_constraintProvenanceHints
 
       var first = true

shared/src/main/scala/mlscript/JSBackend.scala

@@ -1202,10 +1202,10 @@ abstract class JSBackend {
 
     def prepare(nme: Str, fs: Ls[Opt[Var] -> Fld], pars: Ls[Term], unit: TypingUnit) = {
       val params = fs.map {
-        case (S(nme), Fld(FldFlags(mut, spec, _), trm)) =>
+        case (S(nme), Fld(FldFlags(mut, spec, opt, _), trm)) =>
           val ty = tt(trm)
-          nme -> Field(if (mut) S(ty) else N, ty)
-        case (N, Fld(FldFlags(mut, spec, _), nme: Var)) => nme -> Field(if (mut) S(Bot) else N, Top)
+          nme -> Field(if (mut) S(ty) else N, ty, opt)
+        case (N, Fld(FldFlags(mut, spec, opt, _), nme: Var)) => nme -> Field(if (mut) S(Bot) else N, Top, opt)
         case _ => die
       }
       val publicCtors = fs.filter {

shared/src/main/scala/mlscript/MLParser.scala

@@ -31,7 +31,7 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
   }
   def toParamsTy(t: Type): Tuple = t match {
     case t: Tuple => t
-    case _ => Tuple((N, Field(None, t)) :: Nil)
+    case _ => Tuple((N, Field(None, t, false)) :: Nil)
   }
 
   def letter[p: P]     = P( lowercase | uppercase )
@@ -69,14 +69,14 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
 
   def parens[p: P]: P[Term] = locate(P( "(" ~/ parenCell.rep(0, ",") ~ ",".!.? ~ ")" ).map {
     case (Seq(Right(t -> false)), N) => Bra(false, t)
-    case (Seq(Right(t -> true)), N) => Tup(N -> Fld(FldFlags(true, false, false), t) :: Nil) // ? single tuple with mutable
+    case (Seq(Right(t -> true)), N) => Tup(N -> Fld(FldFlags(true, false, false, false), t) :: Nil) // ? single tuple with mutable
     case (ts, _) => 
       if (ts.forall(_.isRight)) Tup(ts.iterator.map {
-        case R(f) => N -> Fld(FldFlags(f._2, false, false), f._1)
+        case R(f) => N -> Fld(FldFlags(f._2, false, false, false), f._1)
         case _ => die // left unreachable
       }.toList)
       else Splc(ts.map {
-        case R((v, m)) => R(Fld(FldFlags(m, false, false), v))
+        case R((v, m)) => R(Fld(FldFlags(m, false, false, false), v))
         case L(spl) => L(spl)
       }.toList)
   })
@@ -106,8 +106,8 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
       "{" ~/ (kw("mut").!.? ~ fieldName ~ "=" ~ term map L.apply).|(kw("mut").!.? ~
         variable map R.apply).rep(sep = ";" | ",") ~ "}"
     ).map { fs => Rcd(fs.map{ 
-        case L((mut, v, t)) => v -> Fld(FldFlags(mut.isDefined, false, false), t)
-        case R(mut -> id) => id -> Fld(FldFlags(mut.isDefined, false, false), id) }.toList)})
+        case L((mut, v, t)) => v -> Fld(FldFlags(mut.isDefined, false, false, false), t)
+        case R(mut -> id) => id -> Fld(FldFlags(mut.isDefined, false, false, false), id) }.toList)})
 
   def fun[p: P]: P[Term] = locate(P( kw("fun") ~/ term ~ "->" ~ term ).map(nb => Lam(toParams(nb._1), nb._2)))
 
@@ -274,8 +274,8 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
   def rcd[p: P]: P[Record] =
     locate(P( "{" ~/ ( kw("mut").!.? ~ fieldName ~ ":" ~ ty).rep(sep = ";") ~ "}" )
       .map(_.toList.map {
-        case (None, v, t) => v -> Field(None, t)
-        case (Some(_), v, t) => v -> Field(Some(t), t)
+        case (None, v, t) => v -> Field(None, t, false)
+        case (Some(_), v, t) => v -> Field(Some(t), t, false)
       } pipe Record))
 
   def parTyCell[p: P]: P[Either[Type, (Type, Boolean)]] = (("..." | kw("mut")).!.? ~ ty). map {
@@ -289,14 +289,14 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
     case (fs, _) => 
       if (fs.forall(_._2.isRight))
         Tuple(fs.map {
-          case (l, Right(t -> false)) => l -> Field(None, t)
-          case (l, Right(t -> true)) => l -> Field(Some(t), t)
+          case (l, Right(t -> false)) => l -> Field(None, t, false)
+          case (l, Right(t -> true)) => l -> Field(Some(t), t, false)
           case _ => ??? // unreachable
         })
       else Splice(fs.map{ _._2 match { 
         case L(l) => L(l) 
-        case R(r -> true) => R(Field(Some(r), r))
-        case R(r -> false) => R(Field(None, r))
+        case R(r -> true) => R(Field(Some(r), r, false))
+        case R(r -> false) => R(Field(None, r, false))
       } })
   })
   def litTy[p: P]: P[Type] = P( lit.map(l => Literal(l).withLocOf(l)) )
@@ -327,7 +327,7 @@ class MLParser(origin: Origin, indent: Int = 0, recordLocations: Bool = true) {
     }
     def tup = parTy.map {
       case t: Tuple => t
-      case t => Tuple(N -> Field(N, t) :: Nil)
+      case t => Tuple(N -> Field(N, t, false) :: Nil)
     }
     P((ctorName ~ tup.?).map {
       case (id, S(body: Tuple)) =>

shared/src/main/scala/mlscript/NewLexer.scala

@@ -51,10 +51,11 @@ class NewLexer(origin: Origin, raise: Diagnostic => Unit, dbg: Bool) {
     ";",
     // ",",
     "#",
-    "`"
+    "`",
     // ".",
     // "<",
     // ">",
+    "?:"
   )
 
   private val isAlphaOp = Set(
@@ -342,9 +343,12 @@ class NewLexer(origin: Origin, raise: Diagnostic => Unit, dbg: Bool) {
             lex(k, ind, next(k, SELECT(name)))
           }
           else lex(j, ind, next(j, if (isSymKeyword.contains(n)) KEYWORD(n) else IDENT(n, true)))
+        } 
+        else {
+          // println(s"dbg [NewLexer.scala]: n: $n, j: $j, isSymKeyword: ${isSymKeyword.contains(n)}")
+          // else go(j, i   f (isSymKeyword.contains(n)) KEYWORD(n) else IDENT(n, true))
+          lex(j, ind, next(j, if (isSymKeyword.contains(n)) KEYWORD(n) else IDENT(n, true)))
         }
-        // else go(j, if (isSymKeyword.contains(n)) KEYWORD(n) else IDENT(n, true))
-        else lex(j, ind, next(j, if (isSymKeyword.contains(n)) KEYWORD(n) else IDENT(n, true)))
       case _ if isDigit(c) =>
         val (lit, j) = num(i)
         // go(j, LITVAL(IntLit(BigInt(str))))