Optional arguments

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

@@ -51,10 +51,11 @@ class NewLexer(origin: Origin, raise: Diagnostic => Unit, dbg: Bool) {
     ";",
     // ",",
     "#",
-    "`"
+    "`",
     // ".",
     // "<",
     // ">",
+    "?:"
   )
 
   private val isAlphaOp = Set(

shared/src/main/scala/mlscript/NewParser.scala

@@ -1427,37 +1427,34 @@ abstract class NewParser(origin: Origin, tokens: Ls[Stroken -> Loc], newDefs: Bo
         S(l0)
       case _ => N
     }
-    val (argName, argOpt) = yeetSpaces match {
-      case (IDENT(idStr, false), l0) :: (IDENT("?:", true), l1) :: _ =>
+    val (argName, isOpt) = yeetSpaces match {
+      case (IDENT(idStr, false), l0) :: (KEYWORD("?:"), l1) :: _ => 
+        // println(s"dbg [NewParser.scala]: idStr: ${idStr}, l0: ${l0}, keyword: ?:, l1: ${l1}")
         consume
         consume
-        (S(Var(idStr).withLoc(S(l0))), S(l1))
+        (S(Var(idStr).withLoc(S(l0))), true)
       case (IDENT(idStr, false), l0) :: (KEYWORD(":"), _) :: _ => // TODO: | ...
         consume
         consume
-        (S(Var(idStr).withLoc(S(l0))), N)
-      case (LITVAL(IntLit(i)), l0) :: (IDENT("?:", true), l1) :: _ => // TODO: | ...
-        consume
-        consume
-        (S(Var(i.toString).withLoc(S(l0))), S(l1))
+        (S(Var(idStr).withLoc(S(l0))), false)
       case (LITVAL(IntLit(i)), l0) :: (KEYWORD(":"), _) :: _ => // TODO: | ...
         consume
         consume
-        (S(Var(i.toString).withLoc(S(l0))), N)
-      case _ => (N, N)
+        (S(Var(i.toString).withLoc(S(l0))), false)
+      case _ => (N, false)
     }
     val body = exprOrIf(prec, true, anns)
-
-    // println(s"dbg [NewParser.scala]: argName: ${argName}, argOpt: ${argOpt.isDefined}")
-
-    val isOpt = cur match {
+    // println(s"dbg [NewParser.scala]: argName: ${argName}, argOpt: ${isOpt}")
+    val isOpt2 = cur match {
       case (IDENT("?", true), l0) :: _ =>
+        // println(s"dbg [NewParser.scala]: cur: ${cur}, isOpt2: true")
         consume
         true
       case _ =>
         false
     }
-    val e = body.map(Fld(FldFlags(argMut.isDefined, argSpec.isDefined, argOpt.isDefined || isOpt, argVal.isDefined), _))
+
+    val e = body.map(Fld(FldFlags(argMut.isDefined, argSpec.isDefined, isOpt || isOpt2, argVal.isDefined), _))
     def mkSeq = if (seqAcc.isEmpty) argName -> e else e match {
       case L(_) => ???
       case R(Fld(flags, res)) =>

shared/src/test/diff/nu/OptionalArgs.mls

@@ -1,6 +1,6 @@
 :NewDefs
 
-fun (??) oops(a, b) = a + b
+fun (??) oops(a123, b123) = a123 + b123
 //│ fun (??) oops: (Int, Int) -> Int
 
 1 ?? 2
@@ -9,8 +9,8 @@ fun (??) oops(a, b) = a + b
 //│     = 3
 
 
-fun f1(a?: Int, b?: Int) = a + b
-//│ fun f1: (a: (Int)?, b: (Int)?) -> Int
+fun f1(aOpt?: Int, bOpt?: Int) = aOpt + bOpt
+//│ fun f1: (aOpt: (Int)?, bOpt: (Int)?) -> Int
 
 fun f1(a: Int, b: Int) = a + b
 //│ fun f1: (a: Int, b: Int) -> Int
@@ -116,3 +116,56 @@ fun foo(xs: [Int] & 'a) = xs : [Int, Int?]
 //│ fun foo: (xs: [Int]) -> [Int, (Int)?]
 
 // fun foo(xs: [Int] & 'a) = [xs : [Int, Int?], xs]
+
+:p
+fun foo0(x?: Int) = if x is undefined then 0 else x + 1
+//│ |#fun| |foo0|(|x|#?:| |Int|)| |#=| |#if| |x| |is| |#undefined| |#then| |0| |#else| |x| |+| |1|
+//│ AST: TypingUnit(List(NuFunDef(None,Var(foo0),None,List(),Left(Lam(Tup(List((Some(Var(x)),Fld(_,Var(Int))))),If(IfThen(App(Var(is),Tup(List((None,Fld(_,Var(x))), (None,Fld(_,UnitLit(true)))))),IntLit(0)),Some(App(Var(+),Tup(List((None,Fld(_,Var(x))), (None,Fld(_,IntLit(1)))))))))))))
+//│ Parsed: fun foo0 = (x: Int,) => if (is(x, undefined,)) then 0 else +(x, 1,);
+//│ fun foo0: (x: (Int)?) -> Int
+
+:p
+fun foo1(x?) = if x is undefined then 0 else x + 1
+//│ |#fun| |foo1|(|x|?|)| |#=| |#if| |x| |is| |#undefined| |#then| |0| |#else| |x| |+| |1|
+//│ AST: TypingUnit(List(NuFunDef(None,Var(foo1),None,List(),Left(Lam(Tup(List((None,Fld(_,Var(x))))),If(IfThen(App(Var(is),Tup(List((None,Fld(_,Var(x))), (None,Fld(_,UnitLit(true)))))),IntLit(0)),Some(App(Var(+),Tup(List((None,Fld(_,Var(x))), (None,Fld(_,IntLit(1)))))))))))))
+//│ Parsed: fun foo1 = (x,) => if (is(x, undefined,)) then 0 else +(x, 1,);
+//│ fun foo1: ((Int | ())?) -> Int
+
+foo1(2)
+//│ Int
+//│ res
+//│     = 3
+
+fun foo0(x?:Int) = x + 1
+//│ fun foo0: (x: (Int)?) -> Int
+
+:e
+fun foo1(x?) = x + 1
+//│ ╔══[ERROR] Type mismatch in operator application:
+//│ ║  l.143: 	fun foo1(x?) = x + 1
+//│ ║         	               ^^^^^
+//│ ╟── reference of type `()` is not an instance of type `Int`
+//│ ║  l.143: 	fun foo1(x?) = x + 1
+//│ ╙──       	               ^
+//│ fun foo1: ((Int | ())?) -> (Int | error)
+
+
+fun foo(x?) = if x is undefined then 0 else x + 1
+//│ fun foo: ((Int | ())?) -> Int
+
+
+fun foo: (x: Int) -> Int
+fun foo(x?) = if x is undefined then 0 else x + 1
+//│ fun foo: ((Int | ())?) -> Int
+//│ fun foo: (x: Int) -> Int
+
+fun foo: (x: Int?) -> Int
+fun foo(x) = x + 1
+//│ fun foo: Int -> Int
+//│ fun foo: (x: (Int)?) -> Int
+
+fun f(x) = (x : [Int, Int?]) : ['a, 'b]
+//│ fun f: ([Int, (Int)?]) -> [Int, Int]
+
+fun f(x) = (x : [Int, Int?]) : ['a, 'b]
+//│ fun f: ([Int, (Int)?]) -> [Int, Int]