From ec40f58b6db08b352fdc28fd7987feba40377432 Mon Sep 17 00:00:00 2001
From: "P. Oscar Boykin" <johnynek@users.noreply.github.com>
Date: Sun, 10 Sep 2023 07:19:31 -1000
Subject: [PATCH] Define functions in scala, support up to 32 (#1039)

---
 .../src/main/resources/bosatsu/predef.bosatsu | 10 ----------
 .../main/scala/org/bykn/bosatsu/Package.scala | 19 ++++++++++++++++++-
 .../scala/org/bykn/bosatsu/rankn/Type.scala   |  2 +-
 3 files changed, 19 insertions(+), 12 deletions(-)

diff --git a/core/src/main/resources/bosatsu/predef.bosatsu b/core/src/main/resources/bosatsu/predef.bosatsu
index b56da575e..48cd4a99f 100644
--- a/core/src/main/resources/bosatsu/predef.bosatsu
+++ b/core/src/main/resources/bosatsu/predef.bosatsu
@@ -12,7 +12,6 @@ export (
   Order(),
   Unit(),
   Dict,
-  Fn1, Fn2, Fn3, Fn4, Fn5, Fn6, Fn7, Fn8,
   add,
   add_key,
   cmp_Int,
@@ -53,15 +52,6 @@ struct TupleCons(first, second)
 enum Bool:
   False, True
 
-external struct Fn1[a: -*, z: +*]
-external struct Fn2[a: -*, b: -*, z: +*]
-external struct Fn3[a: -*, b: -*, c: -*, z: +*]
-external struct Fn4[a: -*, b: -*, c: -*, d: -*, z: +*]
-external struct Fn5[a: -*, b: -*, c: -*, d: -*, e: -*, z: +*]
-external struct Fn6[a: -*, b: -*, c: -*, d: -*, e: -*, f: -*, z: +*]
-external struct Fn7[a: -*, b: -*, c: -*, d: -*, e: -*, f: -*, g: -*, z: +*]
-external struct Fn8[a: -*, b: -*, c: -*, d: -*, e: -*, f: -*, g: -*, h: -*, z: +*]
-
 #############
 # Support for built-in lists
 #############
diff --git a/core/src/main/scala/org/bykn/bosatsu/Package.scala b/core/src/main/scala/org/bykn/bosatsu/Package.scala
index 282154bf4..0d26e47bc 100644
--- a/core/src/main/scala/org/bykn/bosatsu/Package.scala
+++ b/core/src/main/scala/org/bykn/bosatsu/Package.scala
@@ -344,7 +344,24 @@ object Package {
    */
   lazy val predefPackage: Package.Parsed =
     parser(None).parse(Predef.predefString) match {
-      case Right((_, pack)) => pack
+      case Right((_, pack)) =>
+        // Make function defs:
+        def paramType(n: Int) = (TypeRef.TypeVar(s"i$n"), Some(Kind.Arg(Variance.contra, Kind.Type)))
+        def makeFns(n: Int,
+          typeArgs: List[(TypeRef.TypeVar, Option[Kind.Arg])],
+          acc: List[Statement.ExternalStruct]): List[Statement.ExternalStruct] =
+          if (n > Type.FnType.MaxSize) acc
+          else {
+            val fn = Statement.ExternalStruct(Identifier.Constructor(s"Fn$n"), typeArgs)(Region(0, 1))
+            val acc1 = fn :: acc
+            makeFns(n + 1, paramType(n) :: typeArgs, acc1)
+          }
+
+        val out = (TypeRef.TypeVar("z"), Some(Kind.Arg(Variance.co, Kind.Type)))
+        val allFns = makeFns(1, paramType(0) :: out :: Nil, Nil).reverse
+        val exported = allFns.map { extstr => ExportedName.TypeName(extstr.name, ()) }
+        // Add functions into the predef
+        pack.copy(exports = exported ::: pack.exports, program = allFns ::: pack.program)
       case Left(err) =>
         val idx = err.failedAtOffset
         val lm = LocationMap(Predef.predefString)
diff --git a/core/src/main/scala/org/bykn/bosatsu/rankn/Type.scala b/core/src/main/scala/org/bykn/bosatsu/rankn/Type.scala
index 1979864ed..01f078891 100644
--- a/core/src/main/scala/org/bykn/bosatsu/rankn/Type.scala
+++ b/core/src/main/scala/org/bykn/bosatsu/rankn/Type.scala
@@ -269,7 +269,7 @@ object Type {
   val DictType: Type.TyConst = TyConst(Const.predef("Dict"))
 
   object FnType {
-    final val MaxSize = 8
+    final val MaxSize = 32
 
     private def predefFn(n: Int) = TyConst(Const.predef(s"Fn$n")) 
     private val tpes = (1 to MaxSize).map(predefFn)