From 858a8a1a01e85a8a0b14ed5da0d7308ab92a91c5 Mon Sep 17 00:00:00 2001
From: cannorin <cannorin@users.noreply.github.com>
Date: Thu, 13 Jul 2023 21:12:38 +0900
Subject: [PATCH 1/2] Update Release action

---
 .github/workflows/publish.yml | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 2d9abc29..847c341e 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -14,9 +14,9 @@ jobs:
         dotnet:
           - 6.0.x
         node-version:
-          - 16.x
+          - 20.x
         ocaml-compiler:
-          - 4.13.x
+          - 5.0.x
 
     runs-on: ${{ matrix.os }}
 
@@ -25,7 +25,7 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Use .NET ${{ matrix.dotnet }}
-        uses: actions/setup-dotnet@v2
+        uses: actions/setup-dotnet@v3
         with:
           dotnet-version: ${{ matrix.dotnet }}
 

From fc9a19a2d2826bacc6c031dd9aebf65617f797e7 Mon Sep 17 00:00:00 2001
From: cannorin <cannorin@users.noreply.github.com>
Date: Thu, 13 Jul 2023 21:35:42 +0900
Subject: [PATCH 2/2] Fix #315

---
 CHANGELOG.md                    |  1 +
 lib/Typer.fs                    | 27 +++++++++++++++++++++------
 src/Targets/JsOfOCaml/Writer.fs |  2 +-
 3 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 83bc3c97..4abbc474 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+- Fix a bug which generated unnecessarily duplicated option type (#315).
 
 ## [1.4.5] - 2023-07-13
 - Fix a bug which caused optional properties not to be recognized as optional (#312).
diff --git a/lib/Typer.fs b/lib/Typer.fs
index b6701197..a0678200 100644
--- a/lib/Typer.fs
+++ b/lib/Typer.fs
@@ -539,20 +539,35 @@ module Type =
         boundTyprms |> List.map (fun x -> TypeVar x.name),
         MultipleLocation (funcs |> List.map (fun f -> f.loc))
       )
+  let normalizeUnion (u: UnionType) : UnionType =
+    let rec go ts =
+      ts |> List.collect (function
+        | Union u -> go u.types
+        | t -> [t]
+      )
+    { u with types = go u.types |> List.distinct }
+
+  let normalizeIntersection (i: IntersectionType) : IntersectionType =
+    let rec go ts =
+      ts |> List.collect (function
+        | Intersection i -> go i.types
+        | t -> [t]
+      )
+    { i with types = go i.types |> List.distinct }
 
   // TODO: more optimization
-  let createUnion (_ctx: TyperContext<_, _>) (types: Type list) =
+  let createUnion (types: Type list) =
     match types with
     | [] -> Prim Never
     | [x] -> x
-    | _ -> Union { types = types }
+    | _ -> Union (normalizeUnion { types = types })
 
   // TODO: more optimization
-  let createIntersection (_ctx: TyperContext<_, _>) (types: Type list) =
+  let createIntersection (types: Type list) =
     match types with
     | [] -> Prim Any
     | [x] -> x
-    | _ -> Intersection { types = types }
+    | _ -> Intersection (normalizeIntersection { types = types })
 
   let substTypeVarInInheritingType subst ctx = function
     | InheritingType.KnownIdent x ->
@@ -694,7 +709,7 @@ module Type =
           let members = c.members |> List.map snd
           let intersection = function
             | [] -> None
-            | ts -> createIntersection ctx ts |> Some
+            | ts -> createIntersection ts |> Some
           let rec go = function
             | TypeLiteral (LString name) ->
               let funcs, others =
@@ -815,7 +830,7 @@ module Type =
               | _ -> None)
           match types with
           | [] -> onFail ()
-          | _ -> createIntersection ctx types
+          | _ -> createIntersection types
 
       | Keyof t ->
         let t = resolveErasedTypeImpl typeQueries ctx t
diff --git a/src/Targets/JsOfOCaml/Writer.fs b/src/Targets/JsOfOCaml/Writer.fs
index ed45dab5..77dd45e6 100644
--- a/src/Targets/JsOfOCaml/Writer.fs
+++ b/src/Targets/JsOfOCaml/Writer.fs
@@ -704,7 +704,7 @@ let rec emitMembers flags overrideFunc ctx (selfTy: Type) (ma: MemberAttribute)
         if ma.isStatic then [Choice2Of2 (Prim Void)]
         else [Choice2Of2 PolymorphicThis]
       let ret =
-        if fl.isOptional then Union { types = [fl.value; Prim Undefined] }
+        if fl.isOptional then createUnion [fl.value; Prim Undefined]
         else fl.value
       func { isVariadic = false; args = args; returnType = ret; loc = ma.loc } |> emitType_ ctx
     yield! comments ()