Example of complex pattern for untagged variant.

CHANGELOG.md

@@ -14,6 +14,7 @@
 
 #### :rocket: New Feature
 - Untagged variants: consider regexp as an object type. https://github.com/rescript-lang/rescript-compiler/pull/6296
+- Semantic-based optimization of code generated for untagged variants https://github.com/rescript-lang/rescript-compiler/issues/6108
 
 # 11.0.0-beta.2
 

jscomp/core/js_exp_make.ml

@@ -618,6 +618,33 @@ let bin ?comment (op : J.binop) (e0 : t) (e1 : t) : t =
      be careful for side effect
 *)
 
+let rec filter_bool (e: t) ~j ~b = match e.expression_desc with
+  | Bin (And, e1, e2) ->
+    (match (filter_bool e1 ~j ~b, filter_bool e2 ~j ~b) with
+    | None, None -> None
+    | Some e, None
+    | None, Some e -> Some e
+    | Some e1, Some e2 ->
+      Some {e with expression_desc = Bin (And, e1, e2)} )
+  | Bin (Or, e1, e2) ->
+    (match (filter_bool e1 ~j ~b, filter_bool e2 ~j ~b) with
+    | None, _ | _, None ->
+      None
+    | Some e1, Some e2 ->
+      Some {e with expression_desc = Bin (Or, e1, e2)} )
+  | Bin
+    ( NotEqEq,
+      {expression_desc = Typeof {expression_desc = Var i}},
+      {expression_desc = Str {txt}}) when Js_op_util.same_vident i j ->
+    if txt <> "bool"
+    then None
+    else assert false
+  | Js_not {expression_desc =
+    Call ({expression_desc = Str {txt = "Array.isArray"}},
+      [{expression_desc = Var i}], _)} when Js_op_util.same_vident i j ->
+    None
+  | _ -> Some e
+
 let and_ ?comment (e1 : t) (e2 : t) : t =
   match (e1.expression_desc, e2.expression_desc) with
   | Var i, Var j when Js_op_util.same_vident i j -> e1
@@ -634,6 +661,15 @@ let and_ ?comment (e1 : t) (e2 : t) : t =
           { expression_desc = Str _ | Number _ } ) )
     when Js_op_util.same_vident i j ->
       e2
+  | ( _,
+      Bin
+      ( EqEqEq,
+        { expression_desc = Var j },
+        { expression_desc = Bool b } )
+        ) ->
+    (match filter_bool e1 ~j ~b with
+     | None -> e2
+     | Some e1 -> { expression_desc = Bin (And, e1, e2); comment })
   | _, _ -> { expression_desc = Bin (And, e1, e2); comment }
 
 let or_ ?comment (e1 : t) (e2 : t) =

jscomp/test/UntaggedVariants.res

@@ -306,4 +306,34 @@ module TestFunctionCase = {
     }
 
     let ff = Function((. x) => x+1)
+}
+
+module ComplexPattern = {
+  @unboxed
+  type rec t =
+    | @as(undefined) Missing
+    | @as(false) False
+    | @as(true) True
+    | @as(null) Null
+    | String(string)
+    | Number(float)
+    | Object(Js.Dict.t<t>)
+    | Array(array<t>)
+
+  type tagged_t =
+    | JSONFalse
+    | JSONTrue
+    | JSONNull
+    | JSONString(string)
+    | JSONNumber(float)
+    | JSONObject(Js.Dict.t<t>)
+    | JSONArray(array<t>)
+
+  let someJson: t = %raw(`'[{"name": "Haan"}, {"name": "Mr"}, false]'`)->Obj.magic
+
+  let check = s =>
+    switch s {
+    | Array([True, False, Array([String("My name is"), Number(10.)])]) => Js.log("yup")
+    | _ => Js.log("Nope...")
+    }
 }