Fix outcome printing of uncurried higher order function types (#6323)

Author: glennsl

CHANGELOG.md

@@ -17,6 +17,10 @@
 #### :boom: Breaking Change
 - Fixed the issue of name collision between the newly defined Js.Json.t and the variant constructor in the existing Js.Json.kind type. To address this, the usage of the existing Js.Json.kind type can be updated to Js.Json.Kind.t. https://github.com/rescript-lang/rescript-compiler/pull/6317
 
+#### :bug: Bug Fix
+- Fixed outcome printing of uncurried higehr order function types. https://github.com/rescript-lang/rescript-compiler/pull/6323
+- Fixed printing of type constraints in template literal substitutions. https://github.com/rescript-lang/rescript-compiler/pull/6324
+
 # 11.0.0-beta.3
 
 #### :rocket: New Feature

jscomp/syntax/src/res_outcome_printer.ml

@@ -354,7 +354,12 @@ and printOutArrowType ~uncurried typ =
     let needsParens =
       match typArgs with
       | _ when uncurried -> true
-      | [(_, (Otyp_tuple _ | Otyp_arrow _))] -> true
+      | [
+       ( _,
+         ( Otyp_tuple _ | Otyp_arrow _
+         | Otyp_constr (Oide_ident "function$", [Otyp_arrow _; _]) ) );
+      ] ->
+        true
       (* single argument should not be wrapped *)
       | [("", _)] -> false
       | _ -> true

jscomp/syntax/tests/oprint/expected/oprint.resi.txt

@@ -217,7 +217,7 @@ type permissions = [#644 | #777]
 type numericPolyVarWithPayload = [#1(string) | #2(int, string)]
 let numericPolyVarMatch: [> #1(string) | #2(int, string)]
 let sort: (module(Set.S with type elt = 'a), list<'a>) => list<'a>
-let make_set: ('a, 'a) => int => module(Set.S with type elt = 'a)
+let make_set: (('a, 'a) => int) => module(Set.S with type elt = 'a)
 type picture = string
 module type DEVICE = {
   let draw: picture => unit
@@ -237,4 +237,6 @@ type emptyObject = {.}
 let f: (~x: 'a=?, ~y: 'b) => option<'a>
 type call = CleanStart
 let f: (~a: int=?, unit) => int
-type opt = {x: int, y?: option<string>}
+type opt = {x: int, y?: option<string>}
+let secondOrder: (unit => 'a) => 'a
+let thirdOrder: ((unit => unit) => 'a) => 'a

jscomp/syntax/tests/oprint/oprint.res

@@ -308,3 +308,6 @@ type call = CleanStart
 let f = (~a=1, ()) => 1
 
 type opt = {x:int, y?: option<string>}
+
+let secondOrder = f => f()
+let thirdOrder = f => f(() => ())