Fix printing of Ptyp_arrow on type constraint arrow expressions

Author: Iwan

src/res_parens.ml

@@ -402,3 +402,7 @@ type kind = Parenthesized | Braced of Location.t | Nothing
   let includeModExpr modExpr = match modExpr.Parsetree.pmod_desc with
   | Parsetree.Pmod_constraint _ -> true
   | _ -> false
+
+let arrowReturnTypExpr typExpr = match typExpr.Parsetree.ptyp_desc with
+  | Parsetree.Ptyp_arrow _ -> true
+  | _ -> false

src/res_parens.mli

@@ -29,4 +29,6 @@ val modExprFunctorConstraint: Parsetree.module_type -> bool
 val bracedExpr: Parsetree.expression -> bool
 val callExpr: Parsetree.expression -> kind
 
-val includeModExpr : Parsetree.module_expr -> bool
+val includeModExpr : Parsetree.module_expr -> bool
+
+val arrowReturnTypExpr: Parsetree.core_type -> bool

src/res_printer.ml

@@ -2967,7 +2967,6 @@ and printExpression (e : Parsetree.expression) cmtTbl =
   | Pexp_let _ ->
     printExpressionBlock ~braces:true e cmtTbl
   | Pexp_fun (Nolabel, None, {ppat_desc = Ppat_var {txt="__x"}}, ({pexp_desc = Pexp_apply _})) ->
-
     (* (__x) => f(a, __x, c) -----> f(a, _, c)  *)
     printExpressionWithComments (ParsetreeViewer.rewriteUnderscoreApply e) cmtTbl
   | Pexp_fun _ | Pexp_newtype _ ->
@@ -3038,7 +3037,15 @@ and printExpression (e : Parsetree.expression) cmtTbl =
         )
     in
     let typConstraintDoc = match typConstraint with
-    | Some(typ) -> Doc.concat [Doc.text ": "; printTypExpr typ cmtTbl]
+    | Some(typ) ->
+      let typDoc =
+        let doc = printTypExpr typ cmtTbl in
+        if Parens.arrowReturnTypExpr typ then
+          addParens doc
+        else
+          doc
+      in
+      Doc.concat [Doc.text ": "; typDoc]
     | _ -> Doc.nil
     in
     let attrs = printAttributes attrs cmtTbl in

tests/printer/expr/__snapshots__/render.spec.js.snap

@@ -2140,6 +2140,18 @@ let f = (~\\\\\\"aria-b\\": string, ~\\\\\\"aria-d\\" as \\\\\\"aria-xyz\\") =>
 }
 
 let f = (type \\\\\\"😎\\", x) => Js.log(x)
+
+let query = (~url, ()): (unit => unit) => {
+  () => Js.log(\\"Queried \\" ++ url)
+}
+
+let query = (~url, ()): ((unit, unit) => unit) => {
+  ((), ()) => Js.log(\\"Queried \\" ++ url)
+}
+
+let query = (~url, ()): ((unit, unit, unit) => unit) => {
+  ((), (), ()) => Js.log(\\"Queried \\" ++ url)
+}
 "
 `;
 

tests/printer/expr/fun.js

@@ -281,3 +281,15 @@ let f = (~\"aria-b": string, ~\"aria-d" as \"aria-xyz" ) => {
 }
 
 let f = (type \"😎", x) => Js.log(x)
+
+let query = (~url, ()): (unit => unit) => {
+  () => Js.log("Queried " ++ url)
+}
+
+let query = (~url, ()): (unit => unit => unit) => {
+  () => () => Js.log("Queried " ++ url)
+}
+
+let query = (~url, ()): (unit => unit => unit => unit) => {
+  () => () => () => Js.log("Queried " ++ url)
+}