Fix incorrect format of function under unary operator (#6953)

* Fix parens in unary operator

* Fix parens in binary expr

* Handle underscore sugar application

* Add tests

* Update CHANGELOG

Author: shulhi

CHANGELOG.md

@@ -13,6 +13,7 @@
 # 11.1.4
 
 - Fix issue where long layout break added a trailing comma in partial application `...`. https://github.com/rescript-lang/rescript-compiler/pull/6949
+- Fix incorrect format of function under unary operator. https://github.com/rescript-lang/rescript-compiler/pull/6953
 
 # 11.1.3
 

jscomp/syntax/src/res_parens.ml

@@ -111,6 +111,11 @@ let unaryExprOperand expr =
       Parenthesized
     | _ when ParsetreeViewer.hasAwaitAttribute expr.pexp_attributes ->
       Parenthesized
+    | {pexp_desc = Pexp_construct ({txt = Lident "Function$"}, Some expr)}
+      when ParsetreeViewer.isUnderscoreApplySugar expr ->
+      Nothing
+    | {pexp_desc = Pexp_construct ({txt = Lident "Function$"}, Some _)} ->
+      Parenthesized
     | _ -> Nothing)
 
 let binaryExprOperand ~isLhs expr =
@@ -276,6 +281,11 @@ let fieldExpr expr =
       Parenthesized
     | _ when ParsetreeViewer.hasAwaitAttribute expr.pexp_attributes ->
       Parenthesized
+    | {pexp_desc = Pexp_construct ({txt = Lident "Function$"}, Some expr)}
+      when ParsetreeViewer.isUnderscoreApplySugar expr ->
+      Nothing
+    | {pexp_desc = Pexp_construct ({txt = Lident "Function$"}, Some _)} ->
+      Parenthesized
     | _ -> Nothing)
 
 let setFieldExprRhs expr =

jscomp/syntax/tests/printer/expr/expected/unary.res.txt

@@ -85,3 +85,5 @@ let () = {
 
 let x = (!truths)[0]
 (!streets)[0] = "foo-street"
+
+!(arg => doStuffWith(arg))

jscomp/syntax/tests/printer/expr/unary.res

@@ -68,3 +68,5 @@ let () = {
 
 let x = (!truths)[0]
 (!streets)[0] = "foo-street" 
+
+!(arg => doStuffWith(arg))