Fix parenthesized conditions in if-else assignment (#4519)

* Fix parenthesized conditions in if-else assignment

* Add compiled output

* Use ‘is’ instead of ‘==‘; ‘right’ is a poor name when you mean ‘correct,’ not the right-hand side of the assignments in this test

lib/coffee-script/nodes.js

@@ -3349,7 +3349,7 @@
         return expr.compileToFragments(o);
       }
       fragments = expr.compileToFragments(o, LEVEL_PAREN);
-      bare = o.level < LEVEL_OP && (expr instanceof Op || expr instanceof Call || (expr instanceof For && expr.returns));
+      bare = o.level < LEVEL_OP && (expr instanceof Op || expr instanceof Call || (expr instanceof For && expr.returns)) && (o.level < LEVEL_COND || fragments.length <= 3);
       if (bare) {
         return fragments;
       } else {

src/nodes.coffee

@@ -2254,7 +2254,8 @@ exports.Parens = class Parens extends Base
       return expr.compileToFragments o
     fragments = expr.compileToFragments o, LEVEL_PAREN
     bare = o.level < LEVEL_OP and (expr instanceof Op or expr instanceof Call or
-      (expr instanceof For and expr.returns))
+      (expr instanceof For and expr.returns)) and (o.level < LEVEL_COND or
+        fragments.length <= 3)
     if bare then fragments else @wrapInBraces fragments
 
 #### StringWithInterpolations

test/control_flow.coffee

@@ -198,6 +198,17 @@ test "#748: trailing reserved identifiers", ->
     nonce
   eq nonce, result
 
+test 'if-else within an assignment, condition parenthesized', ->
+  result = if (1 is 1) then 'correct'
+  eq result, 'correct'
+
+  result = if ('whatever' ? no) then 'correct'
+  eq result, 'correct'
+
+  f = -> 'wrong'
+  result = if (f?()) then 'correct' else 'wrong'
+  eq result, 'correct'
+
 # Postfix
 
 test "#3056: multiple postfix conditionals", ->