Fixes jashkenas#2181 -- conditional assignment as subexpression

Marc Häfner · Marc Häfner · commit 4cc2c305a4d1 · 2013-10-20T22:59:01.000+02:00
* Parenthesize compilation of `||=` and `&amp;&amp;=` (when needed).
* Fix variable caching for `?=`
diff --git a/lib/coffee-script/nodes.js b/lib/coffee-script/nodes.js
diff --git a/src/nodes.coffee b/src/nodes.coffee
@@ -1240,8 +1240,12 @@ exports.Assign = class Assign extends Base
     if not left.properties.length and left.base instanceof Literal and
            left.base.value != "this" and not o.scope.check left.base.value
       @variable.error "the variable \"#{left.base.value}\" can't be assigned with #{@context} because it has not been declared before"
-    if "?" in @context then o.isExistentialEquals = true
-    new Op(@context[...-1], left, new Assign(right, @value, '=')).compileToFragments o
+    if "?" in @context
+      o.isExistentialEquals = true
+      new If(new Existence(left), right, type: 'if').addElse(new Assign(right, @value, '=')).compileToFragments o
+    else
+      fragments = new Op(@context[...-1], left, new Assign(right, @value, '=')).compileToFragments o
+      if o.level <= LEVEL_LIST then fragments else @wrapInBraces fragments
 
   # Compile the assignment from an array splice literal, using JavaScript's
   # `Array#splice` method.
@@ -1652,7 +1656,7 @@ exports.Op = class Op extends Base
 
   # Keep reference to the left expression, unless this an existential assignment
   compileExistence: (o) ->
-    if !o.isExistentialEquals and @first.isComplex()
+    if @first.isComplex()
       ref = new Literal o.scope.freeVariable 'ref'
       fst = new Parens new Assign ref, @first
     else
diff --git a/test/assignment.coffee b/test/assignment.coffee
@@ -81,6 +81,9 @@ test "compound assignment should be careful about caching variables", ->
   eq 5, base.five
   eq 5, count
 
+  eq 5, base().five ?= 6
+  eq 6, count
+
 test "compound assignment with implicit objects", ->
   obj = undefined
   obj ?=
@@ -380,3 +383,9 @@ test "#2613: parens on LHS of destructuring", ->
   a = {}
   [(a).b] = [1, 2, 3]
   eq a.b, 1
+
+test "#2181: conditional assignment as a subexpression", ->
+  a = false
+  false && a or= true
+  eq false, a
+  eq false, not a or= true
