Merge pull request #3777 from lydell/unary-plus-minus-refs

Fix #3598: Make unary + and - generate _refs

lib/coffee-script/nodes.js

@@ -2309,7 +2309,7 @@
 
     Op.prototype.isComplex = function() {
       var _ref2;
-      return !(this.isUnary() && ((_ref2 = this.operator) === '+' || _ref2 === '-')) || this.first.isComplex();
+      return !(this.isUnary() && ((_ref2 = this.operator) === '+' || _ref2 === '-') && this.first instanceof Value && this.first.isSimpleNumber());
     };
 
     Op.prototype.isChainable = function() {

src/nodes.coffee

@@ -1639,7 +1639,8 @@ exports.Op = class Op extends Base
     not @second
 
   isComplex: ->
-    not (@isUnary() and @operator in ['+', '-']) or @first.isComplex()
+    not (@isUnary() and @operator in ['+', '-'] and
+         @first instanceof Value and @first.isSimpleNumber())
 
   # Am I capable of
   # [Python-style comparison chaining](http://docs.python.org/reference/expressions.html#notin)?

test/operators.coffee

@@ -370,3 +370,65 @@ test "#3363: Modulo operator coercing order", ->
   b = valueOf: -> count += 1
   eq 4, a %% b
   eq 5, count
+
+test "#3598: Unary + and - coerce the operand once when it is an identifier", ->
+  # Unary + and - do not generate `_ref`s when the operand is a number, for
+  # readability. To make sure that they do when the operand is an identifier,
+  # test that they are consistent with another unary operator as well as another
+  # complex expression.
+  # Tip: Making one of the tests temporarily fail lets you easily inspect the
+  # compiled JavaScript.
+
+  assertOneCoercion = (fn) ->
+    count = 0
+    value = valueOf: -> count++; 1
+    fn value
+    eq 1, count
+
+  eq 1, 1 ? 0
+  eq 1, +1 ? 0
+  eq -1, -1 ? 0
+  assertOneCoercion (a) ->
+    eq 1, +a ? 0
+  assertOneCoercion (a) ->
+    eq -1, -a ? 0
+  assertOneCoercion (a) ->
+    eq -2, ~a ? 0
+  assertOneCoercion (a) ->
+    eq 0.5, a / 2 ? 0
+
+  ok -2 <= 1 < 2
+  ok -2 <= +1 < 2
+  ok -2 <= -1 < 2
+  assertOneCoercion (a) ->
+    ok -2 <= +a < 2
+  assertOneCoercion (a) ->
+    ok -2 <= -a < 2
+  assertOneCoercion (a) ->
+    ok -2 <= ~a < 2
+  assertOneCoercion (a) ->
+    ok -2 <= a / 2 < 2
+
+  arrayEq [0], (n for n in [0] by 1)
+  arrayEq [0], (n for n in [0] by +1)
+  arrayEq [0], (n for n in [0] by -1)
+  assertOneCoercion (a) ->
+    arrayEq [0], (n for n in [0] by +a)
+  assertOneCoercion (a) ->
+    arrayEq [0], (n for n in [0] by -a)
+  assertOneCoercion (a) ->
+    arrayEq [0], (n for n in [0] by ~a)
+  assertOneCoercion (a) ->
+    arrayEq [0], (n for n in [0] by a * 2 / 2)
+
+  ok 1 in [0, 1]
+  ok +1 in [0, 1]
+  ok -1 in [0, -1]
+  assertOneCoercion (a) ->
+    ok +a in [0, 1]
+  assertOneCoercion (a) ->
+    ok -a in [0, -1]
+  assertOneCoercion (a) ->
+    ok ~a in [0, -2]
+  assertOneCoercion (a) ->
+    ok a / 2 in [0, 0.5]