simplifying generated output for common-case splices.

lib/nodes.js

@@ -1163,15 +1163,23 @@
       return new Op(this.context.slice(0, -1), left, new Assign(rite, this.value, '=')).compile(o);
     };
     Assign.prototype.compileSplice = function(o) {
-      var from, name, plus, range, ref, to, val;
+      var from, name, plus, range, to, val;
       range = this.variable.properties.pop().range;
       name = this.variable.compile(o);
       plus = range.exclusive ? '' : ' + 1';
       from = range.from ? range.from.compile(o) : '0';
-      to = range.to ? range.to.compile(o) + ' - ' + from + plus : "" + name + ".length";
-      ref = o.scope.freeVariable('ref');
+      if (!range.to) {
+        to = "" + name + ".length";
+      }
+      if (!to) {
+        if (range.from && range.from.isSimpleNumber() && range.to.isSimpleNumber()) {
+          to = (+range.to.compile(o)) - +from + +plus;
+        } else {
+          to = range.to.compile(o) + ' - ' + from + plus;
+        }
+      }
       val = this.value.compile(o);
-      return "([].splice.apply(" + name + ", [" + from + ", " + to + "].concat(" + ref + " = " + val + ")), " + ref + ")";
+      return "[].splice.apply(" + name + ", [" + from + ", " + to + "].concat(" + val + "))";
     };
     return Assign;
   }();

src/nodes.coffee

@@ -944,13 +944,17 @@ exports.Assign = class Assign extends Base
   # `Array#splice` method.
   compileSplice: (o) ->
     {range} = @variable.properties.pop()
-    name  = @variable.compile o
-    plus  = if range.exclusive then '' else ' + 1'
-    from  = if range.from then range.from.compile(o) else '0'
-    to    = if range.to then range.to.compile(o) + ' - ' + from + plus else "#{name}.length"
-    ref   = o.scope.freeVariable 'ref'
-    val   = @value.compile(o)
-    "([].splice.apply(#{name}, [#{from}, #{to}].concat(#{ref} = #{val})), #{ref})"
+    name    = @variable.compile o
+    plus    = if range.exclusive then '' else ' + 1'
+    from    = if range.from then range.from.compile(o) else '0'
+    to      = "#{name}.length" unless range.to
+    unless to
+      if range.from and range.from.isSimpleNumber() and range.to.isSimpleNumber()
+        to = (+range.to.compile(o)) - +from + +plus
+      else
+        to = range.to.compile(o) + ' - ' + from + plus
+    val = @value.compile(o)
+    "[].splice.apply(#{name}, [#{from}, #{to}].concat(#{val}))"
 
 #### Code