diff --git a/lib/coffee-script/command.js b/lib/coffee-script/command.js
index 58b45e5d..ad85b479 100644
--- a/lib/coffee-script/command.js
+++ b/lib/coffee-script/command.js
@@ -399,14 +399,14 @@
   };
 
   parseOptions = function() {
-    var i, o, source, _len;
+    var i, o, source, _i, _len;
     optionParser = new optparse.OptionParser(SWITCHES, BANNER);
     o = opts = optionParser.parse(process.argv.slice(2));
     o.compile || (o.compile = !!o.output);
     o.run = !(o.compile || o.print || o.lint);
     o.print = !!(o.print || (o.eval || o.stdio && o.compile));
     sources = o.arguments;
-    for (i = 0, _len = sources.length; i < _len; i++) {
+    for (i = _i = 0, _len = sources.length; _i < _len; i = ++_i) {
       source = sources[i];
       sourceCode[i] = null;
     }
diff --git a/lib/coffee-script/lexer.js b/lib/coffee-script/lexer.js
index 0af3cc05..3d79665d 100644
--- a/lib/coffee-script/lexer.js
+++ b/lib/coffee-script/lexer.js
@@ -451,12 +451,17 @@
     };
 
     Lexer.prototype.balancedString = function(str, end) {
-      var i, letter, match, prev, stack, _ref3;
+      var continueCount, i, letter, match, prev, stack, _i, _ref3;
+      continueCount = 0;
       stack = [end];
-      for (i = 1, _ref3 = str.length; 1 <= _ref3 ? i < _ref3 : i > _ref3; 1 <= _ref3 ? i++ : i--) {
+      for (i = _i = 1, _ref3 = str.length; 1 <= _ref3 ? _i < _ref3 : _i > _ref3; i = 1 <= _ref3 ? ++_i : --_i) {
+        if (continueCount) {
+          --continueCount;
+          continue;
+        }
         switch (letter = str.charAt(i)) {
           case '\\':
-            i++;
+            ++continueCount;
             continue;
           case end:
             stack.pop();
@@ -467,7 +472,7 @@
         if (end === '}' && (letter === '"' || letter === "'")) {
           stack.push(end = letter);
         } else if (end === '}' && letter === '/' && (match = HEREGEX.exec(str.slice(i)) || REGEX.exec(str.slice(i)))) {
-          i += match[0].length - 1;
+          continueCount += match[0].length - 1;
         } else if (end === '}' && letter === '{') {
           stack.push(end = '}');
         } else if (end === '"' && prev === '#' && letter === '{') {
@@ -479,7 +484,7 @@
     };
 
     Lexer.prototype.interpolateString = function(str, options) {
-      var expr, heredoc, i, inner, interpolated, len, letter, nested, pi, regex, tag, tokens, value, _len, _ref3, _ref4, _ref5;
+      var expr, heredoc, i, inner, interpolated, len, letter, nested, pi, regex, tag, tokens, value, _i, _len, _ref3, _ref4, _ref5;
       if (options == null) options = {};
       heredoc = options.heredoc, regex = options.regex;
       tokens = [];
@@ -520,7 +525,7 @@
       if (!tokens.length) return this.token('STRING', '""');
       if (tokens[0][0] !== 'NEOSTRING') tokens.unshift(['', '']);
       if (interpolated = tokens.length > 1) this.token('(', '(');
-      for (i = 0, _len = tokens.length; i < _len; i++) {
+      for (i = _i = 0, _len = tokens.length; _i < _len; i = ++_i) {
         _ref4 = tokens[i], tag = _ref4[0], value = _ref4[1];
         if (i) this.token('+', '+');
         if (tag === 'TOKENS') {
diff --git a/lib/coffee-script/nodes.js b/lib/coffee-script/nodes.js
index 97b9a960..d1a96514 100644
--- a/lib/coffee-script/nodes.js
+++ b/lib/coffee-script/nodes.js
@@ -313,10 +313,10 @@
       prelude = "";
       if (!o.bare) {
         preludeExps = (function() {
-          var _len, _ref2, _results;
+          var _i, _len, _ref2, _results;
           _ref2 = this.expressions;
           _results = [];
-          for (i = 0, _len = _ref2.length; i < _len; i++) {
+          for (i = _i = 0, _len = _ref2.length; _i < _len; i = ++_i) {
             exp = _ref2[i];
             if (!(exp.unwrap() instanceof Comment)) break;
             _results.push(exp);
@@ -338,10 +338,10 @@
     };
 
     Block.prototype.compileWithDeclarations = function(o) {
-      var assigns, code, declars, exp, i, post, rest, scope, spaced, _len, _ref2, _ref3, _ref4;
+      var assigns, code, declars, exp, i, post, rest, scope, spaced, _i, _len, _ref2, _ref3, _ref4;
       code = post = '';
       _ref2 = this.expressions;
-      for (i = 0, _len = _ref2.length; i < _len; i++) {
+      for (i = _i = 0, _len = _ref2.length; _i < _len; i = ++_i) {
         exp = _ref2[i];
         exp = exp.unwrap();
         if (!(exp instanceof Comment || exp instanceof Literal)) break;
@@ -597,13 +597,13 @@
         _this = this;
       if (this.unfoldedSoak != null) return this.unfoldedSoak;
       result = (function() {
-        var fst, i, ifn, prop, ref, snd, _len, _ref2;
+        var fst, i, ifn, prop, ref, snd, _i, _len, _ref2;
         if (ifn = _this.base.unfoldSoak(o)) {
           Array.prototype.push.apply(ifn.body.properties, _this.properties);
           return ifn;
         }
         _ref2 = _this.properties;
-        for (i = 0, _len = _ref2.length; i < _len; i++) {
+        for (i = _i = 0, _len = _ref2.length; _i < _len; i = ++_i) {
           prop = _ref2[i];
           if (!prop.soak) continue;
           prop.soak = false;
@@ -928,17 +928,21 @@
     };
 
     Range.prototype.compileNode = function(o) {
-      var cond, condPart, from, gt, idx, known, lt, stepPart, to, varPart, _ref2, _ref3;
+      var cond, condPart, from, gt, idx, idxName, known, lt, namedIndex, stepPart, to, varPart, _ref2, _ref3;
       if (!this.fromVar) this.compileVariables(o);
       if (!o.index) return this.compileArray(o);
       known = this.fromNum && this.toNum;
       idx = del(o, 'index');
+      idxName = del(o, 'name');
+      namedIndex = idxName && idxName !== idx;
       varPart = "" + idx + " = " + this.fromC;
       if (this.toC !== this.toVar) varPart += ", " + this.toC;
       if (this.step !== this.stepVar) varPart += ", " + this.step;
       _ref2 = ["" + idx + " <" + this.equals, "" + idx + " >" + this.equals], lt = _ref2[0], gt = _ref2[1];
       condPart = this.stepNum ? +this.stepNum > 0 ? "" + lt + " " + this.toVar : "" + gt + " " + this.toVar : known ? ((_ref3 = [+this.fromNum, +this.toNum], from = _ref3[0], to = _ref3[1], _ref3), from <= to ? "" + lt + " " + to : "" + gt + " " + to) : (cond = "" + this.fromVar + " <= " + this.toVar, "" + cond + " ? " + lt + " " + this.toVar + " : " + gt + " " + this.toVar);
-      stepPart = this.stepVar ? "" + idx + " += " + this.stepVar : known ? from <= to ? "" + idx + "++" : "" + idx + "--" : "" + cond + " ? " + idx + "++ : " + idx + "--";
+      stepPart = this.stepVar ? "" + idx + " += " + this.stepVar : known ? namedIndex ? from <= to ? "++" + idx : "--" + idx : from <= to ? "" + idx + "++" : "" + idx + "--" : namedIndex ? "" + cond + " ? ++" + idx + " : --" + idx : "" + cond + " ? " + idx + "++ : " + idx + "--";
+      if (namedIndex) varPart = "" + idxName + " = " + varPart;
+      if (namedIndex) stepPart = "" + idxName + " = " + stepPart;
       return "" + varPart + "; " + condPart + "; " + stepPart;
     };
 
@@ -1035,9 +1039,9 @@
       idt = o.indent += TAB;
       lastNoncom = this.lastNonComment(this.properties);
       props = (function() {
-        var _len2, _results;
+        var _j, _len2, _results;
         _results = [];
-        for (i = 0, _len2 = props.length; i < _len2; i++) {
+        for (i = _j = 0, _len2 = props.length; _j < _len2; i = ++_j) {
           prop = props[i];
           join = i === props.length - 1 ? '' : prop === lastNoncom || prop instanceof Comment ? '\n' : ',\n';
           indent = prop instanceof Comment ? '' : idt;
@@ -1221,11 +1225,11 @@
     Class.prototype.walkBody = function(name, o) {
       var _this = this;
       return this.traverseChildren(false, function(child) {
-        var exps, i, node, _len, _ref2;
+        var exps, i, node, _i, _len, _ref2;
         if (child instanceof Class) return false;
         if (child instanceof Block) {
           _ref2 = exps = child.expressions;
-          for (i = 0, _len = _ref2.length; i < _len; i++) {
+          for (i = _i = 0, _len = _ref2.length; _i < _len; i = ++_i) {
             node = _ref2[i];
             if (node instanceof Value && node.isObject(true)) {
               exps[i] = _this.addProperties(node, name, o);
@@ -1351,7 +1355,7 @@
     };
 
     Assign.prototype.compilePatternMatch = function(o) {
-      var acc, assigns, code, i, idx, isObject, ivar, name, obj, objects, olen, ref, rest, splat, top, val, value, vvar, _len, _ref2, _ref3, _ref4, _ref5, _ref6, _ref7, _ref8;
+      var acc, assigns, code, i, idx, isObject, ivar, name, obj, objects, olen, ref, rest, splat, top, val, value, vvar, _i, _len, _ref2, _ref3, _ref4, _ref5, _ref6, _ref7, _ref8;
       top = o.level === LEVEL_TOP;
       value = this.value;
       objects = this.variable.base.objects;
@@ -1391,7 +1395,7 @@
         assigns.push("" + (ref = o.scope.freeVariable('ref')) + " = " + vvar);
         vvar = ref;
       }
-      for (i = 0, _len = objects.length; i < _len; i++) {
+      for (i = _i = 0, _len = objects.length; _i < _len; i = ++_i) {
         obj = objects[i];
         idx = i;
         if (isObject) {
@@ -1506,7 +1510,7 @@
     Code.prototype.jumps = NO;
 
     Code.prototype.compileNode = function(o) {
-      var code, exprs, i, idt, lit, p, param, ref, splats, v, val, vars, wasEmpty, _i, _j, _k, _len, _len2, _len3, _len4, _ref2, _ref3, _ref4, _ref5, _ref6;
+      var code, exprs, i, idt, lit, p, param, ref, splats, v, val, vars, wasEmpty, _i, _j, _k, _l, _len, _len2, _len3, _len4, _ref2, _ref3, _ref4, _ref5, _ref6;
       o.scope = new Scope(o.scope, this.body, this);
       o.scope.shared = del(o, 'sharedScope');
       o.indent += TAB;
@@ -1559,7 +1563,7 @@
         (_ref5 = this.body.expressions).unshift.apply(_ref5, exprs);
       }
       if (!splats) {
-        for (i = 0, _len4 = vars.length; i < _len4; i++) {
+        for (i = _l = 0, _len4 = vars.length; _l < _len4; i = ++_l) {
           v = vars[i];
           o.scope.parameter(vars[i] = v.compile(o));
         }
@@ -1670,7 +1674,7 @@
     };
 
     Splat.compileSplattedArray = function(o, list, apply) {
-      var args, base, code, i, index, node, _len;
+      var args, base, code, i, index, node, _i, _len;
       index = -1;
       while ((node = list[++index]) && !(node instanceof Splat)) {
         continue;
@@ -1682,7 +1686,7 @@
         return "" + (utility('slice')) + ".call(" + code + ")";
       }
       args = list.slice(index);
-      for (i = 0, _len = args.length; i < _len; i++) {
+      for (i = _i = 0, _len = args.length; _i < _len; i = ++_i) {
         node = args[i];
         code = node.compile(o, LEVEL_LIST);
         args[i] = node instanceof Splat ? "" + (utility('slice')) + ".call(" + code + ")" : "[" + code + "]";
@@ -1691,11 +1695,11 @@
         return args[0] + (".concat(" + (args.slice(1).join(', ')) + ")");
       }
       base = (function() {
-        var _i, _len2, _ref2, _results;
+        var _j, _len2, _ref2, _results;
         _ref2 = list.slice(0, index);
         _results = [];
-        for (_i = 0, _len2 = _ref2.length; _i < _len2; _i++) {
-          node = _ref2[_i];
+        for (_j = 0, _len2 = _ref2.length; _j < _len2; _j++) {
+          node = _ref2[_j];
           _results.push(node.compile(o, LEVEL_LIST));
         }
         return _results;
@@ -1985,10 +1989,10 @@
       _ref2 = this.object.cache(o, LEVEL_OP), sub = _ref2[0], ref = _ref2[1];
       _ref3 = this.negated ? [' !== ', ' && '] : [' === ', ' || '], cmp = _ref3[0], cnj = _ref3[1];
       tests = (function() {
-        var _len, _ref4, _results;
+        var _i, _len, _ref4, _results;
         _ref4 = this.array.base.objects;
         _results = [];
-        for (i = 0, _len = _ref4.length; i < _len; i++) {
+        for (i = _i = 0, _len = _ref4.length; _i < _len; i = ++_i) {
           item = _ref4[i];
           _results.push((i ? ref : sub) + cmp + item.compile(o, LEVEL_ACCESS));
         }
@@ -2198,7 +2202,7 @@
     For.prototype.children = ['body', 'source', 'guard', 'step'];
 
     For.prototype.compileNode = function(o) {
-      var body, defPart, forPart, forVarPart, guardPart, idt1, index, ivar, lastJumps, lvar, name, namePart, ref, resultPart, returnResult, rvar, scope, source, stepPart, stepvar, svar, varPart, _ref2;
+      var body, defPart, forPart, forVarPart, guardPart, idt1, index, ivar, kvar, kvarAssign, lastJumps, lvar, name, namePart, ref, resultPart, returnResult, rvar, scope, source, stepPart, stepvar, svar, varPart, _ref2;
       body = Block.wrap([this.body]);
       lastJumps = (_ref2 = last(body.expressions)) != null ? _ref2.jumps() : void 0;
       if (lastJumps && lastJumps instanceof Return) this.returns = false;
@@ -2217,7 +2221,9 @@
         });
       }
       if (this.returns) rvar = scope.freeVariable('results');
-      ivar = (this.range ? name : index) || scope.freeVariable('i');
+      ivar = (this.object && index) || scope.freeVariable('i');
+      kvar = (this.range && name) || index || ivar;
+      kvarAssign = kvar !== ivar ? "" + kvar + " = " : "";
       if (this.step && !this.range) stepvar = scope.freeVariable("step");
       if (this.pattern) name = ivar;
       varPart = '';
@@ -2227,6 +2233,7 @@
       if (this.range) {
         forPart = source.compile(merge(o, {
           index: ivar,
+          name: name,
           step: this.step
         }));
       } else {
@@ -2236,12 +2243,15 @@
           svar = ref;
         }
         if (name && !this.pattern) {
-          namePart = "" + name + " = " + svar + "[" + ivar + "]";
+          namePart = "" + name + " = " + svar + "[" + kvar + "]";
         }
         if (!this.object) {
           lvar = scope.freeVariable('len');
-          forVarPart = ("" + ivar + " = 0, " + lvar + " = " + svar + ".length") + (this.step ? ", " + stepvar + " = " + (this.step.compile(o, LEVEL_OP)) : '');
-          stepPart = this.step ? "" + ivar + " += " + stepvar : "" + ivar + "++";
+          forVarPart = "" + kvarAssign + ivar + " = 0, " + lvar + " = " + svar + ".length";
+          if (this.step) {
+            forVarPart += ", " + stepvar + " = " + (this.step.compile(o, LEVEL_OP));
+          }
+          stepPart = "" + kvarAssign + (this.step ? "" + ivar + " += " + stepvar : (kvar !== ivar ? "++" + ivar : "" + ivar + "++"));
           forPart = "" + forVarPart + "; " + ivar + " < " + lvar + "; " + stepPart;
         }
       }
@@ -2258,14 +2268,14 @@
         }
       }
       if (this.pattern) {
-        body.expressions.unshift(new Assign(this.name, new Literal("" + svar + "[" + ivar + "]")));
+        body.expressions.unshift(new Assign(this.name, new Literal("" + svar + "[" + kvar + "]")));
       }
       defPart += this.pluckDirectCall(o, body);
       if (namePart) varPart = "\n" + idt1 + namePart + ";";
       if (this.object) {
-        forPart = "" + ivar + " in " + svar;
+        forPart = "" + kvar + " in " + svar;
         if (this.own) {
-          guardPart = "\n" + idt1 + "if (!" + (utility('hasProp')) + ".call(" + svar + ", " + ivar + ")) continue;";
+          guardPart = "\n" + idt1 + "if (!" + (utility('hasProp')) + ".call(" + svar + ", " + kvar + ")) continue;";
         }
       }
       body = body.compile(merge(o, {
@@ -2276,10 +2286,10 @@
     };
 
     For.prototype.pluckDirectCall = function(o, body) {
-      var base, defs, expr, fn, idx, ref, val, _len, _ref2, _ref3, _ref4, _ref5, _ref6, _ref7;
+      var base, defs, expr, fn, idx, ref, val, _i, _len, _ref2, _ref3, _ref4, _ref5, _ref6, _ref7;
       defs = '';
       _ref2 = body.expressions;
-      for (idx = 0, _len = _ref2.length; idx < _len; idx++) {
+      for (idx = _i = 0, _len = _ref2.length; _i < _len; idx = ++_i) {
         expr = _ref2[idx];
         expr = expr.unwrapAll();
         if (!(expr instanceof Call)) continue;
@@ -2347,16 +2357,16 @@
     };
 
     Switch.prototype.compileNode = function(o) {
-      var block, body, code, cond, conditions, expr, i, idt1, idt2, _i, _len, _len2, _ref2, _ref3, _ref4, _ref5;
+      var block, body, code, cond, conditions, expr, i, idt1, idt2, _i, _j, _len, _len2, _ref2, _ref3, _ref4, _ref5;
       idt1 = o.indent + TAB;
       idt2 = o.indent = idt1 + TAB;
       code = this.tab + ("switch (" + (((_ref2 = this.subject) != null ? _ref2.compile(o, LEVEL_PAREN) : void 0) || false) + ") {\n");
       _ref3 = this.cases;
-      for (i = 0, _len = _ref3.length; i < _len; i++) {
+      for (i = _i = 0, _len = _ref3.length; _i < _len; i = ++_i) {
         _ref4 = _ref3[i], conditions = _ref4[0], block = _ref4[1];
         _ref5 = flatten([conditions]);
-        for (_i = 0, _len2 = _ref5.length; _i < _len2; _i++) {
-          cond = _ref5[_i];
+        for (_j = 0, _len2 = _ref5.length; _j < _len2; _j++) {
+          cond = _ref5[_j];
           if (!this.subject) cond = cond.invert();
           code += idt1 + ("case " + (cond.compile(o, LEVEL_PAREN)) + ":\n");
         }
diff --git a/lib/coffee-script/optparse.js b/lib/coffee-script/optparse.js
index a73f7e7c..fb027732 100644
--- a/lib/coffee-script/optparse.js
+++ b/lib/coffee-script/optparse.js
@@ -9,15 +9,20 @@
     }
 
     OptionParser.prototype.parse = function(args) {
-      var arg, i, isOption, matchedRule, options, originalArgs, pos, rule, value, _i, _len, _len2, _ref;
+      var arg, i, isOption, matchedRule, options, originalArgs, pos, rule, skippingArgument, value, _i, _j, _len, _len2, _ref;
       options = {
         arguments: [],
         literals: []
       };
+      skippingArgument = false;
       originalArgs = args;
       args = normalizeArguments(args);
-      for (i = 0, _len = args.length; i < _len; i++) {
+      for (i = _i = 0, _len = args.length; _i < _len; i = ++_i) {
         arg = args[i];
+        if (skippingArgument) {
+          skippingArgument = false;
+          continue;
+        }
         if (arg === '--') {
           pos = originalArgs.indexOf('--');
           options.arguments = [originalArgs[1 + pos]];
@@ -27,10 +32,10 @@
         isOption = !!(arg.match(LONG_FLAG) || arg.match(SHORT_FLAG));
         matchedRule = false;
         _ref = this.rules;
-        for (_i = 0, _len2 = _ref.length; _i < _len2; _i++) {
-          rule = _ref[_i];
+        for (_j = 0, _len2 = _ref.length; _j < _len2; _j++) {
+          rule = _ref[_j];
           if (rule.shortFlag === arg || rule.longFlag === arg) {
-            value = rule.hasArgument ? args[i += 1] : true;
+            value = rule.hasArgument ? (skippingArgument = true, args[i + 1]) : true;
             options[rule.name] = rule.isList ? (options[rule.name] || []).concat(value) : value;
             matchedRule = true;
             break;
diff --git a/lib/coffee-script/rewriter.js b/lib/coffee-script/rewriter.js
index 4f977d5a..bfd29492 100644
--- a/lib/coffee-script/rewriter.js
+++ b/lib/coffee-script/rewriter.js
@@ -50,9 +50,9 @@
     };
 
     Rewriter.prototype.removeLeadingNewlines = function() {
-      var i, tag, _len, _ref;
+      var i, tag, _i, _len, _ref;
       _ref = this.tokens;
-      for (i = 0, _len = _ref.length; i < _len; i++) {
+      for (i = _i = 0, _len = _ref.length; _i < _len; i = ++_i) {
         tag = _ref[i][0];
         if (tag !== 'TERMINATOR') break;
       }
diff --git a/src/lexer.coffee b/src/lexer.coffee
index 8be31160..b504a618 100644
--- a/src/lexer.coffee
+++ b/src/lexer.coffee
@@ -407,11 +407,15 @@ exports.Lexer = class Lexer
   # contents of the string. This method allows us to have strings within
   # interpolations within strings, ad infinitum.
   balancedString: (str, end) ->
+    continueCount = 0
     stack = [end]
     for i in [1...str.length]
+      if continueCount
+        --continueCount
+        continue
       switch letter = str.charAt i
         when '\\'
-          i++
+          ++continueCount
           continue
         when end
           stack.pop()
@@ -422,7 +426,7 @@ exports.Lexer = class Lexer
       if end is '}' and letter in ['"', "'"]
         stack.push end = letter
       else if end is '}' and letter is '/' and match = (HEREGEX.exec(str.slice i) or REGEX.exec(str.slice i))
-        i += match[0].length - 1
+        continueCount += match[0].length - 1
       else if end is '}' and letter is '{'
         stack.push end = '}'
       else if end is '"' and prev is '#' and letter is '{'
diff --git a/src/nodes.coffee b/src/nodes.coffee
index c07bfdbc..8bf04386 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -677,6 +677,8 @@ exports.Range = class Range extends Base
     # Set up endpoints.
     known    = @fromNum and @toNum
     idx      = del o, 'index'
+    idxName  = del o, 'name'
+    namedIndex = idxName and idxName isnt idx
     varPart  = "#{idx} = #{@fromC}"
     varPart += ", #{@toC}" if @toC isnt @toVar
     varPart += ", #{@step}" if @step isnt @stepVar
@@ -696,9 +698,18 @@ exports.Range = class Range extends Base
     stepPart = if @stepVar
       "#{idx} += #{@stepVar}"
     else if known
-      if from <= to then "#{idx}++" else "#{idx}--"
+      if namedIndex
+        if from <= to then "++#{idx}" else "--#{idx}"
+      else
+        if from <= to then "#{idx}++" else "#{idx}--"
     else
-      "#{cond} ? #{idx}++ : #{idx}--"
+      if namedIndex
+        "#{cond} ? ++#{idx} : --#{idx}"
+      else
+        "#{cond} ? #{idx}++ : #{idx}--"
+
+    varPart  = "#{idxName} = #{varPart}" if namedIndex
+    stepPart = "#{idxName} = #{stepPart}" if namedIndex
 
     # The final loop body.
     "#{varPart}; #{condPart}; #{stepPart}"
@@ -1606,7 +1617,9 @@ exports.For = class For extends While
     scope.find(name,  immediate: yes) if name and not @pattern
     scope.find(index, immediate: yes) if index
     rvar      = scope.freeVariable 'results' if @returns
-    ivar      = (if @range then name else index) or scope.freeVariable 'i'
+    ivar      = (@object and index) or scope.freeVariable 'i'
+    kvar      = (@range and name) or index or ivar
+    kvarAssign = if kvar isnt ivar then "#{kvar} = " else ""
     # the `_by` variable is created twice in `Range`s if we don't prevent it from being declared here
     stepvar   = scope.freeVariable "step" if @step and not @range
     name      = ivar if @pattern
@@ -1615,18 +1628,19 @@ exports.For = class For extends While
     defPart   = ''
     idt1      = @tab + TAB
     if @range
-      forPart = source.compile merge(o, {index: ivar, @step})
+      forPart = source.compile merge(o, {index: ivar, name, @step})
     else
       svar    = @source.compile o, LEVEL_LIST
       if (name or @own) and not IDENTIFIER.test svar
         defPart    = "#{@tab}#{ref = scope.freeVariable 'ref'} = #{svar};\n"
         svar       = ref
       if name and not @pattern
-        namePart   = "#{name} = #{svar}[#{ivar}]"
+        namePart   = "#{name} = #{svar}[#{kvar}]"
       unless @object
         lvar       = scope.freeVariable 'len'
-        forVarPart = "#{ivar} = 0, #{lvar} = #{svar}.length" + if @step then ", #{stepvar} = #{@step.compile(o, LEVEL_OP)}" else ''
-        stepPart   = if @step then "#{ivar} += #{stepvar}" else "#{ivar}++"
+        forVarPart = "#{kvarAssign}#{ivar} = 0, #{lvar} = #{svar}.length"
+        forVarPart += ", #{stepvar} = #{@step.compile o, LEVEL_OP}" if @step
+        stepPart   = "#{kvarAssign}#{if @step then "#{ivar} += #{stepvar}" else (if kvar isnt ivar then "++#{ivar}" else "#{ivar}++")}"
         forPart    = "#{forVarPart}; #{ivar} < #{lvar}; #{stepPart}"
     if @returns
       resultPart   = "#{@tab}#{rvar} = [];\n"
@@ -1638,12 +1652,12 @@ exports.For = class For extends While
       else
         body = Block.wrap [new If @guard, body] if @guard
     if @pattern
-      body.expressions.unshift new Assign @name, new Literal "#{svar}[#{ivar}]"
+      body.expressions.unshift new Assign @name, new Literal "#{svar}[#{kvar}]"
     defPart     += @pluckDirectCall o, body
     varPart     = "\n#{idt1}#{namePart};" if namePart
     if @object
-      forPart   = "#{ivar} in #{svar}"
-      guardPart = "\n#{idt1}if (!#{utility 'hasProp'}.call(#{svar}, #{ivar})) continue;" if @own
+      forPart   = "#{kvar} in #{svar}"
+      guardPart = "\n#{idt1}if (!#{utility 'hasProp'}.call(#{svar}, #{kvar})) continue;" if @own
     body        = body.compile merge(o, indent: idt1), LEVEL_TOP
     body        = '\n' + body + '\n' if body
     """
diff --git a/src/optparse.coffee b/src/optparse.coffee
index 0b453d37..94bfb94a 100644
--- a/src/optparse.coffee
+++ b/src/optparse.coffee
@@ -25,9 +25,13 @@ exports.OptionParser = class OptionParser
   # for interpreting the options object.
   parse: (args) ->
     options = arguments: [], literals: []
+    skippingArgument = no
     originalArgs = args
     args = normalizeArguments args
     for arg, i in args
+      if skippingArgument
+        skippingArgument = no
+        continue
       if arg is '--'
         pos = originalArgs.indexOf '--'
         options.arguments = [originalArgs[1 + pos]]
@@ -37,7 +41,11 @@ exports.OptionParser = class OptionParser
       matchedRule = no
       for rule in @rules
         if rule.shortFlag is arg or rule.longFlag is arg
-          value = if rule.hasArgument then args[i += 1] else true
+          value = if rule.hasArgument
+            skippingArgument = yes
+            args[i + 1]
+          else
+            true
           options[rule.name] = if rule.isList then (options[rule.name] or []).concat value else value
           matchedRule = yes
           break
diff --git a/test/comprehensions.coffee b/test/comprehensions.coffee
index 428b1b6a..0e8acb9c 100644
--- a/test/comprehensions.coffee
+++ b/test/comprehensions.coffee
@@ -460,3 +460,28 @@ test "#1850: inner `for` should not be expression-ized if `return`ing", ->
     for b in [1..9]
       c = Math.sqrt a*a + b*b
       return String [a, b, c] unless c % 1
+
+test "#1910: loop index should be mutable within a loop iteration and immutable between loop iterations", ->
+  n = 1
+  iterations = 0
+  arr = [0..n]
+  for v, k in arr
+    ++iterations
+    v = k = 5
+    eq 5, k
+  eq 2, k
+  eq 2, iterations
+
+  iterations = 0
+  for v in [0..n]
+    ++iterations
+  eq 2, k
+  eq 2, iterations
+
+  arr = ([v, v + 1] for v in [0..5])
+  iterations = 0
+  for own [v0, v1], k in arr when v0
+    k += 3
+    ++iterations
+  eq 6, k
+  eq 5, iterations
diff --git a/test/control_flow.coffee b/test/control_flow.coffee
index a502e1ad..2aa288d0 100644
--- a/test/control_flow.coffee
+++ b/test/control_flow.coffee
@@ -422,11 +422,9 @@ test "Issue #997. Switch doesn't fallthrough.", ->
 
 
 test "Throw should be usable as an expression.", ->
-  
+
   try
     false or throw 'up'
     throw new Error 'failed'
   catch e
     ok e is 'up'
-    
-  
\ No newline at end of file
diff --git a/test/option_parser.coffee b/test/option_parser.coffee
index eef1fd08..835f33af 100644
--- a/test/option_parser.coffee
+++ b/test/option_parser.coffee
@@ -15,14 +15,14 @@ opt = new OptionParser [
 
 result = opt.parse ['one', 'two', 'three', '-r', 'dir']
 
-ok result.arguments.length is 5
-ok result.arguments[3] is '-r'
+eq 5, result.arguments.length
+eq '-r', result.arguments[3]
 
 result = opt.parse ['--optional', '-r', 'folder', 'one', 'two']
 
-ok result.optional is true
-ok result.required is 'folder'
-ok result.arguments.join(' ') is 'one two'
+ok result.optional
+eq 'folder', result.required
+eq 'one two', result.arguments.join ' '
 
 result = opt.parse ['-l', 'one.txt', '-l', 'two.txt', 'three']