Minimize variable scope

Where possible, move "let" statements into inner blocks, loop headers,
etc.

See #442.

benchmark/runner.js

@@ -68,19 +68,17 @@ let Runner = {
 
     function testRunner(benchmark, test) {
       return function() {
-        let input, parseTime, averageParseTime, i, t;
-
         callbacks.testStart(benchmark, test);
 
-        input = callbacks.readFile(benchmark.id + "/" + test.file);
+        let input = callbacks.readFile(benchmark.id + "/" + test.file);
 
-        parseTime = 0;
-        for (i = 0; i < runCount; i++) {
-          t = (new Date()).getTime();
+        let parseTime = 0;
+        for (let i = 0; i < runCount; i++) {
+          let t = (new Date()).getTime();
           state.parser.parse(input);
           parseTime += (new Date()).getTime() - t;
         }
-        averageParseTime = parseTime / runCount;
+        let averageParseTime = parseTime / runCount;
 
         callbacks.testFinish(benchmark, test, input.length, averageParseTime);
 

lib/compiler/index.js

@@ -42,8 +42,6 @@ let compiler = {
   compile: function(ast, passes, options) {
     options = options !== undefined ? options : {};
 
-    let stage;
-
     options = objects.clone(options);
     objects.defaults(options, {
       allowedStartRules: [ast.rules[0].name],
@@ -56,7 +54,7 @@ let compiler = {
       trace:             false
     });
 
-    for (stage in passes) {
+    for (let stage in passes) {
       if (passes.hasOwnProperty(stage)) {
         passes[stage].forEach(function(p) { p(ast, options); });
       }

lib/compiler/passes/generate-bytecode.js

@@ -368,10 +368,8 @@ function generateBytecode(ast) {
 
     sequence: function(node, context) {
       function buildElementsCode(elements, context) {
-        let processedCount, functionIndex;
-
         if (elements.length > 0) {
-          processedCount = node.elements.length - elements.slice(1).length;
+          let processedCount = node.elements.length - elements.slice(1).length;
 
           return buildSequence(
             generate(elements[0], {
@@ -395,7 +393,7 @@ function generateBytecode(ast) {
           );
         } else {
           if (context.action) {
-            functionIndex = addFunctionConst(
+            let functionIndex = addFunctionConst(
               Object.keys(context.env),
               context.action.code
             );
@@ -531,16 +529,14 @@ function generateBytecode(ast) {
     },
 
     literal: function(node) {
-      let stringIndex, expectedIndex;
-
       if (node.value.length > 0) {
-        stringIndex = addConst('"'
+        let stringIndex = addConst('"'
           + js.stringEscape(
               node.ignoreCase ? node.value.toLowerCase() : node.value
             )
           + '"'
         );
-        expectedIndex = addConst(
+        let expectedIndex = addConst(
           'peg$literalExpectation('
             + '"' + js.stringEscape(node.value) + '", '
             + node.ignoreCase
@@ -562,7 +558,7 @@ function generateBytecode(ast) {
           [op.FAIL, expectedIndex]
         );
       } else {
-        stringIndex = addConst('""');
+        let stringIndex = addConst('""');
 
         return [op.PUSH, stringIndex];
       }

lib/compiler/passes/generate-js.js

@@ -428,12 +428,10 @@ function generateJS(ast, options) {
           },
 
           pop: function(n) {
-            let values;
-
             if (n === undefined) {
               return s(this.sp--);
             } else {
-              values = arrays.range(this.sp - n + 1, this.sp + 1).map(s);
+              let values = arrays.range(this.sp - n + 1, this.sp + 1).map(s);
               this.sp -= n;
 
               return values;
@@ -745,10 +743,7 @@ function generateJS(ast, options) {
   }
 
   function generateToplevel() {
-    let parts = [],
-        startRuleIndices,   startRuleIndex,
-        startRuleFunctions, startRuleFunction,
-        ruleNames;
+    let parts = [];
 
     parts.push([
       'function peg$subclass(child, parent) {',
@@ -940,24 +935,24 @@ function generateJS(ast, options) {
     ].join('\n'));
 
     if (options.optimize === "size") {
-      startRuleIndices = '{ '
+      let startRuleIndices = '{ '
                        + options.allowedStartRules.map(
                            function(r) { return r + ': ' + asts.indexOfRule(ast, r); }
                          ).join(', ')
                        + ' }';
-      startRuleIndex = asts.indexOfRule(ast, options.allowedStartRules[0]);
+      let startRuleIndex = asts.indexOfRule(ast, options.allowedStartRules[0]);
 
       parts.push([
         '      peg$startRuleIndices = ' + startRuleIndices + ',',
         '      peg$startRuleIndex   = ' + startRuleIndex + ','
       ].join('\n'));
     } else {
-      startRuleFunctions = '{ '
+      let startRuleFunctions = '{ '
                        + options.allowedStartRules.map(
                            function(r) { return r + ': peg$parse' + r; }
                          ).join(', ')
                        + ' }';
-      startRuleFunction = 'peg$parse' + options.allowedStartRules[0];
+      let startRuleFunction = 'peg$parse' + options.allowedStartRules[0];
 
       parts.push([
         '      peg$startRuleFunctions = ' + startRuleFunctions + ',',
@@ -989,7 +984,7 @@ function generateJS(ast, options) {
 
     if (options.trace) {
       if (options.optimize === "size") {
-        ruleNames = '['
+        let ruleNames = '['
                   + ast.rules.map(
                       function(r) { return '"' + js.stringEscape(r.name) + '"'; }
                     ).join(', ')

lib/peg.js

@@ -25,9 +25,9 @@ let peg = {
     options = options !== undefined ? options : {};
 
     function convertPasses(passes) {
-      let converted = {}, stage;
+      let converted = {};
 
-      for (stage in passes) {
+      for (let stage in passes) {
         if (passes.hasOwnProperty(stage)) {
           converted[stage] = objects.values(passes[stage]);
         }

lib/utils/arrays.js

@@ -4,10 +4,9 @@
 let arrays = {
   range: function(start, stop) {
     let length = stop - start,
-        result = new Array(length),
-        i, j;
+        result = new Array(length);
 
-    for (i = 0, j = start; i < length; i++, j++) {
+    for (let i = 0, j = start; i < length; i++, j++) {
       result[i] = j;
     }
 
@@ -15,16 +14,16 @@ let arrays = {
   },
 
   find: function(array, valueOrPredicate) {
-    let length = array.length, i;
+    let length = array.length;
 
     if (typeof valueOrPredicate === "function") {
-      for (i = 0; i < length; i++) {
+      for (let i = 0; i < length; i++) {
         if (valueOrPredicate(array[i])) {
           return array[i];
         }
       }
     } else {
-      for (i = 0; i < length; i++) {
+      for (let i = 0; i < length; i++) {
         if (array[i] === valueOrPredicate) {
           return array[i];
         }
@@ -33,16 +32,16 @@ let arrays = {
   },
 
   indexOf: function(array, valueOrPredicate) {
-    let length = array.length, i;
+    let length = array.length;
 
     if (typeof valueOrPredicate === "function") {
-      for (i = 0; i < length; i++) {
+      for (let i = 0; i < length; i++) {
         if (valueOrPredicate(array[i])) {
           return i;
         }
       }
     } else {
-      for (i = 0; i < length; i++) {
+      for (let i = 0; i < length; i++) {
         if (array[i] === valueOrPredicate) {
           return i;
         }

lib/utils/objects.js

@@ -3,9 +3,9 @@
 /* Object utilities. */
 let objects = {
   values: function(object) {
-    let result = [], key;
+    let result = [];
 
-    for (key in object) {
+    for (let key in object) {
       if (object.hasOwnProperty(key)) {
         result.push(object[key]);
       }
@@ -15,9 +15,9 @@ let objects = {
   },
 
   clone: function(object) {
-    let result = {}, key;
+    let result = {};
 
-    for (key in object) {
+    for (let key in object) {
       if (object.hasOwnProperty(key)) {
         result[key] = object[key];
       }
@@ -27,9 +27,7 @@ let objects = {
   },
 
   defaults: function(object, defaults) {
-    let key;
-
-    for (key in defaults) {
+    for (let key in defaults) {
       if (defaults.hasOwnProperty(key)) {
         if (!(key in object)) {
           object[key] = defaults[key];

spec/behavior/generated-parser-behavior.spec.js

@@ -8,9 +8,9 @@ let peg = require("../../lib/peg");
 describe("generated parser behavior", function() {
   function varyOptimizationOptions(block) {
     function clone(object) {
-      let result = {}, key;
+      let result = {};
 
-      for (key in object) {
+      for (let key in object) {
         if (object.hasOwnProperty(key)) {
           result[key] = object[key];
         }
@@ -77,7 +77,7 @@ describe("generated parser behavior", function() {
       toFailToParse: function(input, details, options) {
         options = options !== undefined ? options : {};
 
-        let result, key;
+        let result;
 
         try {
           result = this.actual.parse(input, options);
@@ -92,7 +92,7 @@ describe("generated parser behavior", function() {
             };
           } else {
             if (details) {
-              for (key in details) {
+              for (let key in details) {
                 if (details.hasOwnProperty(key)) {
                   if (!this.env.equals_(e[key], details[key])) {
                     this.message = function() {

spec/unit/compiler/passes/helpers.js

@@ -16,13 +16,11 @@ beforeEach(function() {
           return value !== null && typeof value === "object";
         }
 
-        let i, key;
-
         if (isArray(details)) {
           if (!isArray(value)) { return false; }
 
           if (value.length !== details.length) { return false; }
-          for (i = 0; i < details.length; i++) {
+          for (let i = 0; i < details.length; i++) {
             if (!matchDetails(value[i], details[i])) { return false; }
           }
 
@@ -30,7 +28,7 @@ beforeEach(function() {
         } else if (isObject(details)) {
           if (!isObject(value)) { return false; }
 
-          for (key in details) {
+          for (let key in details) {
             if (details.hasOwnProperty(key)) {
               if (!(key in value)) { return false; }
 
@@ -61,8 +59,7 @@ beforeEach(function() {
     },
 
     toReportError: function(grammar, details) {
-      let ast = peg.parser.parse(grammar),
-          key;
+      let ast = peg.parser.parse(grammar);
 
       try {
         this.actual(ast);
@@ -75,7 +72,7 @@ beforeEach(function() {
           };
         } else {
           if (details) {
-            for (key in details) {
+            for (let key in details) {
               if (details.hasOwnProperty(key)) {
                 if (!this.env.equals_(e[key], details[key])) {
                   this.message = function() {

spec/unit/parser.spec.js

@@ -194,7 +194,7 @@ describe("PEG.js grammar parser", function() {
       },
 
       toFailToParse: function(details) {
-        let result, key;
+        let result;
 
         try {
           result = peg.parser.parse(this.actual);
@@ -207,7 +207,7 @@ describe("PEG.js grammar parser", function() {
             };
           } else {
             if (details) {
-              for (key in details) {
+              for (let key in details) {
                 if (details.hasOwnProperty(key)) {
                   if (!this.env.equals_(e[key], details[key])) {
                     this.message = function() {