Use const for const/final top-levels, types, symbols.

lib/runtime/dart/core.js

 dart_library.library('dart/core', null, /* Imports */[
   "dart/_runtime"
 ], /* Lazy imports */[
   'dart/_js_helper',
   'dart/_internal',
   'dart/collection',
   'dart/_interceptors',
   'dart/convert'
 ], function(exports, dart, _js_helper, _internal, collection, _interceptors, convert) {
   'use strict';
@@ skipping 41 matching lines @@
   dart.setSignature(Deprecated, {
     constructors: () => ({Deprecated: [Deprecated, [String]]})
   });
   class _Override extends Object {
     _Override() {
     }
   }
   dart.setSignature(_Override, {
     constructors: () => ({_Override: [_Override, []]})
   });
-  let deprecated = dart.const(new Deprecated("next release"));
-  let override = dart.const(new _Override());
+  const deprecated = dart.const(new Deprecated("next release"));
+  const override = dart.const(new _Override());
   class _Proxy extends Object {
     _Proxy() {
     }
   }
   dart.setSignature(_Proxy, {
     constructors: () => ({_Proxy: [_Proxy, []]})
   });
-  let proxy = dart.const(new _Proxy());
+  const proxy = dart.const(new _Proxy());
   dart.defineExtensionNames([
     'toString'
   ]);
   class bool extends Object {
     static fromEnvironment(name, opts) {
       let defaultValue = opts && 'defaultValue' in opts ? opts.defaultValue : false;
       dart.throw(new UnsupportedError('bool.fromEnvironment can only be used as a const constructor'));
     }
     toString() {
       return this ? "true" : "false";
     }
   }
   dart.setSignature(bool, {
     constructors: () => ({fromEnvironment: [bool, [String], {defaultValue: bool}]})
   });
-  let Comparator$ = dart.generic(function(T) {
-    let Comparator = dart.typedef('Comparator', () => dart.functionType(int, [T, T]));
+  const Comparator$ = dart.generic(function(T) {
+    const Comparator = dart.typedef('Comparator', () => dart.functionType(int, [T, T]));
     return Comparator;
   });
   let Comparator = Comparator$();
-  let Comparable$ = dart.generic(function(T) {
+  const Comparable$ = dart.generic(function(T) {
     class Comparable extends Object {
       static compare(a, b) {
         return a[dartx.compareTo](b);
       }
     }
     dart.setSignature(Comparable, {
       statics: () => ({compare: [int, [Comparable$(), Comparable$()]]}),
       names: ['compare']
     });
     return Comparable;
@@ skipping 347 matching lines @@
   }
   dart.setSignature(double, {
     statics: () => ({parse: [double, [String], [dart.functionType(double, [String])]]}),
     names: ['parse']
   });
   double.NAN = 0.0 / 0.0;
   double.INFINITY = 1.0 / 0.0;
   double.NEGATIVE_INFINITY = -dart.notNull(double.INFINITY);
   double.MIN_POSITIVE = 5e-324;
   double.MAX_FINITE = 1.7976931348623157e+308;
-  let _duration = dart.JsSymbol('_duration');
+  const _duration = dart.JsSymbol('_duration');
   class Duration extends Object {
     Duration(opts) {
       let days = opts && 'days' in opts ? opts.days : 0;
       let hours = opts && 'hours' in opts ? opts.hours : 0;
       let minutes = opts && 'minutes' in opts ? opts.minutes : 0;
       let seconds = opts && 'seconds' in opts ? opts.seconds : 0;
       let milliseconds = opts && 'milliseconds' in opts ? opts.milliseconds : 0;
       let microseconds = opts && 'microseconds' in opts ? opts.microseconds : 0;
       this._microseconds(dart.notNull(days) * dart.notNull(Duration.MICROSECONDS_PER_DAY) + dart.notNull(hours) * dart.notNull(Duration.MICROSECONDS_PER_HOUR) + dart.notNull(minutes) * dart.notNull(Duration.MICROSECONDS_PER_MINUTE) + dart.notNull(seconds) * dart.notNull(Duration.MICROSECONDS_PER_SECOND) + dart.notNull(milliseconds) * dart.notNull(Duration.MICROSECONDS_PER_MILLISECOND) + dart.notNull(microseconds));
     }
@@ skipping 175 matching lines @@
     }
   }
   class NullThrownError extends Error {
     NullThrownError() {
       super.Error();
     }
     toString() {
       return "Throw of null.";
     }
   }
-  let _hasValue = dart.JsSymbol('_hasValue');
+  const _hasValue = dart.JsSymbol('_hasValue');
   class ArgumentError extends Error {
     ArgumentError(message) {
       if (message === void 0)
         message = null;
       this.message = message;
       this.invalidValue = null;
       this[_hasValue] = false;
       this.name = null;
       super.Error();
     }
@@ skipping 185 matching lines @@
     constructors: () => ({IndexError: [IndexError, [int, dart.dynamic], [String, String, int]]})
   });
   class FallThroughError extends Error {
     FallThroughError() {
       super.Error();
     }
   }
   dart.setSignature(FallThroughError, {
     constructors: () => ({FallThroughError: [FallThroughError, []]})
   });
-  let _className = dart.JsSymbol('_className');
+  const _className = dart.JsSymbol('_className');
   class AbstractClassInstantiationError extends Error {
     AbstractClassInstantiationError(className) {
       this[_className] = className;
       super.Error();
     }
     toString() {
       return `Cannot instantiate abstract class: '${this[_className]}'`;
     }
   }
   dart.setSignature(AbstractClassInstantiationError, {
     constructors: () => ({AbstractClassInstantiationError: [AbstractClassInstantiationError, [String]]})
   });
-  let _receiver = dart.JsSymbol('_receiver');
-  let _memberName = dart.JsSymbol('_memberName');
-  let _arguments = dart.JsSymbol('_arguments');
-  let _namedArguments = dart.JsSymbol('_namedArguments');
-  let _existingArgumentNames = dart.JsSymbol('_existingArgumentNames');
+  const _receiver = dart.JsSymbol('_receiver');
+  const _memberName = dart.JsSymbol('_memberName');
+  const _arguments = dart.JsSymbol('_arguments');
+  const _namedArguments = dart.JsSymbol('_namedArguments');
+  const _existingArgumentNames = dart.JsSymbol('_existingArgumentNames');
   class NoSuchMethodError extends Error {
     NoSuchMethodError(receiver, memberName, positionalArguments, namedArguments, existingArgumentNames) {
       if (existingArgumentNames === void 0)
         existingArgumentNames = null;
       this[_receiver] = receiver;
       this[_memberName] = memberName;
       this[_arguments] = positionalArguments;
       this[_namedArguments] = namedArguments;
       this[_existingArgumentNames] = existingArgumentNames;
       super.Error();
@@ skipping 259 matching lines @@
     IntegerDivisionByZeroException() {
     }
     toString() {
       return "IntegerDivisionByZeroException";
     }
   }
   IntegerDivisionByZeroException[dart.implements] = () => [Exception];
   dart.setSignature(IntegerDivisionByZeroException, {
     constructors: () => ({IntegerDivisionByZeroException: [IntegerDivisionByZeroException, []]})
   });
-  let _getKey = dart.JsSymbol('_getKey');
-  let Expando$ = dart.generic(function(T) {
+  const _getKey = dart.JsSymbol('_getKey');
+  const Expando$ = dart.generic(function(T) {
     class Expando extends Object {
       Expando(name) {
         if (name === void 0)
           name = null;
         this.name = name;
       }
       toString() {
         return `Expando:${this.name}`;
       }
       get(object) {
@@ skipping 80 matching lines @@
   dart.setSignature(int, {
     constructors: () => ({fromEnvironment: [int, [String], {defaultValue: int}]}),
     statics: () => ({parse: [int, [String], {radix: int, onError: dart.functionType(int, [String])}]}),
     names: ['parse']
   });
   class Invocation extends Object {
     get isAccessor() {
       return dart.notNull(this.isGetter) || dart.notNull(this.isSetter);
     }
   }
-  let Iterable$ = dart.generic(function(E) {
+  const Iterable$ = dart.generic(function(E) {
     dart.defineExtensionNames([
       'join'
     ]);
     class Iterable extends Object {
       Iterable() {
       }
       static generate(count, generator) {
         if (generator === void 0)
           generator = null;
         if (dart.notNull(count) <= 0)
@@ skipping 14 matching lines @@
     dart.setSignature(Iterable, {
       constructors: () => ({
         Iterable: [Iterable$(E), []],
         generate: [Iterable$(E), [int], [dart.functionType(E, [int])]]
       }),
       methods: () => ({[dartx.join]: [String, [], [String]]})
     });
     return Iterable;
   });
   let Iterable = Iterable$();
-  let _Generator$ = dart.generic(function(E) {
-    let _Generator = dart.typedef('_Generator', () => dart.functionType(E, [int]));
+  const _Generator$ = dart.generic(function(E) {
+    const _Generator = dart.typedef('_Generator', () => dart.functionType(E, [int]));
     return _Generator;
   });
   let _Generator = _Generator$();
-  let _end = dart.JsSymbol('_end');
-  let _start = dart.JsSymbol('_start');
-  let _generator = dart.JsSymbol('_generator');
-  let _GeneratorIterable$ = dart.generic(function(E) {
+  const _end = dart.JsSymbol('_end');
+  const _start = dart.JsSymbol('_start');
+  const _generator = dart.JsSymbol('_generator');
+  const _GeneratorIterable$ = dart.generic(function(E) {
     class _GeneratorIterable extends collection.IterableBase$(E) {
       _GeneratorIterable(end, generator) {
         this[_end] = end;
         this[_start] = 0;
         this[_generator] = dart.as(generator != null ? generator : exports._GeneratorIterable$()._id, _Generator$(E));
         super.IterableBase();
       }
       slice(start, end, generator) {
         this[_start] = start;
         this[_end] = end;
@@ skipping 39 matching lines @@
         skip: [Iterable$(E), [int]],
         take: [Iterable$(E), [int]]
       }),
       statics: () => ({_id: [int, [int]]}),
       names: ['_id']
     });
     dart.defineExtensionMembers(_GeneratorIterable, ['skip', 'take', 'iterator', 'length']);
     return _GeneratorIterable;
   });
   dart.defineLazyClassGeneric(exports, '_GeneratorIterable', {get: _GeneratorIterable$});
-  let _index = dart.JsSymbol('_index');
-  let _current = dart.JsSymbol('_current');
-  let _GeneratorIterator$ = dart.generic(function(E) {
+  const _index = dart.JsSymbol('_index');
+  const _current = dart.JsSymbol('_current');
+  const _GeneratorIterator$ = dart.generic(function(E) {
     class _GeneratorIterator extends Object {
       _GeneratorIterator(index, end, generator) {
         this[_index] = index;
         this[_end] = end;
         this[_generator] = generator;
         this[_current] = null;
       }
       moveNext() {
         if (dart.notNull(this[_index]) < dart.notNull(this[_end])) {
           this[_current] = this[_generator](this[_index]);
           this[_index] = dart.notNull(this[_index]) + 1;
           return true;
         } else {
           this[_current] = null;
           return false;
         }
       }
       get current() {
         return this[_current];
       }
     }
     _GeneratorIterator[dart.implements] = () => [Iterator$(E)];
     dart.setSignature(_GeneratorIterator, {
       constructors: () => ({_GeneratorIterator: [_GeneratorIterator$(E), [int, int, _Generator$(E)]]}),
       methods: () => ({moveNext: [bool, []]})
     });
     return _GeneratorIterator;
   });
   let _GeneratorIterator = _GeneratorIterator$();
-  let BidirectionalIterator$ = dart.generic(function(E) {
+  const BidirectionalIterator$ = dart.generic(function(E) {
     class BidirectionalIterator extends Object {}
     BidirectionalIterator[dart.implements] = () => [Iterator$(E)];
     return BidirectionalIterator;
   });
   let BidirectionalIterator = BidirectionalIterator$();
-  let Iterator$ = dart.generic(function(E) {
+  const Iterator$ = dart.generic(function(E) {
     class Iterator extends Object {}
     return Iterator;
   });
   let Iterator = Iterator$();
-  let List$ = dart.generic(function(E) {
+  const List$ = dart.generic(function(E) {
     class List extends Object {
       static new(length) {
         if (length === void 0)
           length = null;
         let list = null;
         if (length == null) {
           list = [];
         } else {
           if (!(typeof length == 'number') || dart.notNull(length) < 0) {
             dart.throw(new ArgumentError(`Length must be a non-negative integer: ${length}`));
@@ skipping 44 matching lines @@
       constructors: () => ({
         new: [List$(E), [], [int]],
         filled: [List$(E), [int, E]],
         from: [List$(E), [Iterable], {growable: bool}],
         generate: [List$(E), [int, dart.functionType(E, [int])], {growable: bool}]
       })
     });
     return List;
   });
   let List = List$();
-  let Map$ = dart.generic(function(K, V) {
+  const Map$ = dart.generic(function(K, V) {
     class Map extends Object {
       static new() {
         return collection.LinkedHashMap$(K, V).new();
       }
       static from(other) {
         return collection.LinkedHashMap$(K, V).from(other);
       }
       static identity() {
         return collection.LinkedHashMap$(K, V).identity();
       }
@@ skipping 43 matching lines @@
     static new(source, opts) {
       let multiLine = opts && 'multiLine' in opts ? opts.multiLine : false;
       let caseSensitive = opts && 'caseSensitive' in opts ? opts.caseSensitive : true;
       return new _js_helper.JSSyntaxRegExp(source, {multiLine: multiLine, caseSensitive: caseSensitive});
     }
   }
   RegExp[dart.implements] = () => [Pattern];
   dart.setSignature(RegExp, {
     constructors: () => ({new: [RegExp, [String], {multiLine: bool, caseSensitive: bool}]})
   });
-  let Set$ = dart.generic(function(E) {
+  const Set$ = dart.generic(function(E) {
     class Set extends collection.IterableBase$(E) {
       static new() {
         return collection.LinkedHashSet$(E).new();
       }
       static identity() {
         return collection.LinkedHashSet$(E).identity();
       }
       static from(elements) {
         return collection.LinkedHashSet$(E).from(elements);
       }
     }
     Set[dart.implements] = () => [_internal.EfficientLength];
     dart.setSignature(Set, {
       constructors: () => ({
         new: [exports.Set$(E), []],
         identity: [exports.Set$(E), []],
         from: [exports.Set$(E), [Iterable]]
       })
     });
     return Set;
   });
   dart.defineLazyClassGeneric(exports, 'Set', {get: Set$});
-  let Sink$ = dart.generic(function(T) {
+  const Sink$ = dart.generic(function(T) {
     class Sink extends Object {}
     return Sink;
   });
   let Sink = Sink$();
   class StackTrace extends Object {}
-  let _stop = dart.JsSymbol('_stop');
+  const _stop = dart.JsSymbol('_stop');
   class Stopwatch extends Object {
     get frequency() {
       return Stopwatch._frequency;
     }
     Stopwatch() {
       this[_start] = null;
       this[_stop] = null;
       Stopwatch._initTicker();
     }
     start() {
@@ skipping 164 matching lines @@
   }
   dart.fn(_isLeadSurrogate, bool, [int]);
   function _isTrailSurrogate(code) {
     return (dart.notNull(code) & 64512) == 56320;
   }
   dart.fn(_isTrailSurrogate, bool, [int]);
   function _combineSurrogatePair(start, end) {
     return 65536 + ((dart.notNull(start) & 1023) << 10) + (dart.notNull(end) & 1023);
   }
   dart.fn(_combineSurrogatePair, int, [int, int]);
-  let _position = dart.JsSymbol('_position');
-  let _nextPosition = dart.JsSymbol('_nextPosition');
-  let _currentCodePoint = dart.JsSymbol('_currentCodePoint');
-  let _checkSplitSurrogate = dart.JsSymbol('_checkSplitSurrogate');
+  const _position = dart.JsSymbol('_position');
+  const _nextPosition = dart.JsSymbol('_nextPosition');
+  const _currentCodePoint = dart.JsSymbol('_currentCodePoint');
+  const _checkSplitSurrogate = dart.JsSymbol('_checkSplitSurrogate');
   class RuneIterator extends Object {
     RuneIterator(string) {
       this.string = string;
       this[_position] = 0;
       this[_nextPosition] = 0;
       this[_currentCodePoint] = null;
     }
     at(string, index) {
       this.string = string;
       this[_position] = index;
@@ skipping 84 matching lines @@
       RuneIterator: [RuneIterator, [String]],
       at: [RuneIterator, [String, int]]
     }),
     methods: () => ({
       [_checkSplitSurrogate]: [dart.void, [int]],
       reset: [dart.void, [], [int]],
       moveNext: [bool, []],
       movePrevious: [bool, []]
     })
   });
-  let _contents = dart.JsSymbol('_contents');
-  let _writeString = dart.JsSymbol('_writeString');
+  const _contents = dart.JsSymbol('_contents');
+  const _writeString = dart.JsSymbol('_writeString');
   class StringBuffer extends Object {
     StringBuffer(content) {
       if (content === void 0)
         content = "";
       this[_contents] = `${content}`;
     }
     get length() {
       return this[_contents][dartx.length];
     }
     get isEmpty() {
@@ skipping 57 matching lines @@
   class StringSink extends Object {}
   class Symbol extends Object {
     static new(name) {
       return new _internal.Symbol(name);
     }
   }
   dart.setSignature(Symbol, {
     constructors: () => ({new: [Symbol, [String]]})
   });
   class Type extends Object {}
-  let _writeAuthority = dart.JsSymbol('_writeAuthority');
-  let _userInfo = dart.JsSymbol('_userInfo');
-  let _host = dart.JsSymbol('_host');
-  let _port = dart.JsSymbol('_port');
-  let _path = dart.JsSymbol('_path');
-  let _query = dart.JsSymbol('_query');
-  let _fragment = dart.JsSymbol('_fragment');
-  let _pathSegments = dart.JsSymbol('_pathSegments');
-  let _queryParameters = dart.JsSymbol('_queryParameters');
-  let _merge = dart.JsSymbol('_merge');
-  let _hasDotSegments = dart.JsSymbol('_hasDotSegments');
-  let _removeDotSegments = dart.JsSymbol('_removeDotSegments');
-  let _toWindowsFilePath = dart.JsSymbol('_toWindowsFilePath');
-  let _toFilePath = dart.JsSymbol('_toFilePath');
-  let _isPathAbsolute = dart.JsSymbol('_isPathAbsolute');
+  const _writeAuthority = dart.JsSymbol('_writeAuthority');
+  const _userInfo = dart.JsSymbol('_userInfo');
+  const _host = dart.JsSymbol('_host');
+  const _port = dart.JsSymbol('_port');
+  const _path = dart.JsSymbol('_path');
+  const _query = dart.JsSymbol('_query');
+  const _fragment = dart.JsSymbol('_fragment');
+  const _pathSegments = dart.JsSymbol('_pathSegments');
+  const _queryParameters = dart.JsSymbol('_queryParameters');
+  const _merge = dart.JsSymbol('_merge');
+  const _hasDotSegments = dart.JsSymbol('_hasDotSegments');
+  const _removeDotSegments = dart.JsSymbol('_removeDotSegments');
+  const _toWindowsFilePath = dart.JsSymbol('_toWindowsFilePath');
+  const _toFilePath = dart.JsSymbol('_toFilePath');
+  const _isPathAbsolute = dart.JsSymbol('_isPathAbsolute');
   class Uri extends Object {
     get authority() {
       if (!dart.notNull(this.hasAuthority))
         return "";
       let sb = new StringBuffer();
       this[_writeAuthority](sb);
       return dart.toString(sb);
     }
     get userInfo() {
       return this[_userInfo];
@@ skipping 1404 matching lines @@
   exports.StackTrace = StackTrace;
   exports.Stopwatch = Stopwatch;
   exports.String = String;
   exports.RuneIterator = RuneIterator;
   exports.StringBuffer = StringBuffer;
   exports.StringSink = StringSink;
   exports.Symbol = Symbol;
   exports.Type = Type;
   exports.Uri = Uri;
 });