fixes #206, add checking for unary ops

lib/runtime/dart/core.js

Index: lib/runtime/dart/core.js
diff --git a/lib/runtime/dart/core.js b/lib/runtime/dart/core.js
index 1eac80377c7c89eab07b7075358d231fc00895a9..b1d09ff1c2fc8e33c4a7117564214d9b0d545e27 100644
--- a/lib/runtime/dart/core.js
+++ b/lib/runtime/dart/core.js
@@ -860,7 +860,7 @@ var convert = dart.lazyImport(convert);
       dart.assert(this[_hasValue]);
       let target = Error.safeToString(this.indexable);
       let explanation = `index should be less than ${this.length}`;
-      if (dart.dsend(this.invalidValue, '<', 0)) {
+      if (dart.as(dart.dsend(this.invalidValue, '<', 0), bool)) {
         explanation = "index must not be negative";
       }
       return `RangeError: ${this.message} (${target}[${this.invalidValue}]): ${explanation}`;
@@ -2688,7 +2688,7 @@ var convert = dart.lazyImport(convert);
     }
     static _checkNonWindowsPathReservedCharacters(segments, argumentError) {
       segments[$forEach](dart.fn(segment => {
-        if (dart.dsend(segment, 'contains', "/")) {
+        if (dart.as(dart.dsend(segment, 'contains', "/"), bool)) {
           if (argumentError) {
             throw new ArgumentError(`Illegal path character ${segment}`);
           } else {
@@ -2701,7 +2701,7 @@ var convert = dart.lazyImport(convert);
       if (firstSegment === void 0)
         firstSegment = 0;
       segments[$skip](firstSegment)[$forEach](dart.fn(segment => {
-        if (dart.dsend(segment, 'contains', RegExp.new('["*/:<>?\\\\|]'))) {
+        if (dart.as(dart.dsend(segment, 'contains', RegExp.new('["*/:<>?\\\\|]')), bool)) {
           if (argumentError) {
             throw new ArgumentError("Illegal character in path");
           } else {
@@ -2984,7 +2984,7 @@ var convert = dart.lazyImport(convert);
       } else {
         result = pathSegments[$map](dart.fn(s => Uri._uriEncode(dart.as(Uri._pathCharTable, List$(int)), dart.as(s, String)), String, [Object]))[$join]("/");
       }
-      if (dart.dload(result, 'isEmpty')) {
+      if (dart.as(dart.dload(result, 'isEmpty'), bool)) {
         if (isFile)
           return "/";
       } else if ((dart.notNull(isFile) || dart.notNull(ensureLeadingSlash)) && dart.notNull(!dart.equals(dart.dsend(result, 'codeUnitAt', 0), Uri._SLASH))) {
@@ -3008,7 +3008,7 @@ var convert = dart.lazyImport(convert);
         }
         first = false;
         result.write(Uri.encodeQueryComponent(dart.as(key, String)));
-        if (dart.notNull(value != null) && dart.notNull(dart.dsend(dart.dload(value, 'isEmpty'), '!'))) {
+        if (dart.notNull(value != null) && !dart.notNull(dart.as(dart.dload(value, 'isEmpty'), bool))) {
           result.write("=");
           result.write(Uri.encodeQueryComponent(dart.as(value, String)));
         }
@@ -3065,7 +3065,7 @@ var convert = dart.lazyImport(convert);
       dart.assert(dart.dsend(char, '<=', 1114111));
       let hexDigits = "0123456789ABCDEF";
       let codeUnits = null;
-      if (dart.dsend(char, '<', 128)) {
+      if (dart.as(dart.dsend(char, '<', 128), bool)) {
         codeUnits = List.new(3);
         codeUnits[$set](0, Uri._PERCENT);
         codeUnits[$set](1, hexDigits.codeUnitAt(dart.as(dart.dsend(char, '>>', 4), int)));
@@ -3073,10 +3073,10 @@ var convert = dart.lazyImport(convert);
       } else {
         let flag = 192;
         let encodedBytes = 2;
-        if (dart.dsend(char, '>', 2047)) {
+        if (dart.as(dart.dsend(char, '>', 2047), bool)) {
           flag = 224;
           encodedBytes = 3;
-          if (dart.dsend(char, '>', 65535)) {
+          if (dart.as(dart.dsend(char, '>', 65535), bool)) {
             encodedBytes = 4;
             flag = 240;
           }