Make VM JSON parser parse doubles without doing substring.

tests/lib/convert/json_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library json_test;
 
 import "package:expect/expect.dart";
 import "dart:convert";
 
 bool badFormat(e) => e is FormatException;
 
 void testJson(json, expected) {
-  var value = JSON.decode(json);
   compare(expected, actual, path) {
     if (expected is List) {
       Expect.isTrue(actual is List);
       Expect.equals(expected.length, actual.length, "$path: List length");
       for (int i = 0; i < expected.length; i++) {
         compare(expected[i], actual[i], "$path[$i]");
       }
     } else if (expected is Map) {
       Expect.isTrue(actual is Map);
       Expect.equals(expected.length, actual.length, "$path: Map size");
       expected.forEach((key, value) {
         Expect.isTrue(actual.containsKey(key));
         compare(value, actual[key], "$path[$key]");
       });
     } else if (expected is num) {
       Expect.equals(expected is int, actual is int, "$path: same number type");
       Expect.isTrue(expected.compareTo(actual) == 0,
                     "$path: $expected vs. $actual");
     } else {
       // String, bool, null.
       Expect.equals(expected, actual, path);
     }
   }
-  compare(expected, value, "value");
+  for (var reviver in [null, (k, v) => v]) {
+    var value = JSON.decode(json, reviver: reviver);
+    compare(expected, value, "$value");
+    value = JSON.decode(" $json ", reviver: reviver);
+    compare(expected, value, "-$value-");
+    value = JSON.decode("[$json]", reviver: reviver);
+    compare([expected], value, "[$value]");
+    value = JSON.decode('{"x":$json}', reviver: reviver);
+    compare({"x":expected}, value, "{x:$value}");
+  }
 }
 
 String escape(String s) {
   var sb = new StringBuffer();
   for (int i = 0; i < s.length; i++) {
     int code = s.codeUnitAt(i);
     if (code == '\\'.codeUnitAt(0)) sb.write(r'\\');
     else if (code == '\"'.codeUnitAt(0)) sb.write(r'\"');
     else if (code >= 32 && code < 127) sb.writeCharCode(code);
     else {
@@ skipping 97 matching lines @@
 }
 
 testStrings() {
   // String parser accepts and understands escapes.
   var input = r'"\u0000\uffff\n\r\f\t\b\/\\\"' '\x20\ufffd\uffff"';
   var expected = "\u0000\uffff\n\r\f\t\b\/\\\"\x20\ufffd\uffff";
   testJson(input, expected);
   // Empty string.
   testJson(r'""', "");
   // Escape first.
-  testJson(r'"\"........"', "\"........");
-  // Escape last.
-  testJson(r'"........\""', "........\"");
-  // Escape middle.
-  testJson(r'"....\"...."', "....\"....");
+  var escapes = {
+    "f": "\f",
+    "b": "\b",
+    "n": "\n",
+    "r": "\r",
+    "t": "\t",
+    r"\": r"\",
+    '"': '"',
+    "/": "/",
+  };
+  escapes.forEach((esc, lit) {
+    testJson('"\\$esc........"', "$lit........");
+    // Escape last.
+    testJson('"........\\$esc"', "........$lit");
+    // Escape middle.
+    testJson('"....\\$esc...."', "....$lit....");
+  });
 
   // Does not accept single quotes.
   testThrows(r"''");
   // Throws on unterminated strings.
   testThrows(r'"......\"');
   // Throws on unterminated escapes.
   testThrows(r'"\');  // ' is not escaped.
   testThrows(r'"\a"');
   testThrows(r'"\u"');
   testThrows(r'"\u1"');
@@ skipping 97 matching lines @@
 }
 
 main() {
   testNumbers();
   testStrings();
   testWords();
   testObjects();
   testArrays();
   testWhitespace();
 }