Make sure Bigint._digits is always a Uint32List (instead of sometimes null).

runtime/lib/bigint.dart

 // Copyright (c) 2014, 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.
 
 // Copyright 2009 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 /*
  * Copyright (c) 2003-2005  Tom Wu
@@ skipping 52 matching lines @@
 
   // Digit conversion table for parsing.
   static final Map<int, int> DIGIT_TABLE = _createDigitTable();
 
   // Internal data structure.
   bool get _neg native "Bigint_getNeg";
   void set _neg(bool neg) native "Bigint_setNeg";
   int get _used native "Bigint_getUsed";
   void set _used(int used) native "Bigint_setUsed";
   Uint32List get _digits native "Bigint_getDigits";
-  void set _digits(Uint32List digits) native "Bigint_setDigits";
+  void set _digits(Uint32List digits) {
+    // The VM expects digits_ to be a Uint32List.
+    assert(digits != null);
+    _set_digits(digits);
+  }
+
+  void _set_digits(Uint32List digits) native "Bigint_setDigits";
 
   // Factory returning an instance initialized to value 0.
   factory _Bigint() native "Bigint_allocate";
 
   // Factory returning an instance initialized to an integer value.
   factory _Bigint._fromInt(int i) {
     return new _Bigint()._setInt(i);
   }
 
   // Factory returning an instance initialized to a hex string.
@@ skipping 110 matching lines @@
   }
 
   // Conversion from int to bigint.
   _Bigint _toBigint() => this;
 
   // Make sure at least 'length' _digits are allocated.
   // Copy existing _digits if reallocation is necessary.
   // TODO(regis): Check that we are not preserving _digits unnecessarily.
   void _ensureLength(int length) {
     var digits = _digits;
-    if (length > 0 && (digits == null || length > digits.length)) {
+    if (length > 0 && (length > digits.length)) {
       var new_digits = new Uint32List(length + EXTRA_DIGITS);
-      if (digits != null) {
-        for (var i = _used; --i >= 0; ) {
-          new_digits[i] = digits[i];
-        }
+      for (var i = _used; --i >= 0; ) {
+        new_digits[i] = digits[i];
       }
       _digits = new_digits;
     }
   }
 
   // Clamp off excess high _digits.
   void _clamp() {
     var digits = _digits;
     while (_used > 0 && digits[_used - 1] == 0) {
       --_used;
@@ skipping 760 matching lines @@
     if (_neg) return (~this).bitLength;
     return DIGIT_BITS*(_used - 1) + _nbits(_digits[_used - 1]);
   }
 
   // This method must support smi._toBigint()._shrFromInt(int).
   int _shrFromInt(int other) {
     if (_used == 0) return other;  // Shift amount is zero.
     if (_neg) throw "negative shift amount";  // TODO(regis): What exception?
     assert(DIGIT_BITS == 32);  // Otherwise this code needs to be revised.
     var shift;
-    if (_used > 2 || (_used == 2 && _digits[1] > 0x10000000)) {
+    if ((_used > 2) || ((_used == 2) && (_digits[1] > 0x10000000))) {
       if (other < 0) {
         return -1;
       } else {
         return 0;
       }
     } else {
       shift = ((_used == 2) ? (_digits[1] << DIGIT_BITS) : 0) + _digits[0];
     }
     _Bigint result = new _Bigint();
     other._toBigint()._rShiftTo(shift, result);
@@ skipping 404 matching lines @@
   void _sqrTo(_Bigint x, _Bigint r) {
     x._sqrTo(r);
     _reduce(r);
   }
 
   void _mulTo(_Bigint x, _Bigint y, _Bigint r) {
     x._mulTo(y, r);
     _reduce(r);
   }
 }