| Index: sdk/lib/core/errors.dart
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| diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
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| index a67340660307349df0f7f3866c9965b091d7601f..3d36b3919fd1fb25665eed725d6275acffbc7650 100644
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| --- a/sdk/lib/core/errors.dart
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| +++ b/sdk/lib/core/errors.dart
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| @@ -171,7 +171,7 @@ class ArgumentError extends Error {
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|        : this.value(null, name, "Must not be null");
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|  
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|    // Helper functions for toString overridden in subclasses.
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| -  String get _errorName => "Invalid argument${name == null ? "(s)" : ""}";
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| +  String get _errorName => "Invalid argument${!_hasValue ? "(s)" : ""}";
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|    String get _errorExplanation => "";
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|  
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|    String toString() {
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| @@ -179,9 +179,9 @@ class ArgumentError extends Error {
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|      if (name != null) {
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|        nameString = " ($name)";
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|      }
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| -    var message = this.message == null ? "" : ": ${this.message}";
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| +    var message = (this.message == null) ? "" : ": ${this.message}";
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|      String prefix = "$_errorName$nameString$message";
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| -    if (invalidValue == null) return prefix;
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| +    if (!_hasValue) return prefix;
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|      // If we know the invalid value, we can try to describe the problem.
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|      String explanation = _errorExplanation;
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|      String errorValue = Error.safeToString(invalidValue);
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| 
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