public void CS0472WRN_NubExprIsConstBool()
{
// Due to a long-standing bug, the native compiler does not produce warnings for "guid == null",
// but does for "int == null". Roslyn corrects this lapse and produces warnings for both built-in
// and user-defined lifted equality operators, but the new warnings for user-defined types are
// only given in "strict" more.
var text = @"
using System;
class MyClass
{
public static void W(bool b)
{
System.Console.Write(b ? 't' : 'f');
}
enum E : int { };
public static void Main()
{
Guid g = default(Guid);
Guid? h = g;
int i = 0;
int? n = i;
W(i == null); // CS0472
W(i != null); // CS0472
W(n == null); // no error
W(n != null); // no error
W(g == null); // CS0472
W(g != null); // CS0472
W(h == null); // no error
W(h != null); // no error
W(i == default(short?)); // CS0472
W(i != default(short?)); // CS0472
W(n == default(short?)); // no error
W(n != default(short?)); // no error
W(g == default(Guid?)); // CS0472
W(g != default(Guid?)); // CS0472
W(h == default(Guid?)); // no error
W(h != default(Guid?)); // no error
W(i == new sbyte?()); // CS0472
W(i != new sbyte?()); // CS0472
W(n == new sbyte?()); // no error
W(n != new sbyte?()); // no error
W(g == new Guid?()); // CS0472
W(g != new Guid?()); // CS0472
W(h == new Guid?()); // no error
W(h != new Guid?()); // no error
System.Console.WriteLine();
W(null == i); // CS0472
W(null != i); // CS0472
W(null == n); // no error
W(null != n); // no error
W(null == g); // CS0472
W(null != g); // CS0472
W(null == h); // no error
W(null != h); // no error
W(default(long?) == i); // CS0472
W(default(long?) != i); // CS0472
W(default(long?) == n); // no error
W(default(long?) != n); // no error
W(default(Guid?) == g); // CS0472
W(default(Guid?) != g); // CS0472
W(default(Guid?) == h); // no error
W(default(Guid?) != h); // no error
W(new double?() == i); // CS0472
W(new double?() != i); // CS0472
W(new double?() == n); // no error
W(new double?() != n); // no error
W(new Guid?() == g); // CS0472
W(new Guid?() != g); // CS0472
W(new Guid?() == h); // no error
W(new Guid?() != h); // no error
System.Console.WriteLine();
W(null == null); // No error, because both sides are nullable, but of course
W(null != null); // we could give a warning here as well.
System.Console.WriteLine();
//check comparisons with converted constants
W((E?)1 == null);
W(null != (E?)1);
W((int?)1 == null);
W(null != (int?)1);
//check comparisons when null is converted
W(0 == (int?)null);
W((int?)null != 0);
W(0 == (E?)null);
W((E?)null != 0);
}
}
";
string expected = @"ftftftftftftftftftftftft
ftftftftftftftftftftftft
tf
ftftftft";
var fullExpected = new DiagnosticDescription[] {
// (19,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(i == null); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i == null").WithArguments("false", "int", "int?").WithLocation(19, 11),
// (20,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(i != null); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i != null").WithArguments("true", "int", "int?").WithLocation(20, 11),
// (23,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g == null); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g == null").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(23, 11),
// (24,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g != null); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g != null").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(24, 11),
// (28,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'short?'
// W(i == default(short?)); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i == default(short?)").WithArguments("false", "int", "short?").WithLocation(28, 11),
// (29,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'short?'
// W(i != default(short?)); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i != default(short?)").WithArguments("true", "int", "short?").WithLocation(29, 11),
// (32,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g == default(Guid?)); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g == default(Guid?)").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(32, 11),
// (33,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g != default(Guid?)); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g != default(Guid?)").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(33, 11),
// (37,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'sbyte?'
// W(i == new sbyte?()); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i == new sbyte?()").WithArguments("false", "int", "sbyte?").WithLocation(37, 11),
// (38,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'sbyte?'
// W(i != new sbyte?()); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "i != new sbyte?()").WithArguments("true", "int", "sbyte?").WithLocation(38, 11),
// (41,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g == new Guid?()); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g == new Guid?()").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(41, 11),
// (42,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(g != new Guid?()); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "g != new Guid?()").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(42, 11),
// (49,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(null == i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "null == i").WithArguments("false", "int", "int?").WithLocation(49, 11),
// (50,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(null != i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "null != i").WithArguments("true", "int", "int?").WithLocation(50, 11),
// (53,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(null == g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "null == g").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(53, 11),
// (54,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(null != g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "null != g").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(54, 11),
// (58,11): warning CS0472: The result of the expression is always 'false' since a value of type 'long' is never equal to 'null' of type 'long?'
// W(default(long?) == i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "default(long?) == i").WithArguments("false", "long", "long?").WithLocation(58, 11),
// (59,11): warning CS0472: The result of the expression is always 'true' since a value of type 'long' is never equal to 'null' of type 'long?'
// W(default(long?) != i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "default(long?) != i").WithArguments("true", "long", "long?").WithLocation(59, 11),
// (62,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(default(Guid?) == g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "default(Guid?) == g").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(62, 11),
// (63,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(default(Guid?) != g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "default(Guid?) != g").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(63, 11),
// (67,11): warning CS0472: The result of the expression is always 'false' since a value of type 'double' is never equal to 'null' of type 'double?'
// W(new double?() == i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "new double?() == i").WithArguments("false", "double", "double?").WithLocation(67, 11),
// (68,11): warning CS0472: The result of the expression is always 'true' since a value of type 'double' is never equal to 'null' of type 'double?'
// W(new double?() != i); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "new double?() != i").WithArguments("true", "double", "double?").WithLocation(68, 11),
// (71,11): warning CS8073: The result of the expression is always 'false' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(new Guid?() == g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "new Guid?() == g").WithArguments("false", "System.Guid", "System.Guid?").WithLocation(71, 11),
// (72,11): warning CS8073: The result of the expression is always 'true' since a value of type 'System.Guid' is never equal to 'null' of type 'System.Guid?'
// W(new Guid?() != g); // CS0472
Diagnostic(ErrorCode.WRN_NubExprIsConstBool2, "new Guid?() != g").WithArguments("true", "System.Guid", "System.Guid?").WithLocation(72, 11),
// (84,11): warning CS0472: The result of the expression is always 'false' since a value of type 'MyClass.E' is never equal to 'null' of type 'MyClass.E?'
// W((E?)1 == null);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "(E?)1 == null").WithArguments("false", "MyClass.E", "MyClass.E?").WithLocation(84, 11),
// (85,11): warning CS0472: The result of the expression is always 'true' since a value of type 'MyClass.E' is never equal to 'null' of type 'MyClass.E?'
// W(null != (E?)1);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "null != (E?)1").WithArguments("true", "MyClass.E", "MyClass.E?").WithLocation(85, 11),
// (87,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'int?'
// W((int?)1 == null);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "(int?)1 == null").WithArguments("false", "int", "int?").WithLocation(87, 11),
// (88,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(null != (int?)1);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "null != (int?)1").WithArguments("true", "int", "int?").WithLocation(88, 11),
// (92,11): warning CS0472: The result of the expression is always 'false' since a value of type 'int' is never equal to 'null' of type 'int?'
// W(0 == (int?)null);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "0 == (int?)null").WithArguments("false", "int", "int?").WithLocation(92, 11),
// (93,11): warning CS0472: The result of the expression is always 'true' since a value of type 'int' is never equal to 'null' of type 'int?'
// W((int?)null != 0);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "(int?)null != 0").WithArguments("true", "int", "int?").WithLocation(93, 11),
// (95,11): warning CS0472: The result of the expression is always 'false' since a value of type 'MyClass.E' is never equal to 'null' of type 'MyClass.E?'
// W(0 == (E?)null);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "0 == (E?)null").WithArguments("false", "MyClass.E", "MyClass.E?").WithLocation(95, 11),
// (96,11): warning CS0472: The result of the expression is always 'true' since a value of type 'MyClass.E' is never equal to 'null' of type 'MyClass.E?'
// W((E?)null != 0);
Diagnostic(ErrorCode.WRN_NubExprIsConstBool, "(E?)null != 0").WithArguments("true", "MyClass.E", "MyClass.E?").WithLocation(96, 11)
};
var compatibleExpected = fullExpected.Where(d => !d.Code.Equals((int)ErrorCode.WRN_NubExprIsConstBool2)).ToArray();
this.CompileAndVerify(source: text, expectedOutput: expected).VerifyDiagnostics(compatibleExpected);
this.CompileAndVerify(source: text, expectedOutput: expected, options: TestOptions.ReleaseExe, parseOptions: TestOptions.Regular.WithStrictFeature()).VerifyDiagnostics(fullExpected);
}
