Description
Consider adding an [ConstantExpected] attribute that could be put on parameters to indicate that arguments should be constants rather than variables. See #30740 (comment) for details.
The attribute proposal
namespace System.Runtime.CompilerServices
{
[AttributeUsage(AttributeTargets.Parameter, AllowMultiple = false, Inherited = false)]
public sealed class ConstantExpectedAttribute : Attribute
{
public object? Min { get; set; }
public object? Max { get; set; }
}
}Usage and Diagnostic examples
public static class C
{
public static void MyBool1([ConstantExpected] bool b) { }
public static void MyLong1([ConstantExpected] long b) { }
public static void MyLong2([ConstantExpected(Min = -5, Max = 10)] long b) { }
public static void MyFloat1([ConstantExpected] float b) { }
public static void MyFloat2([ConstantExpected(Min = -5.3f, Max = 10.1f)] float b) { }
// Might want to warn for the negative values and out of range values
public static void MyInvalidUshort([ConstantExpected(Min = -5, Max = -1)] ushort b) { }
public static void MyInvalidRange([ConstantExpected(Min = 5, Max = -5)] int b) { }
// flag any ref type usage as not applicable
public static void MyString([ConstantExpected] string b) { }
// Diagnostics examples
public static void Test(long b, ushort u)
{
// OK
const long a = 10;
MyLong1(a);
MyLong2(a);
MyLong1(1L);
MyLong2(2L);
MyInvalidUshort(1);
const ushort us = 0;
MyInvalidUshort(us); // Flag
MyLong1(b); // Flag
MyLong2(b); // Flag
MyLong2(20); // Flag, out of range
MyInvalidUshort(u); // Flag
MyInvalidUshort(10); // Flag, out of the range
}
}Category: Reliability
Severity: Info