Constrain parameter of [Not]HaveFlag struct enums #1315
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What does that do to the binary and source-code compatibility? |
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Author
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Currently one can pass in null to using System;
public class Program {
enum MyEnum
{
A
}
static bool Foo(Enum t)
=> MyEnum.A.HasFlag(t);
static bool Bar<TEnum>(TEnum t)
where TEnum : struct, Enum
=> MyEnum.A.HasFlag(t);
static bool Baz<TEnum>(TEnum t)
where TEnum : Enum
=> MyEnum.A.HasFlag(t);
static void Main()
{
MyEnum nativeEnum = MyEnum.A;
Enum classEnum = MyEnum.A;
Enum nullEnum = null;
Foo(nativeEnum);
Foo(classEnum);
Foo(nullEnum); // NRE
Bar(nativeEnum);
//Bar<MyEnum>(classEnum); // does not compile
//Bar<MyEnum>(nullEnum); // does not compile
Baz(nativeEnum);
Baz(classEnum);
Baz(nullEnum); // NRE
}
}Reading up on the initial implementation in #250 it seems the only/main reason this wasn't moved to a separate It has nice potential. MyEnum.A.Should().Be(OtherEnum.A)
MyEnum.A.Should().Be((object)42)will simply be turned into compile time errors. |
dennisdoomen
approved these changes
Apr 22, 2020
|
Will it be merged? Why the PR is still draft. |
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In C# 7.3 the enum constraint was introduced, which lets us restrict the parameter of
[Not]HaveFlagto a struct enum.This prevents an NRE if one passed in
null- as it no longer compiles.