bool does not implement IParsable<TSelf>

[znakeeye]

Description

I'm writing a parser and this one is quite problematic. For the most basic type, a boolean, the new IParsable<TSelf> interface is not available. This makes no sense.

I realize that there is little need for a bool.Parse(string, IFormatProvider?) but since the second parameter may be null, it would be a no-brainer to implement. See Boolean.cs(228). Just add the interface, and these methods:

public static bool Parse(string value, IFormatProvider? _) => Parse(value);
public static bool TryParse([NotNullWhen(true)] string? s, IFormatProvider? _, [MaybeNullWhen(false)] out TSelf result)
{
    return TryParse(s, out result);
}

Reproduction Steps

Running VS 17.5 targeting .NET 7.0, simply create a console app with the code below.

internal class Program
{
    static void Main(string[] args)
    {
        Cast<int>("123");   // OK
        Cast<bool>("true"); // CS0315
    }

    public static TSelf Cast<TSelf>(string s) where TSelf : IParsable<TSelf> => TSelf.Parse(s, null);
}

Expected behavior

Boolean implements IParsable<TSelf>, just like all other primitive types.

Actual behavior

Boolean does not implement IParsable<TSelf>.

Regression?

No

Known Workarounds

Wherever a method expects IParsable<T> you can duplicate that method to handle bool specifically. E.g.:

internal class Program
{
    static void Main(string[] args)
    {
        Cast<int>("123");
        CastBool("true"); // CS0315
    }

    public static TSelf Cast<TSelf>(string s) where TSelf : IParsable<TSelf> => TSelf.Parse(s, null);
    public static bool CastBool(string s) => bool.Parse(s);
}

Configuration

.NET 7.0
Windows 11 (x64)

Other information

https://github.com/dotnet/runtime/blob/main/src/libraries/System.Private.CoreLib/src/System/Boolean.cs#L24

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[svick]

This is a subset of #67388.

[znakeeye]

This is a subset of #67388.

Ah, really cool. I want to see that feature in .NET 7.01 😄

I guess my suggestion could theoretically break once #67388 is shipped. Though, I would still argue that my bug report is valid. Not having this interface for booleans is painful.

[teo-tsirpanis]

I want to see that feature in .NET 7.0[.]1

Not going to happen. Servicing releases do not get new APIs.

[ghost]

Tagging subscribers to this area: @dotnet/area-system-runtime
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Description

I'm writing a parser and this one is quite problematic. For the most basic type, a boolean, the new IParsable<TSelf> interface is not available. This makes no sense.

I realize that there is little need for a bool.Parse(string, IFormatProvider?) but since the second parameter may be null, it would be a no-brainer to implement. See Boolean.cs(228). Just add the interface, and these methods:

public static bool Parse(string value, IFormatProvider? _) => Parse(value);
public static bool TryParse([NotNullWhen(true)] string? s, IFormatProvider? _, [MaybeNullWhen(false)] out TSelf result)
{
    return TryParse(s, out result);
}

Reproduction Steps

Running VS 17.5 targeting .NET 7.0, simply create a console app with the code below.

internal class Program
{
    static void Main(string[] args)
    {
        Cast<int>("123");   // OK
        Cast<bool>("true"); // CS0315
    }

    public static TSelf Cast<TSelf>(string s) where TSelf : IParsable<TSelf> => TSelf.Parse(s, null);
}

Expected behavior

Boolean implements IParsable<TSelf>, just like all other primitive types.

Actual behavior

Boolean does not implement IParsable<TSelf>.

Regression?

No

Known Workarounds

Wherever a method expects IParsable<T> you can duplicate that method to handle bool specifically. E.g.:

internal class Program
{
    static void Main(string[] args)
    {
        Cast<int>("123");
        CastBool("true"); // CS0315
    }

    public static TSelf Cast<TSelf>(string s) where TSelf : IParsable<TSelf> => TSelf.Parse(s, null);
    public static bool CastBool(string s) => bool.Parse(s);
}

Configuration

.NET 7.0
Windows 11 (x64)

Other information

https://github.com/dotnet/runtime/blob/main/src/libraries/System.Private.CoreLib/src/System/Boolean.cs#L24

Author:	znakeeye
Assignees:	-
Labels:	area-System.Runtime, untriaged
Milestone:	-

[rickbrew]

Yeah I just found myself needing bool support for IFormattable and IParsable<bool>. It already has the methods, it just doesn't specify the interfaces 🤔

[znakeeye]

Can we expect this to be fixed in .NET 8?

[tannergooding]

Depends on what API review says for the API.

[bartonjs]

Adding the interface decl on bool and implementing the methods explicitly seems reasonable, though we should go all the way to ISpanParsable

namespace System;

public partial struct Boolean : ISpanParsable<Boolean>
{
    // ISpanParsable and IParsable members explicitly implemented (if they're not already present)
}

[tannergooding]

Will have a PR up covering this and #78842 shortly