SYSLIB1054 code fixer should not generate a code that try to access to LibraryImport.ThrowOnUnmappableChar

[Tan90909090]

Version Used:
Microsoft Visual Studio Community 2022 (64-bit) - Current Version 17.4.2

Steps to Reproduce:

1. Write <TargetFramework>net7.0</TargetFramework> in csproj
2. Write a following code:

using System;
using System.Runtime.InteropServices;

class NativeMethods
{
    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Ansi, BestFitMapping = false, ThrowOnUnmappableChar = true)]
    static extern IntPtr GetProcAddress(
        IntPtr hModule,
        [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

    static void Main() { }
}

3. Apply a quick-fix Convert to 'LibraryImport' at GetProcAddress

Diagnostic Id:
SYSLIB1054 Mark the method 'GetProcAddress' with 'LibraryImportAttribute' instead of 'DllImportAttribute' to generate P/Invoke marshalling code at compile time

Expected Behavior:
Code fixer generate a code that does not have an error.

Actual Behavior:
Code fixer generate a following code:

using System;
using System.Runtime.InteropServices;

partial class NativeMethods
{
    [LibraryImport("kernel32.dll", SetLastError = true, StringMarshalling = StringMarshalling.Custom, ThrowOnUnmappableChar = true, StringMarshallingCustomType = typeof(System.Runtime.InteropServices.Marshalling.AnsiStringMarshaller))]
    static partial IntPtr GetProcAddress(
        IntPtr hModule,
        [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

    static void Main() { }
}

Because LibraryImportAttribute does not have ThrowOnUnmappableChar member so the above code has an error: CS0246 The type or namespace name 'ThrowOnUnmappableChar' could not be found (are you missing a using directive or an assembly reference?)

Note
I realized that same issue happens to the following code because there is not LibraryImportAttribute.BestFitMapping:

    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Ansi, BestFitMapping = true)]
    static extern IntPtr GetProcAddress(
        IntPtr hModule,
        [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

[CyrusNajmabadi]

SYSLIB1054

This is not roslyn. Moving to runtime.

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

Issue Details

---

Version Used:
Microsoft Visual Studio Community 2022 (64-bit) - Current Version 17.4.2

Steps to Reproduce:

1. Write <TargetFramework>net7.0</TargetFramework> in csproj
2. Write a following code:

using System;
using System.Runtime.InteropServices;

class NativeMethods
{
    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Ansi, BestFitMapping = false, ThrowOnUnmappableChar = true)]
    static extern IntPtr GetProcAddress(
        IntPtr hModule,
        [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

    static void Main() { }
}

3. Apply a quick-fix Convert to 'LibraryImport' at GetProcAddress

Diagnostic Id:
SYSLIB1054 Mark the method 'GetProcAddress' with 'LibraryImportAttribute' instead of 'DllImportAttribute' to generate P/Invoke marshalling code at compile time

Expected Behavior:
Code fixer generate a code that does not have an error.

Actual Behavior:
Code fixer generate a following code:

using System;
using System.Runtime.InteropServices;

partial class NativeMethods
{
    [LibraryImport("kernel32.dll", SetLastError = true, StringMarshalling = StringMarshalling.Custom, ThrowOnUnmappableChar = true, StringMarshallingCustomType = typeof(System.Runtime.InteropServices.Marshalling.AnsiStringMarshaller))]
    static partial IntPtr GetProcAddress(
        IntPtr hModule,
        [MarshalAs(UnmanagedType.LPStr)] string lpProcName);

    static void Main() { }
}

Because LibraryImportAttribute does not have ThrowOnUnmappableChar member so the above code has an error: CS0246 The type or namespace name 'ThrowOnUnmappableChar' could not be found (are you missing a using directive or an assembly reference?)

Author:	Tan90909090
Assignees:	-
Labels:	area-System.Runtime.InteropServices, untriaged
Milestone:	-

[AaronRobinsonMSFT]

@jkoritzinsky I thought we stripped invalid field when converting attributes or indicated the fixer couldn't apply. Am I misremembering this? I think we either need to drop the unsupported field when converting or not flag it. @jtschuster Any chance you could quickly address this?

[Tan90909090]

Another related issue.
When I write a following code then there is a SYSLIB1054:

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

internal static partial class NativeMethods
{
    [DllImport("msvcrt.dll", CallingConvention=CallingConvention.Cdecl)]
    internal static extern int printf([MarshalAs(UnmanagedType.LPStr)] string s, __arglist);
}

If I apply a quick-fix Convert to 'LibraryImport' then I will get a following code:

using System;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;

internal static partial class NativeMethods
{
    [LibraryImport("msvcrt.dll")]
    [UnmanagedCallConv(CallConvs = new Type[] { typeof(CallConvCdecl) })]
    internal static partial int printf([MarshalAs(UnmanagedType.LPStr)] string s, __arglist);
}

The above code has an error:

Error CS8795 Partial method 'NativeMethods.printf(string, __arglist)' must have an implementation part because it has accessibility modifiers.

It seems that LibraryImportGenerator does not support __arglist currently.