Use of delegate* throws a NRE

[albahari]

I appreciate that C# 9 support is still work in progress, but given that function pointers work in other contexts, I figure that this bug report might be helpful.

Steps to reproduce

1. Decompile the following program

using System;
using System.Runtime.InteropServices;

unsafe
{
	EnumWindows(&PrintWindow, IntPtr.Zero);

	[DllImport("user32.dll", CallingConvention = CallingConvention.StdCall)]
	static extern int EnumWindows(delegate*<IntPtr, IntPtr, bool> hWnd, IntPtr lParam);

	static bool PrintWindow(IntPtr hWnd, IntPtr lParam) => true;
}

Error message shown

Error decompiling @06000001 <Program>$.<Main>$
in assembly "C:\Users\mail\source\repos\ConsoleApp34\ConsoleApp34\bin\Debug\net5.0\ConsoleApp34.dll"
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at ICSharpCode.Decompiler.IL.Transforms.LocalFunctionDecompiler.ReplaceReferencesToDisplayClassThis(ValueCollection localFunctions) in offset 20
   at ICSharpCode.Decompiler.IL.Transforms.LocalFunctionDecompiler.Run(ILFunction function, ILTransformContext context) in offset 113
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileBody(IMethod method, EntityDeclaration entityDecl, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in offset 542
-- continuing with outer exception (ICSharpCode.Decompiler.DecompilerException) --
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DecompileBody(IMethod method, EntityDeclaration entityDecl, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in offset 833
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DoDecompile(IMethod method, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in offset 195
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.DoDecompile(ITypeDefinition typeDef, DecompileRun decompileRun, ITypeResolveContext decompilationContext) in offset 648
   at ICSharpCode.Decompiler.CSharp.CSharpDecompiler.Decompile(IEnumerable`1 definitions) in offset 276
   at ICSharpCode.ILSpy.CSharpLanguage.DecompileType(ITypeDefinition type, ITextOutput output, DecompilationOptions options) in offset 37
   at ICSharpCode.ILSpy.TextView.DecompilerTextView.DecompileNodes(DecompilationContext context, ITextOutput textOutput) in offset 124
   at ICSharpCode.ILSpy.TextView.DecompilerTextView.<>c__DisplayClass48_0.<DecompileAsync>b__0() in offset 36

Details

• Product in use: ILSpy version 6.2.1.6137

[siegfriedpammer]

Thanks for reporting this! This is actually not related to function pointers at all, but rather C# 9.0 supports "extern" local functions, the decompiler did not. This should be fixed now.