An unhandled exception of type 'System.StackOverflowException' occurred in ICSharpCode.Decompiler.dll

[ChristianHoe]

Steps to reproduce

1. Open Dll (can be provided)
2. Browsing to a specific class (most other seems okay)
3. Crash

Error message shown

Eine Ausnahme vom Typ "System.StackOverflowException" wurde ausgelöst.

Details

• Product in use: VIsual Studio 2019 (ILSpy)
• Version in use: e.g. 6.2.0.6124
• Opened Dll NETCoreApp, V3.1 / Linux

[siegfriedpammer]

Yes, please provide the DLL. If you prefer a private channel, please send it to siegfried.pammer@gmail.com. Thanks!

[ChristianHoe]

Send. There should be nothing important in the DLL.
PollAnswer in EventBot.Business.Commands.Raid

[siegfriedpammer]

I haven't received anything yet...

[ChristianHoe]

Send again.

[siegfriedpammer]

Still nothing... no spam... nothing... sorry. Might be GMail blocking executables as attachments...

[ChristianHoe]

https://github.com/ChristianHoe/test

[siegfriedpammer]

Downloaded, thanks!

[siegfriedpammer]

@dgrunwald the infinite recursion starts here:

ILSpy/ICSharpCode.Decompiler/CSharp/TranslatedExpression.cs

Lines 504 to 514 in 65a5af2

	if (this.ResolveResult.IsCompileTimeConstant && this.ResolveResult.ConstantValue != null
	&& NullableType.IsNullable(targetType) && !utype.Equals(targetUType))
	{
	// Casts like `(uint?)-1` are only valid in an explicitly unchecked context, but we
	// don't have logic to ensure such a context (usually we emit into an implicitly unchecked context).
	// This only applies with constants as input (int->uint? is fine in implicitly unchecked context).
	// We use an intermediate cast to the nullable's underlying type, which results
	// in a constant conversion, so the final output will be something like `(uint?)uint.MaxValue`
	return ConvertTo(targetUType, expressionBuilder, checkForOverflow, allowImplicitConversion: false)
	.ConvertTo(targetType, expressionBuilder, checkForOverflow, allowImplicitConversion);
	}

I am not sure, what the best fix would be.

[dgrunwald]

We're starting with {0} : {[ConstantResolveResult 0200012B System.Int32 = 0]} and try to convert that to Nullable<Unknown>.
This hits the special case for converting compile-time constants to nullable types, which first converts to Unknown and then to Nullable<Unknown>.
However a conversion to Unknown is actually a no-op, so the function ends up calling itself infinitely.
I think we can restrict the special case to integer types in order to fix the recursion.

Note: the unknown types occur because the assembly references are missing. ILSpy needs to load referenced assemblies for proper decompilation.