anonymous method + dynamic argument + multiply - causes an error

[marbel82]

Steps to reproduce

1. Create Console Application with .NET Framework 4.7.2
2. Write anonymous method:

public static class Program
{
    public static void Main()
    {
        dynamic f = (Action<dynamic>)((dynamic t) =>
        {
            t = t * 20.2;
        });
    }
}

3. Try to decompile with ILSpy version 6.2.1.6137

Error message shown

Error decompiling @06000001 FConverter.Program.Main
in assembly "C:\FConverter\bin\Debug\FConverter.exe"
 ---> System.ArgumentOutOfRangeException: Określony argument jest spoza zakresu prawidłowych wartości.
Nazwa parametru: op
   at ICSharpCode.Decompiler.IL.Transforms.TransformAssignment.HandleCompoundAssign(ILInstruction compoundStore, StatementTransformContext context) in offset 0
   at ICSharpCode.Decompiler.IL.Transforms.StatementTransform.Run(Block block, BlockTransformContext context) in offset 98
   at ICSharpCode.Decompiler.IL.Block.RunTransforms(IEnumerable`1 transforms, BlockTransformContext context) in offset 38
   at ICSharpCode.Decompiler.IL.Transforms.BlockILTransform.VisitBlock(ControlFlowNode cfgNode, BlockTransformContext context) in offset 121
   at ICSharpCode.Decompiler.IL.Transforms.BlockILTransform.VisitBlock(ControlFlowNode cfgNode, BlockTransformContext context) in offset 69
   at ICSharpCode.Decompiler.IL.Transforms.BlockILTransform.Run(ILFunction function, ILTransformContext context) in offset 122
   at ICSharpCode.Decompiler.IL.ILFunction.RunTransforms(IEnumerable`1 transforms, ILTransformContext context) in offset 47
   at ICSharpCode.Decompiler.IL.Transforms.DelegateConstruction.TransformDelegateConstruction(NewObj value, ILInstruction& target) in offset 537
   at ICSharpCode.Decompiler.IL.Transforms.DelegateConstruction.ICSharpCode.Decompiler.IL.Transforms.IILTransform.Run(ILFunction function, ILTransformContext context) in offset 146
   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.Decompile(IEnumerable`1 definitions) in offset 370
   at ICSharpCode.ILSpy.CSharpLanguage.DecompileMethod(IMethod method, ITextOutput output, DecompilationOptions options) in offset 247
   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 in use: 6.2.1.6137
• Version in use: 7.0.0.6372-preview3

Additional information

When I add negation sign decompilation works fine:

public static class Program
{
    public static void Main()
    {
        dynamic f = (Action<dynamic>)((dynamic t) =>
        {
            t = -t * 20.2;
        });
    }
}

Result:

public static void Main()
{
	object f = (Action<object>)delegate(dynamic t)
	{
		t = -t * 20.2;
	};
}