Created attachment 9154 [details]
Compiling the attached sample results in the follow compiler error:
$ mcs -target:library -doc:test.xml test.cs
error CS1569: Error generating XML documentation file `test.xml' (`test.cs(7,24): BatchBlock<T>.ISourceBlock<T>.ConsumeMessage(ITargetBlock<T>)')
Compilation failed: 1 error(s), 0 warnings
Removing the xml doc comment from the ConsumeMessage() method makes the error go away.
I found out that the issue is the nested array.
Here's a PR with a possible fix: https://github.com/mono/mono/pull/1480
Fixed in master