I’m reading through the common mark spec (0.28) for the first time and there is a contradiction in the Infostring spec. It says both that how it is used is not specified and then specifies how it should be used.
The last paragraph of the introduction to 4.5 fenced code blocks says:
The first word of the info string is typically used to specify the language of the code sample, and rendered in the class attribute of the code tag. However, this spec does not mandate any particular treatment of the info string.
But above example 111:
An info string can be provided after the opening code fence. Opening and closing spaces will be stripped, and the first word, prefixed with language-, is used as the value for the class attribute of the code element within the enclosing pre element.