These are the shortcut forms and what they expand to:
@type = project and
@type = task and
@type = note and
However, there are different edge cases, where the expansion behavior is not so clear:
projectat the end of the search string expands to
@type = project(
project taskseems to expand to
@type = project and task(
taskis not expanded)
project or taskexpands to something, what never yields any results.
So the question is, actually, how these and other edge cases are handled by the shortcut expansion algorithm.