new structure for checks

[florianschanda]

Having written several complex checks, its clear to me that the existing format is too simple, quickly resulting in repeated constructs.

I suggest a new form:

type T {

  a Integer
  b Integer
  c String
  d Integer [1 .. *]

  begin checks

    if a > b then
	   assert c == "gt", "blah"
	elif a < b then
	   assert c == "lt", "blah"
	else
	   assert c == "eq", "blah"
	end if

	let tmp = a + b

	forall item in d loop
	   assert d >= tmp, "blah"
        end loop

  end checks

}

For a more detailed proposal see https://github.com/florianschanda/trlc/blob/main/language-reference-manual/proposal-checks.md