These three clauses are all quite trivial, as they take no parameters.
They are mutually exclusive, and 'seq' has some other exclusives that
are implemented here.
The ONE thing that isn't implemented is 2.9's restriction (line 2010):
'A loop associated with a 'loop' construct that does not have a 'seq'
clause must be written to meet all the following conditions'.
Future clauses will require similar work, so it'll be done as a
followup.
This patch implements the 'loop' construct AST, as well as the basic
appertainment rule. Additionally, it sets up the 'parent' compute
construct, which is necessary for codegen/other diagnostics.
A 'loop' can apply to a for or range-for loop, otherwise it has no other
restrictions (though some of its clauses do).
I apparently missed a few other clauses as well when doing my initial
implementation, so this adds tests for all, and fixes up the few that
had problems.
This is something that I'll do better to keep an eye on, though
shouldn't be necessary once the rest of the clauses are implemented and
we can remove the 'default' case.
As a followup to my previous commits, this is an implementation of a
single clause, in this case the 'default' clause. This implements all
semantic analysis for it on compute clauses, and continues to leave it
rejected for all others (some as 'doesnt appertain', others as 'not
implemented' as appropriate).
This also implements and tests the TreeTransform as requested in the
previous patch.
