Use "odd numbers" to represent integer values about sslang

[EmilySillars]

Update on progress!

• I implemented marshaling/unmarshaling of SSLANG integers in Codegen.hs
  and incorporated feedback from my draft PR.

• I added a regression test called 31bitInts.ssl

• Things I have tested and that work in 31bitInts.ssl:
  integer literals
  parameters of reference type
  addition and subtraction of (1) and (2) together

• Things I would like to test:
  Non-reference parameters to functions
  Local variables of both reference and non-reference type
  Bit Not
  Multiplication and division

Errors I'm getting trying to implement these tests:

main ( cout : & Int, x : Int) -> () = //pattern match error
/*sslc: pattern should be desguared into pattern match
CallStack (from HasCallStack):
  error, called at src/IR/LowerAst.hs:176:18 in sslang-0.1.0.0-KI8f4RQ6phR54Leprkbw8R:IR.LowerAst*/

let x = (5:Int) //should already be desugared
/*sslc: Should already be desugared
CallStack (from HasCallStack):
  error, called at src/IR/LowerAst.hs:133:32 in sslang-0.1.0.0-KI8f4RQ6phR54Leprkbw8R:IR.LowerAst*/

after 10 , (cout : & Int) <- (~39):Int //syntax error
/*sslc: 6:33    [241+1] :Syntax error
CallStack (from HasCallStack):
  error, called at .stack-work/dist/x86_64-linux-tinfo6/Cabal-3.2.1.0/build/Front/Parser.hs:1199:5 in sslang-0.1.0.0-KI8f4RQ6phR54Leprkbw8R:Front.Parser*/

after 10 , (cout : & Int) <- (108*1):Int
/*sslc: Prelude.head: empty list*/

[j-hui]

Awesome!

For the errors you're getting:

• for passing multiple parameters, just pass them separately for now, i.e., main (cout: &Int) (x: Int) -> (). We don't have structured binding just yet since we're blocked on pattern matching in the front end.
• I'm not sure what the "should already be desugared" bug is. But you shouldn't need that type annotation.
• we don't have any prefix operators right now other than & as a type operator. I'm not sure how best to fix that easily; you could add a bnot function and then fish for that in the lowering phase, but that might just add to bloat that shouldn't be there in the first place.
• not quite sure what that's about either. Did you add in the typing rule for multiplication?

[j-hui]

Fixed by #41