multiple argument functions fail on AST lowering pass

[EmilySillars]

When writing a SSLANG source program, if I define a function with multiple arguments, the lowerAst IR pass throws an error. Below is an example of this behavior.
Example program:

type Color
  RGB Int Int Int  
  CMYK Int Int Int Int
  White
  Black
  Sparkly


// main (brush : & Color)-> () =

main ( cout : &Int , brush : &Color)-> () = // fails
  brush <- RGB 192 192 192
  // draw brush       
  brush <- Black
  // draw brush
  brush <- RGB 204 255 204
  // draw  brush
  ()

Error ouput from runtests.log:

###### Testing colors
stack exec sslc -- tests/colors.ssl > out/colors.c
sslc: pattern should be desguared into pattern match
CallStack (from HasCallStack):
  error, called at src/IR/LowerAst.hs:225:18 in sslang-0.1.0.0-4TMoE2od9JzCqrGeolufpl:IR.LowerAst
###### FAILED