Parser       
                        | 
                      ReportForall                           Report unnecessary foralls. Hm: report rank>2 foralls
                        |
                      AnnotateForall                         Annotate all unbound type variables with foralls
                        | 
                      Renamer                                Rename type variables and term variables
                        |
                       / \
                      /   \ 
             TypeCheckHm  TypeCheckBi  
                      \   / 
                       \ / 
                        |
                      ReportTEVar                            Report type existential variables and change type AST
                        |
                      RemoveForall                           RemoveForall and change type AST
                        | 
                      Monomorpher                            
                        | 
                      Desugar
                        |
                      CodeGen