followFs [FieldFst:fs] = tell [Instr "ldc" [Lit 1] "select fst"
,Instr "sub" [] "select fst"]
>>| followFs fs
+followFs [FieldSnd] = tell []
followFs [FieldSnd:fs] = tell [Instr "lda" [Lit 0] ""]
>>| followFs fs
-followFs [FieldSnd] = tell []
foldVarDecl :: Int VarDecl -> Gen Int
foldVarDecl x (VarDecl _ mt k e) = g e