+ -- code type notation extension
+ | '<[' incdepth exp decdepth ']>' { sL (comb2 $3 $>) (HsHetMetBrak placeHolderType $3) }
+ | '<{' incdepth1 exp decdepth '}>' { sL (comb2 $3 $>) (HsHetMetBrak placeHolderType $3) }
+ | '~~' pushdepth aexp popdepth {% do { x <- mkHsHetMetEsc placeHolderType placeHolderType $3; return $ sL (comb2 $3 $>) x } }
+ | '%%' pushdepth aexp popdepth { sL (comb2 $3 $>) (HsHetMetCSP placeHolderType $3) }
+