add a Any tag in the expression node, extract a common subset between expr and patt for subtyping
unify the types
turn off AstN temporarily
cold boot seems to be correct
split Record into Record and RecordWith successful
temporarily remove the grammar lift to make bootstrap easier
refine patt seems to succeed
split patt seems to succeed
split the Patt successfully
rename PaEq into RecBind
remove rec_binding into rec_expr syntax category
rename PaRec into Record
ready for exp, patt subtyping
intersection types work, awesome :-)