+type LHsExpr id = Located (HsExpr id)
+
+-------------------------
+-- PostTcExpr is an evidence expression attached to the
+-- syntax tree by the type checker (c.f. postTcType)
+-- We use a PostTcTable where there are a bunch of pieces of
+-- evidence, more than is convenient to keep individually
+type PostTcExpr = HsExpr Id
+type PostTcTable = [(Name, Id)]
+
+noPostTcExpr :: PostTcExpr
+noPostTcExpr = HsLit (HsString FSLIT("noPostTcExpr"))
+
+noPostTcTable :: PostTcTable
+noPostTcTable = []
+
+-------------------------
+-- SyntaxExpr is like PostTcExpr, but it's filled in a little earlier,
+-- by the renamer. It's used for rebindable syntax.
+-- E.g. (>>=) is filled in before the renamer by the appropriate Name
+-- for (>>=), and then instantiated by the type checker with its
+-- type args tec
+
+type SyntaxExpr id = HsExpr id
+
+noSyntaxExpr :: SyntaxExpr id -- Before renaming, and sometimes after,
+ -- (if the syntax slot makes no sense)
+noSyntaxExpr = HsLit (HsString FSLIT("noSyntaxExpr"))
+
+
+type SyntaxTable id = [(Name, SyntaxExpr id)]
+-- *** Currently used only for CmdTop (sigh) ***
+-- * Before the renamer, this list is noSyntaxTable
+--
+-- * After the renamer, it takes the form [(std_name, HsVar actual_name)]
+-- For example, for the 'return' op of a monad
+-- normal case: (GHC.Base.return, HsVar GHC.Base.return)
+-- with rebindable syntax: (GHC.Base.return, return_22)
+-- where return_22 is whatever "return" is in scope
+--
+-- * After the type checker, it takes the form [(std_name, <expression>)]
+-- where <expression> is the evidence for the method
+
+noSyntaxTable :: SyntaxTable id
+noSyntaxTable = []
+
+
+-------------------------