static env association is from expr to its enclosing scope, but let
exprs set their association to their *inner* scope. this skips one level
of envs and will cause segfaults if the parent is a with expr.
fixes#145
Change-Id: I1d22146110f071ede21b4eed7ed34b5850ef2ef3
This is because they are unrepresentable in the source files with
commentary but not in the output, so we should just eat them in
normalization. It's ok.
Change-Id: I2cb7e8b3fc7b00874885bb287cbaa200b41cb16b
