Confusing error for misspelled `Option`

[catamorphism]

To reproduce this, go into syntax::ast and change a use of Option to option. This resulted in a unresolved name : serialize_option error. I think it would have been better to report that option was an unresolved name first. (The particular use I changed was in item_impl, but that's not checked in yet.)

It would be nice to report errors that don't involve macro-expanded code first, but I'm not sure how easy that would be.

[emberian]

Cannot reproduce. Current error message:

/home/cmr/hacking/rust/src/libsyntax/ast.rs:94:20: 94:33 error: use of undeclared type name `option`
/home/cmr/hacking/rust/src/libsyntax/ast.rs:94 pub type fn_ident = option<ident>;