move syntax::ext to new crate syntax_expand

src/libsyntax_ext/deriving/generic/mod.rs

@@ -186,12 +186,12 @@ use rustc_target::spec::abi::Abi;
 use syntax::ast::{self, BinOpKind, EnumDef, Expr, Generics, Ident, PatKind};
 use syntax::ast::{VariantData, GenericParamKind, GenericArg};
 use syntax::attr;
-use syntax::ext::base::{Annotatable, ExtCtxt, SpecialDerives};
 use syntax::source_map::respan;
 use syntax::util::map_in_place::MapInPlace;
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{Symbol, kw, sym};
+use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
 use syntax_pos::{Span};
 
 use ty::{LifetimeBounds, Path, Ptr, PtrTy, Self_, Ty};