move syntax::ext to new crate syntax_expand

113 files changed, 493 insertions, 423 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 6d40b198927..a5a7521abde 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3112,6 +3112,7 @@ dependencies = [
  "serialize",
  "smallvec",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
@@ -3427,6 +3428,7 @@ dependencies = [
  "rustc_target",
  "serialize",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
  "tempfile",
 ]
@@ -3559,6 +3561,7 @@ dependencies = [
  "serialize",
  "smallvec",
  "syntax",
+ "syntax_expand",
  "syntax_ext",
  "syntax_pos",
  "tempfile",
@@ -3630,6 +3633,7 @@ dependencies = [
  "smallvec",
  "stable_deref_trait",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
@@ -3678,6 +3682,7 @@ dependencies = [
  "rustc_index",
  "rustc_target",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
@@ -3695,6 +3700,7 @@ dependencies = [
  "rustc",
  "rustc_metadata",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
@@ -3723,6 +3729,7 @@ dependencies = [
  "rustc_metadata",
  "smallvec",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
@@ -4337,6 +4344,25 @@ dependencies = [
 ]
 
 [[package]]
+name = "syntax_expand"
+version = "0.0.0"
+dependencies = [
+ "bitflags",
+ "lazy_static 1.3.0",
+ "log",
+ "rustc_data_structures",
+ "rustc_errors",
+ "rustc_index",
+ "rustc_lexer",
+ "rustc_target",
+ "scoped-tls",
+ "serialize",
+ "smallvec",
+ "syntax",
+ "syntax_pos",
+]
+
+[[package]]
 name = "syntax_ext"
 version = "0.0.0"
 dependencies = [
@@ -4347,6 +4373,7 @@ dependencies = [
  "rustc_target",
  "smallvec",
  "syntax",
+ "syntax_expand",
  "syntax_pos",
 ]
 
diff --git a/src/librustc/Cargo.toml b/src/librustc/Cargo.toml
index 9b3609eca3e..cf9f36ca37c 100644
--- a/src/librustc/Cargo.toml
+++ b/src/librustc/Cargo.toml
@@ -29,6 +29,7 @@ rustc_index = { path = "../librustc_index" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
 backtrace = "0.3.3"
 parking_lot = "0.9"
diff --git a/src/librustc/hir/def.rs b/src/librustc/hir/def.rs
index f7d31ca06ee..a071a539e01 100644
--- a/src/librustc/hir/def.rs
+++ b/src/librustc/hir/def.rs
@@ -6,7 +6,7 @@ use crate::ty;
 use crate::util::nodemap::DefIdMap;
 
 use syntax::ast;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::ast::NodeId;
 use syntax_pos::Span;
 use rustc_macros::HashStable;
diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs
index e9788a55812..d5287fd415b 100644
--- a/src/librustc/hir/lowering.rs
+++ b/src/librustc/hir/lowering.rs
@@ -64,15 +64,15 @@ use syntax::ast;
 use syntax::ptr::P as AstP;
 use syntax::ast::*;
 use syntax::errors;
-use syntax::ext::base::SpecialDerives;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::base::SpecialDerives;
 use syntax::print::pprust;
-use syntax::tokenstream::{TokenStream, TokenTree};
 use syntax::parse::token::{self, Nonterminal, Token};
+use syntax::tokenstream::{TokenStream, TokenTree};
 use syntax::sess::ParseSess;
 use syntax::source_map::{respan, ExpnData, ExpnKind, DesugaringKind, Spanned};
 use syntax::symbol::{kw, sym, Symbol};
 use syntax::visit::{self, Visitor};
+use syntax_pos::hygiene::ExpnId;
 use syntax_pos::Span;
 
 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
diff --git a/src/librustc/hir/lowering/item.rs b/src/librustc/hir/lowering/item.rs
index 548a2fedfff..73d2ac5c134 100644
--- a/src/librustc/hir/lowering/item.rs
+++ b/src/librustc/hir/lowering/item.rs
@@ -18,7 +18,7 @@ use smallvec::SmallVec;
 use syntax::attr;
 use syntax::ast::*;
 use syntax::visit::{self, Visitor};
-use syntax::ext::base::SpecialDerives;
+use syntax_expand::base::SpecialDerives;
 use syntax::source_map::{respan, DesugaringKind, Spanned};
 use syntax::symbol::{kw, sym};
 use syntax_pos::Span;
diff --git a/src/librustc/hir/map/def_collector.rs b/src/librustc/hir/map/def_collector.rs
index 1997e2aab35..fbef95fec7d 100644
--- a/src/librustc/hir/map/def_collector.rs
+++ b/src/librustc/hir/map/def_collector.rs
@@ -2,7 +2,7 @@ use crate::hir::map::definitions::*;
 use crate::hir::def_id::DefIndex;
 
 use syntax::ast::*;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::hygiene::ExpnId;
 use syntax::visit;
 use syntax::symbol::{kw, sym};
 use syntax::parse::token::{self, Token};
diff --git a/src/librustc/hir/map/definitions.rs b/src/librustc/hir/map/definitions.rs
index 71bf230e37d..cc099fcc40f 100644
--- a/src/librustc/hir/map/definitions.rs
+++ b/src/librustc/hir/map/definitions.rs
@@ -17,7 +17,7 @@ use std::borrow::Borrow;
 use std::fmt::Write;
 use std::hash::Hash;
 use syntax::ast;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::hygiene::ExpnId;
 use syntax::symbol::{Symbol, sym, InternedString};
 use syntax_pos::{Span, DUMMY_SP};
 
diff --git a/src/librustc/hir/map/mod.rs b/src/librustc/hir/map/mod.rs
index 16c4ab7187d..f839087ec02 100644
--- a/src/librustc/hir/map/mod.rs
+++ b/src/librustc/hir/map/mod.rs
@@ -20,7 +20,7 @@ use rustc_data_structures::svh::Svh;
 use rustc_index::vec::IndexVec;
 use syntax::ast::{self, Name, NodeId};
 use syntax::source_map::Spanned;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax_pos::{Span, DUMMY_SP};
 
 pub mod blocks;
diff --git a/src/librustc/ich/hcx.rs b/src/librustc/ich/hcx.rs
index 3e6b271b834..14d0673ecc0 100644
--- a/src/librustc/ich/hcx.rs
+++ b/src/librustc/ich/hcx.rs
@@ -13,7 +13,7 @@ use std::cell::RefCell;
 
 use syntax::ast;
 use syntax::source_map::SourceMap;
-use syntax::ext::hygiene::SyntaxContext;
+use syntax_expand::hygiene::SyntaxContext;
 use syntax::symbol::Symbol;
 use syntax::tokenstream::DelimSpan;
 use syntax_pos::{Span, DUMMY_SP};
diff --git a/src/librustc/ich/impls_syntax.rs b/src/librustc/ich/impls_syntax.rs
index 23a2f115e05..defc3fb25bc 100644
--- a/src/librustc/ich/impls_syntax.rs
+++ b/src/librustc/ich/impls_syntax.rs
@@ -59,7 +59,7 @@ impl_stable_hash_for!(enum ::syntax::ast::AsmDialect {
     Intel
 });
 
-impl_stable_hash_for!(enum ::syntax::ext::base::MacroKind {
+impl_stable_hash_for!(enum ::syntax_expand::base::MacroKind {
     Bang,
     Attr,
     Derive,
diff --git a/src/librustc/lint/mod.rs b/src/librustc/lint/mod.rs
index b31efc24e52..7443cca822a 100644
--- a/src/librustc/lint/mod.rs
+++ b/src/librustc/lint/mod.rs
@@ -39,7 +39,7 @@ use syntax::ast;
 use syntax::source_map::{MultiSpan, ExpnKind, DesugaringKind};
 use syntax::early_buffered_lints::BufferedEarlyLintId;
 use syntax::edition::Edition;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::symbol::{Symbol, sym};
 use syntax_pos::Span;
 
diff --git a/src/librustc/session/mod.rs b/src/librustc/session/mod.rs
index c59df146629..b65bf2230b3 100644
--- a/src/librustc/session/mod.rs
+++ b/src/librustc/session/mod.rs
@@ -24,7 +24,7 @@ use errors::emitter::HumanReadableErrorType;
 use errors::annotate_snippet_emitter_writer::{AnnotateSnippetEmitterWriter};
 use syntax::ast::{self, NodeId};
 use syntax::edition::Edition;
-use syntax::ext::allocator::AllocatorKind;
+use syntax_expand::allocator::AllocatorKind;
 use syntax::feature_gate::{self, AttributeType};
 use syntax::json::JsonEmitter;
 use syntax::source_map;
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 65aea7b459f..ab9fb1df682 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -45,7 +45,7 @@ use std::{mem, ptr};
 use std::ops::Range;
 use syntax::ast::{self, Name, Ident, NodeId};
 use syntax::attr;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::hygiene::ExpnId;
 use syntax::symbol::{kw, sym, Symbol, InternedString};
 use syntax_pos::Span;
 
diff --git a/src/librustc_codegen_llvm/allocator.rs b/src/librustc_codegen_llvm/allocator.rs
index f31765cea4f..8c60c030eac 100644
--- a/src/librustc_codegen_llvm/allocator.rs
+++ b/src/librustc_codegen_llvm/allocator.rs
@@ -3,7 +3,7 @@ use std::ffi::CString;
 use crate::attributes;
 use libc::c_uint;
 use rustc::ty::TyCtxt;
-use syntax::ext::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
+use syntax_expand::allocator::{AllocatorKind, AllocatorTy, ALLOCATOR_METHODS};
 
 use crate::ModuleLlvm;
 use crate::llvm::{self, False, True};
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index fde04a68457..9b55bef0c51 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -39,6 +39,7 @@ extern crate rustc_driver as _;
 
 #[macro_use] extern crate log;
 extern crate syntax;
+extern crate syntax_expand;
 extern crate syntax_pos;
 extern crate rustc_errors as errors;
 
@@ -48,7 +49,7 @@ use rustc_codegen_ssa::back::lto::{SerializedModule, LtoModuleCodegen, ThinModul
 use rustc_codegen_ssa::CompiledModule;
 use errors::{FatalError, Handler};
 use rustc::dep_graph::WorkProduct;
-use syntax::ext::allocator::AllocatorKind;
+use syntax_expand::allocator::AllocatorKind;
 use syntax_pos::symbol::InternedString;
 pub use llvm_util::target_features;
 use std::any::Any;
diff --git a/src/librustc_codegen_ssa/Cargo.toml b/src/librustc_codegen_ssa/Cargo.toml
index c7d09a423d5..6992f93d999 100644
--- a/src/librustc_codegen_ssa/Cargo.toml
+++ b/src/librustc_codegen_ssa/Cargo.toml
@@ -21,6 +21,7 @@ tempfile = "3.1"
 
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
 rustc = { path = "../librustc" }
 rustc_apfloat = { path = "../librustc_apfloat" }
diff --git a/src/librustc_codegen_ssa/back/symbol_export.rs b/src/librustc_codegen_ssa/back/symbol_export.rs
index 9078f77f1f7..d866a10f069 100644
--- a/src/librustc_codegen_ssa/back/symbol_export.rs
+++ b/src/librustc_codegen_ssa/back/symbol_export.rs
@@ -14,7 +14,7 @@ use rustc::ty::query::Providers;
 use rustc::ty::subst::SubstsRef;
 use rustc::util::nodemap::{FxHashMap, DefIdMap};
 use rustc_index::vec::IndexVec;
-use syntax::ext::allocator::ALLOCATOR_METHODS;
+use syntax_expand::allocator::ALLOCATOR_METHODS;
 
 pub type ExportedSymbols = FxHashMap<
     CrateNum,
diff --git a/src/librustc_codegen_ssa/back/write.rs b/src/librustc_codegen_ssa/back/write.rs
index 5339134a2a8..856c280cac0 100644
--- a/src/librustc_codegen_ssa/back/write.rs
+++ b/src/librustc_codegen_ssa/back/write.rs
@@ -27,7 +27,7 @@ use rustc_errors::{Handler, Level, FatalError, DiagnosticId, SourceMapperDyn};
 use rustc_errors::emitter::{Emitter};
 use rustc_target::spec::MergeFunctions;
 use syntax::attr;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::hygiene::ExpnId;
 use syntax_pos::symbol::{Symbol, sym};
 use jobserver::{Client, Acquired};
 
diff --git a/src/librustc_codegen_ssa/traits/backend.rs b/src/librustc_codegen_ssa/traits/backend.rs
index a7faf4eaf10..7cae3e9ade5 100644
--- a/src/librustc_codegen_ssa/traits/backend.rs
+++ b/src/librustc_codegen_ssa/traits/backend.rs
@@ -9,7 +9,7 @@ use rustc::ty::TyCtxt;
 use rustc_codegen_utils::codegen_backend::CodegenBackend;
 use std::sync::Arc;
 use std::sync::mpsc;
-use syntax::ext::allocator::AllocatorKind;
+use syntax_expand::allocator::AllocatorKind;
 use syntax_pos::symbol::InternedString;
 
 pub trait BackendTypes {
diff --git a/src/librustc_interface/Cargo.toml b/src/librustc_interface/Cargo.toml
index bed5febb72e..7a0d931ca73 100644
--- a/src/librustc_interface/Cargo.toml
+++ b/src/librustc_interface/Cargo.toml
@@ -15,6 +15,7 @@ rayon = { version = "0.3.0", package = "rustc-rayon" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
 syntax = { path = "../libsyntax" }
 syntax_ext = { path = "../libsyntax_ext" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 rustc = { path = "../librustc" }
diff --git a/src/librustc_interface/passes.rs b/src/librustc_interface/passes.rs
index 396c5610251..89de5714695 100644
--- a/src/librustc_interface/passes.rs
+++ b/src/librustc_interface/passes.rs
@@ -35,7 +35,7 @@ use rustc_traits;
 use rustc_typeck as typeck;
 use syntax::{self, ast, visit};
 use syntax::early_buffered_lints::BufferedEarlyLint;
-use syntax::ext::base::{NamedSyntaxExtension, ExtCtxt};
+use syntax_expand::base::{NamedSyntaxExtension, ExtCtxt};
 use syntax::mut_visit::MutVisitor;
 use syntax::parse::{self, PResult};
 use syntax::util::node_count::NodeCounter;
@@ -397,12 +397,12 @@ fn configure_and_expand_inner<'a>(
 
         // Create the config for macro expansion
         let features = sess.features_untracked();
-        let cfg = syntax::ext::expand::ExpansionConfig {
+        let cfg = syntax_expand::expand::ExpansionConfig {
             features: Some(&features),
             recursion_limit: *sess.recursion_limit.get(),
             trace_mac: sess.opts.debugging_opts.trace_macros,
             should_test: sess.opts.test,
-            ..syntax::ext::expand::ExpansionConfig::default(crate_name.to_string())
+            ..syntax_expand::expand::ExpansionConfig::default(crate_name.to_string())
         };
 
         let mut ecx = ExtCtxt::new(&sess.parse_sess, cfg, &mut resolver);
@@ -559,7 +559,7 @@ pub fn lower_to_hir(
 
     // Discard hygiene data, which isn't required after lowering to HIR.
     if !sess.opts.debugging_opts.keep_hygiene_data {
-        syntax::ext::hygiene::clear_syntax_context_map();
+        syntax_expand::hygiene::clear_syntax_context_map();
     }
 
     Ok(hir_forest)
diff --git a/src/librustc_metadata/Cargo.toml b/src/librustc_metadata/Cargo.toml
index 032470e1400..18192e35f8a 100644
--- a/src/librustc_metadata/Cargo.toml
+++ b/src/librustc_metadata/Cargo.toml
@@ -22,4 +22,5 @@ rustc_index = { path = "../librustc_index" }
 rustc_serialize = { path = "../libserialize", package = "serialize" }
 stable_deref_trait = "1.0.0"
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
diff --git a/src/librustc_metadata/creader.rs b/src/librustc_metadata/creader.rs
index 9850121d2ce..6a2da5d4988 100644
--- a/src/librustc_metadata/creader.rs
+++ b/src/librustc_metadata/creader.rs
@@ -26,7 +26,7 @@ use std::{cmp, fs};
 
 use syntax::ast;
 use syntax::attr;
-use syntax::ext::allocator::{global_allocator_spans, AllocatorKind};
+use syntax_expand::allocator::{global_allocator_spans, AllocatorKind};
 use syntax::symbol::{Symbol, sym};
 use syntax::{span_err, span_fatal};
 use syntax_pos::{Span, DUMMY_SP};
diff --git a/src/librustc_metadata/cstore.rs b/src/librustc_metadata/cstore.rs
index a5a458e49a3..9a0b98ffb73 100644
--- a/src/librustc_metadata/cstore.rs
+++ b/src/librustc_metadata/cstore.rs
@@ -11,7 +11,7 @@ use rustc_index::vec::IndexVec;
 use rustc::util::nodemap::FxHashMap;
 use rustc_data_structures::sync::{Lrc, RwLock, Lock, MetadataRef, AtomicCell};
 use syntax::ast;
-use syntax::ext::base::SyntaxExtension;
+use syntax_expand::base::SyntaxExtension;
 use syntax_pos;
 use proc_macro::bridge::client::ProcMacro;
 
diff --git a/src/librustc_metadata/decoder.rs b/src/librustc_metadata/decoder.rs
index 6969d608d76..37f3726124a 100644
--- a/src/librustc_metadata/decoder.rs
+++ b/src/librustc_metadata/decoder.rs
@@ -32,11 +32,11 @@ use syntax::attr;
 use syntax::ast::{self, Ident};
 use syntax::source_map::{self, respan, Spanned};
 use syntax::symbol::{Symbol, sym};
-use syntax::ext::base::{MacroKind, SyntaxExtensionKind, SyntaxExtension};
+use syntax_expand::base::{MacroKind, SyntaxExtensionKind, SyntaxExtension};
 use syntax_pos::{self, Span, BytePos, Pos, DUMMY_SP, symbol::{InternedString}};
 use log::debug;
 use proc_macro::bridge::client::ProcMacro;
-use syntax::ext::proc_macro::{AttrProcMacro, ProcMacroDerive, BangProcMacro};
+use syntax_expand::proc_macro::{AttrProcMacro, ProcMacroDerive, BangProcMacro};
 
 crate struct DecodeContext<'a, 'tcx> {
     opaque: opaque::Decoder<'a>,
diff --git a/src/librustc_metadata/encoder.rs b/src/librustc_metadata/encoder.rs
index 03a14f88645..ac20284233a 100644
--- a/src/librustc_metadata/encoder.rs
+++ b/src/librustc_metadata/encoder.rs
@@ -31,7 +31,7 @@ use rustc_data_structures::sync::Lrc;
 use std::u32;
 use syntax::ast;
 use syntax::attr;
-use syntax::ext::proc_macro::is_proc_macro_attr;
+use syntax_expand::proc_macro::is_proc_macro_attr;
 use syntax::source_map::Spanned;
 use syntax::symbol::{kw, sym, Ident, Symbol};
 use syntax_pos::{self, FileName, SourceFile, Span};
diff --git a/src/librustc_passes/Cargo.toml b/src/librustc_passes/Cargo.toml
index 9d29a230314..118deb560d6 100644
--- a/src/librustc_passes/Cargo.toml
+++ b/src/librustc_passes/Cargo.toml
@@ -13,6 +13,7 @@ log = "0.4"
 rustc = { path = "../librustc" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_target = { path = "../librustc_target" }
diff --git a/src/librustc_passes/ast_validation.rs b/src/librustc_passes/ast_validation.rs
index 43c4f720ad4..74de31263d3 100644
--- a/src/librustc_passes/ast_validation.rs
+++ b/src/librustc_passes/ast_validation.rs
@@ -14,7 +14,7 @@ use rustc::session::Session;
 use rustc_data_structures::fx::FxHashMap;
 use syntax::ast::*;
 use syntax::attr;
-use syntax::ext::proc_macro::is_proc_macro_attr;
+use syntax_expand::proc_macro::is_proc_macro_attr;
 use syntax::feature_gate::is_builtin_attr;
 use syntax::source_map::Spanned;
 use syntax::symbol::{kw, sym};
diff --git a/src/librustc_plugin/Cargo.toml b/src/librustc_plugin/Cargo.toml
index 3f11430dc82..e8bf4e7ea8f 100644
--- a/src/librustc_plugin/Cargo.toml
+++ b/src/librustc_plugin/Cargo.toml
@@ -14,4 +14,5 @@ doctest = false
 rustc = { path = "../librustc" }
 rustc_metadata = { path = "../librustc_metadata" }
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
diff --git a/src/librustc_plugin/lib.rs b/src/librustc_plugin/lib.rs
index 4e1a47c503e..38738e20630 100644
--- a/src/librustc_plugin/lib.rs
+++ b/src/librustc_plugin/lib.rs
@@ -21,7 +21,7 @@
 //! extern crate syntax_pos;
 //!
 //! use rustc_driver::plugin::Registry;
-//! use syntax::ext::base::{ExtCtxt, MacResult};
+//! use syntax_expand::base::{ExtCtxt, MacResult};
 //! use syntax_pos::Span;
 //! use syntax::tokenstream::TokenTree;
 //!
diff --git a/src/librustc_plugin/registry.rs b/src/librustc_plugin/registry.rs
index bb3c950edae..b826dd91198 100644
--- a/src/librustc_plugin/registry.rs
+++ b/src/librustc_plugin/registry.rs
@@ -4,8 +4,8 @@ use rustc::lint::{EarlyLintPassObject, LateLintPassObject, LintId, Lint};
 use rustc::session::Session;
 use rustc::util::nodemap::FxHashMap;
 
-use syntax::ext::base::{SyntaxExtension, SyntaxExtensionKind, NamedSyntaxExtension};
-use syntax::ext::base::MacroExpanderFn;
+use syntax_expand::base::{SyntaxExtension, SyntaxExtensionKind, NamedSyntaxExtension};
+use syntax_expand::base::MacroExpanderFn;
 use syntax::symbol::Symbol;
 use syntax::ast;
 use syntax::feature_gate::AttributeType;
diff --git a/src/librustc_resolve/Cargo.toml b/src/librustc_resolve/Cargo.toml
index 936e72ef2c5..06bf3085989 100644
--- a/src/librustc_resolve/Cargo.toml
+++ b/src/librustc_resolve/Cargo.toml
@@ -14,6 +14,7 @@ doctest = false
 bitflags = "1.0"
 log = "0.4"
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 rustc = { path = "../librustc" }
 arena = { path = "../libarena" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
diff --git a/src/librustc_resolve/build_reduced_graph.rs b/src/librustc_resolve/build_reduced_graph.rs
index 0d5361fe8d8..eadae52c250 100644
--- a/src/librustc_resolve/build_reduced_graph.rs
+++ b/src/librustc_resolve/build_reduced_graph.rs
@@ -32,9 +32,9 @@ use syntax::attr;
 
 use syntax::ast::{self, Block, ForeignItem, ForeignItemKind, Item, ItemKind, NodeId};
 use syntax::ast::{MetaItemKind, StmtKind, TraitItem, TraitItemKind};
-use syntax::ext::base::{MacroKind, SyntaxExtension};
-use syntax::ext::expand::AstFragment;
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::base::{MacroKind, SyntaxExtension};
+use syntax_expand::expand::AstFragment;
+use syntax_expand::hygiene::ExpnId;
 use syntax::feature_gate::is_builtin_attr;
 use syntax::parse::token::{self, Token};
 use syntax::print::pprust;
diff --git a/src/librustc_resolve/diagnostics.rs b/src/librustc_resolve/diagnostics.rs
index de875808670..5647d5b2794 100644
--- a/src/librustc_resolve/diagnostics.rs
+++ b/src/librustc_resolve/diagnostics.rs
@@ -10,7 +10,7 @@ use rustc::session::Session;
 use rustc::ty::{self, DefIdTree};
 use rustc::util::nodemap::FxHashSet;
 use syntax::ast::{self, Ident, Path};
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::feature_gate::BUILTIN_ATTRIBUTES;
 use syntax::source_map::SourceMap;
 use syntax::struct_span_err;
diff --git a/src/librustc_resolve/late/diagnostics.rs b/src/librustc_resolve/late/diagnostics.rs
index ace9903a835..412734eabe0 100644
--- a/src/librustc_resolve/late/diagnostics.rs
+++ b/src/librustc_resolve/late/diagnostics.rs
@@ -13,7 +13,7 @@ use rustc::hir::PrimTy;
 use rustc::session::config::nightly_options;
 use rustc::util::nodemap::FxHashSet;
 use syntax::ast::{self, Expr, ExprKind, Ident, NodeId, Path, Ty, TyKind};
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::symbol::kw;
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax_pos::Span;
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index e5b0ef89a41..17d8f0f211a 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -35,18 +35,16 @@ use rustc::span_bug;
 use rustc_metadata::creader::CrateLoader;
 use rustc_metadata::cstore::CStore;
 
-use syntax::ext::hygiene::{ExpnId, Transparency, SyntaxContext};
+use syntax_expand::hygiene::{ExpnId, Transparency, SyntaxContext};
+use syntax_expand::base::{SyntaxExtension, MacroKind, SpecialDerives};
+use syntax::{struct_span_err, unwrap_or};
+use syntax::attr;
 use syntax::ast::{self, Name, NodeId, Ident, FloatTy, IntTy, UintTy};
-use syntax::ext::base::{SyntaxExtension, MacroKind, SpecialDerives};
+use syntax::ast::{ItemKind, Path, CRATE_NODE_ID, Crate};
 use syntax::print::pprust;
 use syntax::symbol::{kw, sym};
-
-use syntax::visit::{self, Visitor};
-use syntax::attr;
-use syntax::ast::{CRATE_NODE_ID, Crate};
-use syntax::ast::{ItemKind, Path};
-use syntax::{struct_span_err, unwrap_or};
 use syntax::source_map::Spanned;
+use syntax::visit::{self, Visitor};
 
 use syntax_pos::{Span, DUMMY_SP};
 use errors::{Applicability, DiagnosticBuilder};
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index 49186088fa0..c91a0b2ed98 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -14,11 +14,11 @@ use rustc::{ty, lint, span_bug};
 use syntax::ast::{self, NodeId, Ident};
 use syntax::attr::StabilityLevel;
 use syntax::edition::Edition;
-use syntax::ext::base::{self, InvocationRes, Indeterminate, SpecialDerives};
-use syntax::ext::base::{MacroKind, SyntaxExtension};
-use syntax::ext::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
-use syntax::ext::hygiene::{self, ExpnId, ExpnData, ExpnKind};
-use syntax::ext::compile_declarative_macro;
+use syntax_expand::base::{self, InvocationRes, Indeterminate, SpecialDerives};
+use syntax_expand::base::{MacroKind, SyntaxExtension};
+use syntax_expand::expand::{AstFragment, AstFragmentKind, Invocation, InvocationKind};
+use syntax_expand::hygiene::{self, ExpnId, ExpnData, ExpnKind};
+use syntax_expand::compile_declarative_macro;
 use syntax::feature_gate::{emit_feature_err, is_builtin_attr_name};
 use syntax::feature_gate::GateIssue;
 use syntax::print::pprust;
diff --git a/src/librustc_resolve/resolve_imports.rs b/src/librustc_resolve/resolve_imports.rs
index 56fd2da2576..424bf31a785 100644
--- a/src/librustc_resolve/resolve_imports.rs
+++ b/src/librustc_resolve/resolve_imports.rs
@@ -28,7 +28,7 @@ use rustc::util::nodemap::FxHashSet;
 use rustc::{bug, span_bug};
 
 use syntax::ast::{Ident, Name, NodeId, CRATE_NODE_ID};
-use syntax::ext::hygiene::ExpnId;
+use syntax_expand::hygiene::ExpnId;
 use syntax::symbol::kw;
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::{struct_span_err, unwrap_or};
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index 532c5f67bf3..63350b2a5d2 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -3,7 +3,7 @@
 use std::iter::once;
 
 use syntax::ast;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::symbol::sym;
 use syntax_pos::Span;
 
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index 212a09ee6e6..ba00631dc6c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -28,7 +28,7 @@ use rustc::ty::layout::VariantIdx;
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
 use syntax::ast::{self, AttrStyle, Ident};
 use syntax::attr;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::source_map::DUMMY_SP;
 use syntax::symbol::{Symbol, kw, sym};
 use syntax::symbol::InternedString;
diff --git a/src/librustdoc/doctree.rs b/src/librustdoc/doctree.rs
index 6e453561f6d..0dc094ae329 100644
--- a/src/librustdoc/doctree.rs
+++ b/src/librustdoc/doctree.rs
@@ -4,7 +4,7 @@ pub use self::StructType::*;
 
 use syntax::ast;
 use syntax::ast::Name;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax_pos::{self, Span};
 
 use rustc::hir;
diff --git a/src/librustdoc/html/item_type.rs b/src/librustdoc/html/item_type.rs
index 5fb9afd6c49..e015739b03c 100644
--- a/src/librustdoc/html/item_type.rs
+++ b/src/librustdoc/html/item_type.rs
@@ -1,7 +1,7 @@
 //! Item types.
 
 use std::fmt;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use crate::clean;
 
 /// Item type. Corresponds to `clean::ItemEnum` variants.
diff --git a/src/librustdoc/html/render.rs b/src/librustdoc/html/render.rs
index b726ad1e0d6..72a72e89281 100644
--- a/src/librustdoc/html/render.rs
+++ b/src/librustdoc/html/render.rs
@@ -45,11 +45,11 @@ use errors;
 use serialize::json::{ToJson, Json, as_json};
 use syntax::ast;
 use syntax::edition::Edition;
-use syntax::ext::base::MacroKind;
+use syntax::feature_gate::UnstableFeatures;
 use syntax::print::pprust;
 use syntax::source_map::FileName;
-use syntax::feature_gate::UnstableFeatures;
 use syntax::symbol::{Symbol, sym};
+use syntax_expand::base::MacroKind;
 use rustc::hir::def_id::DefId;
 use rustc::middle::privacy::AccessLevels;
 use rustc::middle::stability;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 6bcb4a817d7..8cd32a3d1b5 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -34,6 +34,7 @@ extern crate rustc_typeck;
 extern crate rustc_lexer;
 extern crate serialize;
 extern crate syntax;
+extern crate syntax_expand;
 extern crate syntax_pos;
 extern crate test as testing;
 #[macro_use] extern crate log;
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 9186ed51420..4270b162baf 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -7,7 +7,7 @@ use rustc::ty;
 use rustc_resolve::ParentScope;
 use syntax;
 use syntax::ast::{self, Ident};
-use syntax::ext::base::SyntaxExtensionKind;
+use syntax_expand::base::SyntaxExtensionKind;
 use syntax::feature_gate::UnstableFeatures;
 use syntax::symbol::Symbol;
 use syntax_pos::DUMMY_SP;
diff --git a/src/librustdoc/visit_ast.rs b/src/librustdoc/visit_ast.rs
index b6a90e1fb98..70c30687dab 100644
--- a/src/librustdoc/visit_ast.rs
+++ b/src/librustdoc/visit_ast.rs
@@ -8,7 +8,7 @@ use rustc::middle::privacy::AccessLevel;
 use rustc::util::nodemap::{FxHashSet, FxHashMap};
 use rustc::ty::TyCtxt;
 use syntax::ast;
-use syntax::ext::base::MacroKind;
+use syntax_expand::base::MacroKind;
 use syntax::source_map::Spanned;
 use syntax::symbol::sym;
 use syntax_pos::{self, Span};
diff --git a/src/libsyntax/attr/mod.rs b/src/libsyntax/attr/mod.rs
index 65257c7e985..402c2cad72f 100644
--- a/src/libsyntax/attr/mod.rs
+++ b/src/libsyntax/attr/mod.rs
@@ -298,14 +298,14 @@ impl Attribute {
         Ok(result)
     }
 
-    crate fn parse_derive_paths<'a>(&self, sess: &'a ParseSess) -> PResult<'a, Vec<Path>> {
+    pub fn parse_derive_paths<'a>(&self, sess: &'a ParseSess) -> PResult<'a, Vec<Path>> {
         if self.tokens.is_empty() {
             return Ok(Vec::new());
         }
         self.parse(sess, |p| p.parse_derive_paths())
     }
 
-    crate fn parse_meta<'a>(&self, sess: &'a ParseSess) -> PResult<'a, MetaItem> {
+    pub fn parse_meta<'a>(&self, sess: &'a ParseSess) -> PResult<'a, MetaItem> {
         Ok(MetaItem {
             path: self.path.clone(),
             kind: self.parse(sess, |parser| parser.parse_meta_item_kind())?,
diff --git a/src/libsyntax/config.rs b/src/libsyntax/config.rs
index ee5a4eeb3a3..54dc95291d6 100644
--- a/src/libsyntax/config.rs
+++ b/src/libsyntax/config.rs
@@ -56,6 +56,7 @@ pub fn features(mut krate: ast::Crate, sess: &ParseSess, edition: Edition,
     (krate, features)
 }
 
+#[macro_export]
 macro_rules! configure {
     ($this:ident, $node:ident) => {
         match $this.configure($node) {
diff --git a/src/libsyntax/feature_gate/check.rs b/src/libsyntax/feature_gate/check.rs
index c07b6050afe..172511f0f09 100644
--- a/src/libsyntax/feature_gate/check.rs
+++ b/src/libsyntax/feature_gate/check.rs
@@ -56,7 +56,7 @@ macro_rules! gate_feature {
     };
 }
 
-crate fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
+pub fn check_attribute(attr: &ast::Attribute, parse_sess: &ParseSess, features: &Features) {
     PostExpansionVisitor { parse_sess, features }.visit_attribute(attr)
 }
 
diff --git a/src/libsyntax/feature_gate/mod.rs b/src/libsyntax/feature_gate/mod.rs
index ca13ab36205..ba970618c0e 100644
--- a/src/libsyntax/feature_gate/mod.rs
+++ b/src/libsyntax/feature_gate/mod.rs
@@ -58,8 +58,7 @@ pub use builtin_attrs::{
     deprecated_attributes, is_builtin_attr,  is_builtin_attr_name,
 };
 pub use check::{
-    check_crate, get_features, feature_err, emit_feature_err,
+    check_crate, check_attribute, get_features, feature_err, emit_feature_err,
     Stability, GateIssue, UnstableFeatures,
     EXPLAIN_STMT_ATTR_SYNTAX, EXPLAIN_UNSIZED_TUPLE_COERCION,
 };
-crate use check::check_attribute;
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index fa75f5624f8..a68b7fdf931 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -13,17 +13,12 @@
 #![feature(crate_visibility_modifier)]
 #![feature(label_break_value)]
 #![feature(nll)]
-#![feature(proc_macro_diagnostic)]
-#![feature(proc_macro_internals)]
-#![feature(proc_macro_span)]
 #![feature(try_trait)]
 #![feature(slice_patterns)]
 #![feature(unicode_internals)]
 
 #![recursion_limit="256"]
 
-extern crate proc_macro;
-
 pub use errors;
 use rustc_data_structures::sync::Lock;
 use rustc_index::bit_set::GrowableBitSet;
@@ -34,26 +29,7 @@ use syntax_pos::edition::Edition;
 #[cfg(test)]
 mod tests;
 
-const MACRO_ARGUMENTS: Option<&'static str> = Some("macro arguments");
-
-// A variant of 'try!' that panics on an Err. This is used as a crutch on the
-// way towards a non-panic!-prone parser. It should be used for fatal parsing
-// errors; eventually we plan to convert all code using panictry to just use
-// normal try.
-#[macro_export]
-macro_rules! panictry {
-    ($e:expr) => ({
-        use std::result::Result::{Ok, Err};
-        use errors::FatalError;
-        match $e {
-            Ok(e) => e,
-            Err(mut e) => {
-                e.emit();
-                FatalError.raise()
-            }
-        }
-    })
-}
+pub const MACRO_ARGUMENTS: Option<&'static str> = Some("macro arguments");
 
 // A variant of 'panictry!' that works on a Vec<Diagnostic> instead of a single DiagnosticBuilder.
 macro_rules! panictry_buffer {
@@ -157,19 +133,4 @@ pub mod print {
     mod helpers;
 }
 
-pub mod ext {
-    mod placeholders;
-    mod proc_macro_server;
-
-    pub use syntax_pos::hygiene;
-    pub use mbe::macro_rules::compile_declarative_macro;
-    pub mod allocator;
-    pub mod base;
-    pub mod build;
-    pub mod expand;
-    pub mod proc_macro;
-
-    crate mod mbe;
-}
-
 pub mod early_buffered_lints;
diff --git a/src/libsyntax/parse/literal.rs b/src/libsyntax/parse/literal.rs
index 54e523430e4..14e1696610a 100644
--- a/src/libsyntax/parse/literal.rs
+++ b/src/libsyntax/parse/literal.rs
@@ -212,7 +212,7 @@ impl Lit {
     /// Attempts to recover an AST literal from semantic literal.
     /// This function is used when the original token doesn't exist (e.g. the literal is created
     /// by an AST-based macro) or unavailable (e.g. from HIR pretty-printing).
-    crate fn from_lit_kind(kind: LitKind, span: Span) -> Lit {
+    pub fn from_lit_kind(kind: LitKind, span: Span) -> Lit {
         Lit { token: kind.to_lit_token(), kind, span }
     }
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 7914fdbf978..64ec943294a 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -5,7 +5,7 @@ mod item;
 mod module;
 mod ty;
 mod path;
-crate use path::PathStyle;
+pub use path::PathStyle;
 mod stmt;
 mod generics;
 mod diagnostics;
@@ -130,7 +130,7 @@ pub struct Parser<'a> {
     /// Name of the root module this parser originated from. If `None`, then the
     /// name is not known. This does not change while the parser is descending
     /// into modules, and sub-parsers have new values for this name.
-    crate root_module_name: Option<String>,
+    pub root_module_name: Option<String>,
     expected_tokens: Vec<TokenType>,
     token_cursor: TokenCursor,
     desugar_doc_comments: bool,
@@ -148,7 +148,7 @@ pub struct Parser<'a> {
     /// error.
     pub(super) unclosed_delims: Vec<UnmatchedBrace>,
     last_unexpected_token_span: Option<Span>,
-    crate last_type_ascription: Option<(Span, bool /* likely path typo */)>,
+    pub last_type_ascription: Option<(Span, bool /* likely path typo */)>,
     /// If present, this `Parser` is not parsing Rust code but rather a macro call.
     subparser_name: Option<&'static str>,
 }
@@ -330,7 +330,7 @@ enum TokenExpectType {
 }
 
 impl<'a> Parser<'a> {
-    crate fn new(
+    pub fn new(
         sess: &'a ParseSess,
         tokens: TokenStream,
         directory: Option<Directory<'a>>,
@@ -1003,7 +1003,7 @@ impl<'a> Parser<'a> {
         }
     }
 
-    crate fn process_potential_macro_variable(&mut self) {
+    pub fn process_potential_macro_variable(&mut self) {
         self.token = match self.token.kind {
             token::Dollar if self.token.span.from_expansion() &&
                              self.look_ahead(1, |t| t.is_ident()) => {
@@ -1037,7 +1037,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a single token tree from the input.
-    crate fn parse_token_tree(&mut self) -> TokenTree {
+    pub fn parse_token_tree(&mut self) -> TokenTree {
         match self.token.kind {
             token::OpenDelim(..) => {
                 let frame = mem::replace(&mut self.token_cursor.frame,
@@ -1099,7 +1099,7 @@ impl<'a> Parser<'a> {
     /// If the following element can't be a tuple (i.e., it's a function definition), then
     /// it's not a tuple struct field), and the contents within the parentheses isn't valid,
     /// so emit a proper diagnostic.
-    crate fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
+    pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |x| x);
 
         self.expected_tokens.push(TokenType::Keyword(kw::Crate));
diff --git a/src/libsyntax/parse/parser/diagnostics.rs b/src/libsyntax/parse/parser/diagnostics.rs
index a6884ec2c72..32a41bb0e27 100644
--- a/src/libsyntax/parse/parser/diagnostics.rs
+++ b/src/libsyntax/parse/parser/diagnostics.rs
@@ -170,7 +170,7 @@ impl RecoverQPath for Expr {
 }
 
 impl<'a> Parser<'a> {
-    crate fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
+    pub fn fatal(&self, m: &str) -> DiagnosticBuilder<'a> {
         self.span_fatal(self.token.span, m)
     }
 
@@ -190,11 +190,11 @@ impl<'a> Parser<'a> {
         self.sess.span_diagnostic.span_err(sp, m)
     }
 
-    crate fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
+    pub fn struct_span_err<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> DiagnosticBuilder<'a> {
         self.sess.span_diagnostic.struct_span_err(sp, m)
     }
 
-    crate fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
+    pub fn span_bug<S: Into<MultiSpan>>(&self, sp: S, m: &str) -> ! {
         self.sess.span_diagnostic.span_bug(sp, m)
     }
 
diff --git a/src/libsyntax/parse/parser/expr.rs b/src/libsyntax/parse/parser/expr.rs
index bf9526dece2..273f5a5ffa3 100644
--- a/src/libsyntax/parse/parser/expr.rs
+++ b/src/libsyntax/parse/parser/expr.rs
@@ -1233,7 +1233,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Matches `'-' lit | lit` (cf. `ast_validation::AstValidator::check_expr_within_pat`).
-    crate fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
+    pub fn parse_literal_maybe_minus(&mut self) -> PResult<'a, P<Expr>> {
         maybe_whole_expr!(self);
 
         let minus_lo = self.token.span;
diff --git a/src/libsyntax/parse/parser/item.rs b/src/libsyntax/parse/parser/item.rs
index 6a1cbd2ebb7..0acfd1450d8 100644
--- a/src/libsyntax/parse/parser/item.rs
+++ b/src/libsyntax/parse/parser/item.rs
@@ -674,7 +674,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses an impl item.
-    crate fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
+    pub fn parse_impl_item(&mut self, at_end: &mut bool) -> PResult<'a, ImplItem> {
         maybe_whole!(self, NtImplItem, |x| x);
         let attrs = self.parse_outer_attributes()?;
         let mut unclosed_delims = vec![];
@@ -850,7 +850,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses the items in a trait declaration.
-    crate fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
+    pub fn parse_trait_item(&mut self, at_end: &mut bool) -> PResult<'a, TraitItem> {
         maybe_whole!(self, NtTraitItem, |x| x);
         let attrs = self.parse_outer_attributes()?;
         let mut unclosed_delims = vec![];
@@ -1116,7 +1116,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a foreign item.
-    crate fn parse_foreign_item(&mut self, extern_sp: Span) -> PResult<'a, ForeignItem> {
+    pub fn parse_foreign_item(&mut self, extern_sp: Span) -> PResult<'a, ForeignItem> {
         maybe_whole!(self, NtForeignItem, |ni| ni);
 
         let attrs = self.parse_outer_attributes()?;
diff --git a/src/libsyntax/parse/parser/pat.rs b/src/libsyntax/parse/parser/pat.rs
index b30e0636bb1..af795e51792 100644
--- a/src/libsyntax/parse/parser/pat.rs
+++ b/src/libsyntax/parse/parser/pat.rs
@@ -34,7 +34,7 @@ impl<'a> Parser<'a> {
     /// Corresponds to `pat<no_top_alt>` in RFC 2535 and does not admit or-patterns
     /// at the top level. Used when parsing the parameters of lambda expressions,
     /// functions, function pointers, and `pat` macro fragments.
-    crate fn parse_pat(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
+    pub fn parse_pat(&mut self, expected: Expected) -> PResult<'a, P<Pat>> {
         self.parse_pat_with_range_pat(true, expected)
     }
 
diff --git a/src/libsyntax/parse/parser/path.rs b/src/libsyntax/parse/parser/path.rs
index 0f28fb11cde..639d61a2b5c 100644
--- a/src/libsyntax/parse/parser/path.rs
+++ b/src/libsyntax/parse/parser/path.rs
@@ -13,7 +13,7 @@ use errors::{Applicability, pluralise};
 
 /// Specifies how to parse a path.
 #[derive(Copy, Clone, PartialEq)]
-crate enum PathStyle {
+pub enum PathStyle {
     /// In some contexts, notably in expressions, paths with generic arguments are ambiguous
     /// with something else. For example, in expressions `segment < ....` can be interpreted
     /// as a comparison and `segment ( ....` can be interpreted as a function call.
@@ -88,7 +88,7 @@ impl<'a> Parser<'a> {
     /// `a::b::C::<D>` (with disambiguator)
     /// `Fn(Args)` (without disambiguator)
     /// `Fn::(Args)` (with disambiguator)
-    crate fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
+    pub fn parse_path(&mut self, style: PathStyle) -> PResult<'a, Path> {
         maybe_whole!(self, NtPath, |path| {
             if style == PathStyle::Mod &&
                path.segments.iter().any(|segment| segment.args.is_some()) {
diff --git a/src/libsyntax/parse/parser/stmt.rs b/src/libsyntax/parse/parser/stmt.rs
index f656bc11e1c..4b1fdb2eef3 100644
--- a/src/libsyntax/parse/parser/stmt.rs
+++ b/src/libsyntax/parse/parser/stmt.rs
@@ -19,7 +19,7 @@ use errors::Applicability;
 impl<'a> Parser<'a> {
     /// Parses a statement. This stops just before trailing semicolons on everything but items.
     /// e.g., a `StmtKind::Semi` parses to a `StmtKind::Expr`, leaving the trailing `;` unconsumed.
-    crate fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
+    pub fn parse_stmt(&mut self) -> PResult<'a, Option<Stmt>> {
         Ok(self.parse_stmt_(true))
     }
 
@@ -299,7 +299,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a block. No inner attributes are allowed.
-    crate fn parse_block(&mut self) -> PResult<'a, P<Block>> {
+    pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
         maybe_whole!(self, NtBlock, |x| x);
 
         let lo = self.token.span;
@@ -421,7 +421,7 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses a statement, including the trailing semicolon.
-    crate fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
+    pub fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
         // Skip looking for a trailing semicolon when we have an interpolated statement.
         maybe_whole!(self, NtStmt, |x| Some(x));
 
diff --git a/src/libsyntax/parse/parser/ty.rs b/src/libsyntax/parse/parser/ty.rs
index ae9f4d06c05..86c94b680b2 100644
--- a/src/libsyntax/parse/parser/ty.rs
+++ b/src/libsyntax/parse/parser/ty.rs
@@ -433,13 +433,13 @@ impl<'a> Parser<'a> {
         }
     }
 
-    crate fn check_lifetime(&mut self) -> bool {
+    pub fn check_lifetime(&mut self) -> bool {
         self.expected_tokens.push(TokenType::Lifetime);
         self.token.is_lifetime()
     }
 
     /// Parses a single lifetime `'a` or panics.
-    crate fn expect_lifetime(&mut self) -> Lifetime {
+    pub fn expect_lifetime(&mut self) -> Lifetime {
         if let Some(ident) = self.token.lifetime() {
             let span = self.token.span;
             self.bump();
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index eb74ab2b919..e527989fb0b 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -285,7 +285,7 @@ impl TokenKind {
 }
 
 impl Token {
-    crate fn new(kind: TokenKind, span: Span) -> Self {
+    pub fn new(kind: TokenKind, span: Span) -> Self {
         Token { kind, span }
     }
 
@@ -295,12 +295,12 @@ impl Token {
     }
 
     /// Recovers a `Token` from an `ast::Ident`. This creates a raw identifier if necessary.
-    crate fn from_ast_ident(ident: ast::Ident) -> Self {
+    pub fn from_ast_ident(ident: ast::Ident) -> Self {
         Token::new(Ident(ident.name, ident.is_raw_guess()), ident.span)
     }
 
     /// Return this token by value and leave a dummy token in its place.
-    crate fn take(&mut self) -> Self {
+    pub fn take(&mut self) -> Self {
         mem::replace(self, Token::dummy())
     }
 
@@ -321,7 +321,7 @@ impl Token {
     }
 
     /// Returns `true` if the token can appear at the start of an expression.
-    crate fn can_begin_expr(&self) -> bool {
+    pub fn can_begin_expr(&self) -> bool {
         match self.kind {
             Ident(name, is_raw)              =>
                 ident_can_begin_expr(name, self.span, is_raw), // value name or keyword
@@ -353,7 +353,7 @@ impl Token {
     }
 
     /// Returns `true` if the token can appear at the start of a type.
-    crate fn can_begin_type(&self) -> bool {
+    pub fn can_begin_type(&self) -> bool {
         match self.kind {
             Ident(name, is_raw)        =>
                 ident_can_begin_type(name, self.span, is_raw), // type name or keyword
@@ -396,7 +396,7 @@ impl Token {
     }
 
     /// Returns `true` if the token is any literal
-    crate fn is_lit(&self) -> bool {
+    pub fn is_lit(&self) -> bool {
         match self.kind {
             Literal(..) => true,
             _           => false,
@@ -412,7 +412,7 @@ impl Token {
 
     /// Returns `true` if the token is any literal, a minus (which can prefix a literal,
     /// for example a '-42', or one of the boolean idents).
-    crate fn can_begin_literal_or_bool(&self) -> bool {
+    pub fn can_begin_literal_or_bool(&self) -> bool {
         match self.kind {
             Literal(..) | BinOp(Minus) => true,
             Ident(name, false) if name.is_bool_lit() => true,
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 0ff1c26bac2..db6832d6423 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -156,7 +156,7 @@ use IsJoint::*;
 impl TokenStream {
     /// Given a `TokenStream` with a `Stream` of only two arguments, return a new `TokenStream`
     /// separating the two arguments with a comma for diagnostic suggestions.
-    pub(crate) fn add_comma(&self) -> Option<(TokenStream, Span)> {
+    pub fn add_comma(&self) -> Option<(TokenStream, Span)> {
         // Used to suggest if a user writes `foo!(a b);`
         let mut suggestion = None;
         let mut iter = self.0.iter().enumerate().peekable();
diff --git a/src/libsyntax_expand/Cargo.toml b/src/libsyntax_expand/Cargo.toml
new file mode 100644
index 00000000000..f063753f599
--- /dev/null
+++ b/src/libsyntax_expand/Cargo.toml
@@ -0,0 +1,26 @@
+[package]
+authors = ["The Rust Project Developers"]
+name = "syntax_expand"
+version = "0.0.0"
+edition = "2018"
+build = false
+
+[lib]
+name = "syntax_expand"
+path = "lib.rs"
+doctest = false
+
+[dependencies]
+bitflags = "1.0"
+rustc_serialize = { path = "../libserialize", package = "serialize" }
+log = "0.4"
+scoped-tls = "1.0"
+lazy_static = "1.0.0"
+syntax_pos = { path = "../libsyntax_pos" }
+errors = { path = "../librustc_errors", package = "rustc_errors" }
+rustc_data_structures = { path = "../librustc_data_structures" }
+rustc_index = { path = "../librustc_index" }
+rustc_lexer = { path = "../librustc_lexer" }
+rustc_target = { path = "../librustc_target" }
+smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
+syntax = { path = "../libsyntax" }
diff --git a/src/libsyntax/ext/allocator.rs b/src/libsyntax_expand/allocator.rs
index 99aeb5414c5..3526be17721 100644
--- a/src/libsyntax/ext/allocator.rs
+++ b/src/libsyntax_expand/allocator.rs
@@ -1,5 +1,5 @@
-use crate::{ast, attr, visit};
-use crate::symbol::{sym, Symbol};
+use syntax::{ast, attr, visit};
+use syntax::symbol::{sym, Symbol};
 use syntax_pos::Span;
 
 #[derive(Clone, Copy)]
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax_expand/base.rs
index 01be5642d5c..593e06f29b9 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax_expand/base.rs
@@ -1,18 +1,19 @@
-use crate::ast::{self, NodeId, Attribute, Name, PatKind};
-use crate::attr::{self, HasAttrs, Stability, Deprecation};
-use crate::source_map::SourceMap;
-use crate::edition::Edition;
-use crate::ext::expand::{self, AstFragment, Invocation};
-use crate::ext::hygiene::ExpnId;
-use crate::mut_visit::{self, MutVisitor};
-use crate::parse::{self, parser, DirectoryOwnership};
-use crate::parse::token;
-use crate::ptr::P;
-use crate::sess::ParseSess;
-use crate::symbol::{kw, sym, Ident, Symbol};
-use crate::{ThinVec, MACRO_ARGUMENTS};
-use crate::tokenstream::{self, TokenStream};
-use crate::visit::Visitor;
+use crate::expand::{self, AstFragment, Invocation};
+use crate::hygiene::ExpnId;
+
+use syntax::ast::{self, NodeId, Attribute, Name, PatKind};
+use syntax::attr::{self, HasAttrs, Stability, Deprecation};
+use syntax::source_map::SourceMap;
+use syntax::edition::Edition;
+use syntax::mut_visit::{self, MutVisitor};
+use syntax::parse::{self, parser, DirectoryOwnership};
+use syntax::parse::token;
+use syntax::ptr::P;
+use syntax::sess::ParseSess;
+use syntax::symbol::{kw, sym, Ident, Symbol};
+use syntax::{ThinVec, MACRO_ARGUMENTS};
+use syntax::tokenstream::{self, TokenStream};
+use syntax::visit::Visitor;
 
 use errors::{DiagnosticBuilder, DiagnosticId};
 use smallvec::{smallvec, SmallVec};
diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax_expand/build.rs
index 8c5289671c9..105ffe3ee8a 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax_expand/build.rs
@@ -1,10 +1,11 @@
-use crate::ast::{self, Ident, Expr, BlockCheckMode, UnOp, PatKind};
-use crate::attr;
-use crate::source_map::{respan, Spanned};
-use crate::ext::base::ExtCtxt;
-use crate::ptr::P;
-use crate::symbol::{kw, sym, Symbol};
-use crate::ThinVec;
+use crate::base::ExtCtxt;
+
+use syntax::ast::{self, Ident, Expr, BlockCheckMode, UnOp, PatKind};
+use syntax::attr;
+use syntax::source_map::{respan, Spanned};
+use syntax::ptr::P;
+use syntax::symbol::{kw, sym, Symbol};
+use syntax::ThinVec;
 
 use syntax_pos::{Pos, Span};
 
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax_expand/expand.rs
index 44a51a01710..47b4bca314a 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax_expand/expand.rs
@@ -1,24 +1,26 @@
-use crate::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
-use crate::ast::{MacStmtStyle, StmtKind, ItemKind};
-use crate::attr::{self, HasAttrs};
-use crate::source_map::respan;
-use crate::config::StripUnconfigured;
-use crate::ext::base::*;
-use crate::ext::proc_macro::{collect_derives, MarkAttrs};
-use crate::ext::hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind};
-use crate::ext::mbe::macro_rules::annotate_err_with_kind;
-use crate::ext::placeholders::{placeholder, PlaceholderExpander};
-use crate::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
-use crate::mut_visit::*;
-use crate::parse::{DirectoryOwnership, PResult};
-use crate::parse::token;
-use crate::parse::parser::Parser;
-use crate::print::pprust;
-use crate::ptr::P;
-use crate::symbol::{sym, Symbol};
-use crate::tokenstream::{TokenStream, TokenTree};
-use crate::visit::Visitor;
-use crate::util::map_in_place::MapInPlace;
+use crate::base::*;
+use crate::proc_macro::{collect_derives, MarkAttrs};
+use crate::hygiene::{ExpnId, SyntaxContext, ExpnData, ExpnKind};
+use crate::mbe::macro_rules::annotate_err_with_kind;
+use crate::placeholders::{placeholder, PlaceholderExpander};
+
+use syntax::ast::{self, AttrItem, Block, Ident, LitKind, NodeId, PatKind, Path};
+use syntax::ast::{MacStmtStyle, StmtKind, ItemKind};
+use syntax::attr::{self, HasAttrs};
+use syntax::source_map::respan;
+use syntax::configure;
+use syntax::config::StripUnconfigured;
+use syntax::feature_gate::{self, Features, GateIssue, is_builtin_attr, emit_feature_err};
+use syntax::mut_visit::*;
+use syntax::parse::{DirectoryOwnership, PResult};
+use syntax::parse::token;
+use syntax::parse::parser::Parser;
+use syntax::print::pprust;
+use syntax::ptr::P;
+use syntax::symbol::{sym, Symbol};
+use syntax::tokenstream::{TokenStream, TokenTree};
+use syntax::visit::Visitor;
+use syntax::util::map_in_place::MapInPlace;
 
 use errors::{Applicability, FatalError};
 use smallvec::{smallvec, SmallVec};
@@ -116,8 +118,8 @@ macro_rules! ast_fragments {
             }
         }
 
-        impl<'a> MacResult for crate::ext::mbe::macro_rules::ParserAnyMacro<'a> {
-            $(fn $make_ast(self: Box<crate::ext::mbe::macro_rules::ParserAnyMacro<'a>>)
+        impl<'a> MacResult for crate::mbe::macro_rules::ParserAnyMacro<'a> {
+            $(fn $make_ast(self: Box<crate::mbe::macro_rules::ParserAnyMacro<'a>>)
                            -> Option<$AstTy> {
                 Some(self.make(AstFragmentKind::$Kind).$make_ast())
             })*
@@ -752,9 +754,9 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
         span: Span,
     ) -> AstFragment {
         let mut parser = self.cx.new_parser_from_tts(toks);
-        match parser.parse_ast_fragment(kind, false) {
+        match parse_ast_fragment(&mut parser, kind, false) {
             Ok(fragment) => {
-                parser.ensure_complete_parse(path, kind.name(), span);
+                ensure_complete_parse(&mut parser, path, kind.name(), span);
                 fragment
             }
             Err(mut err) => {
@@ -768,100 +770,106 @@ impl<'a, 'b> MacroExpander<'a, 'b> {
     }
 }
 
-impl<'a> Parser<'a> {
-    pub fn parse_ast_fragment(&mut self, kind: AstFragmentKind, macro_legacy_warnings: bool)
-                              -> PResult<'a, AstFragment> {
-        Ok(match kind {
-            AstFragmentKind::Items => {
-                let mut items = SmallVec::new();
-                while let Some(item) = self.parse_item()? {
-                    items.push(item);
-                }
-                AstFragment::Items(items)
+pub fn parse_ast_fragment<'a>(
+    this: &mut Parser<'a>,
+    kind: AstFragmentKind,
+    macro_legacy_warnings: bool,
+) -> PResult<'a, AstFragment> {
+    Ok(match kind {
+        AstFragmentKind::Items => {
+            let mut items = SmallVec::new();
+            while let Some(item) = this.parse_item()? {
+                items.push(item);
             }
-            AstFragmentKind::TraitItems => {
-                let mut items = SmallVec::new();
-                while self.token != token::Eof {
-                    items.push(self.parse_trait_item(&mut false)?);
-                }
-                AstFragment::TraitItems(items)
+            AstFragment::Items(items)
+        }
+        AstFragmentKind::TraitItems => {
+            let mut items = SmallVec::new();
+            while this.token != token::Eof {
+                items.push(this.parse_trait_item(&mut false)?);
             }
-            AstFragmentKind::ImplItems => {
-                let mut items = SmallVec::new();
-                while self.token != token::Eof {
-                    items.push(self.parse_impl_item(&mut false)?);
-                }
-                AstFragment::ImplItems(items)
+            AstFragment::TraitItems(items)
+        }
+        AstFragmentKind::ImplItems => {
+            let mut items = SmallVec::new();
+            while this.token != token::Eof {
+                items.push(this.parse_impl_item(&mut false)?);
             }
-            AstFragmentKind::ForeignItems => {
-                let mut items = SmallVec::new();
-                while self.token != token::Eof {
-                    items.push(self.parse_foreign_item(DUMMY_SP)?);
-                }
-                AstFragment::ForeignItems(items)
+            AstFragment::ImplItems(items)
+        }
+        AstFragmentKind::ForeignItems => {
+            let mut items = SmallVec::new();
+            while this.token != token::Eof {
+                items.push(this.parse_foreign_item(DUMMY_SP)?);
             }
-            AstFragmentKind::Stmts => {
-                let mut stmts = SmallVec::new();
-                while self.token != token::Eof &&
-                      // won't make progress on a `}`
-                      self.token != token::CloseDelim(token::Brace) {
-                    if let Some(stmt) = self.parse_full_stmt(macro_legacy_warnings)? {
-                        stmts.push(stmt);
-                    }
+            AstFragment::ForeignItems(items)
+        }
+        AstFragmentKind::Stmts => {
+            let mut stmts = SmallVec::new();
+            while this.token != token::Eof &&
+                    // won't make progress on a `}`
+                    this.token != token::CloseDelim(token::Brace) {
+                if let Some(stmt) = this.parse_full_stmt(macro_legacy_warnings)? {
+                    stmts.push(stmt);
                 }
-                AstFragment::Stmts(stmts)
             }
-            AstFragmentKind::Expr => AstFragment::Expr(self.parse_expr()?),
-            AstFragmentKind::OptExpr => {
-                if self.token != token::Eof {
-                    AstFragment::OptExpr(Some(self.parse_expr()?))
-                } else {
-                    AstFragment::OptExpr(None)
-                }
-            },
-            AstFragmentKind::Ty => AstFragment::Ty(self.parse_ty()?),
-            AstFragmentKind::Pat => AstFragment::Pat(self.parse_pat(None)?),
-            AstFragmentKind::Arms
-            | AstFragmentKind::Fields
-            | AstFragmentKind::FieldPats
-            | AstFragmentKind::GenericParams
-            | AstFragmentKind::Params
-            | AstFragmentKind::StructFields
-            | AstFragmentKind::Variants
-                => panic!("unexpected AST fragment kind"),
-        })
-    }
+            AstFragment::Stmts(stmts)
+        }
+        AstFragmentKind::Expr => AstFragment::Expr(this.parse_expr()?),
+        AstFragmentKind::OptExpr => {
+            if this.token != token::Eof {
+                AstFragment::OptExpr(Some(this.parse_expr()?))
+            } else {
+                AstFragment::OptExpr(None)
+            }
+        },
+        AstFragmentKind::Ty => AstFragment::Ty(this.parse_ty()?),
+        AstFragmentKind::Pat => AstFragment::Pat(this.parse_pat(None)?),
+        AstFragmentKind::Arms
+        | AstFragmentKind::Fields
+        | AstFragmentKind::FieldPats
+        | AstFragmentKind::GenericParams
+        | AstFragmentKind::Params
+        | AstFragmentKind::StructFields
+        | AstFragmentKind::Variants
+            => panic!("unexpected AST fragment kind"),
+    })
+}
 
-    pub fn ensure_complete_parse(&mut self, macro_path: &Path, kind_name: &str, span: Span) {
-        if self.token != token::Eof {
-            let msg = format!("macro expansion ignores token `{}` and any following",
-                              self.this_token_to_string());
-            // Avoid emitting backtrace info twice.
-            let def_site_span = self.token.span.with_ctxt(SyntaxContext::root());
-            let mut err = self.struct_span_err(def_site_span, &msg);
-            err.span_label(span, "caused by the macro expansion here");
-            let msg = format!(
-                "the usage of `{}!` is likely invalid in {} context",
-                pprust::path_to_string(&macro_path),
-                kind_name,
-            );
-            err.note(&msg);
-            let semi_span = self.sess.source_map().next_point(span);
-
-            let semi_full_span = semi_span.to(self.sess.source_map().next_point(semi_span));
-            match self.sess.source_map().span_to_snippet(semi_full_span) {
-                Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
-                    err.span_suggestion(
-                        semi_span,
-                        "you might be missing a semicolon here",
-                        ";".to_owned(),
-                        Applicability::MaybeIncorrect,
-                    );
-                }
-                _ => {}
+pub fn ensure_complete_parse<'a>(
+    this: &mut Parser<'a>,
+    macro_path: &Path,
+    kind_name: &str,
+    span: Span,
+) {
+    if this.token != token::Eof {
+        let msg = format!("macro expansion ignores token `{}` and any following",
+                            this.this_token_to_string());
+        // Avoid emitting backtrace info twice.
+        let def_site_span = this.token.span.with_ctxt(SyntaxContext::root());
+        let mut err = this.struct_span_err(def_site_span, &msg);
+        err.span_label(span, "caused by the macro expansion here");
+        let msg = format!(
+            "the usage of `{}!` is likely invalid in {} context",
+            pprust::path_to_string(macro_path),
+            kind_name,
+        );
+        err.note(&msg);
+        let semi_span = this.sess.source_map().next_point(span);
+
+        let semi_full_span = semi_span.to(this.sess.source_map().next_point(semi_span));
+        match this.sess.source_map().span_to_snippet(semi_full_span) {
+            Ok(ref snippet) if &snippet[..] != ";" && kind_name == "expression" => {
+                err.span_suggestion(
+                    semi_span,
+                    "you might be missing a semicolon here",
+                    ";".to_owned(),
+                    Applicability::MaybeIncorrect,
+                );
             }
-            err.emit();
+            _ => {}
         }
+        err.emit();
     }
 }
 
diff --git a/src/libsyntax_expand/lib.rs b/src/libsyntax_expand/lib.rs
new file mode 100644
index 00000000000..88e69d79397
--- /dev/null
+++ b/src/libsyntax_expand/lib.rs
@@ -0,0 +1,38 @@
+#![feature(crate_visibility_modifier)]
+#![feature(proc_macro_diagnostic)]
+#![feature(proc_macro_internals)]
+#![feature(proc_macro_span)]
+
+extern crate proc_macro as pm;
+
+// A variant of 'try!' that panics on an Err. This is used as a crutch on the
+// way towards a non-panic!-prone parser. It should be used for fatal parsing
+// errors; eventually we plan to convert all code using panictry to just use
+// normal try.
+#[macro_export]
+macro_rules! panictry {
+    ($e:expr) => ({
+        use std::result::Result::{Ok, Err};
+        use errors::FatalError;
+        match $e {
+            Ok(e) => e,
+            Err(mut e) => {
+                e.emit();
+                FatalError.raise()
+            }
+        }
+    })
+}
+
+mod placeholders;
+mod proc_macro_server;
+
+pub use syntax_pos::hygiene;
+pub use mbe::macro_rules::compile_declarative_macro;
+pub mod allocator;
+pub mod base;
+pub mod build;
+pub mod expand;
+pub mod proc_macro;
+
+crate mod mbe;
diff --git a/src/libsyntax/ext/mbe.rs b/src/libsyntax_expand/mbe.rs
index a87da791c9b..453fe94f1de 100644
--- a/src/libsyntax/ext/mbe.rs
+++ b/src/libsyntax_expand/mbe.rs
@@ -9,9 +9,9 @@ crate mod macro_parser;
 crate mod macro_rules;
 crate mod quoted;
 
-use crate::ast;
-use crate::parse::token::{self, Token, TokenKind};
-use crate::tokenstream::{DelimSpan};
+use syntax::ast;
+use syntax::parse::token::{self, Token, TokenKind};
+use syntax::tokenstream::{DelimSpan};
 
 use syntax_pos::{BytePos, Span};
 
diff --git a/src/libsyntax/ext/mbe/macro_check.rs b/src/libsyntax_expand/mbe/macro_check.rs
index aabaff4e1c3..50abda8d45e 100644
--- a/src/libsyntax/ext/mbe/macro_check.rs
+++ b/src/libsyntax_expand/mbe/macro_check.rs
@@ -104,13 +104,13 @@
 //! Kleene operators under which a meta-variable is repeating is the concatenation of the stacks
 //! stored when entering a macro definition starting from the state in which the meta-variable is
 //! bound.
-use crate::ast::NodeId;
-use crate::early_buffered_lints::BufferedEarlyLintId;
-use crate::ext::mbe::{KleeneToken, TokenTree};
-use crate::parse::token::TokenKind;
-use crate::parse::token::{DelimToken, Token};
-use crate::sess::ParseSess;
-use crate::symbol::{kw, sym};
+use crate::mbe::{KleeneToken, TokenTree};
+
+use syntax::ast::NodeId;
+use syntax::early_buffered_lints::BufferedEarlyLintId;
+use syntax::parse::token::{DelimToken, Token, TokenKind};
+use syntax::sess::ParseSess;
+use syntax::symbol::{kw, sym};
 
 use rustc_data_structures::fx::FxHashMap;
 use smallvec::SmallVec;
diff --git a/src/libsyntax/ext/mbe/macro_parser.rs b/src/libsyntax_expand/mbe/macro_parser.rs
index ff382c316ff..2edb4925512 100644
--- a/src/libsyntax/ext/mbe/macro_parser.rs
+++ b/src/libsyntax_expand/mbe/macro_parser.rs
@@ -74,15 +74,16 @@ crate use NamedMatch::*;
 crate use ParseResult::*;
 use TokenTreeOrTokenTreeSlice::*;
 
-use crate::ast::{Ident, Name};
-use crate::ext::mbe::{self, TokenTree};
-use crate::parse::{Directory, PResult};
-use crate::parse::parser::{Parser, PathStyle};
-use crate::parse::token::{self, DocComment, Nonterminal, Token};
-use crate::print::pprust;
-use crate::sess::ParseSess;
-use crate::symbol::{kw, sym, Symbol};
-use crate::tokenstream::{DelimSpan, TokenStream};
+use crate::mbe::{self, TokenTree};
+
+use syntax::ast::{Ident, Name};
+use syntax::parse::{Directory, PResult};
+use syntax::parse::parser::{Parser, PathStyle};
+use syntax::parse::token::{self, DocComment, Nonterminal, Token};
+use syntax::print::pprust;
+use syntax::sess::ParseSess;
+use syntax::symbol::{kw, sym, Symbol};
+use syntax::tokenstream::{DelimSpan, TokenStream};
 
 use errors::FatalError;
 use smallvec::{smallvec, SmallVec};
@@ -651,7 +652,7 @@ pub(super) fn parse(
         directory,
         recurse_into_modules,
         true,
-        crate::MACRO_ARGUMENTS,
+        syntax::MACRO_ARGUMENTS,
     );
 
     // A queue of possible matcher positions. We initialize it with the matcher position in which
diff --git a/src/libsyntax/ext/mbe/macro_rules.rs b/src/libsyntax_expand/mbe/macro_rules.rs
index b4223298422..9a4130b2d8d 100644
--- a/src/libsyntax/ext/mbe/macro_rules.rs
+++ b/src/libsyntax_expand/mbe/macro_rules.rs
@@ -1,24 +1,25 @@
-use crate::ast;
-use crate::attr::{self, TransparencyError};
-use crate::edition::Edition;
-use crate::ext::base::{DummyResult, ExtCtxt, MacResult, TTMacroExpander};
-use crate::ext::base::{SyntaxExtension, SyntaxExtensionKind};
-use crate::ext::expand::{AstFragment, AstFragmentKind};
-use crate::ext::mbe;
-use crate::ext::mbe::macro_check;
-use crate::ext::mbe::macro_parser::parse;
-use crate::ext::mbe::macro_parser::{Error, Failure, Success};
-use crate::ext::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedParseResult};
-use crate::ext::mbe::transcribe::transcribe;
-use crate::feature_gate::Features;
-use crate::parse::parser::Parser;
-use crate::parse::token::TokenKind::*;
-use crate::parse::token::{self, NtTT, Token};
-use crate::parse::Directory;
-use crate::print::pprust;
-use crate::sess::ParseSess;
-use crate::symbol::{kw, sym, Symbol};
-use crate::tokenstream::{DelimSpan, TokenStream, TokenTree};
+use crate::base::{DummyResult, ExtCtxt, MacResult, TTMacroExpander};
+use crate::base::{SyntaxExtension, SyntaxExtensionKind};
+use crate::expand::{AstFragment, AstFragmentKind, ensure_complete_parse, parse_ast_fragment};
+use crate::mbe;
+use crate::mbe::macro_check;
+use crate::mbe::macro_parser::parse;
+use crate::mbe::macro_parser::{Error, Failure, Success};
+use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedParseResult};
+use crate::mbe::transcribe::transcribe;
+
+use syntax::ast;
+use syntax::attr::{self, TransparencyError};
+use syntax::edition::Edition;
+use syntax::feature_gate::Features;
+use syntax::parse::parser::Parser;
+use syntax::parse::token::TokenKind::*;
+use syntax::parse::token::{self, NtTT, Token};
+use syntax::parse::Directory;
+use syntax::print::pprust;
+use syntax::sess::ParseSess;
+use syntax::symbol::{kw, sym, Symbol};
+use syntax::tokenstream::{DelimSpan, TokenStream};
 
 use errors::{DiagnosticBuilder, FatalError};
 use log::debug;
@@ -66,7 +67,7 @@ crate fn annotate_err_with_kind(
 impl<'a> ParserAnyMacro<'a> {
     crate fn make(mut self: Box<ParserAnyMacro<'a>>, kind: AstFragmentKind) -> AstFragment {
         let ParserAnyMacro { site_span, macro_ident, ref mut parser, arm_span } = *self;
-        let fragment = panictry!(parser.parse_ast_fragment(kind, true).map_err(|mut e| {
+        let fragment = panictry!(parse_ast_fragment(parser, kind, true).map_err(|mut e| {
             if parser.token == token::Eof && e.message().ends_with(", found `<eof>`") {
                 if !e.span.is_dummy() {
                     // early end of macro arm (#52866)
@@ -128,7 +129,7 @@ impl<'a> ParserAnyMacro<'a> {
 
         // Make sure we don't have any tokens left to parse so we don't silently drop anything.
         let path = ast::Path::from_ident(macro_ident.with_span_pos(site_span));
-        parser.ensure_complete_parse(&path, kind.name(), site_span);
+        ensure_complete_parse(parser, &path, kind.name(), site_span);
         fragment
     }
 }
@@ -189,7 +190,7 @@ fn generic_extension<'cx>(
             _ => cx.span_bug(sp, "malformed macro lhs"),
         };
 
-        match TokenTree::parse(cx, lhs_tt, arg.clone()) {
+        match parse_tt(cx, lhs_tt, arg.clone()) {
             Success(named_matches) => {
                 let rhs = match rhses[i] {
                     // ignore delimiters
@@ -265,7 +266,7 @@ fn generic_extension<'cx>(
                 mbe::TokenTree::Delimited(_, ref delim) => &delim.tts[..],
                 _ => continue,
             };
-            match TokenTree::parse(cx, lhs_tt, arg.clone()) {
+            match parse_tt(cx, lhs_tt, arg.clone()) {
                 Success(_) => {
                     if comma_span.is_dummy() {
                         err.note("you might be missing a comma");
@@ -1158,7 +1159,7 @@ fn is_legal_fragment_specifier(
 
 fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String {
     match *tt {
-        mbe::TokenTree::Token(ref token) => crate::print::pprust::token_to_string(&token),
+        mbe::TokenTree::Token(ref token) => pprust::token_to_string(&token),
         mbe::TokenTree::MetaVar(_, name) => format!("${}", name),
         mbe::TokenTree::MetaVarDecl(_, name, kind) => format!("${}:{}", name, kind),
         _ => panic!(
@@ -1168,17 +1169,14 @@ fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String {
     }
 }
 
-impl TokenTree {
-    /// Use this token tree as a matcher to parse given tts.
-    fn parse(cx: &ExtCtxt<'_>, mtch: &[mbe::TokenTree], tts: TokenStream)
-             -> NamedParseResult {
-        // `None` is because we're not interpolating
-        let directory = Directory {
-            path: Cow::from(cx.current_expansion.module.directory.as_path()),
-            ownership: cx.current_expansion.directory_ownership,
-        };
-        parse(cx.parse_sess(), tts, mtch, Some(directory), true)
-    }
+/// Use this token tree as a matcher to parse given tts.
+fn parse_tt(cx: &ExtCtxt<'_>, mtch: &[mbe::TokenTree], tts: TokenStream) -> NamedParseResult {
+    // `None` is because we're not interpolating
+    let directory = Directory {
+        path: Cow::from(cx.current_expansion.module.directory.as_path()),
+        ownership: cx.current_expansion.directory_ownership,
+    };
+    parse(cx.parse_sess(), tts, mtch, Some(directory), true)
 }
 
 /// Generates an appropriate parsing failure message. For EOF, this is "unexpected end...". For
diff --git a/src/libsyntax/ext/mbe/quoted.rs b/src/libsyntax_expand/mbe/quoted.rs
index 3cec4bc60e7..cedd59233ad 100644
--- a/src/libsyntax/ext/mbe/quoted.rs
+++ b/src/libsyntax_expand/mbe/quoted.rs
@@ -1,11 +1,12 @@
-use crate::ast;
-use crate::ext::mbe::macro_parser;
-use crate::ext::mbe::{TokenTree, KleeneOp, KleeneToken, SequenceRepetition, Delimited};
-use crate::parse::token::{self, Token};
-use crate::print::pprust;
-use crate::sess::ParseSess;
-use crate::symbol::kw;
-use crate::tokenstream;
+use crate::mbe::macro_parser;
+use crate::mbe::{TokenTree, KleeneOp, KleeneToken, SequenceRepetition, Delimited};
+
+use syntax::ast;
+use syntax::parse::token::{self, Token};
+use syntax::print::pprust;
+use syntax::sess::ParseSess;
+use syntax::symbol::kw;
+use syntax::tokenstream;
 
 use syntax_pos::Span;
 
diff --git a/src/libsyntax/ext/mbe/transcribe.rs b/src/libsyntax_expand/mbe/transcribe.rs
index da930436d81..94523bbf91b 100644
--- a/src/libsyntax/ext/mbe/transcribe.rs
+++ b/src/libsyntax_expand/mbe/transcribe.rs
@@ -1,10 +1,11 @@
-use crate::ast::{Ident, Mac};
-use crate::ext::base::ExtCtxt;
-use crate::ext::mbe;
-use crate::ext::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedMatch};
-use crate::mut_visit::{self, MutVisitor};
-use crate::parse::token::{self, NtTT, Token};
-use crate::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndJoint};
+use crate::base::ExtCtxt;
+use crate::mbe;
+use crate::mbe::macro_parser::{MatchedNonterminal, MatchedSeq, NamedMatch};
+
+use syntax::ast::{Ident, Mac};
+use syntax::mut_visit::{self, MutVisitor};
+use syntax::parse::token::{self, NtTT, Token};
+use syntax::tokenstream::{DelimSpan, TokenStream, TokenTree, TreeAndJoint};
 
 use smallvec::{smallvec, SmallVec};
 
diff --git a/src/libsyntax/ext/placeholders.rs b/src/libsyntax_expand/placeholders.rs
index 4fae25bbde6..f2c89e14b53 100644
--- a/src/libsyntax/ext/placeholders.rs
+++ b/src/libsyntax_expand/placeholders.rs
@@ -1,11 +1,12 @@
-use crate::ast::{self, NodeId};
-use crate::source_map::{DUMMY_SP, dummy_spanned};
-use crate::ext::base::ExtCtxt;
-use crate::ext::expand::{AstFragment, AstFragmentKind};
-use crate::tokenstream::TokenStream;
-use crate::mut_visit::*;
-use crate::ptr::P;
-use crate::ThinVec;
+use crate::base::ExtCtxt;
+use crate::expand::{AstFragment, AstFragmentKind};
+
+use syntax::ast::{self, NodeId};
+use syntax::source_map::{DUMMY_SP, dummy_spanned};
+use syntax::tokenstream::TokenStream;
+use syntax::mut_visit::*;
+use syntax::ptr::P;
+use syntax::ThinVec;
 
 use smallvec::{smallvec, SmallVec};
 
diff --git a/src/libsyntax/ext/proc_macro.rs b/src/libsyntax_expand/proc_macro.rs
index 72062d2ffbf..07b618c99a5 100644
--- a/src/libsyntax/ext/proc_macro.rs
+++ b/src/libsyntax_expand/proc_macro.rs
@@ -1,22 +1,22 @@
-use crate::ast::{self, ItemKind, Attribute, Mac};
-use crate::attr::{mark_used, mark_known};
-use crate::errors::{Applicability, FatalError};
-use crate::ext::base::{self, *};
-use crate::ext::proc_macro_server;
-use crate::parse::{self, token};
-use crate::symbol::sym;
-use crate::tokenstream::{self, TokenStream};
-use crate::visit::Visitor;
+use crate::base::{self, *};
+use crate::proc_macro_server;
+
+use syntax::ast::{self, ItemKind, Attribute, Mac};
+use syntax::attr::{mark_used, mark_known};
+use syntax::errors::{Applicability, FatalError};
+use syntax::parse::{self, token};
+use syntax::symbol::sym;
+use syntax::tokenstream::{self, TokenStream};
+use syntax::visit::Visitor;
 
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::{Span, DUMMY_SP};
 
-const EXEC_STRATEGY: proc_macro::bridge::server::SameThread =
-    proc_macro::bridge::server::SameThread;
+const EXEC_STRATEGY: pm::bridge::server::SameThread = pm::bridge::server::SameThread;
 
 pub struct BangProcMacro {
-    pub client: proc_macro::bridge::client::Client<
-        fn(proc_macro::TokenStream) -> proc_macro::TokenStream,
+    pub client: pm::bridge::client::Client<
+        fn(pm::TokenStream) -> pm::TokenStream,
     >,
 }
 
@@ -44,9 +44,7 @@ impl base::ProcMacro for BangProcMacro {
 }
 
 pub struct AttrProcMacro {
-    pub client: proc_macro::bridge::client::Client<
-        fn(proc_macro::TokenStream, proc_macro::TokenStream) -> proc_macro::TokenStream,
-    >,
+    pub client: pm::bridge::client::Client<fn(pm::TokenStream, pm::TokenStream) -> pm::TokenStream>,
 }
 
 impl base::AttrProcMacro for AttrProcMacro {
@@ -74,9 +72,7 @@ impl base::AttrProcMacro for AttrProcMacro {
 }
 
 pub struct ProcMacroDerive {
-    pub client: proc_macro::bridge::client::Client<
-        fn(proc_macro::TokenStream) -> proc_macro::TokenStream,
-    >,
+    pub client: pm::bridge::client::Client<fn(pm::TokenStream) -> pm::TokenStream>,
 }
 
 impl MultiItemModifier for ProcMacroDerive {
diff --git a/src/libsyntax/ext/proc_macro_server.rs b/src/libsyntax_expand/proc_macro_server.rs
index e0e1a1c468c..4ce99cfe73b 100644
--- a/src/libsyntax/ext/proc_macro_server.rs
+++ b/src/libsyntax_expand/proc_macro_server.rs
@@ -1,18 +1,19 @@
-use crate::ast;
-use crate::ext::base::ExtCtxt;
-use crate::parse::{self, token};
-use crate::parse::lexer::comments;
-use crate::print::pprust;
-use crate::sess::ParseSess;
-use crate::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint};
+use crate::base::ExtCtxt;
+
+use syntax::ast;
+use syntax::parse::{self, token};
+use syntax::parse::lexer::comments;
+use syntax::print::pprust;
+use syntax::sess::ParseSess;
+use syntax::tokenstream::{self, DelimSpan, IsJoint::*, TokenStream, TreeAndJoint};
 
 use errors::Diagnostic;
 use rustc_data_structures::sync::Lrc;
 use syntax_pos::{BytePos, FileName, MultiSpan, Pos, SourceFile, Span};
 use syntax_pos::symbol::{kw, sym, Symbol};
 
-use proc_macro::{Delimiter, Level, LineColumn, Spacing};
-use proc_macro::bridge::{server, TokenTree};
+use pm::{Delimiter, Level, LineColumn, Spacing};
+use pm::bridge::{server, TokenTree};
 use std::{ascii, panic};
 use std::ops::Bound;
 
@@ -51,7 +52,7 @@ impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
 {
     fn from_internal(((tree, is_joint), sess, stack): (TreeAndJoint, &ParseSess, &mut Vec<Self>))
                     -> Self {
-        use crate::parse::token::*;
+        use syntax::parse::token::*;
 
         let joint = is_joint == Joint;
         let Token { kind, span } = match tree {
@@ -192,7 +193,7 @@ impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
 
 impl ToInternal<TokenStream> for TokenTree<Group, Punct, Ident, Literal> {
     fn to_internal(self) -> TokenStream {
-        use crate::parse::token::*;
+        use syntax::parse::token::*;
 
         let (ch, joint, span) = match self {
             TokenTree::Punct(Punct { ch, joint, span }) => (ch, joint, span),
diff --git a/src/libsyntax_ext/Cargo.toml b/src/libsyntax_ext/Cargo.toml
index 73310df305b..440873f3c2b 100644
--- a/src/libsyntax_ext/Cargo.toml
+++ b/src/libsyntax_ext/Cargo.toml
@@ -17,4 +17,5 @@ rustc_data_structures = { path = "../librustc_data_structures" }
 rustc_target = { path = "../librustc_target" }
 smallvec = { version = "0.6.7", features = ["union", "may_dangle"] }
 syntax = { path = "../libsyntax" }
+syntax_expand = { path = "../libsyntax_expand" }
 syntax_pos = { path = "../libsyntax_pos" }
diff --git a/src/libsyntax_ext/asm.rs b/src/libsyntax_ext/asm.rs
index becbf6d60a0..8c9a34713ea 100644
--- a/src/libsyntax_ext/asm.rs
+++ b/src/libsyntax_ext/asm.rs
@@ -7,7 +7,7 @@ use rustc_data_structures::thin_vec::ThinVec;
 use errors::DiagnosticBuilder;
 
 use syntax::ast;
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::parse::token::{self, Token};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
diff --git a/src/libsyntax_ext/assert.rs b/src/libsyntax_ext/assert.rs
index cbfe14fa439..f4d1f7fb09c 100644
--- a/src/libsyntax_ext/assert.rs
+++ b/src/libsyntax_ext/assert.rs
@@ -1,7 +1,7 @@
 use errors::{Applicability, DiagnosticBuilder};
 
 use syntax::ast::{self, *};
-use syntax::ext::base::*;
+use syntax_expand::base::*;
 use syntax::parse::token::{self, TokenKind};
 use syntax::parse::parser::Parser;
 use syntax::print::pprust;
diff --git a/src/libsyntax_ext/cfg.rs b/src/libsyntax_ext/cfg.rs
index 3c33baf95a5..9e693f29c5a 100644
--- a/src/libsyntax_ext/cfg.rs
+++ b/src/libsyntax_ext/cfg.rs
@@ -5,7 +5,7 @@
 use errors::DiagnosticBuilder;
 
 use syntax::ast;
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::attr;
 use syntax::tokenstream::TokenStream;
 use syntax::parse::token;
diff --git a/src/libsyntax_ext/cmdline_attrs.rs b/src/libsyntax_ext/cmdline_attrs.rs
index 2c3159739e2..2d981526a39 100644
--- a/src/libsyntax_ext/cmdline_attrs.rs
+++ b/src/libsyntax_ext/cmdline_attrs.rs
@@ -2,9 +2,9 @@
 
 use syntax::ast::{self, AttrItem, AttrStyle};
 use syntax::attr::mk_attr;
-use syntax::panictry;
 use syntax::parse::{self, token};
 use syntax::sess::ParseSess;
+use syntax_expand::panictry;
 use syntax_pos::FileName;
 
 pub fn inject(mut krate: ast::Crate, parse_sess: &ParseSess, attrs: &[String]) -> ast::Crate {
diff --git a/src/libsyntax_ext/compile_error.rs b/src/libsyntax_ext/compile_error.rs
index 24f3a66d4ae..cd7f78e9e34 100644
--- a/src/libsyntax_ext/compile_error.rs
+++ b/src/libsyntax_ext/compile_error.rs
@@ -1,6 +1,6 @@
 // The compiler code necessary to support the compile_error! extension.
 
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax_pos::Span;
 use syntax::tokenstream::TokenStream;
 
diff --git a/src/libsyntax_ext/concat.rs b/src/libsyntax_ext/concat.rs
index 790fdad5b3f..47bade698a8 100644
--- a/src/libsyntax_ext/concat.rs
+++ b/src/libsyntax_ext/concat.rs
@@ -1,5 +1,5 @@
 use syntax::ast;
-use syntax::ext::base::{self, DummyResult};
+use syntax_expand::base::{self, DummyResult};
 use syntax::symbol::Symbol;
 use syntax::tokenstream::TokenStream;
 
diff --git a/src/libsyntax_ext/concat_idents.rs b/src/libsyntax_ext/concat_idents.rs
index f6747658c07..a132a4136ea 100644
--- a/src/libsyntax_ext/concat_idents.rs
+++ b/src/libsyntax_ext/concat_idents.rs
@@ -1,7 +1,7 @@
 use rustc_data_structures::thin_vec::ThinVec;
 
 use syntax::ast;
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::parse::token::{self, Token};
 use syntax::ptr::P;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/bounds.rs b/src/libsyntax_ext/deriving/bounds.rs
index d5b8a00c75b..6a9b7092024 100644
--- a/src/libsyntax_ext/deriving/bounds.rs
+++ b/src/libsyntax_ext/deriving/bounds.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::MetaItem;
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax_pos::Span;
 
 pub fn expand_deriving_copy(cx: &mut ExtCtxt<'_>,
diff --git a/src/libsyntax_ext/deriving/clone.rs b/src/libsyntax_ext/deriving/clone.rs
index 9ef2c033b07..eb7d480aa98 100644
--- a/src/libsyntax_ext/deriving/clone.rs
+++ b/src/libsyntax_ext/deriving/clone.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, Expr, GenericArg, Generics, ItemKind, MetaItem, VariantData};
-use syntax::ext::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/cmp/eq.rs b/src/libsyntax_ext/deriving/cmp/eq.rs
index c92339dd2fb..92721dab878 100644
--- a/src/libsyntax_ext/deriving/cmp/eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/eq.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, Ident, Expr, MetaItem, GenericArg};
-use syntax::ext::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
 use syntax::ptr::P;
 use syntax::symbol::{sym, Symbol};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/cmp/ord.rs b/src/libsyntax_ext/deriving/cmp/ord.rs
index 1f4f5aa3709..3eeed95aff7 100644
--- a/src/libsyntax_ext/deriving/cmp/ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/ord.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, Expr, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::sym;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/cmp/partial_eq.rs b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
index 91e1e80e4fb..1615d991792 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_eq.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_eq.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{BinOpKind, Expr, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt, SpecialDerives};
+use syntax_expand::base::{Annotatable, ExtCtxt, SpecialDerives};
 use syntax::ptr::P;
 use syntax::symbol::sym;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/cmp/partial_ord.rs b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
index 13d63aaf2a8..af8aacc6eb9 100644
--- a/src/libsyntax_ext/deriving/cmp/partial_ord.rs
+++ b/src/libsyntax_ext/deriving/cmp/partial_ord.rs
@@ -5,7 +5,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{self, BinOpKind, Expr, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::{sym, Symbol};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/debug.rs b/src/libsyntax_ext/deriving/debug.rs
index 003c2423576..35298211e4d 100644
--- a/src/libsyntax_ext/deriving/debug.rs
+++ b/src/libsyntax_ext/deriving/debug.rs
@@ -6,7 +6,7 @@ use rustc_data_structures::thin_vec::ThinVec;
 
 use syntax::ast::{self, Ident};
 use syntax::ast::{Expr, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::sym;
 use syntax_pos::{DUMMY_SP, Span};
diff --git a/src/libsyntax_ext/deriving/decodable.rs b/src/libsyntax_ext/deriving/decodable.rs
index cde72abbdef..3a0379a0eb0 100644
--- a/src/libsyntax_ext/deriving/decodable.rs
+++ b/src/libsyntax_ext/deriving/decodable.rs
@@ -6,7 +6,7 @@ use crate::deriving::generic::ty::*;
 
 use syntax::ast;
 use syntax::ast::{Expr, MetaItem, Mutability};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::Symbol;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/default.rs b/src/libsyntax_ext/deriving/default.rs
index 2fdea10b76f..6176791c31b 100644
--- a/src/libsyntax_ext/deriving/default.rs
+++ b/src/libsyntax_ext/deriving/default.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{Expr, MetaItem};
-use syntax::ext::base::{Annotatable, DummyResult, ExtCtxt};
+use syntax_expand::base::{Annotatable, DummyResult, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym};
 use syntax::span_err;
diff --git a/src/libsyntax_ext/deriving/encodable.rs b/src/libsyntax_ext/deriving/encodable.rs
index 655d3bb7c4a..2105946b666 100644
--- a/src/libsyntax_ext/deriving/encodable.rs
+++ b/src/libsyntax_ext/deriving/encodable.rs
@@ -90,7 +90,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{Expr, ExprKind, MetaItem, Mutability};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::Symbol;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/generic/mod.rs b/src/libsyntax_ext/deriving/generic/mod.rs
index 9c3ec06d59a..1886a5154b7 100644
--- a/src/libsyntax_ext/deriving/generic/mod.rs
+++ b/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};
diff --git a/src/libsyntax_ext/deriving/generic/ty.rs b/src/libsyntax_ext/deriving/generic/ty.rs
index 6ae02a5cab1..607746597a5 100644
--- a/src/libsyntax_ext/deriving/generic/ty.rs
+++ b/src/libsyntax_ext/deriving/generic/ty.rs
@@ -5,7 +5,7 @@ pub use PtrTy::*;
 pub use Ty::*;
 
 use syntax::ast::{self, Expr, GenericParamKind, Generics, Ident, SelfKind, GenericArg};
-use syntax::ext::base::ExtCtxt;
+use syntax_expand::base::ExtCtxt;
 use syntax::source_map::{respan, DUMMY_SP};
 use syntax::ptr::P;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/hash.rs b/src/libsyntax_ext/deriving/hash.rs
index 2fc594abd70..fe9ef78bb1b 100644
--- a/src/libsyntax_ext/deriving/hash.rs
+++ b/src/libsyntax_ext/deriving/hash.rs
@@ -3,7 +3,7 @@ use crate::deriving::generic::*;
 use crate::deriving::generic::ty::*;
 
 use syntax::ast::{Expr, MetaItem, Mutability};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::sym;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/deriving/mod.rs b/src/libsyntax_ext/deriving/mod.rs
index 60b6eba7a4b..f0471a857dc 100644
--- a/src/libsyntax_ext/deriving/mod.rs
+++ b/src/libsyntax_ext/deriving/mod.rs
@@ -1,7 +1,7 @@
 //! The compiler code necessary to implement the `#[derive]` extensions.
 
 use syntax::ast::{self, MetaItem};
-use syntax::ext::base::{Annotatable, ExtCtxt, MultiItemModifier};
+use syntax_expand::base::{Annotatable, ExtCtxt, MultiItemModifier};
 use syntax::ptr::P;
 use syntax::symbol::{Symbol, sym};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/env.rs b/src/libsyntax_ext/env.rs
index 02757bf6b16..58fe56bd235 100644
--- a/src/libsyntax_ext/env.rs
+++ b/src/libsyntax_ext/env.rs
@@ -4,7 +4,7 @@
 //
 
 use syntax::ast::{self, Ident, GenericArg};
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
 use syntax::tokenstream::TokenStream;
diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 8fc64021b51..45d9f79c28f 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -8,7 +8,7 @@ use errors::Applicability;
 use errors::pluralise;
 
 use syntax::ast;
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax::symbol::{Symbol, sym};
diff --git a/src/libsyntax_ext/global_allocator.rs b/src/libsyntax_ext/global_allocator.rs
index f014b4f4f9f..75dda9535b3 100644
--- a/src/libsyntax_ext/global_allocator.rs
+++ b/src/libsyntax_ext/global_allocator.rs
@@ -2,8 +2,8 @@ use crate::util::check_builtin_macro_attribute;
 
 use syntax::ast::{ItemKind, Mutability, Stmt, Ty, TyKind, Unsafety};
 use syntax::ast::{self, Param, Attribute, Expr, FnHeader, Generics, Ident};
-use syntax::ext::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
-use syntax::ext::base::{Annotatable, ExtCtxt};
+use syntax_expand::allocator::{AllocatorKind, AllocatorMethod, AllocatorTy, ALLOCATOR_METHODS};
+use syntax_expand::base::{Annotatable, ExtCtxt};
 use syntax::ptr::P;
 use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/global_asm.rs b/src/libsyntax_ext/global_asm.rs
index 72fb5b47c21..879ae1e4215 100644
--- a/src/libsyntax_ext/global_asm.rs
+++ b/src/libsyntax_ext/global_asm.rs
@@ -12,7 +12,7 @@ use errors::DiagnosticBuilder;
 
 use syntax::ast;
 use syntax::source_map::respan;
-use syntax::ext::base::{self, *};
+use syntax_expand::base::{self, *};
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax_pos::Span;
diff --git a/src/libsyntax_ext/lib.rs b/src/libsyntax_ext/lib.rs
index 5ba76a52350..5516f276422 100644
--- a/src/libsyntax_ext/lib.rs
+++ b/src/libsyntax_ext/lib.rs
@@ -15,9 +15,9 @@ use crate::deriving::*;
 
 use syntax::ast::Ident;
 use syntax::edition::Edition;
-use syntax::ext::base::{SyntaxExtension, SyntaxExtensionKind, MacroExpanderFn};
-use syntax::ext::proc_macro::BangProcMacro;
 use syntax::symbol::sym;
+use syntax_expand::base::{Resolver, SyntaxExtension, SyntaxExtensionKind, MacroExpanderFn};
+use syntax_expand::proc_macro::BangProcMacro;
 
 mod error_codes;
 
@@ -45,7 +45,7 @@ pub mod proc_macro_harness;
 pub mod standard_library_imports;
 pub mod test_harness;
 
-pub fn register_builtin_macros(resolver: &mut dyn syntax::ext::base::Resolver, edition: Edition) {
+pub fn register_builtin_macros(resolver: &mut dyn Resolver, edition: Edition) {
     let mut register = |name, kind| resolver.register_builtin_macro(
         Ident::with_dummy_span(name), SyntaxExtension {
             is_builtin: true, ..SyntaxExtension::default(kind, edition)
diff --git a/src/libsyntax_ext/log_syntax.rs b/src/libsyntax_ext/log_syntax.rs
index 92130bfaf68..2202375e5e7 100644
--- a/src/libsyntax_ext/log_syntax.rs
+++ b/src/libsyntax_ext/log_syntax.rs
@@ -1,4 +1,4 @@
-use syntax::ext::base;
+use syntax_expand::base;
 use syntax::print;
 use syntax::tokenstream::TokenStream;
 use syntax_pos;
diff --git a/src/libsyntax_ext/plugin_macro_defs.rs b/src/libsyntax_ext/plugin_macro_defs.rs
index 62c7e188eba..1ca9422eb9d 100644
--- a/src/libsyntax_ext/plugin_macro_defs.rs
+++ b/src/libsyntax_ext/plugin_macro_defs.rs
@@ -4,7 +4,7 @@
 use syntax::ast::*;
 use syntax::attr;
 use syntax::edition::Edition;
-use syntax::ext::base::{Resolver, NamedSyntaxExtension};
+use syntax_expand::base::{Resolver, NamedSyntaxExtension};
 use syntax::parse::token;
 use syntax::ptr::P;
 use syntax::source_map::respan;
diff --git a/src/libsyntax_ext/proc_macro_harness.rs b/src/libsyntax_ext/proc_macro_harness.rs
index 1b7068818b0..96d0c3fcab1 100644
--- a/src/libsyntax_ext/proc_macro_harness.rs
+++ b/src/libsyntax_ext/proc_macro_harness.rs
@@ -3,14 +3,14 @@ use std::mem;
 use smallvec::smallvec;
 use syntax::ast::{self, Ident};
 use syntax::attr;
-use syntax::ext::base::ExtCtxt;
-use syntax::ext::expand::{AstFragment, ExpansionConfig};
-use syntax::ext::proc_macro::is_proc_macro_attr;
 use syntax::print::pprust;
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{kw, sym};
 use syntax::visit::{self, Visitor};
+use syntax_expand::base::{ExtCtxt, Resolver};
+use syntax_expand::expand::{AstFragment, ExpansionConfig};
+use syntax_expand::proc_macro::is_proc_macro_attr;
 use syntax_pos::{Span, DUMMY_SP};
 use syntax_pos::hygiene::AstPass;
 
@@ -46,7 +46,7 @@ struct CollectProcMacros<'a> {
 }
 
 pub fn inject(sess: &ParseSess,
-              resolver: &mut dyn (::syntax::ext::base::Resolver),
+              resolver: &mut dyn Resolver,
               mut krate: ast::Crate,
               is_proc_macro_crate: bool,
               has_proc_macro_decls: bool,
diff --git a/src/libsyntax_ext/source_util.rs b/src/libsyntax_ext/source_util.rs
index f74507dcc21..438e199ebdb 100644
--- a/src/libsyntax_ext/source_util.rs
+++ b/src/libsyntax_ext/source_util.rs
@@ -1,5 +1,6 @@
-use syntax::{ast, panictry};
-use syntax::ext::base::{self, *};
+use syntax_expand::panictry;
+use syntax_expand::base::{self, *};
+use syntax::ast;
 use syntax::parse::{self, token, DirectoryOwnership};
 use syntax::print::pprust;
 use syntax::ptr::P;
diff --git a/src/libsyntax_ext/standard_library_imports.rs b/src/libsyntax_ext/standard_library_imports.rs
index 4f17acf2d0f..fd27a218906 100644
--- a/src/libsyntax_ext/standard_library_imports.rs
+++ b/src/libsyntax_ext/standard_library_imports.rs
@@ -1,11 +1,11 @@
 use syntax::{ast, attr};
 use syntax::edition::Edition;
-use syntax::ext::expand::ExpansionConfig;
-use syntax::ext::hygiene::AstPass;
-use syntax::ext::base::{ExtCtxt, Resolver};
 use syntax::ptr::P;
 use syntax::sess::ParseSess;
 use syntax::symbol::{Ident, Symbol, kw, sym};
+use syntax_expand::expand::ExpansionConfig;
+use syntax_expand::hygiene::AstPass;
+use syntax_expand::base::{ExtCtxt, Resolver};
 use syntax_pos::DUMMY_SP;
 
 pub fn inject(
diff --git a/src/libsyntax_ext/test.rs b/src/libsyntax_ext/test.rs
index 4d7441ca0b6..b0da413d63a 100644
--- a/src/libsyntax_ext/test.rs
+++ b/src/libsyntax_ext/test.rs
@@ -5,7 +5,7 @@ use crate::util::check_builtin_macro_attribute;
 
 use syntax::ast;
 use syntax::attr;
-use syntax::ext::base::*;
+use syntax_expand::base::*;
 use syntax::print::pprust;
 use syntax::source_map::respan;
 use syntax::symbol::{Symbol, sym};
diff --git a/src/libsyntax_ext/test_harness.rs b/src/libsyntax_ext/test_harness.rs
index 0bb279c0cb0..33d41a7f53e 100644
--- a/src/libsyntax_ext/test_harness.rs
+++ b/src/libsyntax_ext/test_harness.rs
@@ -6,8 +6,8 @@ use rustc_target::spec::PanicStrategy;
 use syntax::ast::{self, Ident};
 use syntax::attr;
 use syntax::entry::{self, EntryPointType};
-use syntax::ext::base::{ExtCtxt, Resolver};
-use syntax::ext::expand::{AstFragment, ExpansionConfig};
+use syntax_expand::base::{ExtCtxt, Resolver};
+use syntax_expand::expand::{AstFragment, ExpansionConfig};
 use syntax::feature_gate::Features;
 use syntax::mut_visit::{*, ExpectOne};
 use syntax::ptr::P;
diff --git a/src/libsyntax_ext/trace_macros.rs b/src/libsyntax_ext/trace_macros.rs
index d83c24046d9..dbf96d3b561 100644
--- a/src/libsyntax_ext/trace_macros.rs
+++ b/src/libsyntax_ext/trace_macros.rs
@@ -1,4 +1,4 @@
-use syntax::ext::base::{self, ExtCtxt};
+use syntax_expand::base::{self, ExtCtxt};
 use syntax::symbol::kw;
 use syntax_pos::Span;
 use syntax::tokenstream::{TokenTree, TokenStream};
diff --git a/src/libsyntax_ext/util.rs b/src/libsyntax_ext/util.rs
index fbae68057c5..d84fe19b3ea 100644
--- a/src/libsyntax_ext/util.rs
+++ b/src/libsyntax_ext/util.rs
@@ -1,7 +1,7 @@
 use syntax_pos::Symbol;
 use syntax::ast::MetaItem;
 use syntax::attr::{check_builtin_attribute, AttributeTemplate};
-use syntax::ext::base::ExtCtxt;
+use syntax_expand::base::ExtCtxt;
 
 pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
     // All the built-in macro attributes are "words" at the moment.