Auto merge of #61253 - nnethercote:avoid-hygiene_data-lookups, r=petrochenkov

Avoid `hygiene_data` lookups

These commits mostly introduce compound operations that allow two close adjacent `hygiene_data` lookups to be combined.

r? @petrochenkov

21 files changed, 100 insertions, 62 deletions

diff --git a/src/librustc/lint/internal.rs b/src/librustc/lint/internal.rs
index e953c084599..86dae579ca7 100644
--- a/src/librustc/lint/internal.rs
+++ b/src/librustc/lint/internal.rs
@@ -113,7 +113,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TyTyKind {
                             .help("try using `Ty` instead")
                             .emit();
                         } else {
-                            if ty.span.ctxt().outer().expn_info().is_some() {
+                            if ty.span.ctxt().outer_expn_info().is_some() {
                                 return;
                             }
                             if let Some(t) = is_ty_or_ty_ctxt(cx, ty) {
diff --git a/src/librustc/lint/mod.rs b/src/librustc/lint/mod.rs
index c3afca35303..f4eff6121c0 100644
--- a/src/librustc/lint/mod.rs
+++ b/src/librustc/lint/mod.rs
@@ -880,7 +880,7 @@ pub fn provide(providers: &mut Providers<'_>) {
 /// This is used to test whether a lint should not even begin to figure out whether it should
 /// be reported on the current node.
 pub fn in_external_macro(sess: &Session, span: Span) -> bool {
-    let info = match span.ctxt().outer().expn_info() {
+    let info = match span.ctxt().outer_expn_info() {
         Some(info) => info,
         // no ExpnInfo means this span doesn't come from a macro
         None => return false,
@@ -908,7 +908,7 @@ pub fn in_external_macro(sess: &Session, span: Span) -> bool {
 
 /// Returns whether `span` originates in a derive macro's expansion
 pub fn in_derive_expansion(span: Span) -> bool {
-    let info = match span.ctxt().outer().expn_info() {
+    let info = match span.ctxt().outer_expn_info() {
         Some(info) => info,
         // no ExpnInfo means this span doesn't come from a macro
         None => return false,
diff --git a/src/librustc/traits/error_reporting.rs b/src/librustc/traits/error_reporting.rs
index 5a2bf07b065..a29b173880a 100644
--- a/src/librustc/traits/error_reporting.rs
+++ b/src/librustc/traits/error_reporting.rs
@@ -65,7 +65,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                 format: ExpnFormat::CompilerDesugaring(_),
                 def_site: Some(def_span),
                 ..
-            }) = span.ctxt().outer().expn_info() {
+            }) = span.ctxt().outer_expn_info() {
                 span = def_span;
             }
 
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index fa993325e27..0cbc0112a8e 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -2886,7 +2886,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
 
     pub fn find_field_index(self, ident: Ident, variant: &VariantDef) -> Option<usize> {
         variant.fields.iter().position(|field| {
-            self.adjust_ident(ident, variant.def_id, hir::DUMMY_HIR_ID).0 == field.ident.modern()
+            self.hygienic_eq(ident, field.ident, variant.def_id)
         })
     }
 
@@ -3085,19 +3085,32 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
     /// its supposed definition name (`def_name`). The method also needs `DefId` of the supposed
     /// definition's parent/scope to perform comparison.
     pub fn hygienic_eq(self, use_name: Ident, def_name: Ident, def_parent_def_id: DefId) -> bool {
-        self.adjust_ident(use_name, def_parent_def_id, hir::DUMMY_HIR_ID).0 == def_name.modern()
+        // We could use `Ident::eq` here, but we deliberately don't. The name
+        // comparison fails frequently, and we want to avoid the expensive
+        // `modern()` calls required for the span comparison whenever possible.
+        use_name.name == def_name.name &&
+        self.adjust_ident(use_name, def_parent_def_id).span.ctxt() == def_name.modern().span.ctxt()
     }
 
-    pub fn adjust_ident(self, mut ident: Ident, scope: DefId, block: hir::HirId) -> (Ident, DefId) {
-        ident = ident.modern();
-        let target_expansion = match scope.krate {
+    fn expansion_that_defined(self, scope: DefId) -> Mark {
+        match scope.krate {
             LOCAL_CRATE => self.hir().definitions().expansion_that_defined(scope.index),
             _ => Mark::root(),
-        };
-        let scope = match ident.span.adjust(target_expansion) {
+        }
+    }
+
+    pub fn adjust_ident(self, mut ident: Ident, scope: DefId) -> Ident {
+        ident = ident.modern();
+        ident.span.adjust(self.expansion_that_defined(scope));
+        ident
+    }
+
+    pub fn adjust_ident_and_get_scope(self, mut ident: Ident, scope: DefId, block: hir::HirId)
+                                      -> (Ident, DefId) {
+        ident = ident.modern();
+        let scope = match ident.span.adjust(self.expansion_that_defined(scope)) {
             Some(actual_expansion) =>
                 self.hir().definitions().parent_module_of_macro_def(actual_expansion),
-            None if block == hir::DUMMY_HIR_ID => DefId::local(CRATE_DEF_INDEX), // Dummy DefId
             None => self.hir().get_module_parent_by_hir_id(block),
         };
         (ident, scope)
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
index 4a43201dedf..5d6f7036c3e 100644
--- a/src/librustc_codegen_ssa/mir/mod.rs
+++ b/src/librustc_codegen_ssa/mir/mod.rs
@@ -131,7 +131,7 @@ impl<'a, 'tcx: 'a, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             // at the level above that.
             let mut span = source_info.span;
             while span.ctxt() != NO_EXPANSION && span.ctxt() != self.mir.span.ctxt() {
-                if let Some(info) = span.ctxt().outer().expn_info() {
+                if let Some(info) = span.ctxt().outer_expn_info() {
                     span = info.call_site;
                 } else {
                     break;
diff --git a/src/librustc_lint/builtin.rs b/src/librustc_lint/builtin.rs
index d184c671bba..44b727c6925 100644
--- a/src/librustc_lint/builtin.rs
+++ b/src/librustc_lint/builtin.rs
@@ -158,7 +158,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NonShorthandFieldPatterns {
                 if fieldpat.node.is_shorthand {
                     continue;
                 }
-                if fieldpat.span.ctxt().outer().expn_info().is_some() {
+                if fieldpat.span.ctxt().outer_expn_info().is_some() {
                     // Don't lint if this is a macro expansion: macro authors
                     // shouldn't have to worry about this kind of style issue
                     // (Issue #49588)
@@ -1003,7 +1003,7 @@ impl UnreachablePub {
         let mut applicability = Applicability::MachineApplicable;
         match vis.node {
             hir::VisibilityKind::Public if !cx.access_levels.is_reachable(id) => {
-                if span.ctxt().outer().expn_info().is_some() {
+                if span.ctxt().outer_expn_info().is_some() {
                     applicability = Applicability::MaybeIncorrect;
                 }
                 let def_span = cx.tcx.sess.source_map().def_span(span);
diff --git a/src/librustc_lint/unused.rs b/src/librustc_lint/unused.rs
index 34f7e04c164..036820c6d7f 100644
--- a/src/librustc_lint/unused.rs
+++ b/src/librustc_lint/unused.rs
@@ -391,9 +391,8 @@ impl EarlyLintPass for UnusedParens {
                 // trigger in situations that macro authors shouldn't have to care about, e.g.,
                 // when a parenthesized token tree matched in one macro expansion is matched as
                 // an expression in another and used as a fn/method argument (Issue #47775)
-                if e.span.ctxt().outer().expn_info()
-                    .map_or(false, |info| info.call_site.ctxt().outer()
-                            .expn_info().is_some()) {
+                if e.span.ctxt().outer_expn_info()
+                    .map_or(false, |info| info.call_site.ctxt().outer_expn_info().is_some()) {
                         return;
                 }
                 let msg = format!("{} argument", call_kind);
diff --git a/src/librustc_privacy/lib.rs b/src/librustc_privacy/lib.rs
index a08c028390b..20e18d60f07 100644
--- a/src/librustc_privacy/lib.rs
+++ b/src/librustc_privacy/lib.rs
@@ -845,7 +845,7 @@ impl<'a, 'tcx> NamePrivacyVisitor<'a, 'tcx> {
                    field: &'tcx ty::FieldDef) { // definition of the field
         let ident = Ident::new(kw::Invalid, use_ctxt);
         let current_hir = self.current_item;
-        let def_id = self.tcx.adjust_ident(ident, def.did, current_hir).1;
+        let def_id = self.tcx.adjust_ident_and_get_scope(ident, def.did, current_hir).1;
         if !def.is_enum() && !field.vis.is_accessible_from(def_id, self.tcx) {
             struct_span_err!(self.tcx.sess, span, E0451, "field `{}` of {} `{}` is private",
                              field.ident, def.variant_descr(), self.tcx.def_path_str(def.did))
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index 9b7b44025c1..59e5fc149fc 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -762,7 +762,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                 ItemKind::Use(..) => {
                     // don't suggest placing a use before the prelude
                     // import or other generated ones
-                    if item.span.ctxt().outer().expn_info().is_none() {
+                    if item.span.ctxt().outer_expn_info().is_none() {
                         self.span = Some(item.span.shrink_to_lo());
                         self.found_use = true;
                         return;
@@ -772,7 +772,7 @@ impl<'tcx> Visitor<'tcx> for UsePlacementFinder {
                 ItemKind::ExternCrate(_) => {}
                 // but place them before the first other item
                 _ => if self.span.map_or(true, |span| item.span < span ) {
-                    if item.span.ctxt().outer().expn_info().is_none() {
+                    if item.span.ctxt().outer_expn_info().is_none() {
                         // don't insert between attributes and an item
                         if item.attrs.is_empty() {
                             self.span = Some(item.span.shrink_to_lo());
@@ -2308,7 +2308,7 @@ impl<'a> Resolver<'a> {
 
     fn hygienic_lexical_parent(&mut self, module: Module<'a>, span: &mut Span)
                                -> Option<Module<'a>> {
-        if !module.expansion.is_descendant_of(span.ctxt().outer()) {
+        if !module.expansion.outer_is_descendant_of(span.ctxt()) {
             return Some(self.macro_def_scope(span.remove_mark()));
         }
 
@@ -2344,7 +2344,7 @@ impl<'a> Resolver<'a> {
             module.expansion.is_descendant_of(parent.expansion) {
                 // The macro is a proc macro derive
                 if module.expansion.looks_like_proc_macro_derive() {
-                    if parent.expansion.is_descendant_of(span.ctxt().outer()) {
+                    if parent.expansion.outer_is_descendant_of(span.ctxt()) {
                         *poisoned = Some(node_id);
                         return module.parent;
                     }
diff --git a/src/librustc_resolve/macros.rs b/src/librustc_resolve/macros.rs
index 9bb607a2cc2..08ab5b85325 100644
--- a/src/librustc_resolve/macros.rs
+++ b/src/librustc_resolve/macros.rs
@@ -413,7 +413,7 @@ impl<'a> Resolver<'a> {
 
         // Possibly apply the macro helper hack
         if kind == MacroKind::Bang && path.len() == 1 &&
-           path[0].ident.span.ctxt().outer().expn_info()
+           path[0].ident.span.ctxt().outer_expn_info()
                .map_or(false, |info| info.local_inner_macros) {
             let root = Ident::new(kw::DollarCrate, path[0].ident.span);
             path.insert(0, Segment::from_ident(root));
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 5b1a2e29c76..cd53bdc6ed0 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -903,7 +903,7 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
         }?;
 
         let (assoc_ident, def_scope) =
-            tcx.adjust_ident(binding.item_name, candidate.def_id(), hir_ref_id);
+            tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
         let assoc_ty = tcx.associated_items(candidate.def_id()).find(|i| {
             i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident
         }).expect("missing associated type");
@@ -1433,7 +1433,8 @@ impl<'o, 'gcx: 'tcx, 'tcx> dyn AstConv<'gcx, 'tcx> + 'o {
         };
 
         let trait_did = bound.def_id();
-        let (assoc_ident, def_scope) = tcx.adjust_ident(assoc_ident, trait_did, hir_ref_id);
+        let (assoc_ident, def_scope) =
+            tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
         let item = tcx.associated_items(trait_did).find(|i| {
             Namespace::from(i.kind) == Namespace::Type &&
                 i.ident.modern() == assoc_ident
diff --git a/src/librustc_typeck/check/_match.rs b/src/librustc_typeck/check/_match.rs
index 5a84e0cb85a..5cd95a9d834 100644
--- a/src/librustc_typeck/check/_match.rs
+++ b/src/librustc_typeck/check/_match.rs
@@ -1184,7 +1184,7 @@ https://doc.rust-lang.org/reference/types.html#trait-objects");
         let mut inexistent_fields = vec![];
         // Typecheck each field.
         for &Spanned { node: ref field, span } in fields {
-            let ident = tcx.adjust_ident(field.ident, variant.def_id, self.body_id).0;
+            let ident = tcx.adjust_ident(field.ident, variant.def_id);
             let field_ty = match used_fields.entry(ident) {
                 Occupied(occupied) => {
                     struct_span_err!(tcx.sess, span, E0025,
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs
index c3ea9ff40a8..87fc90f53ab 100644
--- a/src/librustc_typeck/check/demand.rs
+++ b/src/librustc_typeck/check/demand.rs
@@ -331,7 +331,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         // Check the `expn_info()` to see if this is a macro; if so, it's hard to
         // extract the text and make a good suggestion, so don't bother.
-        let is_macro = sp.ctxt().outer().expn_info().is_some();
+        let is_macro = sp.ctxt().outer_expn_info().is_some();
 
         match (&expr.node, &expected.sty, &checked_ty.sty) {
             (_, &ty::Ref(_, exp, _), &ty::Ref(_, check, _)) => match (&exp.sty, &check.sty) {
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index d78e0137082..898c15fc77f 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -510,7 +510,8 @@ impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
     {
         let is_accessible = if let Some(name) = self.method_name {
             let item = candidate.item;
-            let def_scope = self.tcx.adjust_ident(name, item.container.id(), self.body_id).1;
+            let def_scope =
+                self.tcx.adjust_ident_and_get_scope(name, item.container.id(), self.body_id).1;
             item.vis.is_accessible_from(def_scope, self.tcx)
         } else {
             true
diff --git a/src/librustc_typeck/check/method/suggest.rs b/src/librustc_typeck/check/method/suggest.rs
index d2fcb987bc2..9ef6112a945 100644
--- a/src/librustc_typeck/check/method/suggest.rs
+++ b/src/librustc_typeck/check/method/suggest.rs
@@ -892,7 +892,7 @@ impl<'a, 'tcx, 'gcx> hir::intravisit::Visitor<'tcx> for UsePlacementFinder<'a, '
                 hir::ItemKind::Use(..) => {
                     // Don't suggest placing a `use` before the prelude
                     // import or other generated ones.
-                    if item.span.ctxt().outer().expn_info().is_none() {
+                    if item.span.ctxt().outer_expn_info().is_none() {
                         self.span = Some(item.span.shrink_to_lo());
                         self.found_use = true;
                         return;
@@ -902,7 +902,7 @@ impl<'a, 'tcx, 'gcx> hir::intravisit::Visitor<'tcx> for UsePlacementFinder<'a, '
                 hir::ItemKind::ExternCrate(_) => {}
                 // ...but do place them before the first other item.
                 _ => if self.span.map_or(true, |span| item.span < span ) {
-                    if item.span.ctxt().outer().expn_info().is_none() {
+                    if item.span.ctxt().outer_expn_info().is_none() {
                         // Don't insert between attributes and an item.
                         if item.attrs.is_empty() {
                             self.span = Some(item.span.shrink_to_lo());
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index c5b85d52566..7a6d02cc33b 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -3339,7 +3339,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
                 ty::Adt(base_def, substs) if !base_def.is_enum() => {
                     debug!("struct named {:?}",  base_t);
                     let (ident, def_scope) =
-                        self.tcx.adjust_ident(field, base_def.did, self.body_id);
+                        self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
                     let fields = &base_def.non_enum_variant().fields;
                     if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
                         let field = &fields[index];
@@ -3510,7 +3510,8 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
     fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
         variant.fields.iter().filter(|field| {
-            let def_scope = self.tcx.adjust_ident(field.ident, variant.def_id, self.body_id).1;
+            let def_scope =
+                self.tcx.adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id).1;
             field.vis.is_accessible_from(def_scope, self.tcx)
         })
         .map(|field| field.ident.name)
@@ -3628,7 +3629,7 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
 
         // Type-check each field.
         for field in ast_fields {
-            let ident = tcx.adjust_ident(field.ident, variant.def_id, self.body_id).0;
+            let ident = tcx.adjust_ident(field.ident, variant.def_id);
             let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
                 seen_fields.insert(ident, field.span);
                 self.write_field_index(field.hir_id, i);
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index d72193ffe12..4b5b9ff7bbe 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -872,7 +872,7 @@ impl<'a> ExtCtxt<'a> {
         let mut ctxt = self.backtrace();
         let mut last_macro = None;
         loop {
-            if ctxt.outer().expn_info().map_or(None, |info| {
+            if ctxt.outer_expn_info().map_or(None, |info| {
                 if info.format.name() == sym::include {
                     // Stop going up the backtrace once include! is encountered
                     return None;
diff --git a/src/libsyntax/source_map.rs b/src/libsyntax/source_map.rs
index e2171a84e23..4b6893b2423 100644
--- a/src/libsyntax/source_map.rs
+++ b/src/libsyntax/source_map.rs
@@ -30,8 +30,8 @@ use errors::SourceMapper;
 /// otherwise return the call site span up to the `enclosing_sp` by
 /// following the `expn_info` chain.
 pub fn original_sp(sp: Span, enclosing_sp: Span) -> Span {
-    let call_site1 = sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
-    let call_site2 = enclosing_sp.ctxt().outer().expn_info().map(|ei| ei.call_site);
+    let call_site1 = sp.ctxt().outer_expn_info().map(|ei| ei.call_site);
+    let call_site2 = enclosing_sp.ctxt().outer_expn_info().map(|ei| ei.call_site);
     match (call_site1, call_site2) {
         (None, _) => sp,
         (Some(call_site1), Some(call_site2)) if call_site1 == call_site2 => sp,
diff --git a/src/libsyntax_ext/proc_macro_server.rs b/src/libsyntax_ext/proc_macro_server.rs
index 53730d2d080..cc05ecf8df5 100644
--- a/src/libsyntax_ext/proc_macro_server.rs
+++ b/src/libsyntax_ext/proc_macro_server.rs
@@ -680,7 +680,7 @@ impl server::Span for Rustc<'_> {
         self.sess.source_map().lookup_char_pos(span.lo()).file
     }
     fn parent(&mut self, span: Self::Span) -> Option<Self::Span> {
-        span.ctxt().outer().expn_info().map(|i| i.call_site)
+        span.ctxt().outer_expn_info().map(|i| i.call_site)
     }
     fn source(&mut self, span: Self::Span) -> Self::Span {
         span.source_callsite()
diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index e8dcd8171c9..445d4271d89 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -112,16 +112,14 @@ impl Mark {
         HygieneData::with(|data| data.marks[self.0 as usize].default_transparency = transparency)
     }
 
-    pub fn is_descendant_of(mut self, ancestor: Mark) -> bool {
-        HygieneData::with(|data| {
-            while self != ancestor {
-                if self == Mark::root() {
-                    return false;
-                }
-                self = data.marks[self.0 as usize].parent;
-            }
-            true
-        })
+    pub fn is_descendant_of(self, ancestor: Mark) -> bool {
+        HygieneData::with(|data| data.is_descendant_of(self, ancestor))
+    }
+
+    /// `mark.outer_is_descendant_of(ctxt)` is equivalent to but faster than
+    /// `mark.is_descendant_of(ctxt.outer())`.
+    pub fn outer_is_descendant_of(self, ctxt: SyntaxContext) -> bool {
+        HygieneData::with(|data| data.is_descendant_of(self, data.outer(ctxt)))
     }
 
     /// Computes a mark such that both input marks are descendants of (or equal to) the returned
@@ -201,6 +199,24 @@ impl HygieneData {
     fn with<T, F: FnOnce(&mut HygieneData) -> T>(f: F) -> T {
         GLOBALS.with(|globals| f(&mut *globals.hygiene_data.borrow_mut()))
     }
+
+    fn outer(&self, ctxt: SyntaxContext) -> Mark {
+        self.syntax_contexts[ctxt.0 as usize].outer_mark
+    }
+
+    fn expn_info(&self, mark: Mark) -> Option<ExpnInfo> {
+        self.marks[mark.0 as usize].expn_info.clone()
+    }
+
+    fn is_descendant_of(&self, mut mark: Mark, ancestor: Mark) -> bool {
+        while mark != ancestor {
+            if mark == Mark::root() {
+                return false;
+            }
+            mark = self.marks[mark.0 as usize].parent;
+        }
+        true
+    }
 }
 
 pub fn clear_markings() {
@@ -416,7 +432,7 @@ impl SyntaxContext {
     /// or `None` if we privacy check as usual (i.e., not w.r.t. a macro definition scope).
     pub fn adjust(&mut self, expansion: Mark) -> Option<Mark> {
         let mut scope = None;
-        while !expansion.is_descendant_of(self.outer()) {
+        while !expansion.outer_is_descendant_of(*self) {
             scope = Some(self.remove_mark());
         }
         scope
@@ -450,7 +466,7 @@ impl SyntaxContext {
     pub fn glob_adjust(&mut self, expansion: Mark, mut glob_ctxt: SyntaxContext)
                        -> Option<Option<Mark>> {
         let mut scope = None;
-        while !expansion.is_descendant_of(glob_ctxt.outer()) {
+        while !expansion.outer_is_descendant_of(glob_ctxt) {
             scope = Some(glob_ctxt.remove_mark());
             if self.remove_mark() != scope.unwrap() {
                 return None;
@@ -476,7 +492,7 @@ impl SyntaxContext {
         }
 
         let mut marks = Vec::new();
-        while !expansion.is_descendant_of(glob_ctxt.outer()) {
+        while !expansion.outer_is_descendant_of(glob_ctxt) {
             marks.push(glob_ctxt.remove_mark());
         }
 
@@ -499,7 +515,14 @@ impl SyntaxContext {
 
     #[inline]
     pub fn outer(self) -> Mark {
-        HygieneData::with(|data| data.syntax_contexts[self.0 as usize].outer_mark)
+        HygieneData::with(|data| data.outer(self))
+    }
+
+    /// `ctxt.outer_expn_info()` is equivalent to but faster than
+    /// `ctxt.outer().expn_info()`.
+    #[inline]
+    pub fn outer_expn_info(self) -> Option<ExpnInfo> {
+        HygieneData::with(|data| data.expn_info(data.outer(self)))
     }
 
     pub fn dollar_crate_name(self) -> Symbol {
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index cb5aaf7eb88..30e075a3396 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -348,18 +348,18 @@ impl Span {
     /// Returns the source span -- this is either the supplied span, or the span for
     /// the macro callsite that expanded to it.
     pub fn source_callsite(self) -> Span {
-        self.ctxt().outer().expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
+        self.ctxt().outer_expn_info().map(|info| info.call_site.source_callsite()).unwrap_or(self)
     }
 
     /// The `Span` for the tokens in the previous macro expansion from which `self` was generated,
     /// if any.
     pub fn parent(self) -> Option<Span> {
-        self.ctxt().outer().expn_info().map(|i| i.call_site)
+        self.ctxt().outer_expn_info().map(|i| i.call_site)
     }
 
     /// Edition of the crate from which this span came.
     pub fn edition(self) -> edition::Edition {
-        self.ctxt().outer().expn_info().map_or_else(|| {
+        self.ctxt().outer_expn_info().map_or_else(|| {
             Edition::from_session()
         }, |einfo| einfo.edition)
     }
@@ -381,19 +381,19 @@ impl Span {
     /// corresponding to the source callsite.
     pub fn source_callee(self) -> Option<ExpnInfo> {
         fn source_callee(info: ExpnInfo) -> ExpnInfo {
-            match info.call_site.ctxt().outer().expn_info() {
+            match info.call_site.ctxt().outer_expn_info() {
                 Some(info) => source_callee(info),
                 None => info,
             }
         }
-        self.ctxt().outer().expn_info().map(source_callee)
+        self.ctxt().outer_expn_info().map(source_callee)
     }
 
     /// Checks if a span is "internal" to a macro in which `#[unstable]`
     /// items can be used (that is, a macro marked with
     /// `#[allow_internal_unstable]`).
     pub fn allows_unstable(&self, feature: Symbol) -> bool {
-        match self.ctxt().outer().expn_info() {
+        match self.ctxt().outer_expn_info() {
             Some(info) => info
                 .allow_internal_unstable
                 .map_or(false, |features| features.iter().any(|&f|
@@ -405,7 +405,7 @@ impl Span {
 
     /// Checks if this span arises from a compiler desugaring of kind `kind`.
     pub fn is_compiler_desugaring(&self, kind: CompilerDesugaringKind) -> bool {
-        match self.ctxt().outer().expn_info() {
+        match self.ctxt().outer_expn_info() {
             Some(info) => match info.format {
                 ExpnFormat::CompilerDesugaring(k) => k == kind,
                 _ => false,
@@ -417,7 +417,7 @@ impl Span {
     /// Returns the compiler desugaring that created this span, or `None`
     /// if this span is not from a desugaring.
     pub fn compiler_desugaring_kind(&self) -> Option<CompilerDesugaringKind> {
-        match self.ctxt().outer().expn_info() {
+        match self.ctxt().outer_expn_info() {
             Some(info) => match info.format {
                 ExpnFormat::CompilerDesugaring(k) => Some(k),
                 _ => None
@@ -430,7 +430,7 @@ impl Span {
     /// can be used without triggering the `unsafe_code` lint
     //  (that is, a macro marked with `#[allow_internal_unsafe]`).
     pub fn allows_unsafe(&self) -> bool {
-        match self.ctxt().outer().expn_info() {
+        match self.ctxt().outer_expn_info() {
             Some(info) => info.allow_internal_unsafe,
             None => false,
         }
@@ -439,7 +439,7 @@ impl Span {
     pub fn macro_backtrace(mut self) -> Vec<MacroBacktrace> {
         let mut prev_span = DUMMY_SP;
         let mut result = vec![];
-        while let Some(info) = self.ctxt().outer().expn_info() {
+        while let Some(info) = self.ctxt().outer_expn_info() {
             // Don't print recursive invocations.
             if !info.call_site.source_equal(&prev_span) {
                 let (pre, post) = match info.format {