diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index 33d02d0b10a7b..ff23c2fb534d5 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -27,16 +27,16 @@ use std::fmt;
 
 /// A SyntaxContext represents a chain of macro expansions (represented by marks).
 #[derive(Clone, Copy, PartialEq, Eq, Default, PartialOrd, Ord, Hash)]
-pub struct SyntaxContext(pub(super) u32);
+pub struct SyntaxContext(u32);
 
 #[derive(Copy, Clone, Debug)]
-pub struct SyntaxContextData {
-    pub outer_mark: Mark,
-    pub prev_ctxt: SyntaxContext,
+struct SyntaxContextData {
+    outer_mark: Mark,
+    prev_ctxt: SyntaxContext,
     // This context, but with all transparent and semi-transparent marks filtered away.
-    pub opaque: SyntaxContext,
+    opaque: SyntaxContext,
     // This context, but with all transparent marks filtered away.
-    pub opaque_and_semitransparent: SyntaxContext,
+    opaque_and_semitransparent: SyntaxContext,
 }
 
 /// A mark is a unique id associated with a macro expansion.
@@ -198,7 +198,7 @@ impl Mark {
 }
 
 #[derive(Debug)]
-pub struct HygieneData {
+crate struct HygieneData {
     marks: Vec<MarkData>,
     syntax_contexts: Vec<SyntaxContextData>,
     markings: HashMap<(SyntaxContext, Mark), SyntaxContext>,
@@ -206,7 +206,7 @@ pub struct HygieneData {
 }
 
 impl HygieneData {
-    pub fn new() -> Self {
+    crate fn new() -> Self {
         HygieneData {
             marks: vec![MarkData {
                 parent: Mark::root(),
@@ -249,6 +249,14 @@ impl SyntaxContext {
         SyntaxContext(0)
     }
 
+    crate fn as_u32(self) -> u32 {
+        self.0
+    }
+
+    crate fn from_u32(raw: u32) -> SyntaxContext {
+        SyntaxContext(raw)
+    }
+
     // Allocate a new SyntaxContext with the given ExpnInfo. This is used when
     // deserializing Spans from the incr. comp. cache.
     // FIXME(mw): This method does not restore MarkData::parent or
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 491ce720f36c5..61af70af47d85 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -19,10 +19,10 @@
       html_root_url = "https://doc.rust-lang.org/nightly/")]
 
 #![feature(const_fn)]
+#![feature(crate_visibility_modifier)]
 #![feature(custom_attribute)]
 #![feature(non_exhaustive)]
 #![feature(optin_builtin_traits)]
-#![allow(unused_attributes)]
 #![feature(specialization)]
 #![feature(stdsimd)]
 
diff --git a/src/libsyntax_pos/span_encoding.rs b/src/libsyntax_pos/span_encoding.rs
index 601a0273ae911..473aa1bd1b8a4 100644
--- a/src/libsyntax_pos/span_encoding.rs
+++ b/src/libsyntax_pos/span_encoding.rs
@@ -100,7 +100,7 @@ const INTERNED_INDEX_OFFSET: u32 = 1;
 
 #[inline]
 fn encode(sd: &SpanData) -> Span {
-    let (base, len, ctxt) = (sd.lo.0, sd.hi.0 - sd.lo.0, sd.ctxt.0);
+    let (base, len, ctxt) = (sd.lo.0, sd.hi.0 - sd.lo.0, sd.ctxt.as_u32());
 
     let val = if (base >> INLINE_SIZES[BASE_INDEX]) == 0 &&
                  (len >> INLINE_SIZES[LEN_INDEX]) == 0 &&
@@ -132,7 +132,7 @@ fn decode(span: Span) -> SpanData {
         let index = extract(INTERNED_INDEX_OFFSET, INTERNED_INDEX_SIZE);
         return with_span_interner(|interner| *interner.get(index));
     };
-    SpanData { lo: BytePos(base), hi: BytePos(base + len), ctxt: SyntaxContext(ctxt) }
+    SpanData { lo: BytePos(base), hi: BytePos(base + len), ctxt: SyntaxContext::from_u32(ctxt) }
 }
 
 #[derive(Default)]