`crate` shorthand visibility modifier

With regrets, this breaks rustfmt and rls.

This is in the matter of #45388.

4 files changed, 31 insertions, 4 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index f445def9e03..1e9ac66d237 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1787,10 +1787,19 @@ impl PolyTraitRef {
     }
 }
 
+#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
+pub enum CrateSugar {
+    /// Source is `pub(crate)`
+    PubCrate,
+
+    /// Source is (just) `crate`
+    JustCrate,
+}
+
 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Visibility {
     Public,
-    Crate(Span),
+    Crate(Span, CrateSugar),
     Restricted { path: P<Path>, id: NodeId },
     Inherited,
 }
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 9060a613bc1..da1a0107f2f 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -401,6 +401,9 @@ declare_features! (
 
     // Trait object syntax with `dyn` prefix
     (active, dyn_trait, "1.22.0", Some(44662)),
+
+    // `crate` as visibility modifier, synonymous to `pub(crate)`
+    (active, crate_visibility_modifier, "1.23.0", Some(45388)),
 );
 
 declare_features! (
@@ -1582,6 +1585,14 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
         visit::walk_impl_item(self, ii);
     }
 
+    fn visit_vis(&mut self, vis: &'a ast::Visibility) {
+        if let ast::Visibility::Crate(span, ast::CrateSugar::JustCrate) = *vis {
+            gate_feature_post!(&self, crate_visibility_modifier, span,
+                               "`crate` visibility modifier is experimental");
+        }
+        visit::walk_vis(self, vis);
+    }
+
     fn visit_generics(&mut self, g: &'a ast::Generics) {
         for t in &g.ty_params {
             if !t.attrs.is_empty() {
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 8fd2bad4e44..c9e9a8edcb8 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -36,7 +36,7 @@ use ast::SelfKind;
 use ast::{TraitItem, TraitRef, TraitObjectSyntax};
 use ast::{Ty, TyKind, TypeBinding, TyParam, TyParamBounds};
 use ast::{ViewPath, ViewPathGlob, ViewPathList, ViewPathSimple};
-use ast::{Visibility, WhereClause};
+use ast::{Visibility, WhereClause, CrateSugar};
 use ast::{BinOpKind, UnOp};
 use ast::{RangeEnd, RangeSyntax};
 use {ast, attr};
@@ -5325,6 +5325,10 @@ impl<'a> Parser<'a> {
     pub fn parse_visibility(&mut self, can_take_tuple: bool) -> PResult<'a, Visibility> {
         maybe_whole!(self, NtVis, |x| x);
 
+        if self.eat_keyword(keywords::Crate) {
+            return Ok(Visibility::Crate(self.prev_span, CrateSugar::JustCrate));
+        }
+
         if !self.eat_keyword(keywords::Pub) {
             return Ok(Visibility::Inherited)
         }
@@ -5338,7 +5342,7 @@ impl<'a> Parser<'a> {
                 // `pub(crate)`
                 self.bump(); // `(`
                 self.bump(); // `crate`
-                let vis = Visibility::Crate(self.prev_span);
+                let vis = Visibility::Crate(self.prev_span, CrateSugar::PubCrate);
                 self.expect(&token::CloseDelim(token::Paren))?; // `)`
                 return Ok(vis)
             } else if self.look_ahead(1, |t| t.is_keyword(keywords::In)) {
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 02f871c58c7..4082cc03f12 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1440,7 +1440,10 @@ impl<'a> State<'a> {
     pub fn print_visibility(&mut self, vis: &ast::Visibility) -> io::Result<()> {
         match *vis {
             ast::Visibility::Public => self.word_nbsp("pub"),
-            ast::Visibility::Crate(_) => self.word_nbsp("pub(crate)"),
+            ast::Visibility::Crate(_, sugar) => match sugar {
+                ast::CrateSugar::PubCrate => self.word_nbsp("pub(crate)"),
+                ast::CrateSugar::JustCrate => self.word_nbsp("crate")
+            }
             ast::Visibility::Restricted { ref path, .. } => {
                 let path = to_string(|s| s.print_path(path, false, 0, true));
                 if path == "self" || path == "super" {