4 files changed, 28 insertions, 31 deletions

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index 9d54d89e080..bb222675239 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -620,7 +620,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
             }
         };
     }
-    gate_all!(if_let_guard, "`if let` guard is not implemented");
+    gate_all!(if_let_guard, "`if let` guards are experimental");
     gate_all!(let_chains, "`let` expressions in this position are experimental");
     gate_all!(async_closure, "async closures are unstable");
     gate_all!(generators, "yield syntax is experimental");
diff --git a/compiler/rustc_macros/src/symbols.rs b/compiler/rustc_macros/src/symbols.rs
index f449900d5c2..5b932864dff 100644
--- a/compiler/rustc_macros/src/symbols.rs
+++ b/compiler/rustc_macros/src/symbols.rs
@@ -126,7 +126,6 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
 
     let mut keyword_stream = quote! {};
     let mut symbols_stream = quote! {};
-    let mut digits_stream = quote! {};
     let mut prefill_stream = quote! {};
     let mut counter = 0u32;
     let mut keys =
@@ -162,7 +161,6 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
             #value,
         });
         keyword_stream.extend(quote! {
-            #[allow(non_upper_case_globals)]
             pub const #name: Symbol = Symbol::new(#counter);
         });
         counter += 1;
@@ -182,42 +180,39 @@ fn symbols_with_errors(input: TokenStream) -> (TokenStream, Vec<syn::Error>) {
             #value,
         });
         symbols_stream.extend(quote! {
-            #[allow(rustc::default_hash_types)]
-            #[allow(non_upper_case_globals)]
             pub const #name: Symbol = Symbol::new(#counter);
         });
         counter += 1;
     }
 
     // Generate symbols for the strings "0", "1", ..., "9".
+    let digits_base = counter;
+    counter += 10;
     for n in 0..10 {
         let n = n.to_string();
         check_dup(Span::call_site(), &n, &mut errors);
         prefill_stream.extend(quote! {
             #n,
         });
-        digits_stream.extend(quote! {
-            Symbol::new(#counter),
-        });
-        counter += 1;
     }
+    let _ = counter; // for future use
 
     let output = quote! {
-        macro_rules! keywords {
-            () => {
-                #keyword_stream
-            }
-        }
+        const SYMBOL_DIGITS_BASE: u32 = #digits_base;
 
-        macro_rules! define_symbols {
-            () => {
-                #symbols_stream
+        #[doc(hidden)]
+        #[allow(non_upper_case_globals)]
+        mod kw_generated {
+            use super::Symbol;
+            #keyword_stream
+        }
 
-                #[allow(non_upper_case_globals)]
-                pub const digits_array: &[Symbol; 10] = &[
-                    #digits_stream
-                ];
-            }
+        #[allow(rustc::default_hash_types)]
+        #[allow(non_upper_case_globals)]
+        #[doc(hidden)]
+        pub mod sym_generated {
+            use super::Symbol;
+            #symbols_stream
         }
 
         impl Interner {
diff --git a/compiler/rustc_parse/src/parser/nonterminal.rs b/compiler/rustc_parse/src/parser/nonterminal.rs
index c007f96a798..76ad5acd530 100644
--- a/compiler/rustc_parse/src/parser/nonterminal.rs
+++ b/compiler/rustc_parse/src/parser/nonterminal.rs
@@ -27,6 +27,8 @@ impl<'a> Parser<'a> {
                 token.can_begin_expr()
                 // This exception is here for backwards compatibility.
                 && !token.is_keyword(kw::Let)
+                // This exception is here for backwards compatibility.
+                && !token.is_keyword(kw::Const)
             }
             NonterminalKind::Ty => token.can_begin_type(),
             NonterminalKind::Ident => get_macro_ident(token).is_some(),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index f61a32a0f79..4d14763825c 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -1577,8 +1577,7 @@ impl Interner {
 /// Given that `kw` is imported, use them like `kw::keyword_name`.
 /// For example `kw::Loop` or `kw::Break`.
 pub mod kw {
-    use super::Symbol;
-    keywords!();
+    pub use super::kw_generated::*;
 }
 
 // This module has a very short name because it's used a lot.
@@ -1586,22 +1585,23 @@ pub mod kw {
 ///
 /// Given that `sym` is imported, use them like `sym::symbol_name`.
 /// For example `sym::rustfmt` or `sym::u8`.
-#[allow(rustc::default_hash_types)]
 pub mod sym {
     use super::Symbol;
     use std::convert::TryInto;
 
-    define_symbols!();
+    pub use super::sym_generated::*;
 
     // Used from a macro in `librustc_feature/accepted.rs`
     pub use super::kw::MacroRules as macro_rules;
 
-    // Get the symbol for an integer. The first few non-negative integers each
-    // have a static symbol and therefore are fast.
+    /// Get the symbol for an integer.
+    ///
+    /// The first few non-negative integers each have a static symbol and therefore
+    /// are fast.
     pub fn integer<N: TryInto<usize> + Copy + ToString>(n: N) -> Symbol {
         if let Result::Ok(idx) = n.try_into() {
-            if let Option::Some(&sym_) = digits_array.get(idx) {
-                return sym_;
+            if idx < 10 {
+                return Symbol::new(super::SYMBOL_DIGITS_BASE + idx as u32);
             }
         }
         Symbol::intern(&n.to_string())
@@ -1632,7 +1632,7 @@ impl Symbol {
         self == kw::True || self == kw::False
     }
 
-    /// This symbol can be a raw identifier.
+    /// Returns `true` if this symbol can be a raw identifier.
     pub fn can_be_raw(self) -> bool {
         self != kw::Invalid && self != kw::Underscore && !self.is_path_segment_keyword()
     }