Auto merge of #56245 - mark-i-m:stabilize_ques_kleene, r=alexcrichton

Stabilize feature `macro_at_most_once_rep`

a.k.a. `?` Kleene operator 🎉

cc #48075

r? @Centril

Author: bors

src/doc/unstable-book/src/language-features/macro-at-most-once-rep.md

@@ -181,7 +181,6 @@ that warns about any item named `lintme`.
 ```rust,ignore
 #![feature(plugin_registrar)]
 #![feature(box_syntax, rustc_private)]
-#![feature(macro_at_most_once_rep)]
 
 extern crate syntax;
 

src/doc/unstable-book/src/language-features/plugin.md

@@ -93,7 +93,6 @@
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(exhaustive_patterns)]
-#![feature(macro_at_most_once_rep)]
 #![feature(no_core)]
 #![feature(on_unimplemented)]
 #![feature(optin_builtin_traits)]

src/libcore/lib.rs

@@ -67,7 +67,6 @@
 #![feature(integer_atomics)]
 #![feature(test)]
 #![feature(in_band_lifetimes)]
-#![feature(macro_at_most_once_rep)]
 #![feature(crate_visibility_modifier)]
 #![feature(transpose_result)]
 

src/librustc/lib.rs

@@ -29,7 +29,6 @@
 #![feature(nll)]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
-#![feature(macro_at_most_once_rep)]
 
 #[macro_use]
 extern crate syntax;

src/librustc_lint/lib.rs

@@ -14,7 +14,6 @@
 
 #![feature(box_patterns)]
 #![feature(libc)]
-#![feature(macro_at_most_once_rep)]
 #![feature(nll)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]

src/librustc_metadata/lib.rs

@@ -11,13 +11,13 @@
 use ast::NodeId;
 use early_buffered_lints::BufferedEarlyLintId;
 use ext::tt::macro_parser;
-use feature_gate::{self, emit_feature_err, Features, GateIssue};
+use feature_gate::Features;
 use parse::{token, ParseSess};
 use print::pprust;
 use symbol::keywords;
 use syntax_pos::{edition::Edition, BytePos, Span};
 use tokenstream::{self, DelimSpan};
-use {ast, attr};
+use ast;
 
 use rustc_data_structures::sync::Lrc;
 use std::iter::Peekable;
@@ -566,32 +566,17 @@ fn parse_sep_and_kleene_op_2018<I>(
     input: &mut Peekable<I>,
     span: Span,
     sess: &ParseSess,
-    features: &Features,
-    attrs: &[ast::Attribute],
+    _features: &Features,
+    _attrs: &[ast::Attribute],
 ) -> (Option<token::Token>, KleeneOp)
 where
     I: Iterator<Item = tokenstream::TokenTree>,
 {
     // We basically look at two token trees here, denoted as #1 and #2 below
     let span = match parse_kleene_op(input, span) {
         // #1 is a `?` (needs feature gate)
-        Ok(Ok((op, op1_span))) if op == KleeneOp::ZeroOrOne => {
-            if !features.macro_at_most_once_rep
-                && !attr::contains_name(attrs, "allow_internal_unstable")
-            {
-                let explain = feature_gate::EXPLAIN_MACRO_AT_MOST_ONCE_REP;
-                emit_feature_err(
-                    sess,
-                    "macro_at_most_once_rep",
-                    op1_span,
-                    GateIssue::Language,
-                    explain,
-                );
-
-                op1_span
-            } else {
-                return (None, op);
-            }
+        Ok(Ok((op, _op1_span))) if op == KleeneOp::ZeroOrOne => {
+            return (None, op);
         }
 
         // #1 is a `+` or `*` KleeneOp
@@ -600,24 +585,12 @@ where
         // #1 is a separator followed by #2, a KleeneOp
         Ok(Err((tok, span))) => match parse_kleene_op(input, span) {
             // #2 is the `?` Kleene op, which does not take a separator (error)
-            Ok(Ok((op, op2_span))) if op == KleeneOp::ZeroOrOne => {
+            Ok(Ok((op, _op2_span))) if op == KleeneOp::ZeroOrOne => {
                 // Error!
-
-                if !features.macro_at_most_once_rep
-                    && !attr::contains_name(attrs, "allow_internal_unstable")
-                {
-                    // FIXME: when `?` as a Kleene op is stabilized, we only need the "does not
-                    // take a macro separator" error (i.e. the `else` case).
-                    sess.span_diagnostic
-                        .struct_span_err(op2_span, "expected `*` or `+`")
-                        .note("`?` is not a macro repetition operator")
-                        .emit();
-                } else {
-                    sess.span_diagnostic.span_err(
-                        span,
-                        "the `?` macro repetition operator does not take a separator",
-                    );
-                }
+                sess.span_diagnostic.span_err(
+                    span,
+                    "the `?` macro repetition operator does not take a separator",
+                );
 
                 // Return a dummy
                 return (None, KleeneOp::ZeroOrMore);
@@ -638,13 +611,8 @@ where
     };
 
     // If we ever get to this point, we have experienced an "unexpected token" error
-
-    if !features.macro_at_most_once_rep && !attr::contains_name(attrs, "allow_internal_unstable") {
-        sess.span_diagnostic.span_err(span, "expected `*` or `+`");
-    } else {
-        sess.span_diagnostic
-            .span_err(span, "expected one of: `*`, `+`, or `?`");
-    }
+    sess.span_diagnostic
+        .span_err(span, "expected one of: `*`, `+`, or `?`");
 
     // Return a dummy
     (None, KleeneOp::ZeroOrMore)

src/libsyntax/ext/tt/quoted.rs

@@ -393,9 +393,6 @@ declare_features! (
     // `extern` in paths
     (active, extern_in_paths, "1.23.0", Some(55600), None),
 
-    // Use `?` as the Kleene "at most one" operator
-    (active, macro_at_most_once_rep, "1.25.0", Some(48075), None),
-
     // Infer static outlives requirements; RFC 2093
     (active, infer_static_outlives_requirements, "1.26.0", Some(54185), None),
 
@@ -689,6 +686,8 @@ declare_features! (
     (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
     // Allows use of the :literal macro fragment specifier (RFC 1576)
     (accepted, macro_literal_matcher, "1.31.0", Some(35625), None),
+    // Use `?` as the Kleene "at most one" operator
+    (accepted, macro_at_most_once_rep, "1.32.0", Some(48075), None),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must
@@ -1427,9 +1426,6 @@ pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
 pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str =
     "unsized tuple coercion is not stable enough for use and is subject to change";
 
-pub const EXPLAIN_MACRO_AT_MOST_ONCE_REP: &'static str =
-    "using the `?` macro Kleene operator for \"at most one\" repetition is unstable";
-
 struct PostExpansionVisitor<'a> {
     context: &'a Context<'a>,
 }

src/libsyntax/feature_gate.rs

@@ -20,7 +20,6 @@
        test(attr(deny(warnings))))]
 
 #![feature(crate_visibility_modifier)]
-#![feature(macro_at_most_once_rep)]
 #![feature(nll)]
 #![feature(rustc_attrs)]
 #![feature(rustc_diagnostic_macros)]

src/libsyntax/lib.rs

@@ -12,7 +12,6 @@
 
 #![feature(plugin_registrar, rustc_private)]
 #![feature(box_syntax)]
-#![feature(macro_at_most_once_rep)]
 
 #[macro_use] extern crate rustc;
 extern crate rustc_plugin;