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

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

@@ -1,22 +0,0 @@
-# `macro_at_most_once_rep`
-
-NOTE: This feature is only available in the 2018 Edition.
-
-The tracking issue for this feature is: #48075
-
-With this feature gate enabled, one can use `?` as a Kleene operator meaning "0
-or 1 repetitions" in a macro definition. Previously only `+` and `*` were allowed.
-
-For example:
-
-```rust,ignore
-#![feature(macro_at_most_once_rep)]
-
-macro_rules! foo {
-    (something $(,)?) // `?` indicates `,` is "optional"...
-        => {}
-}
-```
-
-------------------------
-

src/doc/unstable-book/src/language-features/plugin.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/libcore/lib.rs

@@ -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/librustc/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_lint/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_metadata/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/libsyntax/ext/tt/quoted.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;
@@ -566,8 +566,8 @@ 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>,
@@ -575,23 +575,8 @@ where
     // 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/feature_gate.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/lib.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/test/compile-fail-fulldeps/auxiliary/lint_for_crate.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;

src/test/compile-fail-fulldeps/auxiliary/lint_group_plugin_test.rs

@@ -12,7 +12,6 @@
 
 #![feature(plugin_registrar)]
 #![feature(box_syntax, rustc_private)]
-#![feature(macro_at_most_once_rep)]
 
 // Load rustc as a plugin to get macros
 #[macro_use]

src/test/compile-fail-fulldeps/auxiliary/lint_plugin_test.rs

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

src/test/run-pass-fulldeps/auxiliary/lint_for_crate.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;

src/test/run-pass-fulldeps/proc-macro/auxiliary/issue-40001-plugin.rs

@@ -9,7 +9,6 @@
 // except according to those terms.
 
 #![feature(box_syntax, plugin, plugin_registrar, rustc_private)]
-#![feature(macro_at_most_once_rep)]
 #![crate_type = "dylib"]
 
 #[macro_use]

src/test/run-pass/macros/macro-at-most-once-rep.rs

@@ -22,8 +22,6 @@
 
 // edition:2018
 
-#![feature(macro_at_most_once_rep)]
-
 macro_rules! foo {
     ($($a:ident)? ; $num:expr) => { {
         let mut x = 0;

src/test/ui-fulldeps/auxiliary/lint_group_plugin_test.rs

@@ -12,7 +12,6 @@
 
 #![feature(plugin_registrar)]
 #![feature(box_syntax, rustc_private)]
-#![feature(macro_at_most_once_rep)]
 
 // Load rustc as a plugin to get macros
 #[macro_use]

src/test/ui-fulldeps/auxiliary/lint_plugin_test.rs

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

src/test/ui-fulldeps/auxiliary/lint_tool_test.rs

@@ -10,7 +10,6 @@
 
 #![feature(plugin_registrar)]
 #![feature(box_syntax, rustc_private)]
-#![feature(macro_at_most_once_rep)]
 
 extern crate syntax;
 

src/test/ui/macros/macro-at-most-once-rep-2015-ques-rep-feature-flag.rs

@@ -1,28 +0,0 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// Test behavior of `?` macro _kleene op_ under the 2015 edition. Namely, it doesn't exist, even
-// with the feature flag.
-
-// gate-test-macro_at_most_once_rep
-// edition:2015
-
-#![feature(macro_at_most_once_rep)]
-
-macro_rules! bar {
-    ($(a)?) => {} //~ERROR expected `*` or `+`
-}
-
-macro_rules! baz {
-    ($(a),?) => {} //~ERROR expected `*` or `+`
-}
-
-fn main() {}
-

src/test/ui/macros/macro-at-most-once-rep-2015-ques-rep-feature-flag.stderr

@@ -1,18 +0,0 @@
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2015-ques-rep-feature-flag.rs:20:10
-   |
-LL |     ($(a)?) => {} //~ERROR expected `*` or `+`
-   |          ^
-   |
-   = note: `?` is not a macro repetition operator
-
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2015-ques-rep-feature-flag.rs:24:11
-   |
-LL |     ($(a),?) => {} //~ERROR expected `*` or `+`
-   |           ^
-   |
-   = note: `?` is not a macro repetition operator
-
-error: aborting due to 2 previous errors
-

src/test/ui/macros/macro-at-most-once-rep-2018-feature-gate.rs

@@ -1,45 +0,0 @@
-// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-// Feature gate test for macro_at_most_once_rep under 2018 edition.
-
-// gate-test-macro_at_most_once_rep
-// edition:2018
-
-macro_rules! foo {
-    ($(a)?) => {}
-    //~^ERROR using the `?` macro Kleene operator for
-    //~|ERROR expected `*` or `+`
-}
-
-macro_rules! baz {
-    ($(a),?) => {} //~ERROR expected `*` or `+`
-}
-
-macro_rules! barplus {
-    ($(a)?+) => {}
-    //~^ERROR using the `?` macro Kleene operator for
-    //~|ERROR expected `*` or `+`
-}
-
-macro_rules! barstar {
-    ($(a)?*) => {}
-    //~^ERROR using the `?` macro Kleene operator for
-    //~|ERROR expected `*` or `+`
-}
-
-pub fn main() {
-    foo!();
-    foo!(a);
-    foo!(a?); //~ ERROR no rules expected the token `?`
-    foo!(a?a); //~ ERROR no rules expected the token `?`
-    foo!(a?a?a); //~ ERROR no rules expected the token `?`
-}
-

src/test/ui/macros/macro-at-most-once-rep-2018-feature-gate.stderr

@@ -1,80 +0,0 @@
-error[E0658]: using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:17:10
-   |
-LL |     ($(a)?) => {}
-   |          ^
-   |
-   = help: add #![feature(macro_at_most_once_rep)] to the crate attributes to enable
-
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:17:10
-   |
-LL |     ($(a)?) => {}
-   |          ^
-
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:23:11
-   |
-LL |     ($(a),?) => {} //~ERROR expected `*` or `+`
-   |           ^
-   |
-   = note: `?` is not a macro repetition operator
-
-error[E0658]: using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:27:10
-   |
-LL |     ($(a)?+) => {}
-   |          ^
-   |
-   = help: add #![feature(macro_at_most_once_rep)] to the crate attributes to enable
-
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:27:10
-   |
-LL |     ($(a)?+) => {}
-   |          ^
-
-error[E0658]: using the `?` macro Kleene operator for "at most one" repetition is unstable (see issue #48075)
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:33:10
-   |
-LL |     ($(a)?*) => {}
-   |          ^
-   |
-   = help: add #![feature(macro_at_most_once_rep)] to the crate attributes to enable
-
-error: expected `*` or `+`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:33:10
-   |
-LL |     ($(a)?*) => {}
-   |          ^
-
-error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:41:11
-   |
-LL | macro_rules! foo {
-   | ---------------- when calling this macro
-...
-LL |     foo!(a?); //~ ERROR no rules expected the token `?`
-   |           ^ no rules expected this token in macro call
-
-error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:42:11
-   |
-LL | macro_rules! foo {
-   | ---------------- when calling this macro
-...
-LL |     foo!(a?a); //~ ERROR no rules expected the token `?`
-   |           ^ no rules expected this token in macro call
-
-error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018-feature-gate.rs:43:11
-   |
-LL | macro_rules! foo {
-   | ---------------- when calling this macro
-...
-LL |     foo!(a?a?a); //~ ERROR no rules expected the token `?`
-   |           ^ no rules expected this token in macro call
-
-error: aborting due to 10 previous errors
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/macros/macro-at-most-once-rep-2018.rs

@@ -12,22 +12,20 @@
 
 // edition:2018
 
-#![feature(macro_at_most_once_rep)]
-
 macro_rules! foo {
-    ($(a)?) => {}
+    ($(a)?) => {};
 }
 
 macro_rules! baz {
-    ($(a),?) => {} //~ERROR the `?` macro repetition operator
+    ($(a),?) => {}; //~ERROR the `?` macro repetition operator
 }
 
 macro_rules! barplus {
-    ($(a)?+) => {} // ok. matches "a+" and "+"
+    ($(a)?+) => {}; // ok. matches "a+" and "+"
 }
 
 macro_rules! barstar {
-    ($(a)?*) => {} // ok. matches "a*" and "*"
+    ($(a)?*) => {}; // ok. matches "a*" and "*"
 }
 
 pub fn main() {

src/test/ui/macros/macro-at-most-once-rep-2018.stderr

@@ -1,11 +1,11 @@
 error: the `?` macro repetition operator does not take a separator
-  --> $DIR/macro-at-most-once-rep-2018.rs:22:10
+  --> $DIR/macro-at-most-once-rep-2018.rs:20:10
    |
-LL |     ($(a),?) => {} //~ERROR the `?` macro repetition operator
+LL |     ($(a),?) => {}; //~ERROR the `?` macro repetition operator
    |          ^
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:36:11
+  --> $DIR/macro-at-most-once-rep-2018.rs:34:11
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -14,7 +14,7 @@ LL |     foo!(a?); //~ ERROR no rules expected the token `?`
    |           ^ no rules expected this token in macro call
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:37:11
+  --> $DIR/macro-at-most-once-rep-2018.rs:35:11
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -23,7 +23,7 @@ LL |     foo!(a?a); //~ ERROR no rules expected the token `?`
    |           ^ no rules expected this token in macro call
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:38:11
+  --> $DIR/macro-at-most-once-rep-2018.rs:36:11
    |
 LL | macro_rules! foo {
    | ---------------- when calling this macro
@@ -32,7 +32,7 @@ LL |     foo!(a?a?a); //~ ERROR no rules expected the token `?`
    |           ^ no rules expected this token in macro call
 
 error: unexpected end of macro invocation
-  --> $DIR/macro-at-most-once-rep-2018.rs:40:5
+  --> $DIR/macro-at-most-once-rep-2018.rs:38:5
    |
 LL | macro_rules! barplus {
    | -------------------- when calling this macro
@@ -41,7 +41,7 @@ LL |     barplus!(); //~ERROR unexpected end of macro invocation
    |     ^^^^^^^^^^^ missing tokens in macro arguments
 
 error: unexpected end of macro invocation
-  --> $DIR/macro-at-most-once-rep-2018.rs:41:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:39:15
    |
 LL | macro_rules! barplus {
    | -------------------- when calling this macro
@@ -50,7 +50,7 @@ LL |     barplus!(a); //~ERROR unexpected end of macro invocation
    |               ^ missing tokens in macro arguments
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:42:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:40:15
    |
 LL | macro_rules! barplus {
    | -------------------- when calling this macro
@@ -59,7 +59,7 @@ LL |     barplus!(a?); //~ ERROR no rules expected the token `?`
    |               ^ no rules expected this token in macro call
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:43:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:41:15
    |
 LL | macro_rules! barplus {
    | -------------------- when calling this macro
@@ -68,7 +68,7 @@ LL |     barplus!(a?a); //~ ERROR no rules expected the token `?`
    |               ^ no rules expected this token in macro call
 
 error: unexpected end of macro invocation
-  --> $DIR/macro-at-most-once-rep-2018.rs:47:5
+  --> $DIR/macro-at-most-once-rep-2018.rs:45:5
    |
 LL | macro_rules! barstar {
    | -------------------- when calling this macro
@@ -77,7 +77,7 @@ LL |     barstar!(); //~ERROR unexpected end of macro invocation
    |     ^^^^^^^^^^^ missing tokens in macro arguments
 
 error: unexpected end of macro invocation
-  --> $DIR/macro-at-most-once-rep-2018.rs:48:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:46:15
    |
 LL | macro_rules! barstar {
    | -------------------- when calling this macro
@@ -86,7 +86,7 @@ LL |     barstar!(a); //~ERROR unexpected end of macro invocation
    |               ^ missing tokens in macro arguments
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:49:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:47:15
    |
 LL | macro_rules! barstar {
    | -------------------- when calling this macro
@@ -95,7 +95,7 @@ LL |     barstar!(a?); //~ ERROR no rules expected the token `?`
    |               ^ no rules expected this token in macro call
 
 error: no rules expected the token `?`
-  --> $DIR/macro-at-most-once-rep-2018.rs:50:15
+  --> $DIR/macro-at-most-once-rep-2018.rs:48:15
    |
 LL | macro_rules! barstar {
    | -------------------- when calling this macro