rustc: implement unstable(issue = "nnn").

This takes an issue number and points people to it in the printed error
message. This commit does not make it an error to have no `issue` field.

Author: huonw

src/librustc/middle/stability.rs

@@ -289,15 +289,19 @@ impl<'a, 'tcx> Checker<'a, 'tcx> {
         if !cross_crate { return }
 
         match *stab {
-            Some(&Stability { level: attr::Unstable, ref feature, ref reason, .. }) => {
+            Some(&Stability { level: attr::Unstable, ref feature, ref reason, issue, .. }) => {
                 self.used_features.insert(feature.clone(), attr::Unstable);
 
                 if !self.active_features.contains(feature) {
-                    let msg = match *reason {
+                    let mut msg = match *reason {
                         Some(ref r) => format!("use of unstable library feature '{}': {}",
                                                &feature, &r),
                         None => format!("use of unstable library feature '{}'", &feature)
                     };
+                    if let Some(n) = issue {
+                        use std::fmt::Write;
+                        write!(&mut msg, " (see issue #{})", n).unwrap();
+                    }
 
                     emit_feature_err(&self.tcx.sess.parse_sess.span_diagnostic,
                                       &feature, span, &msg);

src/libsyntax/attr.rs

@@ -375,6 +375,8 @@ pub struct Stability {
     // The reason for the current stability level. If deprecated, the
     // reason for deprecation.
     pub reason: Option<InternedString>,
+    // The relevant rust-lang issue
+    pub issue: Option<u32>
 }
 
 /// The available stability levels.
@@ -409,41 +411,54 @@ fn find_stability_generic<'a,
 
         used_attrs.push(attr);
 
-        let (feature, since, reason) = match attr.meta_item_list() {
+        let (feature, since, reason, issue) = match attr.meta_item_list() {
             Some(metas) => {
                 let mut feature = None;
                 let mut since = None;
                 let mut reason = None;
+                let mut issue = None;
                 for meta in metas {
-                    if meta.name() == "feature" {
-                        match meta.value_str() {
-                            Some(v) => feature = Some(v),
-                            None => {
-                                diagnostic.span_err(meta.span, "incorrect meta item");
-                                continue 'outer;
+                    match &*meta.name() {
+                        "feature" => {
+                            match meta.value_str() {
+                                Some(v) => feature = Some(v),
+                                None => {
+                                    diagnostic.span_err(meta.span, "incorrect meta item");
+                                    continue 'outer;
+                                }
                             }
                         }
-                    }
-                    if &meta.name()[..] == "since" {
-                        match meta.value_str() {
-                            Some(v) => since = Some(v),
-                            None => {
-                                diagnostic.span_err(meta.span, "incorrect meta item");
-                                continue 'outer;
+                        "since" => {
+                            match meta.value_str() {
+                                Some(v) => since = Some(v),
+                                None => {
+                                    diagnostic.span_err(meta.span, "incorrect meta item");
+                                    continue 'outer;
+                                }
                             }
                         }
-                    }
-                    if &meta.name()[..] == "reason" {
-                        match meta.value_str() {
-                            Some(v) => reason = Some(v),
-                            None => {
-                                diagnostic.span_err(meta.span, "incorrect meta item");
-                                continue 'outer;
+                        "reason" => {
+                            match meta.value_str() {
+                                Some(v) => reason = Some(v),
+                                None => {
+                                    diagnostic.span_err(meta.span, "incorrect meta item");
+                                    continue 'outer;
+                                }
+                            }
+                        }
+                        "issue" => {
+                            match meta.value_str().and_then(|s| s.parse().ok()) {
+                                Some(v) => issue = Some(v),
+                                None => {
+                                    diagnostic.span_err(meta.span, "incorrect meta item");
+                                    continue 'outer;
+                                }
                             }
                         }
+                        _ => {}
                     }
                 }
-                (feature, since, reason)
+                (feature, since, reason, issue)
             }
             None => {
                 diagnostic.span_err(attr.span(), "incorrect stability attribute type");
@@ -477,7 +492,8 @@ fn find_stability_generic<'a,
                 feature: feature.unwrap_or(intern_and_get_ident("bogus")),
                 since: since,
                 deprecated_since: None,
-                reason: reason
+                reason: reason,
+                issue: issue,
             });
         } else { // "deprecated"
             if deprecated.is_some() {
@@ -501,6 +517,12 @@ fn find_stability_generic<'a,
                                               either stable or unstable attribute");
             }
         }
+    } else if stab.as_ref().map_or(false, |s| s.level == Unstable && s.issue.is_none()) {
+        // non-deprecated unstable items need to point to issues.
+        // FIXME: uncomment this error
+        // diagnostic.span_err(item_sp,
+        //                     "non-deprecated unstable items need to point \
+        //                      to an issue with `issue = \"NNN\"`");
     }
 
     (stab, used_attrs)

src/test/auxiliary/stability_attribute_issue.rs

@@ -0,0 +1,20 @@
+// Copyright 2015 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(staged_api)]
+#![staged_api]
+#![stable(feature = "foo", since = "1.2.0")]
+
+
+#[unstable(feature = "foo", issue = "1")]
+pub fn unstable() {}
+
+#[unstable(feature = "foo", reason = "message", issue = "2")]
+pub fn unstable_msg() {}

src/test/compile-fail/stability-attribute-issue.rs

@@ -0,0 +1,21 @@
+// Copyright 2013-2014 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.
+
+// aux-build:stability_attribute_issue.rs
+
+#![deny(deprecated)]
+
+extern crate stability_attribute_issue;
+use stability_attribute_issue::*;
+
+fn main() {
+    unstable(); //~ ERROR use of unstable library feature 'foo' (see issue #1)
+    unstable_msg(); //~ ERROR use of unstable library feature 'foo': message (see issue #2)
+}