Stabilise `?`

cc [`?` tracking issue](https://github.com/rust-lang/rust/issues/31436)

38 files changed, 28 insertions, 89 deletions

diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 1ae4cf8e5ef..28101d21fc2 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -89,7 +89,7 @@
 #![feature(specialization)]
 #![feature(staged_api)]
 #![feature(unboxed_closures)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(never_type)]
 #![feature(prelude_import)]
 
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 99c24e4c48d..a0768089d52 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -255,6 +255,9 @@ macro_rules! debug_assert_ne {
 /// Helper macro for reducing boilerplate code for matching `Result` together
 /// with converting downstream errors.
 ///
+/// Prefer using `?` syntax to `try!`. `?` is built in to the language and is
+/// more succinct than `try!`, it is the standard method for error propogation.
+///
 /// `try!` matches the given `Result`. In case of the `Ok` variant, the
 /// expression has the value of the wrapped value.
 ///
diff --git a/src/libgraphviz/lib.rs b/src/libgraphviz/lib.rs
index 74cc498a7df..95c46ec5715 100644
--- a/src/libgraphviz/lib.rs
+++ b/src/libgraphviz/lib.rs
@@ -295,7 +295,7 @@
 #![cfg_attr(not(stage0), deny(warnings))]
 
 #![feature(str_escape)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 use self::LabelText::*;
 
diff --git a/src/liblibc b/src/liblibc
-Subproject b474785561d58efbd27add9d22339dcabad742a
+Subproject 5a17b4a733a22d445fdd63326f826fcd8a58432
diff --git a/src/librustc/diagnostics.rs b/src/librustc/diagnostics.rs
index de68cc707ad..12a1a425524 100644
--- a/src/librustc/diagnostics.rs
+++ b/src/librustc/diagnostics.rs
@@ -1327,30 +1327,6 @@ let x: i32 = "I am not a number!";
 //      |
 //    type `i32` assigned to variable `x`
 ```
-
-Another situation in which this occurs is when you attempt to use the `try!`
-macro inside a function that does not return a `Result<T, E>`:
-
-```compile_fail,E0308
-use std::fs::File;
-
-fn main() {
-    let mut f = try!(File::create("foo.txt"));
-}
-```
-
-This code gives an error like this:
-
-```text
-<std macros>:5:8: 6:42 error: mismatched types:
- expected `()`,
-     found `core::result::Result<_, _>`
- (expected (),
-     found enum `core::result::Result`) [E0308]
-```
-
-`try!` returns a `Result<T, E>`, and so the function must. But `main()` has
-`()` as its return type, hence the error.
 "##,
 
 E0309: r##"
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index c34286f0195..25731df4778 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -40,7 +40,7 @@
 #![feature(rustc_private)]
 #![feature(slice_patterns)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![cfg_attr(test, feature(test))]
 
 extern crate arena;
diff --git a/src/librustc_back/lib.rs b/src/librustc_back/lib.rs
index c0f358ca801..e6d1982d31c 100644
--- a/src/librustc_back/lib.rs
+++ b/src/librustc_back/lib.rs
@@ -37,7 +37,7 @@
 #![feature(rustc_private)]
 #![feature(staged_api)]
 #![feature(step_by)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![cfg_attr(test, feature(test, rand))]
 
 extern crate syntax;
diff --git a/src/librustc_borrowck/lib.rs b/src/librustc_borrowck/lib.rs
index 22b590592fe..d3ab9c93185 100644
--- a/src/librustc_borrowck/lib.rs
+++ b/src/librustc_borrowck/lib.rs
@@ -26,7 +26,7 @@
 #![feature(staged_api)]
 #![feature(associated_consts)]
 #![feature(nonzero)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;
 extern crate syntax_pos;
diff --git a/src/librustc_const_eval/lib.rs b/src/librustc_const_eval/lib.rs
index f926fef065e..7b40269ba56 100644
--- a/src/librustc_const_eval/lib.rs
+++ b/src/librustc_const_eval/lib.rs
@@ -27,7 +27,7 @@
 #![feature(staged_api)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(slice_patterns)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 
diff --git a/src/librustc_const_math/lib.rs b/src/librustc_const_math/lib.rs
index 741dd4107e0..31fccb41ce5 100644
--- a/src/librustc_const_math/lib.rs
+++ b/src/librustc_const_math/lib.rs
@@ -25,7 +25,7 @@
 
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 492165e2f2a..0e59ea6560f 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -31,7 +31,7 @@
 #![feature(rustc_private)]
 #![feature(set_stdio)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 extern crate arena;
 extern crate flate;
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index bc599a82076..af8ac81b4fb 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -21,7 +21,7 @@
 #![allow(unused_attributes)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(range_contains)]
 #![feature(libc)]
 #![feature(unicode)]
diff --git a/src/librustc_incremental/lib.rs b/src/librustc_incremental/lib.rs
index 2c1340e566d..67104e912f9 100644
--- a/src/librustc_incremental/lib.rs
+++ b/src/librustc_incremental/lib.rs
@@ -20,7 +20,7 @@
 #![cfg_attr(not(stage0), deny(warnings))]
 
 #![feature(dotdot_in_tuple_patterns)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(rustc_private)]
 #![feature(staged_api)]
 #![feature(rand)]
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index acaafb35425..3d8a10f6c31 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -23,7 +23,7 @@
 #![feature(dotdot_in_tuple_patterns)]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_lib)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(quote)]
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index 12f1eb8535a..02f15602d70 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -26,7 +26,7 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 #[macro_use] extern crate log;
 extern crate graphviz as dot;
diff --git a/src/librustc_trans/lib.rs b/src/librustc_trans/lib.rs
index 41c8d565d41..81c0c184f66 100644
--- a/src/librustc_trans/lib.rs
+++ b/src/librustc_trans/lib.rs
@@ -36,7 +36,7 @@
 #![feature(slice_patterns)]
 #![feature(staged_api)]
 #![feature(unicode)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 use rustc::dep_graph::WorkProduct;
 
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 1f34cee5143..cb9b162cabe 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -82,7 +82,7 @@ This API is completely unstable and subject to change.
 #![feature(rustc_diagnostic_macros)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 #[macro_use] extern crate log;
 #[macro_use] extern crate syntax;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 006dda7d661..0be36eb3a85 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -28,7 +28,7 @@
 #![feature(staged_api)]
 #![feature(test)]
 #![feature(unicode)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 
 extern crate arena;
 extern crate getopts;
diff --git a/src/libserialize/lib.rs b/src/libserialize/lib.rs
index 7cb02e2412c..884f24ddc4c 100644
--- a/src/libserialize/lib.rs
+++ b/src/libserialize/lib.rs
@@ -35,7 +35,7 @@ Core encoding and decoding interfaces.
 #![feature(specialization)]
 #![feature(staged_api)]
 #![feature(unicode)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![cfg_attr(test, feature(test))]
 
 // test harness access
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index eee85798841..5a2eb1c1dc4 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -255,7 +255,7 @@
 #![feature(panic_unwind)]
 #![feature(placement_in_syntax)]
 #![feature(prelude_import)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(rand)]
 #![feature(raw)]
 #![feature(reflect_marker)]
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 9eed1d61244..62b88888fc8 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -253,9 +253,6 @@ declare_features! (
     // a...b and ...b
     (active, inclusive_range_syntax, "1.7.0", Some(28237)),
 
-    // `expr?`
-    (active, question_mark, "1.9.0", Some(31436)),
-
     // impl specialization (RFC 1210)
     (active, specialization, "1.7.0", Some(31844)),
 
@@ -348,6 +345,8 @@ declare_features! (
     (accepted, while_let, "1.0.0", None),
     // Allows `#[deprecated]` attribute
     (accepted, deprecated, "1.9.0", Some(29935)),
+    // `expr?`
+    (accepted, question_mark, "1.14.0", Some(31436)),
 );
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -1072,9 +1071,6 @@ impl<'a> Visitor for PostExpansionVisitor<'a> {
                                   e.span,
                                   "inclusive range syntax is experimental");
             }
-            ast::ExprKind::Try(..) => {
-                gate_feature_post!(&self, question_mark, e.span, "the `?` operator is not stable");
-            }
             ast::ExprKind::InPlace(..) => {
                 gate_feature_post!(&self, placement_in_syntax, e.span, EXPLAIN_PLACEMENT_IN);
             }
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 118ceb17ab4..6e671c9efdc 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -31,7 +31,7 @@
 #![feature(staged_api)]
 #![feature(str_escape)]
 #![feature(unicode)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(rustc_diagnostic_macros)]
 #![feature(specialization)]
 
diff --git a/src/libsyntax_pos/lib.rs b/src/libsyntax_pos/lib.rs
index 13dcf7b188b..e3feaee5369 100644
--- a/src/libsyntax_pos/lib.rs
+++ b/src/libsyntax_pos/lib.rs
@@ -27,7 +27,7 @@
 #![allow(unused_attributes)]
 #![feature(rustc_private)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(specialization)]
 
 use std::cell::{Cell, RefCell};
diff --git a/src/libterm/lib.rs b/src/libterm/lib.rs
index 0244e265796..caef808f474 100644
--- a/src/libterm/lib.rs
+++ b/src/libterm/lib.rs
@@ -59,7 +59,7 @@
 #![cfg_attr(windows, feature(libc))]
 // Handle rustfmt skips
 #![feature(custom_attribute)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![allow(unused_attributes)]
 
 use std::io::prelude::*;
diff --git a/src/libtest/lib.rs b/src/libtest/lib.rs
index bb42351d3b7..625666e641c 100644
--- a/src/libtest/lib.rs
+++ b/src/libtest/lib.rs
@@ -38,7 +38,7 @@
 #![feature(rustc_private)]
 #![feature(set_stdio)]
 #![feature(staged_api)]
-#![feature(question_mark)]
+#![cfg_attr(stage0, feature(question_mark))]
 #![feature(panic_unwind)]
 
 extern crate getopts;
diff --git a/src/test/compile-fail/feature-gate-try-operator.rs b/src/test/compile-fail/feature-gate-try-operator.rs
deleted file mode 100644
index b05c7323962..00000000000
--- a/src/test/compile-fail/feature-gate-try-operator.rs
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright 2016 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.
-
-macro_rules! id {
-    ($e:expr) => { $e }
-}
-
-fn main() {
-    id!(x?);  //~ error: the `?` operator is not stable (see issue #31436)
-    y?;  //~ error: the `?` operator is not stable (see issue #31436)
-}
diff --git a/src/test/compile-fail/issue-32709.rs b/src/test/compile-fail/issue-32709.rs
index f9d11f3a171..09538818dcd 100644
--- a/src/test/compile-fail/issue-32709.rs
+++ b/src/test/compile-fail/issue-32709.rs
@@ -8,12 +8,10 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(question_mark)]
-
 // Make sure that the span of try shorthand does not include the trailing
 // semicolon;
 fn a() -> Result<i32, ()> {
-    Err(5)?; //~ ERROR 16:5: 16:12
+    Err(5)?; //~ ERROR 14:5: 14:12
     Ok(1)
 }
 
diff --git a/src/test/run-pass/ifmt.rs b/src/test/run-pass/ifmt.rs
index 8b5536de12e..0ebe1ca07c7 100644
--- a/src/test/run-pass/ifmt.rs
+++ b/src/test/run-pass/ifmt.rs
@@ -14,7 +14,6 @@
 #![allow(unused_must_use)]
 #![allow(unused_features)]
 #![feature(box_syntax)]
-#![feature(question_mark)]
 
 use std::fmt::{self, Write};
 use std::usize;
diff --git a/src/test/run-pass/impl-trait/example-st.rs b/src/test/run-pass/impl-trait/example-st.rs
index 461d4cf4ff0..e9326ed286a 100644
--- a/src/test/run-pass/impl-trait/example-st.rs
+++ b/src/test/run-pass/impl-trait/example-st.rs
@@ -8,7 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(conservative_impl_trait, question_mark)]
+#![feature(conservative_impl_trait)]
 
 struct State;
 type Error = ();
diff --git a/src/test/run-pass/issue-17121.rs b/src/test/run-pass/issue-17121.rs
index b3c80041ef8..dcbcc2d44b5 100644
--- a/src/test/run-pass/issue-17121.rs
+++ b/src/test/run-pass/issue-17121.rs
@@ -10,8 +10,6 @@
 
 // pretty-expanded FIXME #23616
 
-#![feature(question_mark)]
-
 use std::fs::File;
 use std::io::{self, BufReader, Read};
 
diff --git a/src/test/run-pass/issue-20797.rs b/src/test/run-pass/issue-20797.rs
index de952436650..e45582dc2d3 100644
--- a/src/test/run-pass/issue-20797.rs
+++ b/src/test/run-pass/issue-20797.rs
@@ -10,8 +10,6 @@
 
 // Regression test for #20797.
 
-#![feature(question_mark)]
-
 use std::default::Default;
 use std::io;
 use std::fs;
diff --git a/src/test/run-pass/issue-21400.rs b/src/test/run-pass/issue-21400.rs
index 0d1be964748..6715b71a5f5 100644
--- a/src/test/run-pass/issue-21400.rs
+++ b/src/test/run-pass/issue-21400.rs
@@ -11,8 +11,6 @@
 // Regression test for #21400 which itself was extracted from
 // stackoverflow.com/questions/28031155/is-my-borrow-checker-drunk/28031580
 
-#![feature(question_mark)]
-
 fn main() {
     let mut t = Test;
     assert_eq!(t.method1("one"), Ok(1));
diff --git a/src/test/run-pass/try-operator-hygiene.rs b/src/test/run-pass/try-operator-hygiene.rs
index ae622df498f..53d6185020a 100644
--- a/src/test/run-pass/try-operator-hygiene.rs
+++ b/src/test/run-pass/try-operator-hygiene.rs
@@ -18,8 +18,6 @@
 // This test verifies that the expansion is hygienic, i.e. it's not affected by other `val` and
 // `err` bindings that may be in scope.
 
-#![feature(question_mark)]
-
 use std::num::ParseIntError;
 
 fn main() {
diff --git a/src/test/run-pass/try-operator.rs b/src/test/run-pass/try-operator.rs
index de5ccf09c59..29de6364bf1 100644
--- a/src/test/run-pass/try-operator.rs
+++ b/src/test/run-pass/try-operator.rs
@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(question_mark)]
-
 use std::fs::File;
 use std::io::{Read, self};
 use std::num::ParseIntError;
diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index b81258bd6d7..81478c18d7b 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -13,7 +13,6 @@
 #![feature(box_syntax)]
 #![feature(rustc_private)]
 #![feature(test)]
-#![feature(question_mark)]
 #![feature(libc)]
 
 #![deny(warnings)]
diff --git a/src/tools/error_index_generator/main.rs b/src/tools/error_index_generator/main.rs
index 2c734c8e3e4..7bdf1343aa9 100644
--- a/src/tools/error_index_generator/main.rs
+++ b/src/tools/error_index_generator/main.rs
@@ -9,7 +9,6 @@
 // except according to those terms.
 
 #![feature(rustc_private, rustdoc)]
-#![feature(question_mark)]
 
 extern crate syntax;
 extern crate rustdoc;
diff --git a/src/tools/linkchecker/main.rs b/src/tools/linkchecker/main.rs
index 3e2bc9032a1..f79cc76e67d 100644
--- a/src/tools/linkchecker/main.rs
+++ b/src/tools/linkchecker/main.rs
@@ -24,8 +24,6 @@
 //! A few whitelisted exceptions are allowed as there's known bugs in rustdoc,
 //! but this should catch the majority of "broken link" cases.
 
-#![feature(question_mark)]
-
 extern crate url;
 
 use std::env;
diff --git a/src/tools/rustbook/main.rs b/src/tools/rustbook/main.rs
index 436dc119753..906251db1c2 100644
--- a/src/tools/rustbook/main.rs
+++ b/src/tools/rustbook/main.rs
@@ -12,7 +12,6 @@
 
 #![feature(rustc_private)]
 #![feature(rustdoc)]
-#![feature(question_mark)]
 
 extern crate rustdoc;
 extern crate rustc_back;