Stabilize termination_trait

This stabilizes `main` with non-() return types; see rust-lang#48453.

Author: tmandry

src/librustc_typeck/check/mod.rs

@@ -1106,25 +1106,22 @@ fn check_fn<'a, 'gcx, 'tcx>(inherited: &'a Inherited<'a, 'gcx, 'tcx>,
     }
     fcx.demand_suptype(span, ret_ty, actual_return_ty);
 
-    if fcx.tcx.features().termination_trait {
-        // If the termination trait language item is activated, check that the main return type
-        // implements the termination trait.
-        if let Some(term_id) = fcx.tcx.lang_items().termination() {
-            if let Some((id, _)) = *fcx.tcx.sess.entry_fn.borrow() {
-                if id == fn_id {
-                    match fcx.sess().entry_type.get() {
-                        Some(config::EntryMain) => {
-                            let substs = fcx.tcx.mk_substs(iter::once(Kind::from(ret_ty)));
-                            let trait_ref = ty::TraitRef::new(term_id, substs);
-                            let cause = traits::ObligationCause::new(
-                                span, fn_id, ObligationCauseCode::MainFunctionType);
-
-                            inherited.register_predicate(
-                                traits::Obligation::new(
-                                    cause, param_env, trait_ref.to_predicate()));
-                        },
-                        _ => {},
-                    }
+    // Check that the main return type implements the termination trait.
+    if let Some(term_id) = fcx.tcx.lang_items().termination() {
+        if let Some((id, _)) = *fcx.tcx.sess.entry_fn.borrow() {
+            if id == fn_id {
+                match fcx.sess().entry_type.get() {
+                    Some(config::EntryMain) => {
+                        let substs = fcx.tcx.mk_substs(iter::once(Kind::from(ret_ty)));
+                        let trait_ref = ty::TraitRef::new(term_id, substs);
+                        let cause = traits::ObligationCause::new(
+                            span, fn_id, ObligationCauseCode::MainFunctionType);
+
+                        inherited.register_predicate(
+                            traits::Obligation::new(
+                                cause, param_env, trait_ref.to_predicate()));
+                    },
+                    _ => {},
                 }
             }
         }

src/librustc_typeck/lib.rs

@@ -208,8 +208,7 @@ fn check_main_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
 
             let actual = tcx.fn_sig(main_def_id);
-            let expected_return_type = if tcx.lang_items().termination().is_some()
-                && tcx.features().termination_trait {
+            let expected_return_type = if tcx.lang_items().termination().is_some() {
                 // we take the return type of the given main function, the real check is done
                 // in `check_fn`
                 actual.output().skip_binder()

src/libstd/lib.rs

@@ -308,7 +308,6 @@
 #![feature(str_char)]
 #![feature(str_internals)]
 #![feature(str_utf16)]
-#![feature(termination_trait)]
 #![feature(test, rustc_private)]
 #![feature(thread_local)]
 #![feature(toowned_clone_into)]
@@ -325,6 +324,7 @@
 #![cfg_attr(test, feature(update_panic_count))]
 #![cfg_attr(windows, feature(used))]
 #![cfg_attr(stage0, feature(never_type))]
+#![cfg_attr(stage0, feature(termination_trait))]
 
 #![default_lib_allocator]
 

src/libsyntax/feature_gate.rs

@@ -429,9 +429,6 @@ declare_features! (
     // `foo.rs` as an alternative to `foo/mod.rs`
     (active, non_modrs_mods, "1.24.0", Some(44660), None),
 
-    // Termination trait in main (RFC 1937)
-    (active, termination_trait, "1.24.0", Some(43301), None),
-
     // Termination trait in tests (RFC 1937)
     (active, termination_trait_test, "1.24.0", Some(48854), None),
 
@@ -558,6 +555,8 @@ declare_features! (
     (accepted, inclusive_range_syntax, "1.26.0", Some(28237), None),
     // allow `..=` in patterns (RFC 1192)
     (accepted, dotdoteq_in_patterns, "1.26.0", Some(28237), None),
+    // Termination trait in main (RFC 1937)
+    (accepted, termination_trait, "1.26.0", Some(43301), None),
 );
 
 // If you change this, please modify src/doc/unstable-book as well. You must

src/test/compile-fail/feature-gate-termination_trait.rs renamed to src/test/compile-fail/rfc-1937-termination-trait/termination-trait-main-i32.rs

@@ -8,6 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn main() -> i32 { //~ ERROR main function has wrong type [E0580]
+fn main() -> i32 {
+//~^ ERROR the trait bound `i32: std::process::Termination` is not satisfied [E0277]
     0
 }

src/test/compile-fail/rfc-1937-termination-trait/termination-trait-main-wrong-type.rs

@@ -7,7 +7,6 @@
 // <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(termination_trait)]
 
 fn main() -> char {
 //~^ ERROR: the trait bound `char: std::process::Termination` is not satisfied

src/test/compile-fail/rfc-1937-termination-trait/termination-trait-not-satisfied.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
-
 struct ReturnType {}
 
 fn main() -> ReturnType { //~ ERROR `ReturnType: std::process::Termination` is not satisfied

src/test/run-fail/rfc-1937-termination-trait/termination-trait-for-never.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
-
 // error-pattern:oh, dear
 
 fn main() -> ! {

src/test/run-fail/rfc-1937-termination-trait/termination-trait-for-result-box-error_err.rs

@@ -11,8 +11,6 @@
 // must-compile-successfully
 // failure-status: 1
 
-#![feature(termination_trait)]
-
 use std::io::{Error, ErrorKind};
 
 fn main() -> Result<(), Box<Error>> {

src/test/run-pass/rfc-1937-termination-trait/termination-trait-for-empty.rs

@@ -8,6 +8,4 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
-
 fn main() {}

src/test/run-pass/rfc-1937-termination-trait/termination-trait-for-exitcode.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
 #![feature(process_exitcode_placeholder)]
 
 use std::process::ExitCode;

src/test/run-pass/rfc-1937-termination-trait/termination-trait-for-result-box-error_ok.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
-
 use std::io::Error;
 
 fn main() -> Result<(), Box<Error>> {

src/test/run-pass/rfc-1937-termination-trait/termination-trait-for-result.rs

@@ -8,8 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(termination_trait)]
-
 use std::io::Error;
 
 fn main() -> Result<(), Error> {