Auto merge of #47630 - canndrew:exhaustive-patterns, r=nikomatsakis

Stabilise feature(never_type). Introduce feature(exhaustive_patterns)

This stabilizes `!`, removing the feature gate as well as the old defaulting-to-`()` behavior. The pattern exhaustiveness checks which were covered by `feature(never_type)` have been moved behind a new `feature(exhaustive_patterns)` gate.

src/test/ui/associated-types-ICE-when-projecting-out-of-err.rs

@@ -31,5 +31,5 @@ trait Add<RHS=Self> {
 fn ice<A>(a: A) {
     let r = loop {};
     r = r + a;
-    //~^ ERROR the trait bound `(): Add<A>` is not satisfied
+    //~^ ERROR the trait bound `!: Add<A>` is not satisfied
 }

src/test/ui/associated-types-ICE-when-projecting-out-of-err.stderr

@@ -1,8 +1,8 @@
-error[E0277]: the trait bound `(): Add<A>` is not satisfied
+error[E0277]: the trait bound `!: Add<A>` is not satisfied
   --> $DIR/associated-types-ICE-when-projecting-out-of-err.rs:33:11
    |
 LL |     r = r + a;
-   |           ^ the trait `Add<A>` is not implemented for `()`
+   |           ^ the trait `Add<A>` is not implemented for `!`
 
 error: aborting due to previous error
 

src/test/ui/feature-gate-exhaustive-patterns.rs

@@ -0,0 +1,18 @@
+// Copyright 2018 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.
+
+fn foo() -> Result<u32, !> {
+    Ok(123)
+}
+
+fn main() {
+    let Ok(_x) = foo(); //~ ERROR refutable pattern in local binding
+}
+

src/test/ui/feature-gate-exhaustive-patterns.stderr

@@ -0,0 +1,9 @@
+error[E0005]: refutable pattern in local binding: `Err(_)` not covered
+  --> $DIR/feature-gate-exhaustive-patterns.rs:16:9
+   |
+LL |     let Ok(_x) = foo(); //~ ERROR refutable pattern in local binding
+   |         ^^^^^^ pattern `Err(_)` not covered
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0005`.

src/test/ui/feature-gate-never_type.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 that ! errors when used in illegal positions with feature(never_type) disabled
-
-trait Foo {
-    type Wub;
-}
-
-type Ma = (u32, !, i32); //~ ERROR type is experimental
-type Meeshka = Vec<!>; //~ ERROR type is experimental
-type Mow = &fn(!) -> !; //~ ERROR type is experimental
-type Skwoz = &mut !; //~ ERROR type is experimental
-
-impl Foo for Meeshka {
-    type Wub = !; //~ ERROR type is experimental
-}
-
-fn main() {
-}
-

src/test/ui/feature-gate-never_type.stderr

@@ -1,43 +0,0 @@
-error[E0658]: The `!` type is experimental (see issue #35121)
-  --> $DIR/feature-gate-never_type.rs:17:17
-   |
-LL | type Ma = (u32, !, i32); //~ ERROR type is experimental
-   |                 ^
-   |
-   = help: add #![feature(never_type)] to the crate attributes to enable
-
-error[E0658]: The `!` type is experimental (see issue #35121)
-  --> $DIR/feature-gate-never_type.rs:18:20
-   |
-LL | type Meeshka = Vec<!>; //~ ERROR type is experimental
-   |                    ^
-   |
-   = help: add #![feature(never_type)] to the crate attributes to enable
-
-error[E0658]: The `!` type is experimental (see issue #35121)
-  --> $DIR/feature-gate-never_type.rs:19:16
-   |
-LL | type Mow = &fn(!) -> !; //~ ERROR type is experimental
-   |                ^
-   |
-   = help: add #![feature(never_type)] to the crate attributes to enable
-
-error[E0658]: The `!` type is experimental (see issue #35121)
-  --> $DIR/feature-gate-never_type.rs:20:19
-   |
-LL | type Skwoz = &mut !; //~ ERROR type is experimental
-   |                   ^
-   |
-   = help: add #![feature(never_type)] to the crate attributes to enable
-
-error[E0658]: The `!` type is experimental (see issue #35121)
-  --> $DIR/feature-gate-never_type.rs:23:16
-   |
-LL |     type Wub = !; //~ ERROR type is experimental
-   |                ^
-   |
-   = help: add #![feature(never_type)] to the crate attributes to enable
-
-error: aborting due to 5 previous errors
-
-For more information about this error, try `rustc --explain E0658`.

src/test/ui/print_type_sizes/uninhabited.rs

@@ -11,7 +11,6 @@
 // compile-flags: -Z print-type-sizes
 // must-compile-successfully
 
-#![feature(never_type)]
 #![feature(start)]
 
 #[start]

src/test/ui/reachable/expr_add.rs

@@ -8,7 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-#![feature(never_type)]
 #![allow(unused_variables)]
 #![deny(unreachable_code)]
 

src/test/ui/reachable/expr_add.stderr

@@ -1,11 +1,11 @@
 error: unreachable expression
-  --> $DIR/expr_add.rs:27:13
+  --> $DIR/expr_add.rs:26:13
    |
 LL |     let x = Foo + return; //~ ERROR unreachable
    |             ^^^^^^^^^^^^
    |
 note: lint level defined here
-  --> $DIR/expr_add.rs:13:9
+  --> $DIR/expr_add.rs:12:9
    |
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_array.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {
@@ -21,7 +20,7 @@ fn a() {
 }
 
 fn b() {
-    // the `array is unreachable:
+    // the array is unreachable:
     let x: [usize; 2] = [22, return]; //~ ERROR unreachable
 }
 

src/test/ui/reachable/expr_array.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_array.rs:20:34
+  --> $DIR/expr_array.rs:19:34
    |
 LL |     let x: [usize; 2] = [return, 22]; //~ ERROR unreachable
    |                                  ^^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_array.rs:25:25
+  --> $DIR/expr_array.rs:24:25
    |
 LL |     let x: [usize; 2] = [22, return]; //~ ERROR unreachable
    |                         ^^^^^^^^^^^^

src/test/ui/reachable/expr_assign.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn foo() {
     // No error here.

src/test/ui/reachable/expr_assign.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_assign.rs:20:5
+  --> $DIR/expr_assign.rs:19:5
    |
 LL |     x = return; //~ ERROR unreachable
    |     ^^^^^^^^^^
@@ -11,13 +11,13 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_assign.rs:30:14
+  --> $DIR/expr_assign.rs:29:14
    |
 LL |         *p = return; //~ ERROR unreachable
    |              ^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_assign.rs:36:15
+  --> $DIR/expr_assign.rs:35:15
    |
 LL |     *{return; &mut i} = 22; //~ ERROR unreachable
    |               ^^^^^^

src/test/ui/reachable/expr_block.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn a() {
     // Here the tail expression is considered unreachable:

src/test/ui/reachable/expr_block.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_block.rs:21:9
+  --> $DIR/expr_block.rs:20:9
    |
 LL |         22 //~ ERROR unreachable
    |         ^^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable statement
-  --> $DIR/expr_block.rs:36:9
+  --> $DIR/expr_block.rs:35:9
    |
 LL |         println!("foo");
    |         ^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_call.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn foo(x: !, y: usize) { }
 

src/test/ui/reachable/expr_call.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_call.rs:23:17
+  --> $DIR/expr_call.rs:22:17
    |
 LL |     foo(return, 22); //~ ERROR unreachable
    |                 ^^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_call.rs:28:5
+  --> $DIR/expr_call.rs:27:5
    |
 LL |     bar(return); //~ ERROR unreachable
    |     ^^^^^^^^^^^

src/test/ui/reachable/expr_cast.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {

src/test/ui/reachable/expr_cast.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_cast.rs:20:13
+  --> $DIR/expr_cast.rs:19:13
    |
 LL |     let x = {return} as !; //~ ERROR unreachable
    |             ^^^^^^^^^^^^^

src/test/ui/reachable/expr_if.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn foo() {
     if {return} {

src/test/ui/reachable/expr_if.stderr

@@ -1,5 +1,5 @@
 error: unreachable statement
-  --> $DIR/expr_if.rs:38:5
+  --> $DIR/expr_if.rs:37:5
    |
 LL |     println!("But I am.");
    |     ^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_loop.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn a() {
     loop { return; }

src/test/ui/reachable/expr_loop.stderr

@@ -1,5 +1,5 @@
 error: unreachable statement
-  --> $DIR/expr_loop.rs:19:5
+  --> $DIR/expr_loop.rs:18:5
    |
 LL |     println!("I am dead.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^
@@ -12,7 +12,7 @@ LL | #![deny(unreachable_code)]
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
-  --> $DIR/expr_loop.rs:31:5
+  --> $DIR/expr_loop.rs:30:5
    |
 LL |     println!("I am dead.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^
@@ -20,7 +20,7 @@ LL |     println!("I am dead.");
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
-  --> $DIR/expr_loop.rs:41:5
+  --> $DIR/expr_loop.rs:40:5
    |
 LL |     println!("I am dead.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_match.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn a() {
     // The match is considered unreachable here, because the `return`

src/test/ui/reachable/expr_match.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_match.rs:20:5
+  --> $DIR/expr_match.rs:19:5
    |
 LL |     match {return} { } //~ ERROR unreachable
    |     ^^^^^^^^^^^^^^^^^^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable statement
-  --> $DIR/expr_match.rs:25:5
+  --> $DIR/expr_match.rs:24:5
    |
 LL |     println!("I am dead");
    |     ^^^^^^^^^^^^^^^^^^^^^^
@@ -19,7 +19,7 @@ LL |     println!("I am dead");
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
-  --> $DIR/expr_match.rs:35:5
+  --> $DIR/expr_match.rs:34:5
    |
 LL |     println!("I am dead");
    |     ^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_method.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 struct Foo;
 

src/test/ui/reachable/expr_method.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_method.rs:26:21
+  --> $DIR/expr_method.rs:25:21
    |
 LL |     Foo.foo(return, 22); //~ ERROR unreachable
    |                     ^^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_method.rs:31:5
+  --> $DIR/expr_method.rs:30:5
    |
 LL |     Foo.bar(return); //~ ERROR unreachable
    |     ^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_repeat.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {

src/test/ui/reachable/expr_repeat.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_repeat.rs:20:25
+  --> $DIR/expr_repeat.rs:19:25
    |
 LL |     let x: [usize; 2] = [return; 2]; //~ ERROR unreachable
    |                         ^^^^^^^^^^^

src/test/ui/reachable/expr_return.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {

src/test/ui/reachable/expr_return.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_return.rs:21:22
+  --> $DIR/expr_return.rs:20:22
    |
 LL |     let x = {return {return {return;}}}; //~ ERROR unreachable
    |                      ^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_struct.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 struct Foo {

src/test/ui/reachable/expr_struct.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_struct.rs:25:13
+  --> $DIR/expr_struct.rs:24:13
    |
 LL |     let x = Foo { a: 22, b: 33, ..return }; //~ ERROR unreachable
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -11,19 +11,19 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_struct.rs:30:33
+  --> $DIR/expr_struct.rs:29:33
    |
 LL |     let x = Foo { a: return, b: 33, ..return }; //~ ERROR unreachable
    |                                 ^^
 
 error: unreachable expression
-  --> $DIR/expr_struct.rs:35:39
+  --> $DIR/expr_struct.rs:34:39
    |
 LL |     let x = Foo { a: 22, b: return, ..return }; //~ ERROR unreachable
    |                                       ^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_struct.rs:40:13
+  --> $DIR/expr_struct.rs:39:13
    |
 LL |     let x = Foo { a: 22, b: return }; //~ ERROR unreachable
    |             ^^^^^^^^^^^^^^^^^^^^^^^^

src/test/ui/reachable/expr_tup.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {

src/test/ui/reachable/expr_tup.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_tup.rs:20:38
+  --> $DIR/expr_tup.rs:19:38
    |
 LL |     let x: (usize, usize) = (return, 2); //~ ERROR unreachable
    |                                      ^
@@ -11,7 +11,7 @@ LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
 error: unreachable expression
-  --> $DIR/expr_tup.rs:25:29
+  --> $DIR/expr_tup.rs:24:29
    |
 LL |     let x: (usize, usize) = (2, return); //~ ERROR unreachable
    |                             ^^^^^^^^^^^

src/test/ui/reachable/expr_type.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 #![feature(type_ascription)]
 
 fn a() {

src/test/ui/reachable/expr_type.stderr

@@ -1,5 +1,5 @@
 error: unreachable expression
-  --> $DIR/expr_type.rs:20:13
+  --> $DIR/expr_type.rs:19:13
    |
 LL |     let x = {return}: !; //~ ERROR unreachable
    |             ^^^^^^^^^^^

src/test/ui/reachable/expr_unary.rs

@@ -12,13 +12,9 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![deny(coerce_never)]
-#![feature(never_type)]
 
 fn foo() {
-    let x: ! = ! { return; 22 }; //~ ERROR unreachable
-    //~^ ERROR cannot coerce
-    //~| hard error
+    let x: ! = ! { return; }; //~ ERROR unreachable
     //~| ERROR cannot apply unary operator `!` to type `!`
 }
 

src/test/ui/reachable/expr_unary.stderr

@@ -1,8 +1,14 @@
-error: unreachable expression
-  --> $DIR/expr_unary.rs:19:28
+error[E0600]: cannot apply unary operator `!` to type `!`
+  --> $DIR/expr_unary.rs:17:16
    |
-LL |     let x: ! = ! { return; 22 }; //~ ERROR unreachable
-   |                            ^^
+LL |     let x: ! = ! { return; }; //~ ERROR unreachable
+   |                ^^^^^^^^^^^^^
+
+error: unreachable expression
+  --> $DIR/expr_unary.rs:17:16
+   |
+LL |     let x: ! = ! { return; }; //~ ERROR unreachable
+   |                ^^^^^^^^^^^^^
    |
 note: lint level defined here
   --> $DIR/expr_unary.rs:14:9
@@ -10,26 +16,6 @@ note: lint level defined here
 LL | #![deny(unreachable_code)]
    |         ^^^^^^^^^^^^^^^^
 
-error: cannot coerce `{integer}` to !
-  --> $DIR/expr_unary.rs:19:28
-   |
-LL |     let x: ! = ! { return; 22 }; //~ ERROR unreachable
-   |                            ^^
-   |
-note: lint level defined here
-  --> $DIR/expr_unary.rs:15:9
-   |
-LL | #![deny(coerce_never)]
-   |         ^^^^^^^^^^^^
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #46325 <https://github.com/rust-lang/rust/issues/46325>
-
-error[E0600]: cannot apply unary operator `!` to type `!`
-  --> $DIR/expr_unary.rs:19:16
-   |
-LL |     let x: ! = ! { return; 22 }; //~ ERROR unreachable
-   |                ^^^^^^^^^^^^^^^^
-
-error: aborting due to 3 previous errors
+error: aborting due to 2 previous errors
 
 For more information about this error, try `rustc --explain E0600`.

src/test/ui/reachable/expr_while.rs

@@ -12,7 +12,6 @@
 #![allow(unused_assignments)]
 #![allow(dead_code)]
 #![deny(unreachable_code)]
-#![feature(never_type)]
 
 fn foo() {
     while {return} {

src/test/ui/reachable/expr_while.stderr

@@ -1,5 +1,5 @@
 error: unreachable statement
-  --> $DIR/expr_while.rs:19:9
+  --> $DIR/expr_while.rs:18:9
    |
 LL |         println!("Hello, world!");
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -12,7 +12,7 @@ LL | #![deny(unreachable_code)]
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
-  --> $DIR/expr_while.rs:33:9
+  --> $DIR/expr_while.rs:32:9
    |
 LL |         println!("I am dead.");
    |         ^^^^^^^^^^^^^^^^^^^^^^^
@@ -20,7 +20,7 @@ LL |         println!("I am dead.");
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
 error: unreachable statement
-  --> $DIR/expr_while.rs:35:5
+  --> $DIR/expr_while.rs:34:5
    |
 LL |     println!("I am, too.");
    |     ^^^^^^^^^^^^^^^^^^^^^^^