Generalize async_idents to all new keywords

This commit generalizes the existing `async_idents` lint to easily encompass
other identifiers that will be keywords in future editions. The new lint is
called `keyword_idents` and the old `async_idents` lint is registered as renamed
to this new lint.

As a proof of concept the `try` keyword was added to this list as it looks to be
listed as a keyword in the 2018 edition only. The `await` keyword was not added
as it's not listed as a keyword yet.

Closes #53077

src/test/ui/editions/auxiliary/edition-kw-macro-2015.rs

@@ -10,7 +10,7 @@
 
 // edition:2015
 
-#![allow(async_idents)]
+#![allow(keyword_idents)]
 
 #[macro_export]
 macro_rules! produces_async {

src/test/ui/editions/auxiliary/edition-kw-macro-2018.rs

@@ -10,7 +10,7 @@
 
 // edition:2018
 
-#![allow(async_idents)]
+#![allow(keyword_idents)]
 
 #[macro_export]
 macro_rules! produces_async {

src/test/ui/editions/edition-keywords-2015-2015-expansion.rs

@@ -12,7 +12,7 @@
 // aux-build:edition-kw-macro-2015.rs
 // compile-pass
 
-#![allow(async_idents)]
+#![allow(keyword_idents)]
 
 #[macro_use]
 extern crate edition_kw_macro_2015;

src/test/ui/editions/edition-keywords-2018-2015-expansion.rs

@@ -12,7 +12,7 @@
 // aux-build:edition-kw-macro-2015.rs
 // compile-pass
 
-#![allow(async_idents)]
+#![allow(keyword_idents)]
 
 #[macro_use]
 extern crate edition_kw_macro_2015;

src/test/ui/rust-2018/async-ident-allowed.stderr

@@ -9,7 +9,7 @@ note: lint level defined here
    |
 LL | #![deny(rust_2018_compatibility)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^
-   = note: #[deny(async_idents)] implied by #[deny(rust_2018_compatibility)]
+   = note: #[deny(keyword_idents)] implied by #[deny(rust_2018_compatibility)]
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
    = note: for more information, see issue #49716 <https://github.com/rust-lang/rust/issues/49716>
 

src/test/ui/rust-2018/async-ident.fixed

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 #![allow(dead_code, unused_variables, non_camel_case_types, non_upper_case_globals)]
-#![deny(async_idents)]
+#![deny(keyword_idents)]
 
 // edition:2015
 // run-rustfix

src/test/ui/rust-2018/async-ident.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 #![allow(dead_code, unused_variables, non_camel_case_types, non_upper_case_globals)]
-#![deny(async_idents)]
+#![deny(keyword_idents)]
 
 // edition:2015
 // run-rustfix

src/test/ui/rust-2018/async-ident.stderr

@@ -7,8 +7,8 @@ LL | fn async() {} //~ ERROR async
 note: lint level defined here
   --> $DIR/async-ident.rs:12:9
    |
-LL | #![deny(async_idents)]
-   |         ^^^^^^^^^^^^
+LL | #![deny(keyword_idents)]
+   |         ^^^^^^^^^^^^^^
    = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
    = note: for more information, see issue #49716 <https://github.com/rust-lang/rust/issues/49716>
 

src/test/ui/rust-2018/try-ident.fixed

@@ -0,0 +1,21 @@
+// 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.
+
+// run-rustfix
+// compile-pass
+
+#![warn(rust_2018_compatibility)]
+
+fn main() {
+    r#try();
+}
+
+fn r#try() {
+}

src/test/ui/rust-2018/try-ident.rs

@@ -0,0 +1,21 @@
+// 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.
+
+// run-rustfix
+// compile-pass
+
+#![warn(rust_2018_compatibility)]
+
+fn main() {
+    try();
+}
+
+fn try() {
+}

src/test/ui/rust-2018/try-ident.stderr

@@ -0,0 +1,24 @@
+warning: `try` is a keyword in the 2018 edition
+  --> $DIR/try-ident.rs:17:5
+   |
+LL |     try();
+   |     ^^^ help: you can use a raw identifier to stay compatible: `r#try`
+   |
+note: lint level defined here
+  --> $DIR/try-ident.rs:14:9
+   |
+LL | #![warn(rust_2018_compatibility)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^
+   = note: #[warn(keyword_idents)] implied by #[warn(rust_2018_compatibility)]
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
+   = note: for more information, see issue #49716 <https://github.com/rust-lang/rust/issues/49716>
+
+warning: `try` is a keyword in the 2018 edition
+  --> $DIR/try-ident.rs:20:4
+   |
+LL | fn try() {
+   |    ^^^ help: you can use a raw identifier to stay compatible: `r#try`
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
+   = note: for more information, see issue #49716 <https://github.com/rust-lang/rust/issues/49716>
+