Rollup merge of rust-lang#81645 - m-ou-se:panic-lint, r=estebank,flip1995

Add lint for `panic!(123)` which is not accepted in Rust 2021.

This extends the `panic_fmt` lint to warn for all cases where the first argument cannot be interpreted as a format string, as will happen in Rust 2021.

It suggests to add `"{}",` to format the message as a string. In the case of `std::panic!()`, it also suggests the recently stabilized
`std::panic::panic_any()` function as an alternative.

It renames the lint to `non_fmt_panic` to match the lint naming guidelines.

![image](https://user-images.githubusercontent.com/783247/106520928-675ea680-64d5-11eb-81f7-d8fa48b93a0b.png)

This is part of rust-lang#80162.

r? ```@estebank```

Author: m-ou-se

core/src/macros/panic.md

@@ -10,22 +10,23 @@ tests. `panic!` is closely tied with the `unwrap` method of both
 `panic!` when they are set to [`None`] or [`Err`] variants.
 
 This macro is used to inject panic into a Rust thread, causing the thread to
-panic entirely. Each thread's panic can be reaped as the [`Box`]`<`[`Any`]`>` type,
-and the single-argument form of the `panic!` macro will be the value which
-is transmitted.
+panic entirely. This macro panics with a string and uses the [`format!`] syntax
+for building the message.
+
+Each thread's panic can be reaped as the [`Box`]`<`[`Any`]`>` type,
+which contains either a `&str` or `String` for regular `panic!()` invocations.
+To panic with a value of another other type, [`panic_any`] can be used.
 
 [`Result`] enum is often a better solution for recovering from errors than
 using the `panic!` macro. This macro should be used to avoid proceeding using
 incorrect values, such as from external sources. Detailed information about
 error handling is found in the [book].
 
-The multi-argument form of this macro panics with a string and has the
-[`format!`] syntax for building a string.
-
 See also the macro [`compile_error!`], for raising errors during compilation.
 
 [ounwrap]: Option::unwrap
 [runwrap]: Result::unwrap
+[`panic_any`]: ../std/panic/fn.panic_any.html
 [`Box`]: ../std/boxed/struct.Box.html
 [`Any`]: crate::any::Any
 [`format!`]: ../std/macro.format.html
@@ -42,6 +43,6 @@ program with code `101`.
 # #![allow(unreachable_code)]
 panic!();
 panic!("this is a terrible mistake!");
-panic!(4); // panic with the value of 4 to be collected elsewhere
 panic!("this is a {} {message}", "fancy", message = "message");
+std::panic::panic_any(4); // panic with the value of 4 to be collected elsewhere
 ```

term/src/terminfo/parm/tests.rs

@@ -77,15 +77,15 @@ fn test_comparison_ops() {
     for &(op, bs) in v.iter() {
         let s = format!("%{{1}}%{{2}}%{}%d", op);
         let res = expand(s.as_bytes(), &[], &mut Variables::new());
-        assert!(res.is_ok(), res.unwrap_err());
+        assert!(res.is_ok(), "{}", res.unwrap_err());
         assert_eq!(res.unwrap(), vec![b'0' + bs[0]]);
         let s = format!("%{{1}}%{{1}}%{}%d", op);
         let res = expand(s.as_bytes(), &[], &mut Variables::new());
-        assert!(res.is_ok(), res.unwrap_err());
+        assert!(res.is_ok(), "{}", res.unwrap_err());
         assert_eq!(res.unwrap(), vec![b'0' + bs[1]]);
         let s = format!("%{{2}}%{{1}}%{}%d", op);
         let res = expand(s.as_bytes(), &[], &mut Variables::new());
-        assert!(res.is_ok(), res.unwrap_err());
+        assert!(res.is_ok(), "{}", res.unwrap_err());
         assert_eq!(res.unwrap(), vec![b'0' + bs[2]]);
     }
 }
@@ -95,13 +95,13 @@ fn test_conditionals() {
     let mut vars = Variables::new();
     let s = b"\\E[%?%p1%{8}%<%t3%p1%d%e%p1%{16}%<%t9%p1%{8}%-%d%e38;5;%p1%d%;m";
     let res = expand(s, &[Number(1)], &mut vars);
-    assert!(res.is_ok(), res.unwrap_err());
+    assert!(res.is_ok(), "{}", res.unwrap_err());
     assert_eq!(res.unwrap(), "\\E[31m".bytes().collect::<Vec<_>>());
     let res = expand(s, &[Number(8)], &mut vars);
-    assert!(res.is_ok(), res.unwrap_err());
+    assert!(res.is_ok(), "{}", res.unwrap_err());
     assert_eq!(res.unwrap(), "\\E[90m".bytes().collect::<Vec<_>>());
     let res = expand(s, &[Number(42)], &mut vars);
-    assert!(res.is_ok(), res.unwrap_err());
+    assert!(res.is_ok(), "{}", res.unwrap_err());
     assert_eq!(res.unwrap(), "\\E[38;5;42m".bytes().collect::<Vec<_>>());
 }
 

test/src/tests.rs

@@ -199,7 +199,7 @@ fn test_should_panic_bad_message() {
 fn test_should_panic_non_string_message_type() {
     use crate::tests::TrFailedMsg;
     fn f() {
-        panic!(1i32);
+        std::panic::panic_any(1i32);
     }
     let expected = "foobar";
     let failed_msg = format!(