Change:
<ins> //@ check-pass //@ normalize-stderr-test: "nightly|beta|1.[0-9][0-9].[0-9]" -> "$$CHANNEL" //! [struct@m!()]   //~ WARN: unmatched disambiguator `struct` and suffix `!()` //! [struct@m!{}] //! [struct@m![]] //! [struct@f()]    //~ WARN: unmatched disambiguator `struct` and suffix `()` //! [struct@m!]     //~ WARN: unmatched disambiguator `struct` and suffix `!` //! //! [enum@m!()]     //~ WARN: unmatched disambiguator `enum` and suffix `!()` //! [enum@m!{}] //! [enum@m![]] //! [enum@f()]      //~ WARN: unmatched disambiguator `enum` and suffix `()` //! [enum@m!]       //~ WARN: unmatched disambiguator `enum` and suffix `!` //! //! [trait@m!()]    //~ WARN: unmatched disambiguator `trait` and suffix `!()` //! [trait@m!{}] //! [trait@m![]] //! [trait@f()]     //~ WARN: unmatched disambiguator `trait` and suffix `()` //! [trait@m!]      //~ WARN: unmatched disambiguator `trait` and suffix `!` //! //! [module@m!()]   //~ WARN: unmatched disambiguator `module` and suffix `!()` //! [module@m!{}] //! [module@m![]] //! [module@f()]    //~ WARN: unmatched disambiguator `module` and suffix `()` //! [module@m!]     //~ WARN: unmatched disambiguator `module` and suffix `!` //! //! [mod@m!()]      //~ WARN: unmatched disambiguator `mod` and suffix `!()` //! [mod@m!{}] //! [mod@m![]] //! [mod@f()]       //~ WARN: unmatched disambiguator `mod` and suffix `()` //! [mod@m!]        //~ WARN: unmatched disambiguator `mod` and suffix `!` //! //! [const@m!()]    //~ WARN: unmatched disambiguator `const` and suffix `!()` //! [const@m!{}] //! [const@m![]] //! [const@f()]     //~ WARN: incompatible link kind for `f` //! [const@m!]      //~ WARN: unmatched disambiguator `const` and suffix `!` //! //! [constant@m!()]   //~ WARN: unmatched disambiguator `constant` and suffix `!()` //! [constant@m!{}] //! [constant@m![]] //! [constant@f()]    //~ WARN: incompatible link kind for `f` //! [constant@m!]     //~ WARN: unmatched disambiguator `constant` and suffix `!` //! //! [static@m!()]   //~ WARN: unmatched disambiguator `static` and suffix `!()` //! [static@m!{}] //! [static@m![]] //! [static@f()]    //~ WARN: incompatible link kind for `f` //! [static@m!]     //~ WARN: unmatched disambiguator `static` and suffix `!` //! //! [function@m!()]   //~ WARN: unmatched disambiguator `function` and suffix `!()` //! [function@m!{}] //! [function@m![]] //! [function@f()] //! [function@m!]     //~ WARN: unmatched disambiguator `function` and suffix `!` //! //! [fn@m!()]   //~ WARN: unmatched disambiguator `fn` and suffix `!()` //! [fn@m!{}] //! [fn@m![]] //! [fn@f()] //! [fn@m!]     //~ WARN: unmatched disambiguator `fn` and suffix `!` //! //! [method@m!()]   //~ WARN: unmatched disambiguator `method` and suffix `!()` //! [method@m!{}] //! [method@m![]] //! [method@f()] //! [method@m!]     //~ WARN: unmatched disambiguator `method` and suffix `!` //! //! [derive@m!()]   //~ WARN: incompatible link kind for `m` //! [derive@m!{}]   //~ WARN: incompatible link kind for `m` //! [derive@m![]] //! [derive@f()]    //~ WARN: unmatched disambiguator `derive` and suffix `()` //! [derive@m!]     //~ WARN: incompatible link kind for `m` //! //! [type@m!()]   //~ WARN: unmatched disambiguator `type` and suffix `!()` //! [type@m!{}] //! [type@m![]] //! [type@f()]    //~ WARN: unmatched disambiguator `type` and suffix `()` //! [type@m!]     //~ WARN: unmatched disambiguator `type` and suffix `!` //! //! [value@m!()]   //~ WARN: unmatched disambiguator `value` and suffix `!()` //! [value@m!{}] //! [value@m![]] //! [value@f()] //! [value@m!]     //~ WARN: unmatched disambiguator `value` and suffix `!` //! //! [macro@m!()] //! [macro@m!{}] //! [macro@m![]] //! [macro@f()]    //~ WARN: unmatched disambiguator `macro` and suffix `()` //! [macro@m!] //! //! [prim@m!()]   //~ WARN: unmatched disambiguator `prim` and suffix `!()` //! [prim@m!{}] //! [prim@m![]] //! [prim@f()]    //~ WARN: unmatched disambiguator `prim` and suffix `()` //! [prim@m!]     //~ WARN: unmatched disambiguator `prim` and suffix `!` //! //! [primitive@m!()]   //~ WARN: unmatched disambiguator `primitive` and suffix `!()` //! [primitive@m!{}] //! [primitive@m![]] //! [primitive@f()]    //~ WARN: unmatched disambiguator `primitive` and suffix `()` //! [primitive@m!]     //~ WARN: unmatched disambiguator `primitive` and suffix `!` #[macro_export] macro_rules! m { () => {}; } pub fn f() {} </ins>

Discussion:
<!-- If you're using the stable version of the compiler, you should also check if the bug also exists in the beta or nightly versions. --Occurs on stable + nightly : : i replaced backtrace with for readability since it's displayed without any flags: <!-- Include a backtrace in the code block by setting in your environment. E.g. . --<details<summary<strongBacktrace</strong</summary<p</p</details
The combination of course seems invalid, but the compiler shouldn't panic, right?
That was quick, thank you!