&&&&&&&&&&&&&&str

While adding a failing test to the Rust compiler, I stumbled upon a peculiar code generation test : pub fn thirteen_ref ( input: &&&&&&&&&&&&& str ) -> String { // CHECK-NOT: {{(call|invoke)}}{{.*}}@{{.*}}core{{.*}}fmt{{.*}} input . to_string () } // This is a known performance cliff because of the macro-generated // specialized impl. If this test suddenly starts failing, // consider removing the…