Add edition supporting C string literals to proc macro UI test

Author: novafacing

tests/ui/proc-macro/auxiliary/api/mod.rs

@@ -1,11 +1,11 @@
 // force-host
 // no-prefer-dynamic
+// edition: 2021
 
 #![crate_type = "proc-macro"]
 #![crate_name = "proc_macro_api_tests"]
 #![feature(proc_macro_span)]
 #![feature(proc_macro_byte_character)]
-#![feature(c_str_literals)]
 #![deny(dead_code)] // catch if a test function is never called
 
 extern crate proc_macro;

tests/ui/proc-macro/auxiliary/api/parse.rs

@@ -19,14 +19,8 @@ fn test_display_literal() {
         "10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.0",
     );
 
-    assert_eq!(
-        Literal::string("a \t ❤ ' \" \u{1}").to_string(),
-        "\"a \\t ❤ ' \\\" \\u{1}\"",
-    );
-    assert_eq!(
-        Literal::c_string(c"a \t ❤ ' \" \u{1}").to_string(),
-        "\"a \\t ❤ ' \\\" \\u{1}\"",
-    );
+    assert_eq!(Literal::string("a \t ❤ ' \" \u{1}").to_string(), "\"a \\t ❤ ' \\\" \\u{1}\"",);
+    assert_eq!(Literal::c_string(c"\'\"\x7f\u{7fff}").to_string(), r#"c"\'\"\x7f\xe7\xbf\xbf""#);
     assert_eq!(Literal::character('a').to_string(), "'a'");
     assert_eq!(Literal::character('\t').to_string(), "'\\t'");
     assert_eq!(Literal::character('❤').to_string(), "'❤'");

tests/ui/proc-macro/test.rs

@@ -1,5 +1,6 @@
 // check-pass
 // aux-build:api/mod.rs
+// edition: 2021
 
 //! This is for everything that *would* be a #[test] inside of libproc_macro,
 //! except for the fact that proc_macro objects are not capable of existing