minor: Add more proc-macro tests for parsing negative literals

Author: Veykril

crates/proc-macro-srv/proc-macro-test/imp/src/lib.rs

@@ -31,12 +31,17 @@ pub fn fn_like_mk_literals(_args: TokenStream) -> TokenStream {
         TokenTree::from(Literal::byte_string(b"byte_string")),
         TokenTree::from(Literal::character('c')),
         TokenTree::from(Literal::string("string")),
+        TokenTree::from(Literal::c_string(c"cstring")),
         // as of 2022-07-21, there's no method on `Literal` to build a raw
         // string or a raw byte string
         TokenTree::from(Literal::f64_suffixed(3.14)),
+        TokenTree::from(Literal::f64_suffixed(-3.14)),
         TokenTree::from(Literal::f64_unsuffixed(3.14)),
+        TokenTree::from(Literal::f64_unsuffixed(-3.14)),
         TokenTree::from(Literal::i64_suffixed(123)),
+        TokenTree::from(Literal::i64_suffixed(-123)),
         TokenTree::from(Literal::i64_unsuffixed(123)),
+        TokenTree::from(Literal::i64_unsuffixed(-123)),
     ];
     TokenStream::from_iter(trees)
 }