Rollup merge of rust-lang#87267 - dtolnay:negspace, r=Aaron1011

Remove space after negative sign in Literal to_string

Negative proc macro literal tokens used to be printed with a space between the minus sign and the magnitude. That's because `impl ToString for Literal` used to convert the Literal into a TokenStream, which splits the minus sign into a separate Punct token.

```rust
Literal::isize_unsuffixed(-10).to_string()  // "- 10"
```

This PR updates the ToString impl to directly use `rustc_ast::token::Lit`'s ToString, which matches the way Rust negative numbers are idiomatically written without a space.

```rust
Literal::isize_unsuffixed(-10).to_string()  // "-10"
```

compiler/rustc_expand/src/proc_macro_server.rs

@@ -582,6 +582,9 @@ impl server::Literal for Rustc<'_> {
 
         Ok(Literal { lit, span: self.call_site })
     }
+    fn to_string(&mut self, literal: &Self::Literal) -> String {
+        literal.lit.to_string()
+    }
     fn debug_kind(&mut self, literal: &Self::Literal) -> String {
         format!("{:?}", literal.lit.kind)
     }

library/proc_macro/src/bridge/mod.rs

@@ -109,6 +109,7 @@ macro_rules! with_api {
                 fn drop($self: $S::Literal);
                 fn clone($self: &$S::Literal) -> $S::Literal;
                 fn from_str(s: &str) -> Result<$S::Literal, ()>;
+                fn to_string($self: &$S::Literal) -> String;
                 fn debug_kind($self: &$S::Literal) -> String;
                 fn symbol($self: &$S::Literal) -> String;
                 fn suffix($self: &$S::Literal) -> Option<String>;

library/proc_macro/src/lib.rs

@@ -1195,7 +1195,7 @@ impl FromStr for Literal {
 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
 impl ToString for Literal {
     fn to_string(&self) -> String {
-        TokenStream::from(TokenTree::from(self.clone())).to_string()
+        self.0.to_string()
     }
 }
 

src/test/ui/proc-macro/auxiliary/api/parse.rs

@@ -6,8 +6,8 @@ pub fn test() {
 }
 
 fn test_display_literal() {
-    assert_eq!(Literal::isize_unsuffixed(-10).to_string(), "- 10");
-    assert_eq!(Literal::isize_suffixed(-10).to_string(), "- 10isize");
+    assert_eq!(Literal::isize_unsuffixed(-10).to_string(), "-10");
+    assert_eq!(Literal::isize_suffixed(-10).to_string(), "-10isize");
 }
 
 fn test_parse_literal() {
@@ -18,7 +18,7 @@ fn test_parse_literal() {
     assert_eq!("b\"\"".parse::<Literal>().unwrap().to_string(), "b\"\"");
     assert_eq!("r##\"\"##".parse::<Literal>().unwrap().to_string(), "r##\"\"##");
     assert_eq!("10ulong".parse::<Literal>().unwrap().to_string(), "10ulong");
-    assert_eq!("-10ulong".parse::<Literal>().unwrap().to_string(), "- 10ulong");
+    assert_eq!("-10ulong".parse::<Literal>().unwrap().to_string(), "-10ulong");
 
     assert!("true".parse::<Literal>().is_err());
     assert!(".8".parse::<Literal>().is_err());