Delete no_literal_from_str config for rustc older than 1.54

Author: dtolnay

build.rs

@@ -58,10 +58,6 @@ fn main() {
         println!("cargo:rustc-cfg=span_locations");
     }
 
-    if version.minor < 54 {
-        println!("cargo:rustc-cfg=no_literal_from_str");
-    }
-
     if version.minor < 55 {
         println!("cargo:rustc-cfg=no_group_open_close");
     }

src/wrapper.rs

@@ -888,21 +888,7 @@ impl FromStr for Literal {
 }
 
 fn compiler_literal_from_str(repr: &str) -> Result<proc_macro::Literal, LexError> {
-    #[cfg(not(no_literal_from_str))]
-    {
-        proc_macro::Literal::from_str(repr).map_err(LexError::Compiler)
-    }
-    #[cfg(no_literal_from_str)]
-    {
-        let tokens = proc_macro_parse(repr)?;
-        let mut iter = tokens.into_iter();
-        if let (Some(proc_macro::TokenTree::Literal(literal)), None) = (iter.next(), iter.next()) {
-            if literal.to_string().len() == repr.len() {
-                return Ok(literal);
-            }
-        }
-        Err(LexError::call_site())
-    }
+    proc_macro::Literal::from_str(repr).map_err(LexError::Compiler)
 }
 
 impl Display for Literal {