Distinguish string literals from identifiers in custom syntax parser.

src/parser.rs

@@ -2461,7 +2461,7 @@ impl Engine {
         use crate::api::custom_syntax::markers::*;
 
         let mut settings = settings;
-        let mut inputs = StaticVec::<Expr>::new();
+        let mut inputs = StaticVec::new_const();
         let mut segments = StaticVec::new_const();
         let mut tokens = StaticVec::new_const();
 

src/tokenizer.rs

@@ -699,7 +699,7 @@ impl Token {
             FloatConstant(f) => f.to_string().into(),
             #[cfg(feature = "decimal")]
             DecimalConstant(d) => d.to_string().into(),
-            StringConstant(..) => "string".into(),
+            StringConstant(s) => format!("\"{s}\"").into(),
             InterpolatedString(..) => "string".into(),
             CharConstant(c) => c.to_string().into(),
             Identifier(s) => s.to_string().into(),