Quote map property names.

src/packages/string_basic.rs

@@ -172,8 +172,7 @@ mod print_debug_functions {
             let len = map.len();
 
             map.iter_mut().enumerate().for_each(|(i, (k, v))| {
-                result.push_str(k);
-                result.push_str(": ");
+                result.push_str(&format!("{:?}: ", k));
                 result.push_str(&print_with_func(FUNC_TO_DEBUG, &ctx, v));
                 if i < len - 1 {
                     result.push_str(", ");

tests/print.rs

@@ -73,6 +73,6 @@ fn test_print_custom_type() -> Result<(), Box<EvalAltResult>> {
                 x.to_string()
             "#
         )?
-        .contains("e: hello: 42"));
+        .contains(r#""e": hello: 42"#));
     Ok(())
 }