Suppress unused variable warning for debug_print macros (#1258)

* Suppress unused variable error for debug_print macros

* Add explicit seperator

* Let's try to match expressions

crates/env/src/lib.rs

@@ -131,7 +131,7 @@ cfg_if::cfg_if! {
         /// `"pallet-contracts/unstable-interface"` feature to be enabled in the target runtime.
         #[macro_export]
         macro_rules! debug_print {
-            ($($arg:tt)*) => ($crate::debug_message(&$crate::format!($($arg)*)));
+            ($($arg:expr),*) => ($crate::debug_message(&$crate::format!($($arg),*)));
         }
 
         /// Appends a formatted string to the `debug_message` buffer, as per [`debug_print`] but
@@ -144,22 +144,32 @@ cfg_if::cfg_if! {
         #[macro_export]
         macro_rules! debug_println {
             () => ($crate::debug_print!("\n"));
-            ($($arg:tt)*) => (
-                $crate::debug_print!("{}\n", $crate::format!($($arg)*));
+            ($($arg:expr),*) => (
+                $crate::debug_print!("{}\n", $crate::format!($($arg),*));
             )
         }
     } else {
         #[macro_export]
         /// Debug messages disabled. Enable the `ink-debug` feature for contract debugging.
         macro_rules! debug_print {
-            ($($arg:tt)*) => ();
+            ($($arg:expr),*) =>
+            {
+                {
+                    let _ = || ($(&$arg),*);
+                }
+            };
         }
 
         #[macro_export]
         /// Debug messages disabled. Enable the `ink-debug` feature for contract debugging.
         macro_rules! debug_println {
-            () => ();
-            ($($arg:tt)*) => ();
+            () => {};
+            ($($arg:expr),*) =>
+            {
+                {
+                    let _ = || ($(&$arg),*);
+                }
+            };
         }
     }
 }