Extract non-generic part of push_topic to reduce code size (#1026)

* Extract non-generic part of `push_topic`

* Move to inner fn

Author: ascjones

crates/env/src/engine/on_chain/impls.rs

@@ -149,19 +149,24 @@ where
     where
         T: scale::Encode,
     {
+        fn inner<E: Environment>(encoded: &mut [u8]) -> <E as Environment>::Hash {
+            let len_encoded = encoded.len();
+            let mut result = <E as Environment>::Hash::clear();
+            let len_result = result.as_ref().len();
+            if len_encoded <= len_result {
+                result.as_mut()[..len_encoded].copy_from_slice(encoded);
+            } else {
+                let mut hash_output = <Blake2x256 as HashOutput>::Type::default();
+                <Blake2x256 as CryptoHash>::hash(encoded, &mut hash_output);
+                let copy_len = core::cmp::min(hash_output.len(), len_result);
+                result.as_mut()[0..copy_len].copy_from_slice(&hash_output[0..copy_len]);
+            }
+            result
+        }
+
         let mut split = self.scoped_buffer.split();
         let encoded = split.take_encoded(topic_value);
-        let len_encoded = encoded.len();
-        let mut result = <E as Environment>::Hash::clear();
-        let len_result = result.as_ref().len();
-        if len_encoded <= len_result {
-            result.as_mut()[..len_encoded].copy_from_slice(encoded);
-        } else {
-            let mut hash_output = <Blake2x256 as HashOutput>::Type::default();
-            <Blake2x256 as CryptoHash>::hash(encoded, &mut hash_output);
-            let copy_len = core::cmp::min(hash_output.len(), len_result);
-            result.as_mut()[0..copy_len].copy_from_slice(&hash_output[0..copy_len]);
-        }
+        let result = inner::<E>(encoded);
         self.scoped_buffer.append_encoded(&result);
     }