Validating u256->usize conversion

ethcore/src/evm/evm.rs

@@ -238,7 +238,7 @@ fn should_validate_u256_to_usize_conversion() {
 	let v = U256::from(::std::usize::MAX) + U256::from(1);
 
 	// when
-	let res = Gas::<usize>::from_u256(v);
+	let res = usize::from_u256(v);
 
 	// then
 	assert!(res.is_err());

ethcore/src/evm/interpreter/mod.rs

@@ -538,7 +538,7 @@ impl<Cost: CostType> Interpreter<Cost> {
 
 		if source_offset < source_size {
 			let output_begin = source_offset.low_u64() as usize;
-			self.mem.write_slice(dest_offset, &data[output_begin..output_end]);
+			self.mem.write_slice(dest_offset, &source[output_begin..output_end]);
 		}
 	}