Fix type conversion related to as_u* (#2847)

* fix type conversion related to as_u*

* fix clippy

modules/evm-bridge/src/lib.rs

@@ -368,16 +368,20 @@ impl<T: Config> Pallet<T> {
 			Error::<T>::InvalidReturnValue
 		);
 
-		let offset = U256::from_big_endian(&output[0..32]);
-		let length = U256::from_big_endian(&output[offset.as_usize()..offset.as_usize() + 32]);
+		let offset = U256::from_big_endian(output.get(0..32).unwrap_or_default());
+		let offset: usize = offset.try_into().map_err(|_| Error::<T>::InvalidReturnValue)?;
+		let offset_end = offset.checked_add(32).ok_or(Error::<T>::InvalidReturnValue)?;
+		let length = U256::from_big_endian(output.get(offset..offset_end).unwrap_or_default());
+		let length: usize = length.try_into().map_err(|_| Error::<T>::InvalidReturnValue)?;
+		let length_end = offset_end.checked_add(length).ok_or(Error::<T>::InvalidReturnValue)?;
 		ensure!(
 			// output is 32-byte aligned. ensure total_length >= offset + string length + string data length.
-			output.len() >= offset.as_usize() + 32 + length.as_usize(),
+			output.len() >= length_end,
 			Error::<T>::InvalidReturnValue
 		);
 
 		let mut data = Vec::new();
-		data.extend_from_slice(&output[offset.as_usize() + 32..offset.as_usize() + 32 + length.as_usize()]);
+		data.extend_from_slice(output.get(offset_end..length_end).unwrap_or_default());
 
 		Ok(data.to_vec())
 	}

modules/evm/src/precompiles/modexp.rs

@@ -279,16 +279,20 @@ impl Precompile for IstanbulModexp {
 			});
 		}
 		let cost = ModexpPricer::cost(Self::DIVISOR, input);
+		let cost = TryInto::<u64>::try_into(cost).map_err(|_| PrecompileFailure::Error {
+			exit_status: ExitError::OutOfGas,
+		})?;
+
 		if let Some(target_gas) = target_gas {
-			if cost > U256::from(u64::MAX) || target_gas < cost.as_u64() {
+			if target_gas < cost {
 				return Err(PrecompileFailure::Error {
 					exit_status: ExitError::OutOfGas,
 				});
 			}
 		}
 
 		let output = Self::execute_modexp(input);
-		handle.record_cost(cost.as_u64())?;
+		handle.record_cost(cost)?;
 
 		Ok(PrecompileOutput {
 			exit_status: ExitSucceed::Returned,

modules/evm/src/runner/stack.rs

@@ -633,11 +633,11 @@ impl<'vicinity, 'config, T: Config> BackendT for SubstrateStackState<'vicinity,
 	}
 
 	fn block_hash(&self, number: U256) -> H256 {
-		if number > U256::from(u32::MAX) {
-			H256::default()
-		} else {
-			let number = BlockNumberFor::<T>::from(number.as_u32());
+		if let Ok(number) = TryInto::<u32>::try_into(number) {
+			let number = BlockNumberFor::<T>::from(number);
 			H256::from_slice(frame_system::Pallet::<T>::block_hash(number).as_ref())
+		} else {
+			H256::default()
 		}
 	}