some bikeshedding

Signed-off-by: xermicus <cyrill@parity.io>

substrate/frame/revive/fixtures/contracts/return_data_api.rs

@@ -112,11 +112,11 @@ pub extern "C" fn deploy() {}
 pub extern "C" fn call() {
 	input!(code_hash: &[u8; 32],);
 
-	recursion_guard();
-
 	// we didn't do anything yet; return data size should be 0
 	assert_return_data_size_of(0);
 
+	recursion_guard();
+
 	let mut address_buf = [0; 20];
 	let construct_input = |exit_flag| {
 		let mut input = INPUT_DATA;

substrate/frame/revive/src/exec.rs

@@ -424,10 +424,10 @@ pub trait Ext: sealing::Sealed {
 	/// Check if running in read-only context.
 	fn is_read_only(&self) -> bool;
 
-	/// Returns an immutable reference to saved output of the last executed call frame.
+	/// Returns an immutable reference to the output of the last executed call frame.
 	fn last_frame_output(&self) -> &ExecReturnValue;
 
-	/// Returns a mutable reference to saved output of the last executed call frame.
+	/// Returns a mutable reference to the output of the last executed call frame.
 	fn last_frame_output_mut(&mut self) -> &mut ExecReturnValue;
 }
 
@@ -549,7 +549,7 @@ struct Frame<T: Config> {
 	read_only: bool,
 	/// The caller of the currently executing frame which was spawned by `delegate_call`.
 	delegate_caller: Option<Origin<T>>,
-	/// The output of the last call frame
+	/// The output of the last executed call frame. 
 	last_frame_output: ExecReturnValue,
 }
 
@@ -1274,10 +1274,10 @@ where
 		T::Currency::reducible_balance(who, Preservation::Preserve, Fortitude::Polite).into()
 	}
 
-	/// Replaces the last frame output with the default value, dropping it.
+	/// Replaces the `last_frame_output` of the **caller** frame with the default value.
 	fn take_caller_output(&mut self) {
 		let len = self.frames.len();
-		core::mem::take(match len {
+		mem::take(match len {
 			0 => return,
 			1 => &mut self.first_frame.last_frame_output,
 			_ => &mut self.frames.get_mut(len - 2).expect("len >= 2; qed").last_frame_output,

substrate/frame/revive/src/wasm/runtime.rs

@@ -28,7 +28,7 @@ use crate::{
 };
 use alloc::{boxed::Box, vec, vec::Vec};
 use codec::{Decode, DecodeLimit, Encode, MaxEncodedLen};
-use core::{fmt, marker::PhantomData};
+use core::{mem, fmt, marker::PhantomData};
 use frame_support::{
 	dispatch::DispatchInfo, ensure, pallet_prelude::DispatchResultWithPostInfo, parameter_types,
 	traits::Get, weights::Weight,
@@ -1026,7 +1026,7 @@ impl<'a, E: Ext, M: ?Sized + Memory<E::T>> Runtime<'a, E, M> {
 			},
 		};
 
-		let output = core::mem::take(self.ext.last_frame_output_mut());
+		let output = mem::take(self.ext.last_frame_output_mut());
 		match call_outcome {
 			// `TAIL_CALL` only matters on an `OK` result. Otherwise the call stack comes to
 			// a halt anyways without anymore code being executed.
@@ -1088,7 +1088,7 @@ impl<'a, E: Ext, M: ?Sized + Memory<E::T>> Runtime<'a, E, M> {
 			salt.as_ref(),
 		) {
 			Ok(address) => {
-				let output = core::mem::take(self.ext.last_frame_output_mut());
+				let output = mem::take(self.ext.last_frame_output_mut());
 				if !output.flags.contains(ReturnFlags::REVERT) {
 					self.write_fixed_sandbox_output(
 						memory,
@@ -1992,7 +1992,7 @@ pub mod env {
 		)?)
 	}
 
-	/// Stores data returned by the last call starting from `offset` into the supplied buffer.
+	/// Stores data returned by the last call, starting from `offset`, into the supplied buffer.
 	/// See [`pallet_revive_uapi::HostFn::return_data`].
 	#[api_version(0)]
 	fn return_data_copy(
@@ -2002,7 +2002,7 @@ pub mod env {
 		out_len_ptr: u32,
 		offset: u32,
 	) -> Result<(), TrapReason> {
-		let output = core::mem::take(self.ext.last_frame_output_mut());
+		let output = mem::take(self.ext.last_frame_output_mut());
 		if offset as usize > output.data.len() {
 			return Err(Error::<E::T>::OutOfBounds.into());
 		}