[FRAME] Warn on unchecked weight witness (#1818)

Adds a warning to FRAME pallets when a function argument that starts
with `_` is used in the weight formula.
This is in most cases an error since the weight witness needs to be
checked.

Example:

```rust
#[pallet::call_index(0)]
#[pallet::weight(T::SystemWeightInfo::remark(_remark.len() as u32))]
pub fn remark(_origin: OriginFor<T>, _remark: Vec<u8>) -> DispatchResultWithPostInfo {
	Ok(().into())
}
```

Produces this warning:

```pre
warning: use of deprecated constant `pallet::warnings::UncheckedWeightWitness_0::_w`: 
                 It is deprecated to not check weight witness data.
                 Please instead ensure that all witness data for weight calculation is checked before usage.
         
                 For more info see:
                     <https://github.com/paritytech/polkadot-sdk/pull/1818>
   --> substrate/frame/system/src/lib.rs:424:40
    |
424 |         pub fn remark(_origin: OriginFor<T>, _remark: Vec<u8>) -> DispatchResultWithPostInfo {
    |                                              ^^^^^^^
    |
    = note: `#[warn(deprecated)]` on by default
```

Can be suppressed like this, since in this case it is legit:

```rust
#[pallet::call_index(0)]
#[pallet::weight(T::SystemWeightInfo::remark(remark.len() as u32))]
pub fn remark(_origin: OriginFor<T>, remark: Vec<u8>) -> DispatchResultWithPostInfo {
	let _ = remark; // We dont need to check the weight witness.
	Ok(().into())
}
```

Changes:
- Add warning on uncheded weight witness
- Respect `subkeys` limit in `System::kill_prefix`
- Fix HRMP pallet and other warnings
- Update`proc_macro_warning` dependency
- Delete random folder `substrate/src/src` 🙈 
- Adding Prdoc

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com>

substrate/frame/support/procedural/src/construct_runtime/mod.rs

@@ -414,7 +414,7 @@ fn construct_runtime_final_expansion(
 				)
 				.help_links(&["https://github.com/paritytech/substrate/pull/14437"])
 				.span(where_section.span)
-				.build(),
+				.build_or_panic(),
 		)
 	});
 

substrate/frame/support/procedural/src/pallet/expand/call.rs

@@ -17,12 +17,14 @@
 
 use crate::{
 	pallet::{
+		expand::warnings::{weight_constant_warning, weight_witness_warning},
 		parse::call::{CallVariantDef, CallWeightDef},
 		Def,
 	},
 	COUNTER,
 };
 use proc_macro2::TokenStream as TokenStream2;
+use proc_macro_warning::Warning;
 use quote::{quote, ToTokens};
 use syn::spanned::Spanned;
 
@@ -68,7 +70,7 @@ pub fn expand_call(def: &mut Def) -> proc_macro2::TokenStream {
 			continue
 		}
 
-		let warning = proc_macro_warning::Warning::new_deprecated("ImplicitCallIndex")
+		let warning = Warning::new_deprecated("ImplicitCallIndex")
 			.index(call_index_warnings.len())
 			.old("use implicit call indices")
 			.new("ensure that all calls have a `pallet::call_index` attribute or put the pallet into `dev` mode")
@@ -77,7 +79,7 @@ pub fn expand_call(def: &mut Def) -> proc_macro2::TokenStream {
 				"https://github.com/paritytech/substrate/pull/11381"
 			])
 			.span(method.name.span())
-			.build();
+			.build_or_panic();
 		call_index_warnings.push(warning);
 	}
 
@@ -86,18 +88,12 @@ pub fn expand_call(def: &mut Def) -> proc_macro2::TokenStream {
 	for method in &methods {
 		match &method.weight {
 			CallWeightDef::DevModeDefault => fn_weight.push(syn::parse_quote!(0)),
-			CallWeightDef::Immediate(e @ syn::Expr::Lit(lit)) if !def.dev_mode => {
-				let warning = proc_macro_warning::Warning::new_deprecated("ConstantWeight")
-					.index(weight_warnings.len())
-					.old("use hard-coded constant as call weight")
-					.new("benchmark all calls or put the pallet into `dev` mode")
-					.help_link("https://github.com/paritytech/substrate/pull/13798")
-					.span(lit.span())
-					.build();
-				weight_warnings.push(warning);
+			CallWeightDef::Immediate(e) => {
+				weight_constant_warning(e, def.dev_mode, &mut weight_warnings);
+				weight_witness_warning(method, def.dev_mode, &mut weight_warnings);
+
 				fn_weight.push(e.into_token_stream());
 			},
-			CallWeightDef::Immediate(e) => fn_weight.push(e.into_token_stream()),
 			CallWeightDef::Inherited => {
 				let pallet_weight = def
 					.call

substrate/frame/support/procedural/src/pallet/expand/mod.rs

@@ -34,6 +34,7 @@ mod store_trait;
 mod tt_default_parts;
 mod type_value;
 mod validate_unsigned;
+mod warnings;
 
 use crate::pallet::Def;
 use quote::ToTokens;

substrate/frame/support/procedural/src/pallet/expand/warnings.rs

@@ -0,0 +1,102 @@
+// This file is part of Substrate.
+
+// Copyright (C) Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Generates warnings for undesirable pallet code.
+
+use crate::pallet::parse::call::{CallVariantDef, CallWeightDef};
+use proc_macro_warning::Warning;
+use syn::{
+	spanned::Spanned,
+	visit::{self, Visit},
+};
+
+/// Warn if any of the call arguments starts with a underscore and is used in a weight formula.
+pub(crate) fn weight_witness_warning(
+	method: &CallVariantDef,
+	dev_mode: bool,
+	warnings: &mut Vec<Warning>,
+) {
+	if dev_mode {
+		return
+	}
+	let CallWeightDef::Immediate(w) = &method.weight else {
+		return;
+	};
+
+	let partial_warning = Warning::new_deprecated("UncheckedWeightWitness")
+		.old("not check weight witness data")
+		.new("ensure that all witness data for weight calculation is checked before usage")
+		.help_link("https://github.com/paritytech/polkadot-sdk/pull/1818");
+
+	for (_, arg_ident, _) in method.args.iter() {
+		if !arg_ident.to_string().starts_with('_') || !contains_ident(w.clone(), &arg_ident) {
+			continue
+		}
+
+		let warning = partial_warning
+			.clone()
+			.index(warnings.len())
+			.span(arg_ident.span())
+			.build_or_panic();
+
+		warnings.push(warning);
+	}
+}
+
+/// Warn if the weight is a constant and the pallet not in `dev_mode`.
+pub(crate) fn weight_constant_warning(
+	weight: &syn::Expr,
+	dev_mode: bool,
+	warnings: &mut Vec<Warning>,
+) {
+	if dev_mode {
+		return
+	}
+	let syn::Expr::Lit(lit) = weight else {
+		return;
+	};
+
+	let warning = Warning::new_deprecated("ConstantWeight")
+		.index(warnings.len())
+		.old("use hard-coded constant as call weight")
+		.new("benchmark all calls or put the pallet into `dev` mode")
+		.help_link("https://github.com/paritytech/substrate/pull/13798")
+		.span(lit.span())
+		.build_or_panic();
+
+	warnings.push(warning);
+}
+
+/// Returns whether `expr` contains `ident`.
+fn contains_ident(mut expr: syn::Expr, ident: &syn::Ident) -> bool {
+	struct ContainsIdent {
+		ident: syn::Ident,
+		found: bool,
+	}
+
+	impl<'a> Visit<'a> for ContainsIdent {
+		fn visit_ident(&mut self, i: &syn::Ident) {
+			if *i == self.ident {
+				self.found = true;
+			}
+		}
+	}
+
+	let mut visitor = ContainsIdent { ident: ident.clone(), found: false };
+	visit::visit_expr(&mut visitor, &mut expr);
+	visitor.found
+}