Allow pallet error enum variants to contain fields (#10242)

* Allow pallet errors to contain at most one field

* Update docs on pallet::error

* Reword documentation

* cargo fmt

* Introduce CompactPalletError trait and require #[pallet::error] fields to implement them

* cargo fmt

* Do not assume tuple variants

* Add CompactPalletError derive macro

* Check for error type compactness in construct_runtime

* cargo fmt

* Derive CompactPalletError instead of implementing it directly during macro expansion

* Implement CompactPalletError on OptionBool instead of Option<bool>

* Check for type idents instead of variant ident

* Add doc comments for ErrorCompactnessTest

* Add an trait implementation of ErrorCompactnessTest for ()

* Convert the error field of DispatchError to a 4-element byte array

* Add static check for pallet error size

* Rename to MAX_PALLET_ERROR_ENCODED_SIZE

* Remove ErrorCompactnessTest trait

* Remove check_compactness

* Return only the most significant byte when constructing a custom InvalidTransaction

* Rename CompactPalletError to PalletError

* Use counter to generate unique idents for assert macros

* Make declarative pallet macros compile with pallet error size checks

* Remove unused doc comment

* Try and fix build errors

* Fix build errors

* Add macro_use for some test modules

* Test fix

* Fix compilation errors

* Remove unneeded #[macro_use]

* Resolve import ambiguity

* Make path to pallet Error enum more specific

* Fix test expectation

* Disambiguate imports

* Fix test expectations

* Revert appending pallet module name to path

* Rename bags_list::list::Error to BagError

* Fixes

* Fixes

* Fixes

* Fix test expectations

* Fix test expectation

* Add more implementations for PalletError

* Lift the 1-field requirement for nested pallet errors

* Fix UI test expectation

* Remove PalletError impl for OptionBool

* Use saturating operations

* cargo fmt

* Delete obsolete test

* Fix test expectation

* Try and use assert macro in const context

* Pull out the pallet error size check macro

* Fix UI test for const assertion

* cargo fmt

* Apply clippy suggestion

* Fix doc comment

* Docs for create_tt_return_macro

* Ensure TryInto is imported in earlier Rust editions

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* Fix up comments and names

* Implement PalletError for Never

* cargo fmt

* Don't compile example code

* Bump API version for block builder

* Factor in codec attributes while derving PalletError

* Rename module and fix unit test

* Add missing attribute

* Check API version and convert ApplyExtrinsicResult accordingly

* Rename BagError to ListError

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

* Use codec crate re-exported from frame support

* Add links to types mentioned in doc comments

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* cargo fmt

* cargo fmt

* Re-add attribute for hidden docs

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>
Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

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

@@ -241,6 +241,7 @@ fn construct_runtime_final_expansion(
 		expand::expand_outer_inherent(&name, &block, &unchecked_extrinsic, &pallets, &scrate);
 	let validate_unsigned = expand::expand_outer_validate_unsigned(&name, &pallets, &scrate);
 	let integrity_test = decl_integrity_test(&scrate);
+	let static_assertions = decl_static_assertions(&name, &pallets, &scrate);
 
 	let res = quote!(
 		#scrate_decl
@@ -282,6 +283,8 @@ fn construct_runtime_final_expansion(
 		#validate_unsigned
 
 		#integrity_test
+
+		#static_assertions
 	);
 
 	Ok(res)
@@ -471,3 +474,34 @@ fn decl_integrity_test(scrate: &TokenStream2) -> TokenStream2 {
 		}
 	)
 }
+
+fn decl_static_assertions(
+	runtime: &Ident,
+	pallet_decls: &[Pallet],
+	scrate: &TokenStream2,
+) -> TokenStream2 {
+	let error_encoded_size_check = pallet_decls.iter().map(|decl| {
+		let path = &decl.path;
+		let assert_message = format!(
+			"The maximum encoded size of the error type in the `{}` pallet exceeds \
+			`MAX_MODULE_ERROR_ENCODED_SIZE`",
+			decl.name,
+		);
+
+		quote! {
+			#scrate::tt_call! {
+				macro = [{ #path::tt_error_token }]
+				frame_support = [{ #scrate }]
+				~~> #scrate::assert_error_encoded_size! {
+					path = [{ #path }]
+					runtime = [{ #runtime }]
+					assert_message = [{ #assert_message }]
+				}
+			}
+		}
+	});
+
+	quote! {
+		#(#error_encoded_size_check)*
+	}
+}

substrate/frame/support/procedural/src/lib.rs

@@ -28,9 +28,11 @@ mod dummy_part_checker;
 mod key_prefix;
 mod match_and_insert;
 mod pallet;
+mod pallet_error;
 mod partial_eq_no_bound;
 mod storage;
 mod transactional;
+mod tt_macro;
 
 use proc_macro::TokenStream;
 use std::{cell::RefCell, str::FromStr};
@@ -41,9 +43,9 @@ thread_local! {
 	static COUNTER: RefCell<Counter> = RefCell::new(Counter(0));
 }
 
-/// Counter to generate a relatively unique identifier for macros querying for the existence of
-/// pallet parts. This is necessary because declarative macros gets hoisted to the crate root,
-/// which shares the namespace with other pallets containing the very same query macros.
+/// Counter to generate a relatively unique identifier for macros. This is necessary because
+/// declarative macros gets hoisted to the crate root, which shares the namespace with other pallets
+/// containing the very same macros.
 struct Counter(u64);
 
 impl Counter {
@@ -562,3 +564,14 @@ pub fn __generate_dummy_part_checker(input: TokenStream) -> TokenStream {
 pub fn match_and_insert(input: TokenStream) -> TokenStream {
 	match_and_insert::match_and_insert(input)
 }
+
+#[proc_macro_derive(PalletError, attributes(codec))]
+pub fn derive_pallet_error(input: TokenStream) -> TokenStream {
+	pallet_error::derive_pallet_error(input)
+}
+
+/// Internal macro used by `frame_support` to create tt-call-compliant macros
+#[proc_macro]
+pub fn __create_tt_macro(input: TokenStream) -> TokenStream {
+	tt_macro::create_tt_return_macro(input)
+}

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

@@ -15,20 +15,48 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::pallet::Def;
+use crate::{
+	pallet::{parse::error::VariantField, Def},
+	COUNTER,
+};
 use frame_support_procedural_tools::get_doc_literals;
+use syn::spanned::Spanned;
 
 ///
 /// * impl various trait on Error
 pub fn expand_error(def: &mut Def) -> proc_macro2::TokenStream {
-	let error = if let Some(error) = &def.error { error } else { return Default::default() };
+	let count = COUNTER.with(|counter| counter.borrow_mut().inc());
+	let error_token_unique_id =
+		syn::Ident::new(&format!("__tt_error_token_{}", count), def.item.span());
 
-	let error_ident = &error.error;
 	let frame_support = &def.frame_support;
 	let frame_system = &def.frame_system;
+	let config_where_clause = &def.config.where_clause;
+
+	let error = if let Some(error) = &def.error {
+		error
+	} else {
+		return quote::quote! {
+			#[macro_export]
+			#[doc(hidden)]
+			macro_rules! #error_token_unique_id {
+				{
+					$caller:tt
+					frame_support = [{ $($frame_support:ident)::* }]
+				} => {
+					$($frame_support::)*tt_return! {
+						$caller
+					}
+				};
+			}
+
+			pub use #error_token_unique_id as tt_error_token;
+		}
+	};
+
+	let error_ident = &error.error;
 	let type_impl_gen = &def.type_impl_generics(error.attr_span);
 	let type_use_gen = &def.type_use_generics(error.attr_span);
-	let config_where_clause = &def.config.where_clause;
 
 	let phantom_variant: syn::Variant = syn::parse_quote!(
 		#[doc(hidden)]
@@ -39,13 +67,19 @@ pub fn expand_error(def: &mut Def) -> proc_macro2::TokenStream {
 		)
 	);
 
-	let as_u8_matches = error.variants.iter().enumerate().map(
-		|(i, (variant, _))| quote::quote_spanned!(error.attr_span => Self::#variant => #i as u8,),
-	);
-
-	let as_str_matches = error.variants.iter().map(|(variant, _)| {
-		let variant_str = format!("{}", variant);
-		quote::quote_spanned!(error.attr_span => Self::#variant => #variant_str,)
+	let as_str_matches = error.variants.iter().map(|(variant, field_ty, _)| {
+		let variant_str = variant.to_string();
+		match field_ty {
+			Some(VariantField { is_named: true }) => {
+				quote::quote_spanned!(error.attr_span => Self::#variant { .. } => #variant_str,)
+			},
+			Some(VariantField { is_named: false }) => {
+				quote::quote_spanned!(error.attr_span => Self::#variant(..) => #variant_str,)
+			},
+			None => {
+				quote::quote_spanned!(error.attr_span => Self::#variant => #variant_str,)
+			},
+		}
 	});
 
 	let error_item = {
@@ -62,9 +96,14 @@ pub fn expand_error(def: &mut Def) -> proc_macro2::TokenStream {
 	let capture_docs = if cfg!(feature = "no-metadata-docs") { "never" } else { "always" };
 
 	// derive TypeInfo for error metadata
-	error_item
-		.attrs
-		.push(syn::parse_quote!( #[derive(#frame_support::scale_info::TypeInfo)] ));
+	error_item.attrs.push(syn::parse_quote! {
+		#[derive(
+			#frame_support::codec::Encode,
+			#frame_support::codec::Decode,
+			#frame_support::scale_info::TypeInfo,
+			#frame_support::PalletError,
+		)]
+	});
 	error_item.attrs.push(syn::parse_quote!(
 		#[scale_info(skip_type_params(#type_use_gen), capture_docs = #capture_docs)]
 	));
@@ -90,14 +129,6 @@ pub fn expand_error(def: &mut Def) -> proc_macro2::TokenStream {
 		}
 
 		impl<#type_impl_gen> #error_ident<#type_use_gen> #config_where_clause {
-			#[doc(hidden)]
-			pub fn as_u8(&self) -> u8 {
-				match &self {
-					Self::__Ignore(_, _) => unreachable!("`__Ignore` can never be constructed"),
-					#( #as_u8_matches )*
-				}
-			}
-
 			#[doc(hidden)]
 			pub fn as_str(&self) -> &'static str {
 				match &self {
@@ -120,18 +151,37 @@ pub fn expand_error(def: &mut Def) -> proc_macro2::TokenStream {
 			#config_where_clause
 		{
 			fn from(err: #error_ident<#type_use_gen>) -> Self {
+				use #frame_support::codec::Encode;
 				let index = <
 					<T as #frame_system::Config>::PalletInfo
 					as #frame_support::traits::PalletInfo
 				>::index::<Pallet<#type_use_gen>>()
 					.expect("Every active module has an index in the runtime; qed") as u8;
+				let mut encoded = err.encode();
+				encoded.resize(#frame_support::MAX_MODULE_ERROR_ENCODED_SIZE, 0);
 
 				#frame_support::sp_runtime::DispatchError::Module(#frame_support::sp_runtime::ModuleError {
 					index,
-					error: err.as_u8(),
+					error: core::convert::TryInto::try_into(encoded).expect("encoded error is resized to be equal to the maximum encoded error size; qed"),
 					message: Some(err.as_str()),
 				})
 			}
 		}
+
+		#[macro_export]
+		#[doc(hidden)]
+		macro_rules! #error_token_unique_id {
+			{
+				$caller:tt
+				frame_support = [{ $($frame_support:ident)::* }]
+			} => {
+				$($frame_support::)*tt_return! {
+					$caller
+					error = [{ #error_ident }]
+				}
+			};
+		}
+
+		pub use #error_token_unique_id as tt_error_token;
 	)
 }

substrate/frame/support/procedural/src/pallet/parse/error.rs

@@ -18,20 +18,26 @@
 use super::helper;
 use frame_support_procedural_tools::get_doc_literals;
 use quote::ToTokens;
-use syn::spanned::Spanned;
+use syn::{spanned::Spanned, Fields};
 
 /// List of additional token to be used for parsing.
 mod keyword {
 	syn::custom_keyword!(Error);
 }
 
+/// Records information about the error enum variants.
+pub struct VariantField {
+	/// Whether or not the field is named, i.e. whether it is a tuple variant or struct variant.
+	pub is_named: bool,
+}
+
 /// This checks error declaration as a enum declaration with only variants without fields nor
 /// discriminant.
 pub struct ErrorDef {
 	/// The index of error item in pallet module.
 	pub index: usize,
-	/// Variants ident and doc literals (ordered as declaration order)
-	pub variants: Vec<(syn::Ident, Vec<syn::Lit>)>,
+	/// Variants ident, optional field and doc literals (ordered as declaration order)
+	pub variants: Vec<(syn::Ident, Option<VariantField>, Vec<syn::Lit>)>,
 	/// A set of usage of instance, must be check for consistency with trait.
 	pub instances: Vec<helper::InstanceUsage>,
 	/// The keyword error used (contains span).
@@ -70,18 +76,19 @@ impl ErrorDef {
 			.variants
 			.iter()
 			.map(|variant| {
-				if !matches!(variant.fields, syn::Fields::Unit) {
-					let msg = "Invalid pallet::error, unexpected fields, must be `Unit`";
-					return Err(syn::Error::new(variant.fields.span(), msg))
-				}
+				let field_ty = match &variant.fields {
+					Fields::Unit => None,
+					Fields::Named(_) => Some(VariantField { is_named: true }),
+					Fields::Unnamed(_) => Some(VariantField { is_named: false }),
+				};
 				if variant.discriminant.is_some() {
-					let msg = "Invalid pallet::error, unexpected discriminant, discriminant \
+					let msg = "Invalid pallet::error, unexpected discriminant, discriminants \
 						are not supported";
 					let span = variant.discriminant.as_ref().unwrap().0.span();
 					return Err(syn::Error::new(span, msg))
 				}
 
-				Ok((variant.ident.clone(), get_doc_literals(&variant.attrs)))
+				Ok((variant.ident.clone(), field_ty, get_doc_literals(&variant.attrs)))
 			})
 			.collect::<Result<_, _>>()?;
 

substrate/frame/support/procedural/src/pallet_error.rs

@@ -0,0 +1,197 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2021 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.
+
+use frame_support_procedural_tools::generate_crate_access_2018;
+use quote::ToTokens;
+use std::str::FromStr;
+
+// Derive `PalletError`
+pub fn derive_pallet_error(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+	let syn::DeriveInput { ident: name, generics, data, .. } = match syn::parse(input) {
+		Ok(input) => input,
+		Err(e) => return e.to_compile_error().into(),
+	};
+
+	let frame_support = match generate_crate_access_2018("frame-support") {
+		Ok(c) => c,
+		Err(e) => return e.into_compile_error().into(),
+	};
+	let frame_support = &frame_support;
+	let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
+
+	let max_encoded_size = match data {
+		syn::Data::Struct(syn::DataStruct { fields, .. }) => match fields {
+			syn::Fields::Named(syn::FieldsNamed { named: fields, .. }) |
+			syn::Fields::Unnamed(syn::FieldsUnnamed { unnamed: fields, .. }) => {
+				let maybe_field_tys = fields
+					.iter()
+					.map(|f| generate_field_types(f, &frame_support))
+					.collect::<syn::Result<Vec<_>>>();
+				let field_tys = match maybe_field_tys {
+					Ok(tys) => tys.into_iter().flatten(),
+					Err(e) => return e.into_compile_error().into(),
+				};
+				quote::quote! {
+					0_usize
+					#(
+						.saturating_add(<
+							#field_tys as #frame_support::traits::PalletError
+						>::MAX_ENCODED_SIZE)
+					)*
+				}
+			},
+			syn::Fields::Unit => quote::quote!(0),
+		},
+		syn::Data::Enum(syn::DataEnum { variants, .. }) => {
+			let field_tys = variants
+				.iter()
+				.map(|variant| generate_variant_field_types(variant, &frame_support))
+				.collect::<Result<Vec<Option<Vec<proc_macro2::TokenStream>>>, syn::Error>>();
+
+			let field_tys = match field_tys {
+				Ok(tys) => tys.into_iter().flatten().collect::<Vec<_>>(),
+				Err(e) => return e.to_compile_error().into(),
+			};
+
+			// We start with `1`, because the discriminant of an enum is stored as u8
+			if field_tys.is_empty() {
+				quote::quote!(1)
+			} else {
+				let variant_sizes = field_tys.into_iter().map(|variant_field_tys| {
+					quote::quote! {
+						1_usize
+						#(.saturating_add(<
+							#variant_field_tys as #frame_support::traits::PalletError
+						>::MAX_ENCODED_SIZE))*
+					}
+				});
+
+				quote::quote! {{
+					let mut size = 1_usize;
+					let mut tmp = 0_usize;
+					#(
+						tmp = #variant_sizes;
+						size = if tmp > size { tmp } else { size };
+						tmp = 0_usize;
+					)*
+					size
+				}}
+			}
+		},
+		syn::Data::Union(syn::DataUnion { union_token, .. }) => {
+			let msg = "Cannot derive `PalletError` for union; please implement it directly";
+			return syn::Error::new(union_token.span, msg).into_compile_error().into()
+		},
+	};
+
+	quote::quote!(
+		const _: () = {
+			impl #impl_generics #frame_support::traits::PalletError
+				for #name #ty_generics #where_clause
+			{
+				const MAX_ENCODED_SIZE: usize = #max_encoded_size;
+			}
+		};
+	)
+	.into()
+}
+
+fn generate_field_types(
+	field: &syn::Field,
+	scrate: &syn::Ident,
+) -> syn::Result<Option<proc_macro2::TokenStream>> {
+	let attrs = &field.attrs;
+
+	for attr in attrs {
+		if attr.path.is_ident("codec") {
+			match attr.parse_meta()? {
+				syn::Meta::List(ref meta_list) if meta_list.nested.len() == 1 => {
+					match meta_list
+						.nested
+						.first()
+						.expect("Just checked that there is one item; qed")
+					{
+						syn::NestedMeta::Meta(syn::Meta::Path(path))
+							if path.get_ident().map_or(false, |i| i == "skip") =>
+							return Ok(None),
+
+						syn::NestedMeta::Meta(syn::Meta::Path(path))
+							if path.get_ident().map_or(false, |i| i == "compact") =>
+						{
+							let field_ty = &field.ty;
+							return Ok(Some(quote::quote!(#scrate::codec::Compact<#field_ty>)))
+						},
+
+						syn::NestedMeta::Meta(syn::Meta::NameValue(syn::MetaNameValue {
+							path,
+							lit: syn::Lit::Str(lit_str),
+							..
+						})) if path.get_ident().map_or(false, |i| i == "encoded_as") => {
+							let ty = proc_macro2::TokenStream::from_str(&lit_str.value())?;
+							return Ok(Some(ty))
+						},
+
+						_ => (),
+					}
+				},
+				_ => (),
+			}
+		}
+	}
+
+	Ok(Some(field.ty.to_token_stream()))
+}
+
+fn generate_variant_field_types(
+	variant: &syn::Variant,
+	scrate: &syn::Ident,
+) -> syn::Result<Option<Vec<proc_macro2::TokenStream>>> {
+	let attrs = &variant.attrs;
+
+	for attr in attrs {
+		if attr.path.is_ident("codec") {
+			match attr.parse_meta()? {
+				syn::Meta::List(ref meta_list) if meta_list.nested.len() == 1 => {
+					match meta_list
+						.nested
+						.first()
+						.expect("Just checked that there is one item; qed")
+					{
+						syn::NestedMeta::Meta(syn::Meta::Path(path))
+							if path.get_ident().map_or(false, |i| i == "skip") =>
+							return Ok(None),
+
+						_ => (),
+					}
+				},
+				_ => (),
+			}
+		}
+	}
+
+	match &variant.fields {
+		syn::Fields::Named(syn::FieldsNamed { named: fields, .. }) |
+		syn::Fields::Unnamed(syn::FieldsUnnamed { unnamed: fields, .. }) => {
+			let field_tys = fields
+				.iter()
+				.map(|field| generate_field_types(field, scrate))
+				.collect::<syn::Result<Vec<_>>>()?;
+			Ok(Some(field_tys.into_iter().flatten().collect()))
+		},
+		syn::Fields::Unit => Ok(None),
+	}
+}

substrate/frame/support/procedural/src/tt_macro.rs

@@ -0,0 +1,110 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2022 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.
+
+//! Implementation of the `create_tt_return_macro` macro
+
+use crate::COUNTER;
+use frame_support_procedural_tools::generate_crate_access_2018;
+use proc_macro2::{Ident, TokenStream};
+use quote::format_ident;
+
+struct CreateTtReturnMacroDef {
+	name: Ident,
+	args: Vec<(Ident, TokenStream)>,
+}
+
+impl syn::parse::Parse for CreateTtReturnMacroDef {
+	fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
+		let name = input.parse()?;
+		let _ = input.parse::<syn::Token![,]>()?;
+
+		let mut args = Vec::new();
+		while !input.is_empty() {
+			let mut value;
+			let key: Ident = input.parse()?;
+			let _ = input.parse::<syn::Token![=]>()?;
+			let _: syn::token::Bracket = syn::bracketed!(value in input);
+			let _: syn::token::Brace = syn::braced!(value in value);
+			let value: TokenStream = value.parse()?;
+
+			args.push((key, value))
+		}
+
+		Ok(Self { name, args })
+	}
+}
+
+/// A proc macro that accepts a name and any number of key-value pairs, to be used to create a
+/// declarative macro that follows tt-call conventions and simply calls [`tt_call::tt_return`],
+/// accepting an optional `frame-support` argument and returning the key-value pairs that were
+/// supplied to the proc macro.
+///
+/// # Example
+/// ```ignore
+/// __create_tt_macro! {
+///     my_tt_macro,
+///     foo = [{ bar }]
+/// }
+///
+/// // Creates the following declarative macro:
+///
+/// macro_rules! my_tt_macro {
+///     {
+///         $caller:tt
+///         $(frame_support = [{ $($frame_support:ident)::* }])?
+///     } => {
+///         frame_support::tt_return! {
+///             $caller
+///             foo = [{ bar }]
+///         }
+///     }
+/// }
+/// ```
+pub fn create_tt_return_macro(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+	let CreateTtReturnMacroDef { name, args } =
+		syn::parse_macro_input!(input as CreateTtReturnMacroDef);
+
+	let frame_support = match generate_crate_access_2018("frame-support") {
+		Ok(i) => i,
+		Err(e) => return e.into_compile_error().into(),
+	};
+	let (keys, values): (Vec<_>, Vec<_>) = args.into_iter().unzip();
+	let count = COUNTER.with(|counter| counter.borrow_mut().inc());
+	let unique_name = format_ident!("{}_{}", name, count);
+
+	let decl_macro = quote::quote! {
+		#[macro_export]
+		#[doc(hidden)]
+		macro_rules! #unique_name {
+			{
+				$caller:tt
+				$(frame_support = [{ $($frame_support:ident)::* }])?
+			} => {
+				#frame_support::tt_return! {
+					$caller
+					#(
+						#keys = [{ #values }]
+					)*
+				}
+			}
+		}
+
+		pub use #unique_name as #name;
+	};
+
+	decl_macro.into()
+}