Implement #[pallet::composite_enum] (#13722)

* Implement #[pallet::hold_reason]

* Appease clippy

* cargo fmt

* Update test expectations

* Update test expectations

* Support composite_enum attribute instead

* Update test expectations

* Change hold_reason to composite_enum

* Add UI test for unsupported identifier when using composite_enum

* Fix comment

* Add documentation for pallet::composable_enum

* More docs

* cargo fmt

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

@@ -38,6 +38,10 @@ mod keyword {
 	syn::custom_keyword!(Origin);
 	syn::custom_keyword!(Inherent);
 	syn::custom_keyword!(ValidateUnsigned);
+	syn::custom_keyword!(FreezeReason);
+	syn::custom_keyword!(HoldReason);
+	syn::custom_keyword!(LockId);
+	syn::custom_keyword!(SlashReason);
 	syn::custom_keyword!(exclude_parts);
 	syn::custom_keyword!(use_parts);
 }
@@ -370,6 +374,10 @@ pub enum PalletPartKeyword {
 	Origin(keyword::Origin),
 	Inherent(keyword::Inherent),
 	ValidateUnsigned(keyword::ValidateUnsigned),
+	FreezeReason(keyword::FreezeReason),
+	HoldReason(keyword::HoldReason),
+	LockId(keyword::LockId),
+	SlashReason(keyword::SlashReason),
 }
 
 impl Parse for PalletPartKeyword {
@@ -392,6 +400,14 @@ impl Parse for PalletPartKeyword {
 			Ok(Self::Inherent(input.parse()?))
 		} else if lookahead.peek(keyword::ValidateUnsigned) {
 			Ok(Self::ValidateUnsigned(input.parse()?))
+		} else if lookahead.peek(keyword::FreezeReason) {
+			Ok(Self::FreezeReason(input.parse()?))
+		} else if lookahead.peek(keyword::HoldReason) {
+			Ok(Self::HoldReason(input.parse()?))
+		} else if lookahead.peek(keyword::LockId) {
+			Ok(Self::LockId(input.parse()?))
+		} else if lookahead.peek(keyword::SlashReason) {
+			Ok(Self::SlashReason(input.parse()?))
 		} else {
 			Err(lookahead.error())
 		}
@@ -410,6 +426,10 @@ impl PalletPartKeyword {
 			Self::Origin(_) => "Origin",
 			Self::Inherent(_) => "Inherent",
 			Self::ValidateUnsigned(_) => "ValidateUnsigned",
+			Self::FreezeReason(_) => "FreezeReason",
+			Self::HoldReason(_) => "HoldReason",
+			Self::LockId(_) => "LockId",
+			Self::SlashReason(_) => "SlashReason",
 		}
 	}
 
@@ -435,6 +455,10 @@ impl Spanned for PalletPartKeyword {
 			Self::Origin(inner) => inner.span(),
 			Self::Inherent(inner) => inner.span(),
 			Self::ValidateUnsigned(inner) => inner.span(),
+			Self::FreezeReason(inner) => inner.span(),
+			Self::HoldReason(inner) => inner.span(),
+			Self::LockId(inner) => inner.span(),
+			Self::SlashReason(inner) => inner.span(),
 		}
 	}
 }