Don't require module name in inherents (#6576)

* Start

* Cleanup `construct_runtime!`

* Add tests

* Fix after merge

* Update the docs

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

@@ -279,18 +279,6 @@ impl ModulePartKeyword {
 		Ident::new(self.name(), self.span())
 	}
 
-	/// Returns `true` if this module part allows to have an argument.
-	///
-	/// For example `Inherent(Timestamp)`.
-	fn allows_arg(&self) -> bool {
-		Self::all_allow_arg().iter().any(|n| *n == self.name())
-	}
-
-	/// Returns the names of all module parts that allow to have an argument.
-	fn all_allow_arg() -> &'static [&'static str] {
-		&["Inherent"]
-	}
-
 	/// Returns `true` if this module part is allowed to have generic arguments.
 	fn allows_generic(&self) -> bool {
 		Self::all_generic_arg().iter().any(|n| *n == self.name())
@@ -321,7 +309,6 @@ impl Spanned for ModulePartKeyword {
 pub struct ModulePart {
 	pub keyword: ModulePartKeyword,
 	pub generics: syn::Generics,
-	pub args: Option<ext::Parens<ext::Punctuated<Ident, Token![,]>>>,
 }
 
 impl Parse for ModulePart {
@@ -339,27 +326,10 @@ impl Parse for ModulePart {
 			);
 			return Err(syn::Error::new(keyword.span(), msg));
 		}
-		let args = if input.peek(token::Paren) {
-			if !keyword.allows_arg() {
-				let syn::group::Parens { token: parens, .. } = syn::group::parse_parens(input)?;
-				let valid_names = ModulePart::format_names(ModulePartKeyword::all_allow_arg());
-				let msg = format!(
-					"`{}` is not allowed to have arguments in parens. \
-					 Only the following modules are allowed to have arguments in parens: {}.",
-					keyword.name(),
-					valid_names,
-				);
-				return Err(syn::Error::new(parens.span, msg));
-			}
-			Some(input.parse()?)
-		} else {
-			None
-		};
 
 		Ok(Self {
 			keyword,
 			generics,
-			args,
 		})
 	}
 }