Refactor decl storage (#3765)

* split implementation in multiple files:
  * transformation -> genesis_config/  getters.rs  instance_trait.rs  metadata.rs  mod.rs  store_trait.rs
  * mod.rs -> parser.rs
  * impl.rs -> storage_struct.rs
* parser is isolated into parse module, it could be improved as well but this can be done in another PR
* modules contains a defintion of decl_storage input which must be ok to work with.
* implementation change:
  * T: Trait might be more often bound to 'static (anyway we only use static one and it is needed for metadata current implementation).
  * GenesisConfig no longer requires its fields to be Clone (possible since to EncodeLike feature)
  * builder for map storages must return precise type Vec<(key, value)>

substrate/srml/support/procedural/tools/src/syn_ext.rs

@@ -184,13 +184,15 @@ impl<P: ToTokens> ToTokens for Opt<P> {
 	}
 }
 
-pub fn extract_type_option(typ: &syn::Type) -> Option<TokenStream> {
+pub fn extract_type_option(typ: &syn::Type) -> Option<syn::Type> {
 	if let syn::Type::Path(ref path) = typ {
 		let v = path.path.segments.last()?;
 		if v.value().ident == "Option" {
-			if let syn::PathArguments::AngleBracketed(ref a) = v.value().arguments {
-				let args = &a.args;
-				return Some(quote!{ #args })
+			// Option has only one type argument in angle bracket.
+			if let syn::PathArguments::AngleBracketed(a) = &v.value().arguments {
+				if let syn::GenericArgument::Type(typ) = a.args.last()?.value() {
+					return Some(typ.clone())
+				}
 			}
 		}
 	}
@@ -253,4 +255,4 @@ pub fn expr_contains_ident(expr: &syn::Expr, ident: &Ident) -> bool {
 
 	visit::visit_expr(&mut visit, expr);
 	visit.result
-}
+}