Migrate away from SimpleDispatchInfo (#5686)

* Migrate away from SimpleDispatchInfo

* Fix imports

* Better doc

* Update lib.rs

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/example/src/lib.rs

@@ -256,10 +256,7 @@
 use sp_std::marker::PhantomData;
 use frame_support::{
 	dispatch::DispatchResult, decl_module, decl_storage, decl_event,
-	weights::{
-		SimpleDispatchInfo, DispatchClass, ClassifyDispatch, WeighData, Weight, PaysFee,
-		MINIMUM_WEIGHT,
-	},
+	weights::{DispatchClass, ClassifyDispatch, WeighData, Weight, PaysFee, MINIMUM_WEIGHT},
 };
 use sp_std::prelude::*;
 use frame_system::{self as system, ensure_signed, ensure_root};
@@ -469,7 +466,7 @@ decl_module! {
 		// weight (a numeric representation of pure execution time and difficulty) of the
 		// transaction and the latter demonstrates the [`DispatchClass`] of the call. A higher
 		// weight means a larger transaction (less of which can be placed in a single block).
-		#[weight = SimpleDispatchInfo::FixedNormal(MINIMUM_WEIGHT)]
+		#[weight = MINIMUM_WEIGHT]
 		fn accumulate_dummy(origin, increase_by: T::Balance) -> DispatchResult {
 			// This is a public call, so we ensure that the origin is some signed account.
 			let _sender = ensure_signed(origin)?;
@@ -518,8 +515,7 @@ decl_module! {
 
 		// The signature could also look like: `fn on_initialize()`.
 		// This function could also very well have a weight annotation, similar to any other. The
-		// only difference being that if it is not annotated, the default is
-		// `SimpleDispatchInfo::zero()`, which resolves into no weight.
+		// only difference is that it mut be returned, not annotated.
 		fn on_initialize(_n: T::BlockNumber) -> Weight {
 			// Anything that needs to be done at the start of the block.
 			// We don't do anything here.