Simplify deposit_event declaration in decl_module (#3506)

* simplify module deposit_event declaration

* fix

* bump version

* fix

* fix test

* fix doc

substrate/srml/support/test/tests/instance.rs

@@ -55,7 +55,7 @@ mod module1 {
 		{
 			fn offchain_worker() {}
 
-			fn deposit_event<T, I>() = default;
+			fn deposit_event() = default;
 
 			fn one(origin) {
 				system::ensure_root(origin)?;
@@ -132,7 +132,7 @@ mod module2 {
 		pub struct Module<T: Trait<I>, I: Instance=DefaultInstance> for enum Call where
 			origin: <T as system::Trait>::Origin
 		{
-			fn deposit_event<T, I>() = default;
+			fn deposit_event() = default;
 		}
 	}
 

substrate/srml/support/test/tests/reserved_keyword/on_initialize.stderr

@@ -38,7 +38,7 @@ error: Invalid call fn name: `offchain_worker`, name is reserved and doesn't mat
    |
    = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
 
-error: Invalid call fn name: `deposit_event`, name is reserved and doesn't match expected signature, please refer to `decl_module!` documentation to see the appropriate usage, or rename it to an unreserved keyword.
+error: `deposit_event` function is reserved and must follow the syntax: `$vis:vis fn deposit_event() = default;`
   --> $DIR/on_initialize.rs:30:1
    |
 30 | reserved!(on_finalize on_initialize on_finalise on_initialise offchain_worker deposit_event);

substrate/srml/support/test/tests/system.rs

@@ -12,8 +12,11 @@ pub trait Trait: 'static + Eq + Clone {
 
 srml_support::decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin {
-		pub fn deposit_event(_event: T::Event) {
-		}
+	}
+}
+
+impl<T: Trait> Module<T> {
+	pub fn deposit_event(_event: impl Into<T::Event>) {
 	}
 }
 
@@ -49,4 +52,4 @@ pub fn ensure_root<OuterOrigin, AccountId>(o: OuterOrigin) -> Result<(), &'stati
 	where OuterOrigin: Into<Result<RawOrigin<AccountId>, OuterOrigin>>
 {
 	o.into().map(|_| ()).map_err(|_| "bad origin: expected to be a root origin")
-}
+}