Implement a proper generic resolution in decl_storage! (#2913)

* Add failing test case

* move storage maps to blake2_128 (#2268)

* remove default hash, introduce twox_128 and blake2

* use blake2_128 & create ext_blake2_128

* refactor code

* add benchmark

* factorize generator

* fix

* parameterizable hasher

* some fix

* fix

* fix

* fix

* metadata

* fix

* remove debug print

* map -> blake2_256

* fix test

* fix test

* Apply suggestions from code review

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* impl twox 128 concat (#2353)

* impl twox_128_concat

* comment addressed

* fix

* impl twox_128->64_concat

* fix test

* Fix compilation and cleanup some docs

* Lol

* Remove traits from storage types that are not generic

* Get instance test almost working as wanted

* Make `srml-support-test` compile again :)

* Fixes test of srml-support

* Fix compilation

* Break some lines

* Remove incorrect macro match arm

* Integrates review feedback

* Update documentation

* Fix compilation

substrate/srml/support/procedural/src/lib.rs

@@ -98,7 +98,7 @@ use proc_macro::TokenStream;
 ///
 /// Storage items are accessible in multiple ways:
 ///
-/// * The structure: `Foo::<T>`
+/// * The structure: `Foo` or `Foo::<T>` depending if the value type is generic or not.
 /// * The `Store` trait structure: `<Module<T> as Store>::Foo`
 /// * The getter on the module that calls get on the structure: `Module::<T>::foo()`
 ///
@@ -136,9 +136,9 @@ use proc_macro::TokenStream;
 /// trait Store for Module<T: Trait<I>, I: Instance=DefaultInstance> as Example {}
 /// ```
 ///
-/// Then the genesis config is generated with two generic parameters (i.e. `GenesisConfig<T, I>`)
-/// and storage items are accessible using two generic parameters, e.g.:
-/// `<Dummy<T, I>>::get()` or `Dummy::<T, I>::get()`.
+/// Accessing the structure no requires the instance as generic parameter:
+/// * `Foo::<I>` if the value type is not generic
+/// * `Foo::<T, I>` if the value type is generic
 #[proc_macro]
 pub fn decl_storage(input: TokenStream) -> TokenStream {
 	storage::transformation::decl_storage_impl(input)