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/example/src/lib.rs

@@ -510,8 +510,7 @@ mod tests {
 	// The testing primitives are very useful for avoiding having to work with signatures
 	// or public keys. `u64` is used as the `AccountId` and no `Signature`s are requried.
 	use sr_primitives::{
-		BuildStorage, traits::{BlakeTwo256, OnInitialize, OnFinalize, IdentityLookup},
-		testing::Header
+		traits::{BlakeTwo256, OnInitialize, OnFinalize, IdentityLookup}, testing::Header
 	};
 
 	impl_outer_origin! {
@@ -551,7 +550,7 @@ mod tests {
 	// This function basically just builds a genesis storage key/value store according to
 	// our desired mockup.
 	fn new_test_ext() -> sr_io::TestExternalities<Blake2Hasher> {
-		let mut t = system::GenesisConfig::<Test>::default().build_storage().unwrap().0;
+		let mut t = system::GenesisConfig::default().build_storage::<Test>().unwrap().0;
 		// We use default for brevity, but you can configure as desired if needed.
 		t.extend(balances::GenesisConfig::<Test>::default().build_storage().unwrap().0);
 		t.extend(GenesisConfig::<Test>{