Aggregate all liquidity restrictions in a single place (#1921)

* Clean up session key rotation

* Fix build

* Bump version

* Introduce feature to balances.

* Move staking locking logic over to central point

* ^^^ rest

* First part of assimilation

* More assimilation

* More assimilation

* Fix most tests

* Fix build

* Move Balances to new locking system

* :q!

* Bump runtime version

* Build runtime

* Convenience function

* Test fix.

* Whitespace

* Improve type legibility.

* Fix comment.

* More tests.

* More tests.

* Bump version

* Caps

* Whitespace

* Whitespace

* Remove unneeded function.

substrate/srml/contract/Cargo.toml

@@ -5,7 +5,7 @@ authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-serde = { version = "1.0", default-features = false }
+serde = { version = "1.0", optional = true }
 serde_derive = { version = "1.0", optional = true }
 pwasm-utils = { version = "0.6.1", default-features = false }
 parity-codec = { version = "3.1", default-features = false, features = ["derive"] }
@@ -30,7 +30,7 @@ consensus = { package = "srml-consensus", path = "../consensus" }
 [features]
 default = ["std"]
 std = [
-	"serde/std",
+	"serde",
 	"serde_derive",
 	"parity-codec/std",
 	"substrate-primitives/std",

substrate/srml/contract/src/exec.rs

@@ -20,8 +20,8 @@ use crate::gas::{GasMeter, Token, approx_gas_for_balance};
 
 use rstd::prelude::*;
 use runtime_primitives::traits::{CheckedAdd, CheckedSub, Zero};
+use srml_support::traits::WithdrawReason;
 use timestamp;
-use srml_support::traits::EnsureAccountLiquid;
 
 pub type BalanceOf<T> = <T as balances::Trait>::Balance;
 pub type AccountIdOf<T> = <T as system::Trait>::AccountId;
@@ -520,7 +520,7 @@ fn transfer<'a, T: Trait, V: Vm<T>, L: Loader<T>>(
 	if would_create && value < ctx.config.existential_deposit {
 		return Err("value too low to create account");
 	}
-	<T as balances::Trait>::EnsureAccountLiquid::ensure_account_liquid(transactor)?;
+	<balances::Module<T>>::ensure_account_can_withdraw(transactor, value, WithdrawReason::Transfer, new_from_balance)?;
 
 	let new_to_balance = match to_balance.checked_add(&value) {
 		Some(b) => b,

substrate/srml/contract/src/tests.rs

@@ -77,7 +77,6 @@ impl balances::Trait for Test {
 	type Balance = u64;
 	type OnFreeBalanceZero = Contract;
 	type OnNewAccount = ();
-	type EnsureAccountLiquid = ();
 	type Event = MetaEvent;
 }
 impl timestamp::Trait for Test {