Add support for ext_terminate (#352)

* [core, lang] add support for ext_terminate

* [lang] apply rustfmt

Author: Robbepop

core/src/env/api.rs

@@ -395,6 +395,25 @@ pub fn restore_contract<T>(
     })
 }
 
+/// Terminates the existence of the currently executed smart contract.
+///
+/// This removes the calling account and transfers all remaining balance
+/// to the given beneficiary.
+///
+/// # Note
+///
+/// This function never returns. Either the termination was successful and the
+/// execution of the destroyed contract is halted. Or it failed during the termination
+/// which is considered fatal and results in a trap + rollback.
+pub fn terminate_contract<T>(beneficiary: T::AccountId) -> !
+where
+    T: EnvTypes,
+{
+    <EnvInstance as OnInstance>::on_instance(|instance| {
+        TypedEnv::terminate_contract::<T>(instance, beneficiary)
+    })
+}
+
 /// Transfers value from the contract to the destination account ID.
 ///
 /// # Note

core/src/env/backend.rs

@@ -234,6 +234,15 @@ pub trait TypedEnv: Env {
     ) where
         T: EnvTypes;
 
+    /// Terminates a smart contract.
+    ///
+    /// # Note
+    ///
+    /// For more details visit: [`ink_core::env::terminate_contract`]
+    fn terminate_contract<T>(&mut self, beneficiary: T::AccountId) -> !
+    where
+        T: EnvTypes;
+
     /// Transfers value from the contract to the destination account ID.
     ///
     /// # Note

core/src/env/engine/off_chain/impls.rs

@@ -249,6 +249,13 @@ impl TypedEnv for EnvInstance {
         unimplemented!("off-chain environment does not support contract instantiation")
     }
 
+    fn terminate_contract<T>(&mut self, _beneficiary: T::AccountId) -> !
+    where
+        T: EnvTypes,
+    {
+        unimplemented!("off-chain environment does not support contract termination")
+    }
+
     fn restore_contract<T>(
         &mut self,
         _account_id: T::AccountId,

core/src/env/engine/on_chain/ext.rs

@@ -77,6 +77,7 @@ mod sys {
             delta_ptr: u32,
             delta_count: u32,
         );
+        pub fn ext_terminate(beneficiary_ptr: u32, beneficiary_len: u32) -> !;
 
         pub fn ext_dispatch_call(call_ptr: u32, call_len: u32);
 
@@ -243,6 +244,10 @@ pub fn restore_to(
     }
 }
 
+pub fn terminate(beneficiary: &[u8]) -> ! {
+    unsafe { sys::ext_terminate(beneficiary.as_ptr() as u32, beneficiary.len() as u32) }
+}
+
 pub fn dispatch_call(call: &[u8]) {
     unsafe { sys::ext_dispatch_call(call.as_ptr() as u32, call.len() as u32) }
 }

core/src/env/engine/on_chain/impls.rs

@@ -330,6 +330,14 @@ impl TypedEnv for EnvInstance {
         ext::restore_to(account_id, code_hash, rent_allowance, filtered_keys);
     }
 
+    fn terminate_contract<T>(&mut self, beneficiary: T::AccountId) -> !
+    where
+        T: EnvTypes,
+    {
+        self.encode_into_buffer(beneficiary);
+        ext::terminate(&self.buffer[..]);
+    }
+
     fn transfer<T>(&mut self, destination: T::AccountId, value: T::Balance) -> Result<()>
     where
         T: EnvTypes,

lang/src/env_access.rs

@@ -263,6 +263,18 @@ where
         env::restore_contract::<T>(account_id, code_hash, rent_allowance, filtered_keys)
     }
 
+    /// Terminates the existence of a smart contract.
+    ///
+    /// # Note
+    ///
+    /// For more details visit: [`ink_core::env::terminate_contract`]
+    pub fn terminate_contract(self, beneficiary: T::AccountId) -> !
+    where
+        T: EnvTypes,
+    {
+        env::terminate_contract::<T>(beneficiary)
+    }
+
     /// Transfers value from the contract to the destination account ID.
     ///
     /// # Note