Use Flush derives and generally update the Flush trait (#269)

* [core] add core/derive crate to add derive macro for Flush

* [core/derive] change license from GPL-3.0 to APACHE-2.0

* [core/derive] implement Flush and AllocateUsing derives based on synstructure

* [core] re-export AllocateUsing and Flush derives from within core

* [core/derive] fix AllocateUsing derive impl

* [core/derive] adjust AllocateUsing tests

* [core/derive] apply cargo fmt

* [core/derive] add test::utils and improve AllocateUsing tests

* [core/derive] add explanation docs

* [core/derive] add doc for a hack

* [core/derive] forbid deriving empty enums for Flush

* [core/derive] update compile tests

* [core] remove derive crate feature

* [core/derive] remove `extern crate ink_core` edition 2015 compat

* [core, examples, lang] update Flush impls

* [core] apply rustfmt

* [core] simplify Flush impl for StashHeader

* [core] remove derive crate feature

* [examples] fix clippy warning about Flush in delegator

core/Cargo.toml

@@ -18,7 +18,7 @@ include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 ink_abi = { path = "../abi/", default-features = false, features = ["derive"], optional = true }
 ink_alloc = { path = "../alloc/", default-features = false }
 ink_utils = { path = "../utils/" }
-ink_core_derive = { version = "0.1.0", path = "derive", default-features = false, optional = true }
+ink_core_derive = { version = "0.1.0", path = "derive", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "1.1", default-features = false, features = ["derive", "full"] }
 type-metadata = { git = "https://github.com/type-metadata/type-metadata.git", default-features = false, features = ["derive"], optional = true }
@@ -28,9 +28,6 @@ cfg-if = "0.1"
 
 [features]
 default = ["test-env"]
-derive = [
-    "ink_core_derive",
-]
 test-env = [
     "std",
 ]

core/derive/src/lib.rs

@@ -51,8 +51,6 @@ pub(crate) fn flush_derive(mut s: synstructure::Structure) -> TokenStream2 {
         quote! {}
     };
     s.gen_impl(quote! {
-        extern crate ink_core;
-
         gen impl ink_core::storage::Flush for @Self {
             fn flush(&mut self) {
                 #body
@@ -81,8 +79,6 @@ pub(crate) fn allocate_using_derive(mut s: synstructure::Structure) -> TokenStre
         }
     });
     s.gen_impl(quote! {
-        extern crate ink_core;
-
         gen impl ink_core::storage::alloc::AllocateUsing for @Self {
             unsafe fn allocate_using<A>(alloc: &mut A) -> Self
             where

core/src/env/srml/types.rs

@@ -12,21 +12,20 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+use crate::{
+    env::EnvTypes,
+    ink_core,
+    storage::Flush,
+};
 use core::{
     array::TryFromSliceError,
     convert::TryFrom,
 };
-
 use scale::{
     Decode,
     Encode,
 };
 
-use crate::{
-    env::EnvTypes,
-    storage::Flush,
-};
-
 #[cfg(feature = "ink-generate-abi")]
 use type_metadata::Metadata;
 
@@ -66,7 +65,7 @@ impl EnvTypes for DefaultSrmlTypes {
 }
 
 /// The default SRML address type.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encode, Decode)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encode, Decode, Flush)]
 #[cfg_attr(feature = "ink-generate-abi", derive(Metadata))]
 pub struct AccountId([u8; 32]);
 
@@ -89,7 +88,7 @@ impl<'a> TryFrom<&'a [u8]> for AccountId {
 pub type Balance = u128;
 
 /// The default SRML hash type.
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encode, Decode)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encode, Decode, Flush)]
 #[cfg_attr(feature = "ink-generate-abi", derive(Metadata))]
 pub struct Hash([u8; 32]);
 
@@ -119,11 +118,3 @@ pub type Moment = u64;
 
 /// The default SRML blocknumber type.
 pub type BlockNumber = u64;
-
-impl Flush for AccountId {
-    fn flush(&mut self) {}
-}
-
-impl Flush for Hash {
-    fn flush(&mut self) {}
-}

core/src/env2/env_access/immutable.rs

@@ -122,10 +122,7 @@ impl<E> AllocateUsing for EnvAccess<E> {
     }
 }
 
-impl<E> Flush for EnvAccess<E> {
-    #[inline(always)]
-    fn flush(&mut self) {}
-}
+impl<E> Flush for EnvAccess<E> {}
 
 impl<E> Initialize for EnvAccess<E> {
     type Args = ();

core/src/env2/env_access/mutable.rs

@@ -74,10 +74,7 @@ impl<E> AllocateUsing for EnvAccessMut<E> {
     }
 }
 
-impl<E> Flush for EnvAccessMut<E> {
-    #[inline]
-    fn flush(&mut self) {}
-}
+impl<E> Flush for EnvAccessMut<E> {}
 
 impl<E> Initialize for EnvAccessMut<E> {
     type Args = ();

core/src/env2/types.rs

@@ -119,10 +119,7 @@ impl<'a> TryFrom<&'a [u8]> for AccountId {
     }
 }
 
-impl Flush for AccountId {
-    #[inline]
-    fn flush(&mut self) {}
-}
+impl Flush for AccountId {}
 
 /// The default SRML `Hash` type.
 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Encode, Decode, From, Default)]
@@ -138,7 +135,4 @@ impl<'a> TryFrom<&'a [u8]> for Hash {
     }
 }
 
-impl Flush for Hash {
-    #[inline]
-    fn flush(&mut self) {}
-}
+impl Flush for Hash {}

core/src/lib.rs

@@ -58,3 +58,6 @@ pub mod env;
 pub mod env2;
 pub mod memory;
 pub mod storage;
+
+// Needed for derive macros of `core/derive` sub crate.
+pub(crate) use crate as ink_core;

core/src/storage/alloc/mod.rs

@@ -32,5 +32,4 @@ pub use self::{
     },
 };
 
-#[cfg(feature = "derive")]
 pub use ink_core_derive::AllocateUsing;

core/src/storage/collections/bitvec/block.rs

@@ -30,9 +30,7 @@ pub struct BitBlock {
     packs: [BitPack; Self::PACKS as usize],
 }
 
-impl Flush for BitBlock {
-    fn flush(&mut self) {}
-}
+impl Flush for BitBlock {}
 
 /// Error indicating an invalid bit pack index.
 #[derive(Debug, Copy, Clone)]

core/src/storage/collections/stash/impls.rs

@@ -26,16 +26,19 @@ use scale::{
 #[cfg(feature = "ink-generate-abi")]
 use type_metadata::Metadata;
 
-use crate::storage::{
-    self,
-    alloc::{
-        Allocate,
-        AllocateUsing,
-        Initialize,
+use crate::{
+    ink_core,
+    storage::{
+        self,
+        alloc::{
+            Allocate,
+            AllocateUsing,
+            Initialize,
+        },
+        chunk::SyncChunk,
+        Flush,
+        Key,
     },
-    chunk::SyncChunk,
-    Flush,
-    Key,
 };
 
 /// A stash collection.
@@ -91,14 +94,8 @@ struct StashHeader {
     max_len: u32,
 }
 
-impl Flush for StashHeader {
-    #[inline]
-    fn flush(&mut self) {
-        self.next_vacant.flush();
-        self.len.flush();
-        self.max_len.flush();
-    }
-}
+/// No need to forward flush to fields.
+impl ink_core::storage::Flush for StashHeader {}
 
 /// Iterator over the values of a stash.
 #[derive(Debug)]

core/src/storage/flush.rs

@@ -37,20 +37,18 @@ pub trait Flush {
     /// Needs to take `self` by `&mut` since `SyncChunk` and `SyncCell`
     /// and potentially other abstraction facilities are required to
     /// write back their cached values which is a mutable operation.
-    fn flush(&mut self);
+    #[inline(always)]
+    fn flush(&mut self) {}
 }
 
-#[cfg(feature = "derive")]
 pub use ink_core_derive::Flush;
 
 macro_rules! impl_empty_flush_for {
-	( $($ty:ty),* ) => {
-		$(
-			impl Flush for $ty {
-				fn flush(&mut self) {}
-			}
-		)*
-	};
+    ( $($ty:ty),* ) => {
+        $(
+            impl Flush for $ty {}
+        )*
+    };
 }
 
 impl_empty_flush_for! {
@@ -60,20 +58,20 @@ impl_empty_flush_for! {
 }
 
 macro_rules! impl_tuple_flush_for {
-	( $(($n:tt, $name:ident)),* ) => {
-		impl< $($name),* > Flush for ($($name,)*)
-		where
-			$(
-				$name: Flush,
-			)*
-		{
-			fn flush(&mut self) {
-				$(
-					self.$n.flush();
-				)*
-			}
-		}
-	}
+    ( $(($n:tt, $name:ident)),* ) => {
+        impl< $($name),* > Flush for ($($name,)*)
+        where
+            $(
+                $name: Flush,
+            )*
+        {
+            fn flush(&mut self) {
+                $(
+                    self.$n.flush();
+                )*
+            }
+        }
+    }
 }
 
 impl_tuple_flush_for!();
@@ -167,11 +165,7 @@ where
     }
 }
 
-impl Flush for crate::memory::string::String {
-    fn flush(&mut self) {
-        // Note: Strings contain only characters that need no flushing.
-    }
-}
+impl Flush for crate::memory::string::String {}
 
 impl<K, V> Flush for crate::memory::collections::btree_map::BTreeMap<K, V>
 where
@@ -185,11 +179,7 @@ where
     }
 }
 
-impl<T> Flush for crate::memory::collections::btree_set::BTreeSet<T> {
-    fn flush(&mut self) {
-        // Note: Values within a `BTreeSet` are immutable and thus need not be flushed.
-    }
-}
+impl<T> Flush for crate::memory::collections::btree_set::BTreeSet<T> {}
 
 impl<T> Flush for crate::memory::collections::linked_list::LinkedList<T>
 where
@@ -213,11 +203,4 @@ where
     }
 }
 
-impl<T> Flush for crate::memory::collections::binary_heap::BinaryHeap<T>
-where
-    T: Flush,
-{
-    fn flush(&mut self) {
-        // Note: Values within a `BinaryHeap` are immutable and thus need not be flushed.
-    }
-}
+impl<T> Flush for crate::memory::collections::binary_heap::BinaryHeap<T> {}

examples/lang/delegator/src/lib.rs

@@ -27,9 +27,7 @@ pub enum Which {
     Subber,
 }
 
-impl ink_core::storage::Flush for Which {
-    fn flush(&mut self) {}
-}
+impl ink_core::storage::Flush for Which {}
 
 contract! {
     #![env = ink_core::env::DefaultSrmlTypes]

examples/lang/shared_vec/src/lib.rs

@@ -29,9 +29,7 @@ pub struct Access {
     pub end: Option<u32>,
 }
 
-impl Flush for Access {
-	fn flush(&mut self) {}
-}
+impl Flush for Access {}
 
 impl Access {
     /// Creates unlimited access rights.

examples/lang2/delegator/lib.rs

@@ -15,7 +15,10 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 #![feature(proc_macro_hygiene)]
 
-use ink_core::storage;
+use ink_core::storage::{
+    self,
+    Flush,
+};
 use ink_lang2 as ink;
 
 use accumulator::Accumulator;
@@ -30,17 +33,13 @@ mod delegator {
     /// and in `Subber` state will delegate to the `Subber` contract.
     ///
     /// The initial state is `Adder`.
-    #[derive(Debug, Copy, Clone, PartialEq, Eq, scale::Encode, scale::Decode)]
+    #[derive(Debug, Copy, Clone, PartialEq, Eq, scale::Encode, scale::Decode, Flush)]
     #[cfg_attr(feature = "ink-generate-abi", derive(type_metadata::Metadata))]
     pub enum Which {
         Adder,
         Subber,
     }
 
-    impl ink_core::storage::Flush for Which {
-        fn flush(&mut self) {}
-    }
-
     /// Delegates calls to an adder or subber contract to mutate
     /// a value in an accumulator contract.
     ///

lang/src/gen/as_dependency.rs

@@ -88,9 +88,7 @@ fn generate_state_as_dependency(contract: &hir::Contract) -> TokenStream2 {
             account_id: AccountId,
         }
 
-        impl ink_core::storage::Flush for #name {
-            fn flush(&mut self) {}
-        }
+        impl ink_core::storage::Flush for #name {}
 
         /// Allows to enhance calls to `&self` contract messages.
         pub struct CallEnhancer<'a> {

lang/src/tests/events.rs

@@ -402,9 +402,7 @@ fn contract_compiles() {
                     account_id: AccountId,
                 }
 
-                impl ink_core::storage::Flush for CallCounter {
-                    fn flush(&mut self) {}
-                }
+                impl ink_core::storage::Flush for CallCounter {}
 
                 /// Allows to enhance calls to `&self` contract messages.
                 pub struct CallEnhancer<'a> {

lang/src/tests/flipper.rs

@@ -264,9 +264,7 @@ fn contract_compiles() {
                     account_id: AccountId,
                 }
 
-                impl ink_core::storage::Flush for Flipper {
-                    fn flush(&mut self) {}
-                }
+                impl ink_core::storage::Flush for Flipper {}
 
                 /// Allows to enhance calls to `&self` contract messages.
                 pub struct CallEnhancer<'a> {

lang/src/tests/incrementer.rs

@@ -333,9 +333,7 @@ fn contract_compiles() {
                     account_id: AccountId,
                 }
 
-                impl ink_core::storage::Flush for Incrementer {
-                    fn flush(&mut self) {}
-                }
+                impl ink_core::storage::Flush for Incrementer {}
 
                 /// Allows to enhance calls to `&self` contract messages.
                 pub struct CallEnhancer<'a> {

lang/src/tests/noop.rs

@@ -205,9 +205,7 @@ fn contract_compiles() {
                     account_id: AccountId,
                 }
 
-                impl ink_core::storage::Flush for Noop {
-                    fn flush(&mut self) {}
-                }
+                impl ink_core::storage::Flush for Noop {}
 
                 /// Allows to enhance calls to `&self` contract messages.
                 pub struct CallEnhancer<'a> {

lang2/macro/src/codegen/cross_calling.rs

@@ -156,12 +156,7 @@ impl CrossCalling<'_> {
 
     fn generate_storage_impls(&self) -> TokenStream2 {
         quote! {
-            impl ink_core::storage::Flush for StorageAsDependency {
-                #[inline(always)]
-                fn flush(&mut self) {
-                    // Nothing to do here!
-                }
-            }
+            impl ink_core::storage::Flush for StorageAsDependency {}
 
             #[cfg(feature = "ink-generate-abi")]
             impl ink_core::storage::alloc::AllocateUsing for StorageAsDependency {