diff --git a/RELEASES.md b/RELEASES.md
index d7f0f2555a..dd387668df 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -64,6 +64,7 @@ of key improvements to our testing setup:
       A number of examples have already been converted to support the new testing engine.
 
 ## Changed
+- To reduce a contract's space footprint we switched the default allocator to a bump allocator implementation ‒ [#831](https://github.com/paritytech/ink/pull/831).
 - A couple of readme's have been reworked:
     - Our main ink! readme ‒ [#774](https://github.com/paritytech/ink/pull/774).
     - The `rand-extension` example readme ‒ [#793](https://github.com/paritytech/ink/pull/793).
@@ -84,6 +85,7 @@ of key improvements to our testing setup:
 
 ## Fixed
 - Catch illegal `struct` destructuring pattern in ink! message arguments ‒ [#846](https://github.com/paritytech/ink/pull/846).
+- Removed an erroneous `Salt` type in code generation for cross-contract calls ‒ [#842](https://github.com/paritytech/ink/pull/842).
 - Do not generate metadata if compiled as dependency ‒ [#811](https://github.com/paritytech/ink/pull/811).
 - Fix execution context parameters in DNS example tests ‒ [#723](https://github.com/paritytech/ink/pull/723).
 - Fixed the `Greeter` contract example from our doc comments ‒ [#773](https://github.com/paritytech/ink/pull/773).
diff --git a/crates/allocator/Cargo.toml b/crates/allocator/Cargo.toml
index 97a120d4ed..c7dbc37a30 100644
--- a/crates/allocator/Cargo.toml
+++ b/crates/allocator/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_allocator"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
diff --git a/crates/engine/Cargo.toml b/crates/engine/Cargo.toml
index 42a7ec73c1..b657c938a7 100644
--- a/crates/engine/Cargo.toml
+++ b/crates/engine/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_engine"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Michael Müller <michi@parity.io>"]
 edition = "2018"
 
diff --git a/crates/env/Cargo.toml b/crates/env/Cargo.toml
index 40aeb08a3d..faa25ddeab 100644
--- a/crates/env/Cargo.toml
+++ b/crates/env/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_env"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,11 +15,11 @@ categories = ["no-std", "embedded"]
 include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 
 [dependencies]
-ink_engine = { version = "3.0.0-rc3", path = "../engine/", default-features = false, optional = true }
-ink_metadata = { version = "3.0.0-rc3", path = "../metadata/", default-features = false, features = ["derive"], optional = true }
-ink_allocator = { version = "3.0.0-rc3", path = "../allocator/", default-features = false }
-ink_primitives = { version = "3.0.0-rc3", path = "../primitives/", default-features = false }
-ink_prelude = { version = "3.0.0-rc3", path = "../prelude/", default-features = false }
+ink_engine = { version = "3.0.0-rc4", path = "../engine/", default-features = false, optional = true }
+ink_metadata = { version = "3.0.0-rc4", path = "../metadata/", default-features = false, features = ["derive"], optional = true }
+ink_allocator = { version = "3.0.0-rc4", path = "../allocator/", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../primitives/", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../prelude/", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive", "full"] }
 derive_more = { version = "0.99", default-features = false, features = ["from", "display"] }
diff --git a/crates/lang/Cargo.toml b/crates/lang/Cargo.toml
index 97db22d95a..d9195981a0 100644
--- a/crates/lang/Cargo.toml
+++ b/crates/lang/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_lang"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,12 +15,12 @@ categories = ["no-std", "embedded"]
 include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 
 [dependencies]
-ink_env = { version = "3.0.0-rc3", path = "../env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../storage", default-features = false }
-ink_primitives = { version = "3.0.0-rc3", path = "../primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../metadata", default-features = false, optional = true }
-ink_prelude = { version = "3.0.0-rc3", path = "../prelude", default-features = false }
-ink_lang_macro = { version = "3.0.0-rc3", path = "macro", default-features = false }
+ink_env = { version = "3.0.0-rc4", path = "../env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../storage", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../metadata", default-features = false, optional = true }
+ink_prelude = { version = "3.0.0-rc4", path = "../prelude", default-features = false }
+ink_lang_macro = { version = "3.0.0-rc4", path = "macro", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive", "full"] }
 derive_more = { version = "0.99", default-features = false, features = ["from"] }
diff --git a/crates/lang/codegen/Cargo.toml b/crates/lang/codegen/Cargo.toml
index 226c3cd504..6a009cb164 100644
--- a/crates/lang/codegen/Cargo.toml
+++ b/crates/lang/codegen/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_lang_codegen"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -18,7 +18,7 @@ include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 name = "ink_lang_codegen"
 
 [dependencies]
-ir = { version = "3.0.0-rc3", package = "ink_lang_ir", path = "../ir", default-features = false }
+ir = { version = "3.0.0-rc4", package = "ink_lang_ir", path = "../ir", default-features = false }
 quote = "1"
 syn = { version = "1.0", features = ["parsing", "full", "extra-traits"] }
 proc-macro2 = "1.0"
diff --git a/crates/lang/ir/Cargo.toml b/crates/lang/ir/Cargo.toml
index 1fc60ca393..37dd9ac5a2 100644
--- a/crates/lang/ir/Cargo.toml
+++ b/crates/lang/ir/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_lang_ir"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
diff --git a/crates/lang/macro/Cargo.toml b/crates/lang/macro/Cargo.toml
index 5adc6f3a70..691035a836 100644
--- a/crates/lang/macro/Cargo.toml
+++ b/crates/lang/macro/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_lang_macro"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,20 +15,20 @@ categories = ["no-std", "embedded"]
 include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 
 [dependencies]
-ink_lang_ir = { version = "3.0.0-rc3", path = "../ir", default-features = false }
-ink_lang_codegen = { version = "3.0.0-rc3", path = "../codegen", default-features = false }
-ink_primitives = { version = "3.0.0-rc3", path = "../../primitives/", default-features = false }
+ink_lang_ir = { version = "3.0.0-rc4", path = "../ir", default-features = false }
+ink_lang_codegen = { version = "3.0.0-rc4", path = "../codegen", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../primitives/", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 syn = "1"
 proc-macro2 = "1"
 
 [dev-dependencies]
-ink_metadata = { version = "3.0.0-rc3", path = "../../metadata/" }
-ink_env = { version = "3.0.0-rc3", path = "../../env/" }
-ink_storage = { version = "3.0.0-rc3", path = "../../storage/" }
-ink_lang = { version = "3.0.0-rc3", path = ".." }
-ink_prelude = { version = "3.0.0-rc3", path = "../../prelude/" }
+ink_metadata = { version = "3.0.0-rc4", path = "../../metadata/" }
+ink_env = { version = "3.0.0-rc4", path = "../../env/" }
+ink_storage = { version = "3.0.0-rc4", path = "../../storage/" }
+ink_lang = { version = "3.0.0-rc4", path = ".." }
+ink_prelude = { version = "3.0.0-rc4", path = "../../prelude/" }
 
 trybuild = "1.0.24"
 scale-info = { version = "0.6", default-features = false, features = ["derive"] }
diff --git a/crates/metadata/Cargo.toml b/crates/metadata/Cargo.toml
index a94eeb7829..608269f4b0 100644
--- a/crates/metadata/Cargo.toml
+++ b/crates/metadata/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_metadata"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,8 +15,8 @@ categories = ["no-std", "embedded"]
 include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 
 [dependencies]
-ink_prelude = { version = "3.0.0-rc3", path = "../prelude/", default-features = false }
-ink_primitives = { version = "3.0.0-rc3", path = "../primitives/", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../prelude/", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../primitives/", default-features = false }
 
 serde = { version = "1.0", default-features = false, features = ["derive", "alloc"] }
 impl-serde = "0.3.1"
diff --git a/crates/prelude/Cargo.toml b/crates/prelude/Cargo.toml
index ec04b48f95..cd64ba8de3 100644
--- a/crates/prelude/Cargo.toml
+++ b/crates/prelude/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_prelude"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
diff --git a/crates/primitives/Cargo.toml b/crates/primitives/Cargo.toml
index 1183a40b15..7583fdcd09 100644
--- a/crates/primitives/Cargo.toml
+++ b/crates/primitives/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_primitives"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,7 +15,7 @@ categories = ["no-std", "embedded"]
 include = ["/Cargo.toml", "src/**/*.rs", "/README.md", "/LICENSE"]
 
 [dependencies]
-ink_prelude = { version = "3.0.0-rc3", path = "../prelude/", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../prelude/", default-features = false }
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive", "full"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
 
diff --git a/crates/storage/Cargo.toml b/crates/storage/Cargo.toml
index bd2b636d31..c4967bf191 100644
--- a/crates/storage/Cargo.toml
+++ b/crates/storage/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_storage"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -15,11 +15,11 @@ categories = ["no-std", "embedded"]
 include = ["Cargo.toml", "src/**/*.rs", "README.md", "LICENSE"]
 
 [dependencies]
-ink_env = { version = "3.0.0-rc3", path = "../env/", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../metadata/", default-features = false, features = ["derive"], optional = true }
-ink_primitives = { version = "3.0.0-rc3", path = "../primitives/", default-features = false }
-ink_storage_derive = { version = "3.0.0-rc3", path = "derive", default-features = false }
-ink_prelude = { version = "3.0.0-rc3", path = "../prelude/", default-features = false }
+ink_env = { version = "3.0.0-rc4", path = "../env/", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../metadata/", default-features = false, features = ["derive"], optional = true }
+ink_primitives = { version = "3.0.0-rc4", path = "../primitives/", default-features = false }
+ink_storage_derive = { version = "3.0.0-rc4", path = "derive", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../prelude/", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive", "full"] }
 derive_more = { version = "0.99", default-features = false, features = ["from", "display"] }
diff --git a/crates/storage/derive/Cargo.toml b/crates/storage/derive/Cargo.toml
index 51a631de08..c36df41abf 100644
--- a/crates/storage/derive/Cargo.toml
+++ b/crates/storage/derive/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "ink_storage_derive"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>", "Robin Freyler <robin@parity.io>"]
 edition = "2018"
 
@@ -25,7 +25,7 @@ synstructure = "0.12.4"
 
 [dev-dependencies]
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive", "full"] }
-ink_env = { version = "3.0.0-rc3", path = "../../env" }
-ink_primitives = { version = "3.0.0-rc3", path = "../../primitives" }
-ink_metadata = { version = "3.0.0-rc3", path = "../../metadata" }
-ink_storage = { version = "3.0.0-rc3", path = ".." }
+ink_env = { version = "3.0.0-rc4", path = "../../env" }
+ink_primitives = { version = "3.0.0-rc4", path = "../../primitives" }
+ink_metadata = { version = "3.0.0-rc4", path = "../../metadata" }
+ink_storage = { version = "3.0.0-rc4", path = ".." }
diff --git a/examples/contract-terminate/Cargo.toml b/examples/contract-terminate/Cargo.toml
index fb9b1da158..456ec1d07e 100644
--- a/examples/contract-terminate/Cargo.toml
+++ b/examples/contract-terminate/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "contract_terminate"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/contract-transfer/Cargo.toml b/examples/contract-transfer/Cargo.toml
index 46fc674aaf..17ed441d75 100644
--- a/examples/contract-transfer/Cargo.toml
+++ b/examples/contract-transfer/Cargo.toml
@@ -1,16 +1,16 @@
 [package]
 name = "contract_transfer"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false, features = [ "ink-debug" ] }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
-ink_prelude = { version = "3.0.0-rc3", path = "../../crates/prelude", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false, features = [ "ink-debug" ] }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../../crates/prelude", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/delegator/Cargo.toml b/examples/delegator/Cargo.toml
index b77d08cbcc..e4ce6110b7 100644
--- a/examples/delegator/Cargo.toml
+++ b/examples/delegator/Cargo.toml
@@ -1,21 +1,21 @@
 [package]
 name = "delegator"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 
-adder = { version = "3.0.0-rc3", path = "adder", default-features = false, features = ["ink-as-dependency"] }
-subber = { version = "3.0.0-rc3", path = "subber", default-features = false, features = ["ink-as-dependency"] }
-accumulator = { version = "3.0.0-rc3", path = "accumulator", default-features = false, features = ["ink-as-dependency"] }
+adder = { version = "3.0.0-rc4", path = "adder", default-features = false, features = ["ink-as-dependency"] }
+subber = { version = "3.0.0-rc4", path = "subber", default-features = false, features = ["ink-as-dependency"] }
+accumulator = { version = "3.0.0-rc4", path = "accumulator", default-features = false, features = ["ink-as-dependency"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
 
 [lib]
diff --git a/examples/delegator/accumulator/Cargo.toml b/examples/delegator/accumulator/Cargo.toml
index 9f576978ef..7229e03eba 100644
--- a/examples/delegator/accumulator/Cargo.toml
+++ b/examples/delegator/accumulator/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "accumulator"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/delegator/adder/Cargo.toml b/examples/delegator/adder/Cargo.toml
index f04fcf20fe..70d30c7442 100644
--- a/examples/delegator/adder/Cargo.toml
+++ b/examples/delegator/adder/Cargo.toml
@@ -1,17 +1,17 @@
 [package]
 name = "adder"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../../crates/lang", default-features = false }
 
-accumulator = { version = "3.0.0-rc3", path = "../accumulator", default-features = false, features = ["ink-as-dependency"] }
+accumulator = { version = "3.0.0-rc4", path = "../accumulator", default-features = false, features = ["ink-as-dependency"] }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/delegator/subber/Cargo.toml b/examples/delegator/subber/Cargo.toml
index 5f583a1b1d..7f7e4f9a10 100644
--- a/examples/delegator/subber/Cargo.toml
+++ b/examples/delegator/subber/Cargo.toml
@@ -1,17 +1,17 @@
 [package]
 name = "subber"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../../crates/lang", default-features = false }
 
-accumulator = { version = "3.0.0-rc3", path = "../accumulator", default-features = false, features = ["ink-as-dependency"] }
+accumulator = { version = "3.0.0-rc4", path = "../accumulator", default-features = false, features = ["ink-as-dependency"] }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/dns/Cargo.toml b/examples/dns/Cargo.toml
index b70b6c55ad..1c2bbb8e75 100644
--- a/examples/dns/Cargo.toml
+++ b/examples/dns/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "dns"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/erc1155/Cargo.toml b/examples/erc1155/Cargo.toml
index 87a0a4abee..5222784171 100644
--- a/examples/erc1155/Cargo.toml
+++ b/examples/erc1155/Cargo.toml
@@ -1,16 +1,16 @@
 [package]
 name = "erc1155"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false, features = ["ink-debug"] }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
-ink_prelude = { version = "3.0.0-rc3", path = "../../crates/prelude", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false, features = ["ink-debug"] }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../../crates/prelude", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/erc20/Cargo.toml b/examples/erc20/Cargo.toml
index 9067f4f3de..05b0d8a0e7 100644
--- a/examples/erc20/Cargo.toml
+++ b/examples/erc20/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "erc20"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/erc721/Cargo.toml b/examples/erc721/Cargo.toml
index 1d72b38e93..0b850f3447 100644
--- a/examples/erc721/Cargo.toml
+++ b/examples/erc721/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "erc721"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/flipper/Cargo.toml b/examples/flipper/Cargo.toml
index 5daa4e5a9f..64e6f7e1b0 100644
--- a/examples/flipper/Cargo.toml
+++ b/examples/flipper/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "flipper"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/incrementer/Cargo.toml b/examples/incrementer/Cargo.toml
index 273d555ab0..9759b73267 100644
--- a/examples/incrementer/Cargo.toml
+++ b/examples/incrementer/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "incrementer"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/multisig_plain/Cargo.toml b/examples/multisig_plain/Cargo.toml
index 0f850f279a..b38f3f4d4f 100755
--- a/examples/multisig_plain/Cargo.toml
+++ b/examples/multisig_plain/Cargo.toml
@@ -1,16 +1,16 @@
 [package]
 name = "multisig_plain"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
-ink_prelude = { version = "3.0.0-rc3", path = "../../crates/prelude", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
+ink_prelude = { version = "3.0.0-rc4", path = "../../crates/prelude", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/trait-erc20/Cargo.toml b/examples/trait-erc20/Cargo.toml
index 625314fd57..325c032685 100644
--- a/examples/trait-erc20/Cargo.toml
+++ b/examples/trait-erc20/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "trait_erc20"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }
diff --git a/examples/trait-flipper/Cargo.toml b/examples/trait-flipper/Cargo.toml
index 2d74c36de1..cba038f5df 100644
--- a/examples/trait-flipper/Cargo.toml
+++ b/examples/trait-flipper/Cargo.toml
@@ -1,15 +1,15 @@
 [package]
 name = "trait_flipper"
-version = "3.0.0-rc3"
+version = "3.0.0-rc4"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 
 [dependencies]
-ink_primitives = { version = "3.0.0-rc3", path = "../../crates/primitives", default-features = false }
-ink_metadata = { version = "3.0.0-rc3", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
-ink_env = { version = "3.0.0-rc3", path = "../../crates/env", default-features = false }
-ink_storage = { version = "3.0.0-rc3", path = "../../crates/storage", default-features = false }
-ink_lang = { version = "3.0.0-rc3", path = "../../crates/lang", default-features = false }
+ink_primitives = { version = "3.0.0-rc4", path = "../../crates/primitives", default-features = false }
+ink_metadata = { version = "3.0.0-rc4", path = "../../crates/metadata", default-features = false, features = ["derive"], optional = true }
+ink_env = { version = "3.0.0-rc4", path = "../../crates/env", default-features = false }
+ink_storage = { version = "3.0.0-rc4", path = "../../crates/storage", default-features = false }
+ink_lang = { version = "3.0.0-rc4", path = "../../crates/lang", default-features = false }
 
 scale = { package = "parity-scale-codec", version = "2.1", default-features = false, features = ["derive"] }
 scale-info = { version = "0.6", default-features = false, features = ["derive"], optional = true }