Avert MSRV breakage in WASM & no-std builds.

.github/workflows/ci.yml

@@ -279,7 +279,7 @@ jobs:
       # We use a synthetic crate to ensure no dev-dependencies are enabled, which can
       # be incompatible with some of these targets.
       - name: Create synthetic crate for testing
-        run: cargo init --lib ci-build
+        run: cargo init --lib ci-build --edition 2021
       - name: Copy Rust version into synthetic crate
         run: cp crates/rust-toolchain.toml ci-build/
       - name: Copy patch directives into synthetic crate
@@ -316,7 +316,7 @@ jobs:
       # We use a synthetic crate to ensure no dev-dependencies are enabled, which can
       # be incompatible with some of these targets.
       - name: Create synthetic crate for testing
-        run: cargo init --lib ci-build
+        run: cargo init --lib ci-build --edition 2021
       - name: Copy Rust version into synthetic crate
         run: cp crates/rust-toolchain.toml ci-build/
       - name: Copy patch directives into synthetic crate

Cargo.toml

@@ -69,6 +69,8 @@ pasta_curves = "0.5"
 
 # - Transparent
 bip32 = { version = "=0.6.0-pre.1", default-features = false }
+block-buffer = { version = "=0.11.0-rc.3" } # later RCs require edition2024
+crypto-common = { version = "=0.2.0-rc.1" } # later RCs require edition2024
 ripemd = { version = "0.1", default-features = false }
 secp256k1 = { version = "0.29", default-features = false, features = ["alloc"] }
 transparent = { package = "zcash_transparent", version = "0.2", path = "zcash_transparent", default-features = false }

zcash_primitives/Cargo.toml

@@ -63,6 +63,8 @@ transparent.workspace = true
 # - Transparent inputs
 #   - `Error` type exposed
 bip32.workspace = true
+block-buffer.workspace = true # remove after edition2024 upgrade
+crypto-common.workspace = true # remove after edition2024 upgrade
 #   - `SecretKey` and `PublicKey` types exposed
 secp256k1 = { workspace = true, optional = true }