rand_core: Fix serde1 feature

Author: vks

rand_core/Cargo.toml

@@ -21,9 +21,8 @@ appveyor = { repository = "rust-random/rand" }
 [features]
 std = ["alloc", "getrandom", "getrandom/std"]    # use std library; should be default but for above bug
 alloc = []  # enables Vec and Box support without std
-serde1 = ["serde", "serde_derive"] # enables serde for BlockRng wrapper
+serde1 = ["serde"] # enables serde for BlockRng wrapper
 
 [dependencies]
-serde = { version = "1", optional = true }
-serde_derive = { version = "^1.0.38", optional = true }
+serde = { version = "1", features = ["derive"], optional = true }
 getrandom = { version = "0.1", optional = true }

rand_core/src/block.rs

@@ -52,6 +52,7 @@
 
 use core::convert::AsRef;
 use core::{fmt, ptr};
+#[cfg(feature="serde1")] use serde::{Serialize, Deserialize};
 use crate::{RngCore, CryptoRng, SeedableRng, Error};
 use crate::impls::{fill_via_u32_chunks, fill_via_u64_chunks};