Cargo Features

solana-ed25519-instruction has no features set by default.

[dependencies]
solana-ed25519-instruction = { version = "0.2.1", features = ["anchor"] }
anchor = anchor-lang

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

anchor-lang anchor?