Simplify Mint deserialization and add account type validation

- Remove StateWithExtensions overhead, just unpack base 82-byte mint
- Validate byte 165 == 1 for mints with extensions (rejects token accounts)

Author: ananas-block

spl/Cargo.toml

@@ -26,7 +26,7 @@ token_2022 = ["spl-token-2022"]
 token_2022_extensions = ["spl-token-2022", "spl-token-group-interface", "spl-token-metadata-interface", "spl-pod"]
 
 [dependencies]
-anchor-lang = { path = "../lang", features = ["derive"] }
+anchor-lang = { version = "0.31.1", features = ["derive"] }
 borsh = { version = "0.10.3", optional = true }
 mpl-token-metadata = { version = "5", optional = true }
 spl-associated-token-account = { version = "6", features = ["no-entrypoint"], optional = true }

spl/src/token_interface.rs

@@ -50,7 +50,14 @@ pub struct Mint(spl_token_2022::state::Mint);
 
 impl anchor_lang::AccountDeserialize for Mint {
     fn try_deserialize_unchecked(buf: &mut &[u8]) -> anchor_lang::Result<Self> {
-        spl_token_2022::extension::StateWithExtensions::<spl_token_2022::state::Mint>::unpack(buf)
+        // If >= 166 bytes, validate account type byte is Mint (1)
+        if buf.len() >= 166 && buf[165] != 1 {
+            return Err(anchor_lang::error::ErrorCode::AccountDidNotDeserialize.into());
+        }
+
+        // Deserialize base mint only (82 bytes)
+        let base_slice = &buf[..spl_token_2022::state::Mint::LEN];
+        spl_token_2022::extension::StateWithExtensions::<spl_token_2022::state::Mint>::unpack(base_slice)
             .map(|t| Mint(t.base))
             .map_err(Into::into)
     }