• TimelockController: Migrate _call to _execute and allow inheritance and overriding similar to Governor. (#3317)
• CrossChainEnabledPolygonChild: replace the require statement with the custom error NotCrossChainCall. (#3380)
• ERC20FlashMint: Add customizable flash fee receiver. (#3327)
• ERC4626: add an extension of ERC20 that implements the ERC4626 Tokenized Vault Standard. (#3171)
• SafeERC20: add safePermit as mitigation against phantom permit functions. (#3280)
• Math: add a mulDiv function that can round the result either up or down. (#3171)
• Math: Add a sqrt function to compute square roots of integers, rounding either up or down. (#3242)
• Strings: add a new overloaded function toHexString that converts an address with fixed length of 20 bytes to its not checksummed ASCII string hexadecimal representation. (#3403)
• EnumerableMap: add new UintToUintMap map type. (#3338)
• EnumerableMap: add new Bytes32ToUintMap map type. (#3416)
• SafeCast: add support for many more types, using procedural code generation. (#3245)
• MerkleProof: add multiProofVerify to prove multiple values are part of a Merkle tree. (#3276)
• MerkleProof: add calldata versions of the functions to avoid copying input arrays to memory and save gas. (#3200)
• ERC721, ERC1155: simplified revert reasons. (#3254, (#3438))
• ERC721: removed redundant require statement. (#3434)
• PaymentSplitter: add releasable getters. (#3350)
• Initializable: refactored implementation of modifiers for easier understanding. (#3450)
• Proxies: remove runtime check of ERC1967 storage slots. (#3455)

Breaking changes

• Initializable: functions decorated with the modifier reinitializer(1) may no longer invoke each other.