New Features

• Added user defined macros
  • Defined as items with the keyword macro.
  • Currently only supported for expressions and statements.
  • Hygienic by default: vars defined outside the macro aren't available by default in the macro expanded code, and vars defined in the macro expanded code aren't available after the expansion.

macro assert_zero {
     ($x:expr) => {
            assert!($x == 0);
     };
}

• Added support for self as a leaf of path. #7560
• Recursive match on enums

match opt_opt_v {
      Some(Some(v)) => v,
      Some(None) = 1,
      None => 2,
}

• let-else support

let Some(x) = y else { ... }

• let-chains support.
  • let chain + else is not supported yet.

if let Some(x) = y && let Some(z) = x { ... }

Bug Fixes

• Fixed issue with sort instability of use statements. #7440
• Fixed the assertion macros to not move variables into them if not required. #7443
• Improved block return type to be never in more places. #7858
• Prevented crash caused in cases of destructuring of a snapshot of var. #7907
• Return an error when a loop return core::never and another type. #7904
• Removed unused warning caused by not finding function or method. #7940
• Stopped updating snap-refs - and only introducing top level. #8048

Corelib Updates

• Moved upcast and downcast to bounded_int. #7575
• Made bounded-int pub, and blocked by unstable feature. #7576
• Make VecIter public. #7627
• Made meta_tx_v0_syscall usable for starknet. #7605
• Add gas_reserve_create libfunc. #7756
• Add gas_reserve_utilize libfunc. #7757
• Made core::internal::bounded_int pub, as it is feature bound. #7937
• Removed Identifier not found diagnostics when vars introduced. #7946

Optimizations

Code Size

• Add code deduplication optimization. #7382
• add no-gas option to get-lowering. #7400
• Support Enum and Struct construction in return optimization. #5828
• Add trim_unreachable optimization to trim unreachable code. #7546
• Deduped panic_with_const_felt252 into calling panic_with_felt252. #7556
• Improve match optimization. #7578
• Support compilation with unsafe_panic for local proofs. #7568
• Removed some unwraps from keccak. #7635
• Added an internal numeric Split trait, and used it to remove unwraps. #7636
• Removed some more unwraps in bytearray. #7642
• Using checked_sub instead of compare and then subtract. #7665
• Major refactoring of ByteArray vastly reducing its size. #7669
• Add redeposit_gas only before convergence points. #7686
• Avoid adding redeposit_gas before panic flows. #7687
• Added functions specialization optimization.
• Better heuristic for inlining and specialization of functions based on actual final function size.
• Added inc and dec to const-folding. #7799
• When possible - making a enum-match into a goto. #7839

Compiler runtime

• Allowing caching of compiled crate - allows scarb to cache these and avoid a large part of recompilation.
• Improved block return type to be never in more places. #7858
• Removed extra vectors from semantic statements processing. #7887
• Changed QueryAttrs to be more iterator based. #7889
• Less green lookups. #7921
• added shot circuiting to get text of terminals. #7934
• Removed extra get_children calls at span without trivia. #7948
• improved candidate solver to not use inference when possible. #7949

New Contributors

• @Himess made their first contribution in #7451
• @VolodymyrBg made their first contribution in #7639
• @0xpantera made their first contribution in #7722
• @kkawula made their first contribution in #7749

Full Changelog: v2.11.4...v2.12.0