Neo DevPack for Solidity v0.27.0 — Real-World Compatibility & Performance

neo-devpack-solidity v0.27.0 — Real-World Compatibility & Performance

Release date: 2026-07-02
Compiler / CLI / workspace: v0.27.0
devpack (@neo-devpack-solidity/contracts): v0.27.0
Target Neo N3 node: v3.10.0 (Gorgon-prep; no hardfork activation)

Canonical change list: CHANGELOG.md [v0.27.0].
Previous releases: see the
GitHub releases page
and CHANGELOG.md history (previous: v0.26.0).

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TL;DR

• Real-world contract compatibility — driven by a ~600-contract
  famous-contract evaluation (full dependency trees), the merge/inheritance
  gaps that blocked flagship protocols are fixed: Aave v3 went 71% → 85%
  (every deployable implementation — Pool, PoolConfigurator, AToken —
  compiles), the Compound v2 core stack is unblocked, and USDC/MasterChef/ENS
  -style inherited-event patterns resolve. new X{salt: s}() (CREATE2 sugar)
  is accepted.
• Latest-Solidity semantics — a 168-probe runtime audit of 0.8.x features
  drove fixes for bytesN shifts (big-endian face value), unchecked int256
  two's-complement wrap, fixed-size array .length, and free-function
  overloads — plus loud warnings where NeoVM cannot honor EVM semantics
  (W_USER_DEFINED_OPERATOR for 0.8.19 operator overloading,
  W_TRANSIENT_PERSISTED for 0.8.28 transient storage) instead of silent
  miscompiles.
• ~1.9× faster in-tree NeoVM on compute-heavy workloads (per-instruction
  stack-clone/String-alloc elimination, static opcode tables, allocation-free
  slot loads) plus compiler-side inference and sibling-merge complexity wins.
• 33-contract hermetic sample corpus (third_party/famous-contracts/samples/)
  asserted at 100% by cargo test --release --test famous_samples_compile.
• Zero-regression validation — a 63-repro matrix re-verified every issue
  identified across the campaign: 54 verified fixed, 0 regressions; all
  deferred items fail exactly as documented.

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🌍 Real-world contract compatibility

The famous-contract evaluation compiled ~600 real Ethereum contracts with
their full dependency trees (~87% end-to-end; zero-knowledge 100%,
solmate 100%, solady 99%, Uniswap-v3 93%, OpenZeppelin 89%,
Aave v3 85%). The fixes in this release close the highest-frequency
gaps it found:

• Library-declared events are carried into the consuming contract, so
  Aave v3's library ReserveLogic { event ReserveDataUpdated(...) } pattern
  compiles (previously: "emit references event … which has no resolved
  declaration").
• Abstract-typed fields — a concrete contract holding a field of an
  abstract contract type (Compound v2's PriceOracle /
  InterestRateModel) is no longer forced to implement that abstract's
  virtuals.
• Inherited events through cross-contract new — the sibling-merge now
  walks the full base/interface closure, so contract A is IERC20 emitting
  IERC20.Approval resolves when a factory does new A() (USDC FiatToken,
  SushiSwap MasterChef, ENS PublicResolver).
• new X{salt: s}(args) — CREATE2-style salted creation compiles; the
  salt is evaluated and ignored with a warning (Neo N3 has no CREATE2).

A curated, dependency-free subset — 33 self-contained famous contracts
across DeFi / NFT / GameFi / zero-knowledge / infrastructure-DAO, spanning
Solidity 0.5.x–0.8.x — now lives in-tree with a hermetic-compile test
asserting 100%.

🎯 Latest-Solidity semantics

A 168-probe runtime-semantic audit (assertions on EVM-correct values,
not just "does it parse") drove this wave:

• bytesN << k / >> k shift the big-endian face value with EVM
  truncation (previously faulted for N<32 or read the bytes little-endian).
• unchecked { int256 } Add/Sub/Mul wraps two's-complement mod 2^256
  (type(int256).max + 1 == type(int256).min); checked mode still
  Panics(0x11).
• Fixed-size storage arrays report .length == N (previously 0 — silently
  skipping for (i = 0; i < a.length; i++) loops).
• File-scope free-function overloads are all callable (previously only
  the first survived).
• Honest diagnostics over silent miscompiles: user-defined operators
  (0.8.19) warn W_USER_DEFINED_OPERATOR (raw arithmetic is emitted, not
  the bound function); transient state variables (0.8.28) warn
  W_TRANSIENT_PERSISTED (persisted — NeoVM has no EIP-1153 store).

⚡ Performance

• In-tree NeoVM interpreter ~1.9× faster on a compute-heavy benchmark
  (1.91s → 0.99s): the per-instruction hot path no longer clones the entire
  evaluation stack nor allocates an opcode-name String (debug-tracing only,
  now gated behind enable_debugging); opcode gas/name lookups index static
  [_; 256] tables; slot loads (LDLOC/LDARG/LDSFLD) are
  allocation-free on the success path.
• Compiler front-end: subscript type-inference no longer re-descends the
  same sub-tree up to 4× (exponential in a[i][j][k] depth); the
  sibling-merge transitive closure computes each contract's reference walk
  once per pass (byte-identical output verified).

✅ Validation

• 63-repro validation matrix re-ran every issue identified across the
  bug-hunt backlog, the feature audit, and the famous-contract evaluation
  against this release: 54 verified fixed, 0 regressions, 0 surprises;
  8 deferred items fail exactly as documented (each root-caused in-tree for
  follow-up), 1 known simulator-model artifact behaves as documented.
• Full suite: 1,964 tests across 55 targets green (integration + lib
  unit + cargo-fuzz/proptest); cargo clippy -D warnings + cargo fmt
  clean; CI (Core + Neo-Express Differential + Fuzz) green.

Known limitations (tracked, documented in-tree)

User-defined operator dispatch (0.8.19) and true transient storage
(EIP-1153) need type-system/VM work and currently warn; abi.encodeCall /
abi.encodeWithSignature produce Neo-native call descriptors rather than
raw EVM calldata; bytesN bitwise compound-assign (r |= x) stores a
byte-reversed value (bitwise reads are correct); nested struct-array-member
push, one inherited-getter dispatch shape, and abi.encode of fixed-size
arrays remain deferred with root causes documented.

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📊 Headline numbers

Metric	v0.26.0	v0.27.0
Famous-contract compilation (full deps)	~87% baseline established	merge gaps fixed; Aave 71% → 85%
Hermetic sample corpus	—	33 contracts, 100% compile-tested
Interpreter speed (compute-heavy)	baseline	~1.9×
Latest-Solidity semantic fixes	—	bytesN shifts, int256 wrap, T[N].length, free-fn overloads
Silent-miscompile guards	—	W_USER_DEFINED_OPERATOR, W_TRANSIENT_PERSISTED
Fix-validation matrix	—	63 repros, 54 fixed, 0 regressions
Total tests	1,952	1,964 (55 targets)
Test failures	0	0

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🚀 How to upgrade

Backwards-compatible release — no public-API breaks or renames. Cargo and
npm users pick up v0.27.0 on their next dependency resolution.

CLI users: rebuild with cargo install --path . --version 0.27.0
or download the prebuilt binary from the
release page.

Library users consuming neo_devpack_solidity from another crate:
pick up 0.27.0 via cargo update.

devpack users: npm install @neo-devpack-solidity/contracts@0.27.0.

Sample corpus: browse third_party/famous-contracts/samples/ and verify
locally with cargo test --release --test famous_samples_compile.

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🧪 Verification

• cargo test --release ✅ 1,964 tests / 55 targets / 0 failed
• cargo clippy --all-targets --all-features -- -D warnings ✅
• cargo fmt --all -- --check ✅
• 63-repro fix-validation matrix ✅ 0 regressions