feat(lint): add UnsafeTypecast lint #11046

TropicalDog17 · 2025-07-19T10:35:31Z

Motivation

Closes #11029

Solution

PR Checklist

Added Tests
Added Documentation
Breaking changes

Cargo.toml

crates/lint/testdata/UnsafeTypecast.sol

crates/lint/testdata/UnsafeTypecast.stderr

crates/lint/testdata/UnsafeTypecast.sol

0xClandestine · 2025-07-22T19:33:22Z

Any updates, can update the tests for you if needed @TropicalDog17

…foundry into feat/unsafe-typecast-lint

TropicalDog17 · 2025-07-23T07:09:47Z

Hi @0xClandestine, I've updated the test, but not sure how to emit a helpful fix for the lint, can you help me on that? Thank a lot!

0xrusowsky · 2025-07-23T08:24:35Z

Hi @0xClandestine, I've updated the test, but not sure how to emit a helpful fix for the lint, can you help me on that? Thank a lot!

maybe in this case a warning is enough, and no fix suggestion is required, but you could tell them to consider adding an explicit check like:

if (a > type(uint32).max) revert TypecastOverflow();

0xrusowsky

please address the feedback

crates/lint/src/sol/med/unsafe_typecast.rs

0xrusowsky · 2025-07-23T09:31:12Z

crates/lint/src/sol/med/unsafe_typecast.rs

+            solar_ast::LitKind::Number(num) => {
+                if is_negative_number_literal(num) {
+                    Some(hir::ElementaryType::Int(solar_ast::TypeSize::ZERO))
+                } else {
+                    Some(hir::ElementaryType::UInt(solar_ast::TypeSize::ZERO))
+                }
+            }


the compiler performs checks when assigning literal values, i think it is safe to remove this check, which would also remove the need of the bigint dep.

Please return None and add a comment explaining the reason why

Assigning values which cannot fit into the type gives a compiler error. For example:
uint8 foo = 300;

The largest value an uint8 can hold is (2 8) - 1 = 255. So, the compiler says:
value 300 does not fit into type uint8

ref: https://solang.readthedocs.io/en/latest/language/types.html

crates/lint/testdata/UnsafeTypecast.sol

Cargo.toml

crates/lint/testdata/UnsafeTypecast.sol

…foundry into feat/unsafe-typecast-lint

0xClandestine

Looking good, some nits 🤝

crates/lint/testdata/UnsafeTypecast.stderr

crates/lint/src/sol/med/unsafe_typecast.rs

crates/lint/testdata/UnsafeTypecast.sol

Co-authored-by: clandestine.eth <96172957+0xClandestine@users.noreply.github.com>

Cargo.toml

crates/lint/src/sol/med/unsafe_typecast.rs

crates/lint/testdata/UnsafeTypecast.sol

0xrusowsky · 2025-07-29T10:18:21Z

crates/lint/testdata/UnsafeTypecast.stderr

+warning[unsafe-typecast]: typecasts that can truncate values should be checked
+  --> ROOT/testdata/UnsafeTypecast.sol:LL:CC
+   |
+74 |         uint248 b = uint248(a);
+   |                     ----------
+   |
+   = note: Consider disabling this lint if you're certain the cast is safe:
+
+           - // Cast is safe because [explain why]
+           - // forge-lint: disable-next-line(unsafe-typecast)


CI is failing. Have you updated the blessed files?

If not, run cargo test -p forge --test ui -- --bless and ensure that all tests pass

Hi I ran the tests locally, it worked fine but but ci still fails, can you help me?

let me pull your fork and try myself, will push something this afternoon

fyi

locally it worked cause u hadn't pulled the latest changes from the remote, where u had merged from master, which fixed an issue when printing Snippet::Block as if they were removed diffs (hence the extra - before the block)

Co-authored-by: 0xrusowsky <90208954+0xrusowsky@users.noreply.github.com>

…foundry into feat/unsafe-typecast-lint

0xrusowsky

@TropicalDog17 while we wait for others to review, please open a PR updating the foundry book. Until docs are updated CI will fail.

you need to add a section for the new lint here:
https://github.com/foundry-rs/book/blob/master/vocs/docs/pages/forge/linting.md

stale

0xClandestine · 2025-07-29T17:38:01Z

@TropicalDog17 while we wait for others to review, please open a PR updating the foundry book. Until docs are updated CI will fail.

you need to add a section for the new lint here: foundry-rs/book@master/vocs/docs/pages/forge/linting.md

Went ahead and updated docs 🤝

0xClandestine · 2025-07-29T17:53:22Z

Caught this when testing the lint on a previous audit commit at EigenLayer:

To reproduce

git clone https://github.com/Layr-Labs/eigenlayer-contracts.git
git checkout f7413d9
forge lint --only-lint unsafe-typecast

The application panicked (crashed).
Message:  invalid fixed-bytes size: 46
Location: /Users/gg/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/solar-ast-0.1.5/src/ast/ty.rs:245

This is a bug. Consider reporting it at https://github.com/foundry-rs/foundry

  ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ BACKTRACE ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
                                ⋮ 9 frames hidden ⋮                               
  10: forge_lint::sol::med::unsafe_typecast::infer_source_type::hb9381693201f3de2
      at <unknown source file>:<unknown line>
  11: forge_lint::sol::med::unsafe_typecast::is_unsafe_typecast_hir::hc75a0e499a3756f1
      at <unknown source file>:<unknown line>
  12: forge_lint::sol::med::unsafe_typecast::<impl forge_lint::linter::late::LateLintPass for forge_lint::sol::med::UnsafeTypecast>::check_expr::h86f336a31d5eeb28
      at <unknown source file>:<unknown line>
  13: <forge_lint::linter::late::LateLintVisitor as solar_sema::hir::visit::Visit>::visit_expr::heed864d619e159de
      at <unknown source file>:<unknown line>
  14: <forge_lint::linter::late::LateLintVisitor as solar_sema::hir::visit::Visit>::visit_expr::heed864d619e159de
      at <unknown source file>:<unknown line>
  15: <forge_lint::linter::late::LateLintVisitor as solar_sema::hir::visit::Visit>::visit_function::h3f4620f34a7d0cc2
      at <unknown source file>:<unknown line>
  16: solar_sema::hir::visit::visit_nested_items::{{closure}}::hf18b76f65fc1a551
      at <unknown source file>:<unknown line>
  17: forge_lint::sol::SolidityLinter::process_source_hir::h090419321e5637dd
      at <unknown source file>:<unknown line>
  18: <&rayon::iter::par_bridge::IterParallelProducer<Iter> as rayon::iter::plumbing::UnindexedProducer>::fold_with::h9f490d2ce38eac94
      at <unknown source file>:<unknown line>
  19: <rayon_core::job::StackJob<L,F,R> as rayon_core::job::Job>::execute::ha44f7714e8b09998
      at <unknown source file>:<unknown line>
  20: rayon_core::registry::WorkerThread::wait_until_cold::h0aa2a024b0c4ca85
      at <unknown source file>:<unknown line>
  21: rayon_core::registry::ThreadBuilder::run::haf19535023a3f6b1
      at <unknown source file>:<unknown line>
  22: std::sys::backtrace::__rust_begin_short_backtrace::hed6bf63077d481ec
      at <unknown source file>:<unknown line>
  23: core::ops::function::FnOnce::call_once{{vtable.shim}}::h5bacb7b49023c67c
      at <unknown source file>:<unknown line>
  24: std::sys::pal::unix::thread::Thread::new::thread_start::hf0cf67e969add794
      at <unknown source file>:<unknown line>
  25: __pthread_cond_wait<unknown>
      at <unknown source file>:<unknown line>

Run with COLORBT_SHOW_HIDDEN=1 environment variable to disable frame filtering.
Run with RUST_BACKTRACE=full to include source snippets.
The application panicked (crashed).
Message:  invalid fixed-bytes size: 46
Location: /Users/gg/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/solar-ast-0.1.5/src/ast/ty.rs:245

This is a bug. Consider reporting it at https://github.com/foundry-rs/foundry

  ━━━━━━━━━━━━━━━━━━━━━━━━[1]    86533 abort      forge lint --only-lint unsafe-typecast

0xClandestine · 2025-07-29T18:04:40Z

I also don't think it's throwing a warning for this bug, may be because it's crashing early.

function _addInt128(uint64 a, int128 b) internal pure returns (uint64) {
    return uint64(uint128(int128(uint128(a)) + b));
}

0xrusowsky · 2025-07-29T20:47:48Z

thanks for flagging this, seems to be solar-related.

i'll debug tomorrow and patch it

grandizzy

thank you, lgtm!

0xClandestine · 2025-07-30T16:23:03Z

crates/lint/src/sol/med/unsafe_typecast.rs

+}
+
+/// Infers the elementary type of a source expression.
+/// For cast chains, returns the ultimate source type, not intermediate cast results.


Can we check intermediate casts for cast chains? I think that's why this isn't throwing:

function _addInt128(uint64 a, int128 b) internal pure returns (uint64) { return uint64(uint128(int128(uint128(a)) + b)); }

Would suggest adding a test, you can also reproduce using the following commands:

foundryup --pr 11046 git clone https://github.com/Layr-Labs/eigenlayer-contracts.git git checkout 44ece6d forge lint src/contracts/core/AllocationManager.sol --only-lint unsafe-typecast

bet

e8aafe0

TropicalDog17 requested review from DaniPopes, klkvr and mattsse as code owners July 19, 2025 10:35

github-project-automation bot added this to Foundry Jul 19, 2025

TropicalDog17 requested review from grandizzy, yash-atreya and zerosnacks as code owners July 19, 2025 10:35

Merge branch 'master' into feat/unsafe-typecast-lint

0455b31

0xClandestine suggested changes Jul 19, 2025

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0xClandestine reviewed Jul 19, 2025

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crates/lint/testdata/UnsafeTypecast.sol Outdated Show resolved Hide resolved

TropicalDog17 added 4 commits July 23, 2025 06:57

add more tests, emit fix

befa78a

Merge branch 'feat/unsafe-typecast-lint' of github.com:TropicalDog17/…

34e6a68

…foundry into feat/unsafe-typecast-lint

remove unused deps

45f5bda

test: remove compiler error test

dff52fa

TropicalDog17 added 2 commits July 23, 2025 14:09

Merge branch 'master' into feat/unsafe-typecast-lint

2768187

lint

47e80e4

0xrusowsky requested changes Jul 23, 2025

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0xrusowsky reviewed Jul 23, 2025

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0xrusowsky reviewed Jul 23, 2025

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TropicalDog17 added 2 commits July 24, 2025 07:40

refactor

3614115

Merge branch 'feat/unsafe-typecast-lint' of github.com:TropicalDog17/…

01210d8

…foundry into feat/unsafe-typecast-lint

TropicalDog17 requested review from 0xrusowsky and 0xClandestine July 24, 2025 07:44

Merge branch 'master' into feat/unsafe-typecast-lint

3d4f355

0xClandestine previously requested changes Jul 25, 2025

View reviewed changes

TropicalDog17 and others added 4 commits July 28, 2025 10:34

Update crates/lint/src/sol/med/unsafe_typecast.rs

e7febc7

Co-authored-by: clandestine.eth <96172957+0xClandestine@users.noreply.github.com>

refactor

7b541f9

refactor

a541299

Merge branch 'master' into feat/unsafe-typecast-lint

c140190

TropicalDog17 requested a review from 0xClandestine July 29, 2025 09:27

Merge branch 'master' into feat/unsafe-typecast-lint

403792d

0xrusowsky requested changes Jul 29, 2025

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TropicalDog17 and others added 4 commits July 29, 2025 17:28

Update crates/lint/src/sol/med/unsafe_typecast.rs

df675c8

Co-authored-by: 0xrusowsky <90208954+0xrusowsky@users.noreply.github.com>

bet

8816572

Merge branch 'feat/unsafe-typecast-lint' of github.com:TropicalDog17/…

bcf6760

…foundry into feat/unsafe-typecast-lint

fix: bless files + nits

4883cba

0xrusowsky self-requested a review July 29, 2025 13:29

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0xClandestine mentioned this pull request Jul 29, 2025

docs: add unchecked-typecast foundry-rs/book#1621

Open

0xrusowsky added 2 commits July 30, 2025 08:10

fix: infer_source_type for string literals

f20127b

style: standardize imports

30ee511

0xrusowsky dismissed their stale review via 30ee511 July 30, 2025 06:11

nit: improve lint msg

84f8f1b

0xrusowsky approved these changes Jul 30, 2025

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grandizzy approved these changes Jul 30, 2025

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0xClandestine suggested changes Jul 30, 2025

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feat(lint): add UnsafeTypecast lint #11046

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feat(lint): add UnsafeTypecast lint #11046

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TropicalDog17 commented Jul 19, 2025

Motivation

Solution

PR Checklist

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