Beagle review-verification-protocol

Mandatory verification steps for all code reviews to reduce false positives. Load this skill before reporting ANY code review findings.

install

source · Clone the upstream repo

git clone https://github.com/existential-birds/beagle

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/existential-birds/beagle "$T" && mkdir -p ~/.claude/skills && cp -r "$T/plugins/beagle-rust/skills/review-verification-protocol" ~/.claude/skills/existential-birds-beagle-review-verification-protocol-0d2215 && rm -rf "$T"

manifest: plugins/beagle-rust/skills/review-verification-protocol/SKILL.md

source content

Review Verification Protocol

This protocol MUST be followed before reporting any code review finding. Skipping these steps leads to false positives that waste developer time and erode trust in reviews.

Pre-Report Verification Checklist

Before flagging ANY issue, verify:

I read the actual code - Not just the diff context, but the full function/impl block
I searched for usages - Before claiming "unused", searched all references
I checked surrounding code - The issue may be handled elsewhere (trait impls, error propagation)
I verified syntax against current docs - Rust edition, crate versions, and API changes
I checked the project's Rust edition - Edition 2021 vs 2024 changes what is required vs optional (see Edition-Aware Review)
I distinguished "wrong" from "different style" - Both approaches may be valid
I considered intentional design - Checked comments, CLAUDE.md, architectural context

Verification by Issue Type

"Unused Variable/Function"

Before flagging, you MUST:

Search for ALL references in the codebase (grep/find)
Check if it's
```
pub
```
and used by other crates in the workspace
Check if it's used via derive macros, trait implementations, or conditional compilation (
```
#[cfg]
```
)
Verify it's not a trait method required by the trait definition

Common false positives:

Trait implementations where the method is defined by the trait
```
#[cfg(test)]
```
items only used in test builds
Derive-generated code that uses struct fields
Types used via
```
From
```
/
```
Into
```
conversions

"Missing Error Handling"

Before flagging, you MUST:

Check if the error is handled at a higher level (caller propagates with
```
?
```
)
Check if the crate has a top-level error type that wraps this error
Verify the
```
unwrap()
```
isn't in test code or after a safety-ensuring check

Common false positives:

```
unwrap()
```
in tests and examples (expected pattern)
```
expect("reason")
```
after validation (e.g.,
```
regex::Regex::new
```
on a literal)
Error propagation via
```
?
```
(the caller handles it)
```
let _ = tx.send(...)
```
— intentional when receiver may have dropped

"Unnecessary Lifetime" / RPIT Capture (Edition 2024)

Before flagging, you MUST:

Check the project's Rust edition in
```
Cargo.toml
```
In edition 2024,
```
-> impl Trait
```
captures ALL in-scope lifetimes by default
A lifetime that appears "unnecessary" may be implicitly captured — the code is correct
If the author uses
```
+ use<'a>
```
syntax, this is precise capture control, not a mistake

Common false positives:

Lifetime parameters on functions returning
```
impl Trait
```
— edition 2024 captures them implicitly
```
+ use<'a, T>
```
syntax — this is the new precise capturing syntax, not an error
Removing an explicit lifetime bound that edition 2024 now provides automatically

"Missing Unsafe Block" (Edition 2024)

Before flagging, you MUST:

Check if the code is inside an
```
unsafe fn
```
In edition 2024,
```
unsafe_op_in_unsafe_fn
```
is deny-by-default — unsafe operations inside
```
unsafe fn
```
REQUIRE explicit
```
unsafe {}
```
blocks
This is edition-required behavior, not unnecessary verbosity

Common false positives:

```
unsafe {}
```
blocks inside
```
unsafe fn
```
— REQUIRED in edition 2024, not redundant
```
unsafe extern "C" {}
```
— REQUIRED in edition 2024, not optional

#[unsafe(no_mangle)]

#[unsafe(export_name)]

— REQUIRED in edition 2024

"Unnecessary Clone"

Before flagging, you MUST:

Confirm the clone is actually avoidable (borrow checker may require it)
Check if the value needs to be moved into a closure/thread/task
Verify the type isn't
```
Copy
```
(clone on Copy types is a no-op)
Check if the clone is in a hot path (test/setup code cloning is fine)

Common false positives:

```
Arc::clone(&arc)
```
— this is the recommended explicit clone for Arc
Clone before
```
tokio::spawn
```
— required for
```
'static
```
bound
Clone in test setup — clarity over performance

"Potential Race Condition"

Before flagging, you MUST:

Verify the data is actually shared across threads/tasks
Check if
```
Mutex
```
,
```
RwLock
```
, or atomic operations protect the access
Confirm the type doesn't already guarantee thread safety (e.g.,
```
Arc<Mutex<T>>
```
)
Check if the "race" is actually benign (e.g., logging, metrics)

Common false positives:

```
Arc<Mutex<T>>
```
— already thread-safe
Tokio channel operations — inherently synchronized
```
std::sync::atomic
```
operations — designed for concurrent access

"Performance Issue"

Before flagging, you MUST:

Confirm the code runs frequently enough to matter
Verify the optimization would have measurable impact
Check if the compiler already optimizes this (iterator fusion, inlining)

Do NOT flag:

Allocations in startup/initialization code
String formatting in error paths
Clone in test code
```
.collect()
```
on small iterators

Severity Calibration

Critical (Block Merge)

ONLY use for:

```
unsafe
```
code with unsound invariants
SQL injection via string interpolation
Use-after-free or memory safety violations
Data races (concurrent mutation without synchronization)
Panics in production code paths on user input

Major (Should Fix)

Use for:

Missing error context across module boundaries
Blocking operations in async runtime
Mutex guards held across await points
Missing transaction for multi-statement database writes

Minor (Consider Fixing)

Use for:

Missing doc comments on public items
```
String
```
parameters where
```
&str
```
would work
Suboptimal iterator patterns
Missing
```
#[must_use]
```
on functions with important return values

Informational (No Action Required)

Use for:

Suggestions for newtypes, builder patterns, or type state
Performance optimizations without measured impact
Suggestions to add
```
#[non_exhaustive]
```
Refactoring ideas for trait design

These are NOT review blockers.

Do NOT Flag At All

Style preferences where both approaches are valid (e.g.,
```
if let
```
vs
```
match
```
for single variant)
Optimizations with no measurable benefit
Test code not meeting production standards
Generated code or macro output
Clippy lints that the project has intentionally suppressed

Valid Patterns (Do NOT Flag)

Rust

Pattern	Why It's Valid
`unwrap()` in tests	Standard test behavior — panics on unexpected errors
`.clone()` in test setup	Clarity over performance
`use super::*` in test modules	Standard pattern for accessing parent items
`Box<dyn Error>` in binaries	Not every app needs custom error types
`String` fields in structs	Owned data is correct for struct fields
`Arc::clone(&x)`	Explicit Arc cloning is idiomatic and recommended
`#[allow(clippy::...)]` with reason	Intentional suppression is valid
`#[expect(lint)]` instead of `#[allow]`	Self-cleaning suppression (stable since 1.81) — warns when lint no longer triggers
`unsafe {}` inside `unsafe fn`	Required in edition 2024 ( `unsafe_op_in_unsafe_fn` = deny)
`unsafe extern "C" {}`	Required in edition 2024 for extern blocks
`#[unsafe(no_mangle)]`	Required in edition 2024 for safety-relevant attributes
`#[unsafe(export_name = "...")]`	Required in edition 2024 for safety-relevant attributes
`+ use<'a, T>` on `impl Trait` returns	Precise capture syntax for edition 2024 RPIT
`r#gen` as identifier	`gen` is reserved in edition 2024
`LazyLock` / `LazyCell`	Standard library replacements for `once_cell` / `lazy_static` (stable since 1.80)
`async fn` in trait definitions	No longer needs `async-trait` crate (stable since 1.75)
`#[diagnostic::on_unimplemented]`	Custom trait error messages (stable since 1.78)

Async/Tokio

Pattern	Why It's Valid
`std::sync::Mutex` for short critical sections	Tokio docs recommend this for non-async locks
`tokio::spawn` without join	Valid for background tasks with shutdown signaling
`select!` with `default` branch	Non-blocking check, intentional pattern
`#[tokio::test]` without multi_thread	Default single-thread is fine for most tests

Testing

Pattern	Why It's Valid
`expect()` in tests	Acceptable for test setup/assertions
`#[should_panic]` with `expected`	Valid for testing panic behavior
Large test functions	Integration tests can be long
`let _ = ...` in test cleanup	Cleanup errors are often unactionable

General

Pattern	Why It's Valid
`todo!()` in new code	Valid placeholder during development
`#[allow(dead_code)]` during development	Common during iteration
Multiple `impl` blocks for one type	Organized by trait or concern
Type aliases for complex types	Reduces boilerplate, improves readability

Context-Sensitive Rules

Ownership

Flag unnecessary

.clone()

ONLY IF:

In a hot path (not test/setup code)
A borrow or reference would work
The clone is not required for
```
Send
```
/
```
'static
```
bounds
The type is not
```
Copy
```

Error Handling

Flag missing error context ONLY IF:

Error crosses a module boundary
The error type doesn't already carry context (thiserror messages)
Not in test code
The bare
```
?
```
loses meaningful information about what operation failed

Unsafe Code

Flag unsafe ONLY IF:

Safety comment is missing or doesn't explain the invariant
The unsafe block is broader than necessary
The invariant is not actually upheld by surrounding code
A safe alternative exists with equivalent performance

Edition 2024 unsafe changes — check

Cargo.toml

edition before flagging:

```
unsafe {}
```
inside
```
unsafe fn
```
is required (not style) in edition 2024
```
unsafe extern "C" {}
```
is required in edition 2024 — bare
```
extern "C" {}
```
is a compile error

#[unsafe(no_mangle)]

and

#[unsafe(export_name)]

are required in edition 2024

In edition 2021, these patterns are optional style choices — do not require them

Edition-Aware Review

BEFORE flagging any edition-specific pattern, check

Cargo.toml

for the project's edition:

[package]
edition = "2024"  # or "2021", "2018"

Edition 2024 changes that affect review findings:

Change	Edition 2021	Edition 2024
`unsafe` inside `unsafe fn`	Optional style	Required ( `unsafe_op_in_unsafe_fn` = deny)
`extern "C" {}`	Valid	Must be `unsafe extern "C" {}`
`#[no_mangle]`	Valid	Must be `#[unsafe(no_mangle)]`
`#[export_name]`	Valid	Must be `#[unsafe(export_name)]`
`-> impl Trait` lifetime capture	Explicit only	Captures all in-scope lifetimes
`gen` as identifier	Valid	Reserved keyword (use `r#gen` )
`!` type fallback	Falls back to `()`	Falls back to `!`
`if let` temporaries	Dropped at end of block	Dropped earlier (end of `if let` )
Tail expression temporaries	Dropped after locals	Dropped before local variables
`Box<[T]>` iteration	Needs explicit `.iter()`	Has `IntoIterator` impl

If edition is not specified, Rust defaults to edition 2015. Most modern projects use 2021 or later.

Cross-reference: The

beagle-rust:rust-code-review

and

beagle-rust:rust-best-practices

skills provide edition-specific code review guidance and idiomatic patterns.

Macro-Specific Verification

"Macro Hygiene Issue"

Before flagging, you MUST:

Verify the identifier actually leaks — types, modules, and functions are NOT hygienic in
```
macro_rules!
```
Check if
```
$crate
```
is used correctly for exported macros (not
```
crate
```
or
```
self
```
)
Confirm
```
::core::
```
/
```
::alloc::
```
paths are needed (only for macros used in no_std contexts)
Check whether the macro is internal-only or
```
#[macro_export]
```

Common false positives:

Non-hygienic type names in internal macros — only matters for exported macros
```
$crate
```
not used in macros that are only
```
pub(crate)
```
—
```
$crate
```
is for cross-crate usage
Using
```
::std::
```
in macros for std-only crates — only flag if crate supports no_std

"Procedural Macro Performance"

Before flagging, you MUST:

Verify the macro is actually in a proc-macro crate (check
```
Cargo.toml
```
for
```
proc-macro = true
```
)
Check if
```
syn
```
features are minimized (full
```
syn
```
with
```
"full"
```
feature vs selective features)
Confirm compile-time impact is meaningful (proc macros used across many files vs one-off)

"Wrong Fragment Type"

Before flagging, you MUST:

Verify the suggested fragment type actually works in that position
Check if
```
:tt
```
is intentionally used for flexibility (common in TT munching patterns)
Confirm
```
:expr
```
greediness issues actually manifest (test with the macro's actual call sites)

FFI-Specific Verification

"Missing repr(C)"

Before flagging, you MUST:

Confirm the type actually crosses the FFI boundary (passed to/from C code)
Check if the type is only used on the Rust side of the FFI wrapper
Verify there isn't a
```
#[repr(transparent)]
```
wrapper instead

Common false positives:

Internal Rust types that are converted before FFI call — only the FFI-facing type needs
```
repr(C)
```
Types used with
```
repr(transparent)
```
newtype wrappers — the wrapper handles layout
Opaque pointer types (
```
*mut c_void
```
) — no layout guarantee needed

"FFI Safety"

Before flagging, you MUST:

Check if the unsafe FFI call has a SAFETY comment documenting invariants
Verify ownership transfer is actually ambiguous (check for
```
Box::into_raw
```
/
```
Box::from_raw
```
pairs)
Confirm CString lifetime issues are real (the CString must outlive the pointer passed to C)
Check if callback unwinding is actually possible (pure data functions can't panic across FFI)

Common false positives:

```
extern "C" fn
```
callbacks that never panic —
```
catch_unwind
```
not needed
```
*const c_char
```
from CStr::as_ptr() held within the same scope — lifetime is fine
Bindgen-generated code with
```
unsafe
```
— bindgen output is inherently unsafe-heavy by design

Concurrency-Specific Verification

"Memory Ordering Too Weak"

Before flagging, you MUST:

Verify the atomic is actually shared between threads that need synchronization
Check if
```
Relaxed
```
is sufficient (counters, flags with no dependent data)
Confirm
```
Acquire/Release
```
vs
```
SeqCst
```
choice matters (most code doesn't need SeqCst)

Common false positives:

```
Relaxed
```
on simple counters/metrics — no ordering needed for independent values
```
Relaxed
```
on boolean flags polled in a loop — the loop provides eventual visibility
```
SeqCst
```
used "for safety" — not wrong, just potentially over-synchronized

Before Submitting Review

Final verification:

Re-read each finding and ask: "Did I verify this is actually an issue?"
For each finding, can you point to the specific line that proves the issue exists?
Would a Rust domain expert agree this is a problem, or is it a style preference?
Does fixing this provide real value, or is it busywork?
Format every finding as:
```
[FILE:LINE] ISSUE_TITLE
```
For each finding, ask: "Does this fix existing code, or does it request entirely new code that didn't exist before?" If the latter, downgrade to Informational.
If this is a re-review: ONLY verify previous fixes. Do not introduce new findings.

If uncertain about any finding, either:

Remove it from the review
Mark it as a question rather than an issue
Verify by reading more code context