Rules

Forty-six rules across five families. Every one can be disabled, reweighted, or given a different severity in configuration.

Rules are namespaced by their category, so doc addresses the whole family and doc/work-marker addresses one rule.

rust

Idiomaticity, error handling, and abstractions with no second user.

Rule	Severity	Default	What it reports
rust/unwrap-in-library	high	on	A fallible value is unwrapped outside tests, so the failure path is unhandled
rust/panic-in-library	high	on	Library code panics instead of returning an error
rust/expect-in-library	medium	on	A fallible value is resolved with expect outside tests
rust/panicking-index	medium	on	Indexing can panic on out-of-range input
rust/single-implementor-trait	medium	on	A crate-private trait has one implementor, so the indirection has no second user
rust/oversized-function	medium	on	A function body is longer than the configured maximum
rust/deep-nesting	medium	on	A block is nested more deeply than the configured maximum
rust/single-use-wrapper	low	on	A wrapper type only forwards to its inner value
rust/over-exposed-visibility	low	on	An item is public but referenced only within its own module
rust/manual-index-loop	low	on	A range loop only indexes a collection, where an iterator would read more clearly
rust/match-on-bool	low	on	A match on a boolean where a conditional would read more clearly
rust/needless-return	low	on	An explicit return at the end of a function body
rust/oversized-file	low	on	A file is longer than the configured maximum
rust/single-instantiation-generic	low	off	A generic parameter is instantiated at exactly one type
rust/single-caller-indirection	low	off	A function exists solely to forward to another and has one caller

Error-handling rules are exempt in test code, whether that is an inline #[cfg(test)] module, an integration test target, or a file reached only through a test-only module declaration.

typescript

What a declaration earns its keep doing, and what discards the checking around it.

Rule	Severity	Default	What it reports
typescript/cast-through-unknown	high	on	A cast passes through unknown to reach an unrelated type, defeating the check a single cast would have had
typescript/single-implementor-interface	medium	on	An unexported interface has one implementor, so the indirection has no second user
typescript/explicit-any	medium	on	A position is written as any, discarding the checking the rest of the file relies on
typescript/non-null-assertion	medium	on	An expression asserts a value is present rather than establishing it
typescript/unexplained-suppression	medium	on	A suppression comment carries no reason for suppressing anything
typescript/aliasing-type	low	on	A type alias renames a single named type without adding meaning
typescript/optional-heavy-type	low	on	Most of a type's properties are optional, so it states little about its values
typescript/barrel-module	low	on	A module only forwards names declared elsewhere
typescript/duplicate-shape	low	on	Two declarations describe the same shape under different names
typescript/console-in-library	low	on	Library code writes to the console, which its callers did not ask for
typescript/default-export	low	on	A module exports a value whose name every importing site chooses for itself

.d.ts files are not analyzed. A declaration file states an interface without implementing it and is usually written by tsc, so the rules about implementors, forwarding, and console calls have nothing to read. node_modules is never walked, whether or not the project ignores it.

Six of these are also linter rules

explicit-any, non-null-assertion, unexplained-suppression, console-in-library and default-export have equivalents in Biome or typescript-eslint. cast-through-unknown has none.

They ship because TypeScript linting is opted into twice, by installing a tool and by turning the individual rule on. A project with no configuration is not one that decided these were acceptable; it is one where nothing is checking them. That differs from Rust, where clippy comes with the toolchain, and where rules duplicating it were removed during calibration.

Each therefore asks first whether the project already enforces it:

What the project has	What the rule does
biome.json or .eslintrc.json enabling the equivalent, directly or through a preset	stays silent
No linter configuration at all	reports, confirmed
Configuration only as JavaScript, such as a flat eslint.config.ts	reports, unconfirmed

Configuration is read as data and never executed, for the same reason the analyzer never builds the project it is pointed at.

c

What a declaration does with the reach it is given.

Rule	Severity	Default	What it reports
c/missing-internal-linkage	medium	on	A function is exposed to the whole program while only its own file uses it
c/definition-in-header	medium	on	A header carries a function body, so every including file gets a copy
c/orphan-declaration	medium	on	A header declares a function no analyzed file defines
c/file-scope-mutable-state	medium	on	Mutable state at file scope is readable and writable from every file in the program
c/unincluded-header	low	on	An interface file states an interface no analyzed file includes

.c and .h are both read as C. A header written for C++ produces a parse diagnostic naming the file rather than being silently reported as understood.

Nothing is preprocessed

No macro is expanded, no include resolved, and no condition evaluated, even where the definition needed sits in the analyzed tree. Expanding a macro means resolving include paths and evaluating conditionals, which is running the build.

The cost is measured and large. Across twenty widely deployed C projects, 97.6 percent of c findings came back unconfirmed and nineteen of the twenty carried no score, because every one of them invokes macros at file scope. Read C findings individually; do not expect a c score. See calibration.

doc

Whether the prose informs anyone.

Rule	Severity	Default	What it reports
doc/missing-on-public-item	medium	on	A public item carries no documentation
doc/documented-parameter-absent	medium	on	Documentation describes a parameter the signature does not declare
doc/commented-out-code	medium	on	Commented-out source was left in place
doc/restates-signature	low	on	Documentation adds nothing beyond the item name and signature
doc/undocumented-parameter	low	on	A parameter is undocumented while its siblings are documented
doc/restating-comment	low	on	A comment paraphrases the statement below it
doc/work-marker	low	on	An unresolved work marker was left in source
doc/unresolved-reference	medium	off	Documentation links to an identifier that does not resolve
doc/contentless-banner	low	off	A banner or separator comment carries no content

"Public" means reachable from outside the crate, not merely written pub. An item inside a private module, or one marked #[doc(hidden)], is not part of the documented API and is left alone.

A comment above an unsafe operation is exempt from restating-comment: that is where the reasoning making the operation sound gets written. Code introduced by prose ending in a colon is read as illustration rather than as leftovers.

filler

Volume without meaning. Every rule here is low severity by default, because each pattern has legitimate uses.

Rule	Severity	Default	What it reports
filler/narrating-comments	low	on	Most statements in a function carry a comment restating them
filler/defensive-redundancy	low	on	A check cannot fail given a guarantee already established
filler/templated-documentation	low	on	Many items share one documentation template with only the name substituted
filler/repeated-wrapper	low	on	Structurally identical wrappers repeat across a module
filler/unimplemented-marker	low	on	A non-test function body consists only of an unimplemented marker
filler/simplification-disclaimer	low	on	Prose states that the surrounding code is simplified or not production ready

Nothing in this family makes any claim about who or what wrote the code. It describes patterns, and a test asserts that no message, category name, or serialized field expresses an opinion about authorship.

Rules that ship switched off

Four rules are disabled by default because measurement showed them reporting their own imprecision rather than sloppiness. Each carries its reason in the catalog, and calibration has the numbers.

Turn any of them on for a run:

slopometer . --enable doc/contentless-banner

Or in configuration:

[rules."doc/contentless-banner"]
enabled = true