Canonical lint set for Linebender projects

All Linebender projects should include the following set of lints:

Cargo.toml

[lints]
# This one may vary depending on the project.
rust.unsafe_code = "forbid"

# LINEBENDER LINT SET - Cargo.toml - v4
# See https://linebender.org/wiki/canonical-lints/
rust.keyword_idents_2024 = "forbid"
rust.non_ascii_idents = "forbid"
rust.non_local_definitions = "forbid"
rust.unsafe_op_in_unsafe_fn = "forbid"

rust.elided_lifetimes_in_paths = "warn"
rust.let_underscore_drop = "warn"
rust.missing_debug_implementations = "warn"
rust.missing_docs = "warn"
rust.single_use_lifetimes = "warn"
rust.trivial_numeric_casts = "warn"
rust.unexpected_cfgs = "warn"
rust.unit_bindings = "warn"
rust.unnameable_types = "warn"
rust.unreachable_pub = "warn"
rust.unused_import_braces = "warn"
rust.unused_lifetimes = "warn"
rust.unused_macro_rules = "warn"
rust.unused_qualifications = "warn"
rust.variant_size_differences = "warn"

clippy.too_many_arguments = "allow"

clippy.allow_attributes = "warn"
clippy.allow_attributes_without_reason = "warn"
clippy.cast_possible_truncation = "warn"
clippy.collection_is_never_read = "warn"
clippy.dbg_macro = "warn"
clippy.debug_assert_with_mut_call = "warn"
clippy.doc_markdown = "warn"
clippy.fn_to_numeric_cast_any = "warn"
clippy.infinite_loop = "warn"
clippy.large_include_file = "warn"
clippy.large_stack_arrays = "warn"
clippy.match_same_arms = "warn"
clippy.mismatching_type_param_order = "warn"
clippy.missing_assert_message = "warn"
clippy.missing_errors_doc = "warn"
clippy.missing_fields_in_debug = "warn"
clippy.missing_panics_doc = "warn"
clippy.partial_pub_fields = "warn"
clippy.return_self_not_must_use = "warn"
clippy.same_functions_in_if_condition = "warn"
clippy.semicolon_if_nothing_returned = "warn"
clippy.shadow_unrelated = "warn"
clippy.should_panic_without_expect = "warn"
clippy.todo = "warn"
clippy.unseparated_literal_suffix = "warn"
clippy.use_self = "warn"
clippy.wildcard_imports = "warn"

clippy.cargo_common_metadata = "warn"
clippy.negative_feature_names = "warn"
clippy.redundant_feature_names = "warn"
clippy.wildcard_dependencies = "warn"
# END LINEBENDER LINT SET

lib.rs

// LINEBENDER LINT SET - lib.rs - v3
// See https://linebender.org/wiki/canonical-lints/
// These lints shouldn't apply to examples or tests.
#![cfg_attr(not(test), warn(unused_crate_dependencies))]
// These lints shouldn't apply to examples.
#![warn(clippy::print_stdout, clippy::print_stderr)]
// Targeting e.g. 32-bit means structs containing usize can give false positives for 64-bit.
#![cfg_attr(target_pointer_width = "64", warn(clippy::trivially_copy_pass_by_ref))]
// END LINEBENDER LINT SET
#![cfg_attr(docsrs, feature(doc_auto_cfg))]

.clippy.toml

# LINEBENDER LINT SET - .clippy.toml - v1
# See https://linebender.org/wiki/canonical-lints/

# The default Clippy value is capped at 8 bytes, which was chosen to improve performance on 32-bit.
# Given that we are building for the future and even low-end mobile phones have 64-bit CPUs,
# it makes sense to optimize for 64-bit and accept the performance hits on 32-bit.
# 16 bytes is the number of bytes that fits into two 64-bit CPU registers.
trivial-copy-size-limit = 16

# END LINEBENDER LINT SET

This is a curated list: Clippy has a lot of lints, and most of them are not included above.

You may occasionally want to run cargo clippy with clippy::pedantic on your codebase, which will cast a very wide nets and catch a lot of very minor issues. The lint set above focuses on problems that either impact correctness or tend to snowball over time.

The list above should be considered canonical. If you think a new lint should be added to Linebender projects, add it to this file in alphabetical order, then copy-paste the list across projects.

To keep this process simple, avoid modifying this list in individual projects. If you want to add other per-project lints, add them above the list. If you want to remove a lint, #![allow] or #![expect] it at the crate root.