Useful lint rules for rustc & clippy

lint-rules.md

Must have clippy rules

• rustc allowed-by-default lints: https://doc.rust-lang.org/rustc/lints/listing/allowed-by-default
• clippy lints: https://rust-lang.github.io/rust-clippy/stable/index.html

---

1. For an app
   1. Correctness & Performance
   2. As code
2. For a library
   1. Correctness & Performance
   2. Stability
   3. Cargo
   4. As code
3. In general
   1. Correctness & Performance
   2. Style
   3. Cargo
   4. As code
4. Problem specific
   1. Floating point math
   2. No panic
   3. No debug prints

---

For an app

Correctness & Performance

• unsafe_code

As code

#![forbid(unsafe_code)]

For a library

Correctness & Performance

• clippy::exit
• clippy::future_not_send
• clippy::missing_inline_in_public_items
• clippy::must_use_candidate
• clippy::pattern_type_mismatch

Stability

• clippy::exhaustive_enums // #[non_exhaustive]
• clippy::exhaustive_structs // #[non_exhaustive]
• clippy::must_use_unit // #[must_use]

Cargo

• clippy::cargo_common_metadata

As code

#![forbid(clippy::exit)]

#![deny(clippy::pattern_type_mismatch)]

#![warn(
    clippy::future_not_send,
    clippy::exhaustive_enums,
    clippy::exhaustive_structs,
    clippy::must_use_unit,
    clippy::missing_inline_in_public_items,
    clippy::must_use_candidate,
)]

In general

Correctness & Performance

• must_not_suspend // #[must_not_suspend]
• fuzzy_provenance_casts
• lossy_provenance_casts
• meta_variable_misuse
• missing_abi
• missing_copy_implementations
• missing_debug_implementations
• missing_docs
• non_local_definitions
• unnameable_types
• unreachable_pub
• unsafe_op_in_unsafe_fn
• clippy::arithmetic_side_effects
• clippy::as_conversions OR clippy::cast_lossless & clippy::cast_possible_truncation & clippy::cast_possible_wrap & clippy::cast_possible_truncation & clippy::cast_precision_loss & clippy::cast_sign_loss & clippy::char_lit_as_u8 & clippy::ref_as_ptr & clippy::ptr_as_ptr & clippy::checked_conversions & clippy::borrow_as_ptr & clippy::ref_as_ptr
• clippy::case_sensitive_file_extension_comparisons
• clippy::cfg_not_test
• clippy::clear_with_drain
• clippy::clone_on_ref_ptr
• clippy::cloned_instead_of_copied
• clippy::collection_is_never_read
• clippy::create_dir
• clippy::debug_assert_with_mut_call
• clippy::derive_partial_eq_without_eq
• clippy::error_impl_error
• clippy::fallible_impl_from
• clippy::filetype_is_file
• clippy::filter_map_next
• clippy::flat_map_option
• clippy::fn_to_numeric_cast_any
• clippy::format_push_string
• clippy::index_refutable_slice
• clippy::indexing_slicing
• clippy::inefficient_to_string
• clippy::infinite_loop
• clippy::iter_filter_is_ok
• clippy::iter_not_returning_iterator
• clippy::iter_on_empty_collections
• clippy::iter_on_single_items
• clippy::iter_with_drain
• clippy::large_stack_arrays
• clippy::large_types_passed_by_value
• clippy::linkedlist
• clippy::manual_instant_elapsed
• clippy::match_on_vec_items
• clippy::match_same_arms
• clippy::match_wild_err_arm
• clippy::match_wildcard_for_single_variants
• clippy::mem_forget
• clippy::mismatching_type_param_order
• clippy::missing_assert_message
• clippy::missing_const_for_fn
• clippy::missing_docs_in_private_items
• clippy::missing_errors_doc
• clippy::missing_panics_doc
• clippy::mut_mut
• clippy::mutex_atomic
• clippy::mutex_integer
• clippy::needless_collect
• clippy::needless_pass_by_ref_mut
• clippy::needless_pass_by_value
• clippy::option_as_ref_cloned
• clippy::option_option
• clippy::panic
• clippy::panic_in_result_fn
• clippy::path_buf_push_overwrite
• clippy::pathbuf_init_then_push
• clippy::ptr_cast_constness
• clippy::rc_buffer
• clippy::rc_mutex
• clippy::redundant_pub_crate
• clippy::shadow_unrelated
• clippy::should_panic_without_expect
• clippy::significant_drop_in_scrutinee & clippy::significant_drop_tightening // read the docs
• clippy::str_split_at_newline
• clippy::str_to_string
• clippy::string_add
• clippy::string_lit_as_bytes
• clippy::string_lit_chars_any
• clippy::string_to_string
• clippy::tests_outside_test_module
• clippy::trait_duplication_in_bounds
• clippy::unchecked_duration_subtraction
• clippy::unicode_not_nfc
• clippy::uninhabited_references
• clippy::unnecessary_box_returns
• clippy::unnecessary_join
• clippy::unused_peekable
• clippy::unwrap_used & clippy::expect_used
• clippy::verbose_file_reads
• clippy::while_float

Style

• unit_bindings
• clippy::allow_attributes_without_reason
• clippy::assertions_on_result_states
• clippy::bool_to_int_with_if
• clippy::dbg_macro & clippy::print_stderr & clippy::print_stdout // release-only
• clippy::default_trait_access
• clippy::empty_line_after_doc_comments
• clippy::enum_glob_use
• clippy::equatable_if_let
• clippy::fn_params_excessive_bools
• clippy::from_iter_instead_of_collect
• clippy::if_then_some_else_none
• clippy::ignored_unit_patterns
• clippy::implicit_clone
• clippy::items_after_statements
• clippy::manual_c_str_literals
• clippy::manual_is_variant_and
• clippy::manual_let_else
• clippy::manual_ok_or
• clippy::manual_string_new
• clippy::many_single_char_names
• clippy::map_err_ignore
• clippy::match_bool
• clippy::module_name_repetitions
• clippy::multiple_inherent_impl
• clippy::multiple_unsafe_ops_per_block
• clippy::non_ascii_idents OR non_ascii_idents
• clippy::option_if_let_else
• clippy::partial_pub_fields
• clippy::pub_underscore_fields
• clippy::redundant_closure_for_method_calls
• clippy::ref_patterns
• clippy::rest_pat_in_fully_bound_structs
• clippy::return_self_not_must_use
• clippy::same_name_method
• clippy::self_named_module_files
• clippy::semicolon_if_nothing_returned
• clippy::shadow_same
• clippy::single_char_pattern
• clippy::single_match_else
• clippy::struct_field_names
• clippy::uninlined_format_args
• clippy::unreadable_literal
• clippy::unused_result_ok
• clippy::use_self
• clippy::used_underscore_binding
• clippy::verbose_bit_mask

Cargo

• unused_crate_dependencies
• clippy::negative_feature_names
• clippy::redundant_feature_names
• clippy::unnecessary_safety_comment
• clippy::unnecessary_safety_doc
• clippy::wildcard_dependencies

As code

#![cfg_attr(
    all(not(test), not(debug_assertions)),
    warn(
        clippy::dbg_macro,
        clippy::print_stderr,
        clippy::print_stdout,
        clippy::unwrap_used,
        clippy::expect_used,
        unused_crate_dependencies,
    )
)]

#![forbid(
    meta_variable_misuse,
    non_local_definitions,
    unnameable_types,
    unreachable_pub,
    clippy::cast_lossless,
    clippy::cast_possible_truncation,
    clippy::cast_possible_wrap,
    clippy::cast_possible_truncation,
    clippy::cast_precision_loss,
    clippy::cast_sign_loss,
    clippy::fn_to_numeric_cast_any,
    clippy::char_lit_as_u8,
    clippy::ref_as_ptr,
    clippy::ptr_as_ptr,
    clippy::checked_conversions,
    clippy::borrow_as_ptr,
    clippy::ref_as_ptr,
    clippy::clear_with_drain,
    clippy::clone_on_ref_ptr,
    clippy::debug_assert_with_mut_call,
    clippy::error_impl_error,
    clippy::fallible_impl_from,
    clippy::format_push_string,
    clippy::index_refutable_slice,
    clippy::indexing_slicing,
    clippy::inefficient_to_string,
    clippy::iter_not_returning_iterator,
    clippy::manual_instant_elapsed,
    clippy::match_on_vec_items,
    clippy::mut_mut,
    clippy::mutex_atomic,
    clippy::mutex_integer,
    clippy::path_buf_push_overwrite,
    clippy::vec_init_then_push,
    clippy::ptr_cast_constness,
    clippy::rc_mutex,
    clippy::shadow_unrelated,
    clippy::string_add,
    clippy::string_lit_as_bytes,
    clippy::string_to_string,
    clippy::tests_outside_test_module,
    clippy::trait_duplication_in_bounds,
    clippy::unchecked_duration_subtraction,
    clippy::allow_attributes_without_reason,
    non_ascii_idents,

)]

#![deny(
    missing_abi,
    unsafe_op_in_unsafe_fn,
    clippy::cloned_instead_of_copied,
    clippy::filetype_is_file,
    clippy::flat_map_option,
    clippy::large_stack_arrays,
    clippy::large_types_passed_by_value,
    clippy::match_same_arms,
    clippy::missing_errors_doc,
    clippy::missing_panics_doc,
    clippy::needless_collect,
    clippy::option_as_ref_cloned,
    clippy::option_option,
    clippy::should_panic_without_expect,
    clippy::str_split_at_newline,
    clippy::str_to_string,
    clippy::string_lit_chars_any,
    clippy::unicode_not_nfc,
    clippy::uninhabited_references,
    clippy::verbose_file_reads,
    clippy::while_float,
    clippy::empty_line_after_doc_comments,
    clippy::wildcard_dependencies,
)]

#![warn(
    missing_copy_implementations,
    missing_debug_implementations,
    missing_docs,
    clippy::arithmetic_side_effects,
    clippy::case_sensitive_file_extension_comparisons,
    clippy::collection_is_never_read,
    clippy::create_dir,
    clippy::derive_partial_eq_without_eq,
    clippy::filter_map_next,
    clippy::flat_map_option,
    clippy::infinite_loop,
    clippy::iter_filter_is_ok,
    clippy::iter_on_empty_collections,
    clippy::iter_with_drain,
    clippy::linkedlist,
    clippy::match_wild_err_arm,
    clippy::match_wildcard_for_single_variants,
    clippy::mem_forget,
    clippy::mismatching_type_param_order,
    clippy::missing_assert_message,
    clippy::missing_const_for_fn,
    clippy::missing_docs_in_private_items,
    clippy::needless_pass_by_ref_mut,
    clippy::needless_pass_by_value,
    clippy::panic_in_result_fn,
    clippy::rc_buffer,
    clippy::unnecessary_box_returns,
    clippy::unnecessary_join,
    clippy::unused_peekable,
    unit_bindings,
    clippy::assertions_on_result_states,
    clippy::bool_to_int_with_if,
    clippy::default_trait_access,
    clippy::enum_glob_use,
    clippy::equatable_if_let,
    clippy::fn_params_excessive_bools,
    clippy::from_iter_instead_of_collect,
    clippy::if_then_some_else_none,
    clippy::ignored_unit_patterns,
    clippy::implicit_clone,
    clippy::items_after_statements,
    clippy::manual_c_str_literals,
    clippy::manual_is_variant_and,
    clippy::manual_let_else,
    clippy::manual_ok_or,
    clippy::manual_string_new,
    clippy::many_single_char_names,
    clippy::map_err_ignore,
    clippy::match_bool,
    clippy::module_name_repetitions,
    clippy::multiple_inherent_impl,
    clippy::multiple_unsafe_ops_per_block,
    clippy::option_if_let_else,
    clippy::partial_pub_fields,
    clippy::pub_underscore_fields,
    clippy::redundant_closure_for_method_calls,
    clippy::ref_patterns,
    clippy::rest_pat_in_fully_bound_structs,
    clippy::return_self_not_must_use,
    clippy::same_name_method,
    clippy::self_named_module_files,
    clippy::semicolon_if_nothing_returned,
    clippy::shadow_same,
    clippy::single_char_pattern,
    clippy::single_match_else,
    clippy::struct_field_names,
    clippy::uninlined_format_args,
    clippy::unreadable_literal,
    clippy::use_self,
    clippy::used_underscore_binding,
    clippy::verbose_bit_mask,
    clippy::negative_feature_names,
    clippy::redundant_feature_names,
    clippy::unnecessary_safety_comment,
    clippy::unnecessary_safety_doc,
)]

Problem-specific

Floating point math

• clippy::float_arithmetic
• clippy::float_cmp
• clippy::float_cmp_const
• clippy::imprecise_flops
• clippy::suboptimal_flops
• clippy::suspicious_xor_used_as_pow
• clippy::while_float
• clippy::lossy_float_literal
• clippy::default_numeric_fallback
• clippy::cast_precision_loss

No panic

• clippy::panic
• clippy::unwrap_used
• clippy::expect_used

No debug prints

• clippy::dbg_macro
• clippy::print_stderr
• clippy::print_stdout