.clang-tidy

# Part of the Carbon Language project, under the Apache License v2.0 with LLVM
# Exceptions. See /LICENSE for license information.
# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

---
# Get colors when outputting through `bazel build --config=clang-tidy`.
UseColor: true
# This is necessary for `--config=clang-tidy` to catch errors.
WarningsAsErrors: '*'

# TODO: clang-tidy-16 doesn't support this format; it's retained for comments.
# Switch once we update the minimum version.
#
# # We turn on all of a few categories by default.
# - '-*'
# - 'bugprone-*'
# - 'google-*'
# - 'misc-*'
# - 'modernize-*'
# - 'performance-*'
# - 'readability-*'
#
# # Disabled due to the implied style choices.
# - '-misc-const-correctness'
# - '-misc-include-cleaner'
# - '-misc-use-anonymous-namespace'
# - '-modernize-return-braced-init-list'
# - '-modernize-use-default-member-init'
# - '-modernize-use-integer-sign-comparison'
# - '-modernize-use-emplace'
# - '-readability-avoid-nested-conditional-operator'
# - '-readability-convert-member-functions-to-static'
# - '-readability-else-after-return'
# - '-readability-identifier-length'
# - '-readability-implicit-bool-conversion'
# - '-readability-make-member-function-const'
# - '-readability-math-missing-parentheses'
# - '-readability-static-definition-in-anonymous-namespace'
# - '-readability-use-anyofallof'
#
# # Warns when we have multiple empty cases in switches, which we do for comment
# # reasons.
# - '-bugprone-branch-clone'
# # Frequently warns on multiple parameters of the same type.
# - '-bugprone-easily-swappable-parameters'
# # Finds issues like out-of-memory in main(). We don't use exceptions, so it's
# # unlikely to find real issues.
# - '-bugprone-exception-escape'
# # Has false positives in places such as using an argument to declare a name,
# # which cannot have parentheses. For our limited use of macros, this is a
# # common conflict.
# - '-bugprone-macro-parentheses'
# # Conflicts with integer type C++ style.
# - '-bugprone-narrowing-conversions'
# # Has false positives for `enum_base.h`. Clang's built-in switch warnings
# # cover most of our risk of bugs here.
# - '-bugprone-switch-missing-default-case'
# # In clang-tidy 16, has false positives on code like:
# #     while (auto name_ref = insts().Get(inst_id).TryAs<SemIR::NameRef>()) {
# #       inst_id = name_ref->value_id;
# #                 ^ unchecked access to optional value
# #     }
# - '-bugprone-unchecked-optional-access'
# # Overlaps with `readability-function-size`.
# - '-google-readability-function-size'
# # Suggests usernames on TODOs, which we don't want.
# - '-google-readability-todo'
# # Overlaps with `-Wno-missing-prototypes`.
# - '-misc-use-internal-linkage'
# # Suggests `std::array`, which we could migrate to, but conflicts with the
# # status quo.
# - '-modernize-avoid-c-arrays'
# # Warns on creation of SemIR typed insts, for which we do not currently want
# # to use designated initialization.
# - '-modernize-use-designated-initializers'
# # Only fixes const methods, not non-const, which yields distracting results on
# # accessors.
# - '-modernize-use-nodiscard'
# # Duplicates `modernize-pass-by-value`.
# - '-performance-unnecessary-value-param'
# # Warns on enums which use the `LastValue = Value` pattern if all the other
# # discriminants aren't given an explicit value.
# - '-readability-enum-initial-value'
# # Warns too frequently.
# - '-readability-function-cognitive-complexity'
# # Warns in reasonably documented situations.
# - '-readability-magic-numbers'
# # Warns on `= {}` which is also used to indicate which fields do not need to
# # be explicitly initialized in aggregate initialization.
# - '-readability-redundant-member-init'
# # Warns when callers use similar names as different parameters.
# - '-readability-suspicious-call-argument'
Checks:
  -*, bugprone-*, google-*, misc-*, modernize-*, performance-*, readability-*,
  -misc-const-correctness, -misc-include-cleaner, -misc-use-anonymous-namespace,
  -modernize-return-braced-init-list, -modernize-use-default-member-init,
  -modernize-use-integer-sign-comparison, -modernize-use-emplace,
  -readability-avoid-nested-conditional-operator,
  -readability-convert-member-functions-to-static,
  -readability-else-after-return, -readability-identifier-length,
  -readability-implicit-bool-conversion,
  -readability-make-member-function-const,
  -readability-math-missing-parentheses,
  -readability-static-definition-in-anonymous-namespace,
  -readability-use-anyofallof, -bugprone-branch-clone,
  -bugprone-easily-swappable-parameters, -bugprone-exception-escape,
  -bugprone-macro-parentheses, -bugprone-narrowing-conversions,
  -bugprone-switch-missing-default-case, -bugprone-unchecked-optional-access,
  -google-readability-function-size, -google-readability-todo,
  -misc-use-internal-linkage, -modernize-avoid-c-arrays,
  -modernize-use-designated-initializers, -modernize-use-nodiscard,
  -performance-unnecessary-value-param, -readability-enum-initial-value,
  -readability-function-cognitive-complexity, -readability-magic-numbers,
  -readability-redundant-member-init, -readability-suspicious-call-argument
CheckOptions:
  # Don't warn on structs; done by ignoring when there are only public members.
  - key: misc-non-private-member-variables-in-classes.IgnoreClassesWithAllMemberVariablesBeingPublic
    value: true

  # CamelCase names.
  - key: readability-identifier-naming.ClassCase
    value: CamelCase
  - key: readability-identifier-naming.ClassConstantCase
    value: CamelCase
  - key: readability-identifier-naming.ConstexprVariableCase
    value: CamelCase
  - key: readability-identifier-naming.NamespaceCase
    value: CamelCase
  - key: readability-identifier-naming.StructCase
    value: CamelCase
  - key: readability-identifier-naming.TemplateParameterCase
    value: CamelCase
  - key: readability-identifier-naming.TypeAliasCase
    value: CamelCase
  - key: readability-identifier-naming.TypedefCase
    value: CamelCase
  - key: readability-identifier-naming.UnionCase
    value: CamelCase

  # lower_case names.
  - key: readability-identifier-naming.ClassMemberCase
    value: lower_case
  - key: readability-identifier-naming.ParameterCase
    value: lower_case
  - key: readability-identifier-naming.VariableCase
    value: lower_case

  # TODO: This is for explorer's use of LLVM casting support, so we should be
  # able to remove it once explorer is deleted.
  - key: readability-identifier-naming.MethodIgnoredRegexp
    value: '^classof$'

  # This erroneously fires in C++20 mode with LLVM 16 clang-tidy, due to:
  # https://github.com/llvm/llvm-project/issues/46097
  - key: readability-identifier-naming.TemplateParameterIgnoredRegexp
    value: '^expr-type$'