Fix outstanding `clang-tidy` errors. (#3654)

Recent runs of `clang-tidy` for me started showing more errors, and this
is a collection of changes to address them.

First, I've systematically applied the disabling tag to all C++ rules
under //explorer/... with `buildozer` so we don't spend time analyzing
this code or reporting errors from it. Not sure this was strictly
necessary, but it seemed like a nice consistency improvement.

Next, I disabled a buggy check for missing `default` cases in
`switch`es. It seems to get confused by the fancy conversions in our
`enum_base.h`. We don't miss much with this as the Clang compiler
warnings for `switch` catch most of our actual bugs. I also removed the
local disabling of this now that it is turned off centrally.

Lastly, I added error checking to two file descriptor manipulating calls
in the `file_test` infrastructure.

---------

Co-authored-by: Jon Ross-Perkins <jperkins@google.com>

.clang-tidy

@@ -16,6 +16,8 @@ WarningsAsErrors: '*'
 #       inst_id = name_ref->value_id;
 #                 ^ unchecked access to optional value
 #     }
+# - bugprone-switch-missing-default-case has false positives for `enum_base.h`.
+#   Clang's built-in switch warnings cover most of our risk of bugs here.
 # - google-readability-function-size overlaps with readability-function-size.
 # - modernize-use-nodiscard is disabled because it only fixes const methods,
 #   not non-const, which yields distracting results on accessors.
@@ -24,8 +26,8 @@ WarningsAsErrors: '*'
 Checks:
   -*, bugprone-*, -bugprone-branch-clone, -bugprone-easily-swappable-parameters,
   -bugprone-exception-escape, -bugprone-narrowing-conversions,
-  -bugprone-unchecked-optional-access, google-*,
-  -google-readability-function-size, -google-readability-todo,
+  -bugprone-switch-missing-default-case, -bugprone-unchecked-optional-access,
+  google-*, -google-readability-function-size, -google-readability-todo,
   misc-definitions-in-headers, misc-misplaced-const, misc-redundant-expression,
   misc-static-assert, misc-unconventional-assign-operator,
   misc-uniqueptr-reset-release, misc-unused-*, modernize-*,

explorer/BUILD

@@ -22,6 +22,9 @@ cc_library(
     name = "main",
     srcs = ["main.cpp"],
     hdrs = ["main.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:error",
         "//common:ostream",
@@ -35,6 +38,9 @@ cc_binary(
     name = "explorer",
     srcs = ["main_bin.cpp"],
     env = cc_env(),
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":main",
         "//common:bazel_working_dir",

explorer/ast/BUILD

@@ -74,6 +74,9 @@ cc_library(
         "ast_test_matchers_internal.h",
     ],
     hdrs = ["ast_test_matchers.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast",
         "@com_google_googletest//:gtest",
@@ -85,6 +88,9 @@ cc_test(
     name = "ast_test_matchers_test",
     size = "small",
     srcs = ["ast_test_matchers_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast",
         ":ast_test_matchers",
@@ -114,11 +120,17 @@ cc_test(
 cc_library(
     name = "library_name",
     hdrs = ["library_name.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
 )
 
 cc_library(
     name = "paren_contents",
     hdrs = ["paren_contents.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//explorer/base:error_builders",
         "//explorer/base:source_location",
@@ -129,6 +141,9 @@ cc_test(
     name = "element_test",
     size = "small",
     srcs = ["element_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast",
         ":paren_contents",
@@ -160,6 +175,9 @@ cc_library(
     name = "static_scope",
     srcs = ["static_scope.cpp"],
     hdrs = ["static_scope.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast",
         "//common:check",
@@ -177,5 +195,8 @@ cc_library(
 cc_library(
     name = "expression_category",
     hdrs = ["expression_category.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = ["@llvm-project//llvm:Support"],
 )

explorer/base/BUILD

@@ -35,6 +35,9 @@ cc_test(
 cc_library(
     name = "decompose",
     hdrs = ["decompose.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "@llvm-project//llvm:Support",
     ],
@@ -44,6 +47,9 @@ cc_test(
     name = "decompose_test",
     size = "small",
     srcs = ["decompose_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":decompose",
         "//testing/base:gtest_main",
@@ -54,6 +60,9 @@ cc_test(
 cc_library(
     name = "error_builders",
     hdrs = ["error_builders.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":source_location",
         "//common:error",
@@ -64,6 +73,9 @@ cc_test(
     name = "error_builders_test",
     size = "small",
     srcs = ["error_builders_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":error_builders",
         ":source_location",
@@ -76,6 +88,9 @@ cc_test(
 cc_library(
     name = "nonnull",
     hdrs = ["nonnull.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:check",
     ],
@@ -84,6 +99,9 @@ cc_library(
 cc_library(
     name = "print_as_id",
     hdrs = ["print_as_id.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:ostream",
     ],
@@ -92,6 +110,9 @@ cc_library(
 cc_library(
     name = "source_location",
     hdrs = ["source_location.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":nonnull",
         "//common:ostream",
@@ -101,6 +122,9 @@ cc_library(
 cc_library(
     name = "trace_stream",
     hdrs = ["trace_stream.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":source_location",
         "//common:check",
@@ -114,6 +138,9 @@ cc_test(
     name = "set_program_phase_raii_test",
     size = "small",
     srcs = ["set_program_phase_raii_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":trace_stream",
         "//testing/base:gtest_main",
@@ -125,6 +152,9 @@ cc_test(
     name = "set_file_context_raii_test",
     size = "small",
     srcs = ["set_file_context_raii_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":source_location",
         ":trace_stream",

explorer/fuzzing/BUILD

@@ -10,6 +10,9 @@ cc_library(
     testonly = 1,
     srcs = ["ast_to_proto.cpp"],
     hdrs = ["ast_to_proto.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//explorer/ast",
         "//testing/fuzzing:carbon_cc_proto",
@@ -21,6 +24,9 @@ cc_binary(
     name = "ast_to_proto",
     testonly = 1,
     srcs = ["ast_to_proto_main.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast_to_proto_lib",
         "//common:bazel_working_dir",
@@ -45,6 +51,9 @@ cc_test(
         "//explorer:carbon_files",
         "//explorer:standard_libraries",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":ast_to_proto_lib",
         "//explorer/syntax",
@@ -61,6 +70,9 @@ cc_library(
     testonly = 1,
     srcs = ["fuzzer_util.cpp"],
     hdrs = ["fuzzer_util.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:check",
         "//common:error",
@@ -81,6 +93,9 @@ cc_test(
     data = [
         "//explorer:standard_libraries",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":fuzzer_util",
         "//testing/base:gtest_main",
@@ -98,10 +113,8 @@ cc_fuzz_test(
     corpus = glob(["fuzzer_corpus/*"]),
     shard_count = 8,
     tags = [
-        "proto-fuzzer",
-        # Running clang-tidy is slow, and explorer is currently feature frozen,
-        # so don't spend time linting it.
         "no-clang-tidy",
+        "proto-fuzzer",
     ],
     deps = [
         ":fuzzer_util",

explorer/interpreter/BUILD

@@ -42,6 +42,9 @@ cc_library(
     hdrs = [
         "action_stack.h",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":action",
         ":stack",
@@ -57,6 +60,9 @@ cc_library(
 cc_library(
     name = "dictionary",
     hdrs = ["dictionary.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = ["//explorer/base:arena"],
 )
 
@@ -64,6 +70,9 @@ cc_library(
     name = "exec_program",
     srcs = ["exec_program.cpp"],
     hdrs = ["exec_program.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":interpreter",
         ":resolve_control_flow",
@@ -84,6 +93,9 @@ cc_library(
     name = "heap",
     srcs = ["heap.cpp"],
     hdrs = ["heap.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":action",
         ":heap_allocation_interface",
@@ -102,6 +114,9 @@ cc_library(
 cc_library(
     name = "heap_allocation_interface",
     hdrs = ["heap_allocation_interface.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:error",
         "//explorer/ast",
@@ -147,6 +162,9 @@ cc_library(
     name = "resolve_control_flow",
     srcs = ["resolve_control_flow.cpp"],
     hdrs = ["resolve_control_flow.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:check",
         "//explorer/ast",
@@ -162,6 +180,9 @@ cc_library(
     name = "resolve_names",
     srcs = ["resolve_names.cpp"],
     hdrs = ["resolve_names.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":stack_space",
         "//common:check",
@@ -177,6 +198,9 @@ cc_library(
 cc_library(
     name = "stack",
     hdrs = ["stack.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = ["//common:check"],
 )
 
@@ -188,6 +212,9 @@ cc_library(
     hdrs = [
         "pattern_analysis.h",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":action",
         "//common:error",
@@ -249,6 +276,9 @@ cc_library(
     hdrs = [
         "resolve_unformed.h",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":stack_space",
         "//common:check",
@@ -266,6 +296,9 @@ cc_library(
     name = "stack_space",
     srcs = ["stack_space.cpp"],
     hdrs = ["stack_space.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:check",
         "//common:error",
@@ -301,6 +334,9 @@ cc_library(
     hdrs = [
         "type_utils.h",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//explorer/ast",
         "//explorer/base:nonnull",
@@ -316,6 +352,9 @@ cc_library(
     hdrs = [
         "pattern_match.h",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":action",
         ":type_utils",

explorer/parse_and_execute/BUILD

@@ -13,6 +13,9 @@ cc_library(
     name = "parse_and_execute",
     srcs = ["parse_and_execute.cpp"],
     hdrs = ["parse_and_execute.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         "//common:check",
         "//common:error",
@@ -29,6 +32,9 @@ cc_test(
     name = "parse_and_execute_test",
     size = "small",
     srcs = ["parse_and_execute_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":parse_and_execute",
         "//testing/base:gtest_main",

explorer/syntax/BUILD

@@ -10,6 +10,9 @@ package(default_visibility = ["//explorer/parse_and_execute:__pkg__"])
 cc_library(
     name = "bison_wrap",
     hdrs = ["bison_wrap.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = ["//common:check"],
 )
 
@@ -17,6 +20,9 @@ cc_test(
     name = "parse_test",
     size = "small",
     srcs = ["parse_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":syntax",
         "//explorer/base:arena",
@@ -30,6 +36,9 @@ cc_library(
     testonly = 1,
     srcs = ["parse_test_matchers_internal.h"],
     hdrs = ["parse_test_matchers.h"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":syntax",
         "@com_google_googletest//:gtest",
@@ -42,6 +51,9 @@ cc_library(
     srcs = ["prelude.cpp"],
     hdrs = ["prelude.h"],
     data = ["//explorer:standard_libraries"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":syntax",
         "//common:error",
@@ -77,6 +89,9 @@ cc_library(
         "-Wno-unused-function",
         "-Wno-writable-strings",
     ],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     visibility = [
         "//explorer/fuzzing:__pkg__",
         "//explorer/parse_and_execute:__pkg__",
@@ -150,6 +165,9 @@ cc_test(
     name = "unimplemented_example_test",
     size = "small",
     srcs = ["unimplemented_example_test.cpp"],
+    # Running clang-tidy is slow, and explorer is currently feature frozen, so
+    # don't spend time linting it.
+    tags = ["no-clang-tidy"],
     deps = [
         ":parse_test_matchers",
         ":syntax",

testing/file_test/file_test_base.cpp

@@ -729,8 +729,18 @@ static auto Main(int argc, char** argv) -> int {
   // Tests might try to read from stdin. Ensure those reads fail by closing
   // stdin and reopening it as /dev/null. Note that STDIN_FILENO doesn't exist
   // on Windows, but POSIX requires it to be 0.
-  llvm::sys::Process::SafelyCloseFileDescriptor(0);
-  llvm::sys::Process::FixupStandardFileDescriptors();
+  if (std::error_code error =
+          llvm::sys::Process::SafelyCloseFileDescriptor(0)) {
+    llvm::errs() << "Unable to close standard input: " << error.message()
+                 << "\n";
+    return EXIT_FAILURE;
+  }
+  if (std::error_code error =
+          llvm::sys::Process::FixupStandardFileDescriptors()) {
+    llvm::errs() << "Unable to correct standard file descriptors: "
+                 << error.message() << "\n";
+    return EXIT_FAILURE;
+  }
 
   llvm::SmallVector<std::string> tests = GetTests();
   auto test_factory = GetFileTestFactory();

toolchain/check/check.cpp

@@ -206,8 +206,6 @@ static auto ProcessParseNodes(Context& context,
                               ErrorTrackingDiagnosticConsumer& err_tracker)
     -> bool {
   for (auto parse_node : context.parse_tree().postorder()) {
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (auto parse_kind = context.parse_tree().node_kind(parse_node)) {
 #define CARBON_PARSE_NODE_KIND(Name)                                         \
   case Parse::NodeKind::Name: {                                              \

toolchain/check/context.cpp

@@ -799,8 +799,6 @@ class TypeCompleter {
     CARBON_CHECK(xref_inst.kind() == SemIR::Builtin::Kind)
         << "TODO: Handle other kinds of inst cross-references";
 
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (xref_inst.As<SemIR::Builtin>().builtin_kind) {
       case SemIR::BuiltinKind::TypeType:
       case SemIR::BuiltinKind::Error:
@@ -919,9 +917,6 @@ class TypeCompleter {
     // dedicated file-scope instruction block where possible, or somewhere else
     // that better reflects the definition of the type, rather than wherever the
     // type happens to first be required to be complete.
-
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (inst.kind()) {
       case SemIR::AddrOf::Kind:
       case SemIR::AddrPattern::Kind:

toolchain/check/eval.cpp

@@ -288,9 +288,6 @@ auto TryEvalInst(Context& context, SemIR::InstId inst_id, SemIR::Inst inst)
     -> SemIR::ConstantId {
   // TODO: Ensure we have test coverage for each of these cases that can result
   // in a constant, once those situations are all reachable.
-
-  // clang warns on unhandled enum values; clang-tidy is incorrect here.
-  // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
   switch (inst.kind()) {
     // These cases are constants if their operands are.
     case SemIR::AddrOf::Kind:

toolchain/lower/function_context.cpp

@@ -41,8 +41,6 @@ auto FunctionContext::LowerBlock(SemIR::InstBlockId block_id) -> void {
   for (const auto& inst_id : sem_ir().inst_blocks().Get(block_id)) {
     auto inst = sem_ir().insts().Get(inst_id);
     CARBON_VLOG() << "Lowering " << inst_id << ": " << inst << "\n";
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (inst.kind()) {
 #define CARBON_SEM_IR_INST_KIND(Name)                     \
   case SemIR::Name::Kind:                                 \

toolchain/parse/parse.cpp

@@ -36,8 +36,6 @@ auto Parse(Lex::TokenizedBuffer& tokens, DiagnosticConsumer& consumer,
   context.PushState(State::DeclScopeLoop);
 
   while (!context.state_stack().empty()) {
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (context.state_stack().back().state) {
 #define CARBON_PARSE_STATE(Name) \
   case State::Name:              \

toolchain/sem_ir/file.cpp

@@ -199,8 +199,6 @@ auto File::OutputYaml(bool include_builtins) const -> Yaml::OutputMapping {
 // precedence of that type's syntax. Higher numbers correspond to higher
 // precedence.
 static auto GetTypePrecedence(InstKind kind) -> int {
-  // clang warns on unhandled enum values; clang-tidy is incorrect here.
-  // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
   switch (kind) {
     case ArrayType::Kind:
     case BindSymbolicName::Kind:
@@ -311,8 +309,6 @@ auto File::StringifyTypeExpr(InstId outer_inst_id) const -> std::string {
     }
 
     auto inst = insts().Get(step.inst_id);
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (inst.kind()) {
       case ArrayType::Kind: {
         auto array = inst.As<ArrayType>();
@@ -501,8 +497,6 @@ auto GetExprCategory(const File& file, InstId inst_id) -> ExprCategory {
 
   while (true) {
     auto inst = ir->insts().Get(inst_id);
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (inst.kind()) {
       case Assign::Kind:
       case BaseDecl::Kind:

toolchain/sem_ir/formatter.cpp

@@ -753,8 +753,6 @@ class Formatter {
   }
 
   auto FormatInstruction(InstId inst_id, Inst inst) -> void {
-    // clang warns on unhandled enum values; clang-tidy is incorrect here.
-    // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
     switch (inst.kind()) {
 #define CARBON_SEM_IR_INST_KIND(InstT)            \
   case InstT::Kind:                               \

toolchain/sem_ir/inst.cpp

@@ -19,8 +19,6 @@ auto Inst::Print(llvm::raw_ostream& out) const -> void {
     }
   };
 
-  // clang warns on unhandled enum values; clang-tidy is incorrect here.
-  // NOLINTNEXTLINE(bugprone-switch-missing-default-case)
   switch (kind_) {
 #define CARBON_SEM_IR_INST_KIND(Name)     \
   case Name::Kind:                        \