diff --git a/src/tint/writer/hlsl/generator.cc b/src/tint/writer/hlsl/generator.cc
index b6aa19c433..a24d129983 100644
--- a/src/tint/writer/hlsl/generator.cc
+++ b/src/tint/writer/hlsl/generator.cc
@@ -16,9 +16,7 @@
 
 #include "src/tint/writer/hlsl/generator_impl.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 
 Options::Options() = default;
 Options::~Options() = default;
@@ -63,6 +61,4 @@ Result Generate(const Program* program, const Options& options) {
   return result;
 }
 
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator.h b/src/tint/writer/hlsl/generator.h
index aa7cfa08a7..a2dcd0b04a 100644
--- a/src/tint/writer/hlsl/generator.h
+++ b/src/tint/writer/hlsl/generator.h
@@ -26,16 +26,15 @@
 #include "src/tint/writer/array_length_from_uniform_options.h"
 #include "src/tint/writer/text.h"
 
+// Forward declarations
 namespace tint {
-
-// Forward declarations
 class Program;
-
-namespace writer {
-namespace hlsl {
-
-// Forward declarations
+namespace writer::hlsl {
 class GeneratorImpl;
+}  // namespace writer::hlsl
+}  // namespace tint
+
+namespace tint::writer::hlsl {
 
 /// Configuration options used for generating HLSL.
 struct Options {
@@ -99,8 +98,6 @@ struct Result {
 /// @returns the resulting HLSL and supplementary information
 Result Generate(const Program* program, const Options& options);
 
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
 
 #endif  // SRC_TINT_WRITER_HLSL_GENERATOR_H_
diff --git a/src/tint/writer/hlsl/generator_impl.cc b/src/tint/writer/hlsl/generator_impl.cc
index fccbdcd473..110071f79e 100644
--- a/src/tint/writer/hlsl/generator_impl.cc
+++ b/src/tint/writer/hlsl/generator_impl.cc
@@ -73,9 +73,7 @@
 #include "src/tint/writer/float_to_string.h"
 #include "src/tint/writer/generate_external_texture_bindings.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 const char kTempNamePrefix[] = "tint_tmp";
@@ -4028,6 +4026,4 @@ bool GeneratorImpl::CallBuiltinHelper(std::ostream& out,
   return true;
 }
 
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl.h b/src/tint/writer/hlsl/generator_impl.h
index 84b533d9c5..96481c23c1 100644
--- a/src/tint/writer/hlsl/generator_impl.h
+++ b/src/tint/writer/hlsl/generator_impl.h
@@ -39,18 +39,15 @@
 #include "src/tint/writer/array_length_from_uniform_options.h"
 #include "src/tint/writer/text_generator.h"
 
-namespace tint {
-
 // Forward declarations
-namespace sem {
+namespace tint::sem {
 class Call;
 class Builtin;
 class TypeConstructor;
 class TypeConversion;
-}  // namespace sem
+}  // namespace tint::sem
 
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 
 /// The result of sanitizing a program for generation.
 struct SanitizedResult {
@@ -539,8 +536,6 @@ class GeneratorImpl : public TextGenerator {
   std::unordered_map<const sem::Type*, std::string> value_or_one_if_zero_;
 };
 
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
 
 #endif  // SRC_TINT_WRITER_HLSL_GENERATOR_IMPL_H_
diff --git a/src/tint/writer/hlsl/generator_impl_array_accessor_test.cc b/src/tint/writer/hlsl/generator_impl_array_accessor_test.cc
index 6746e7fbf1..bcf3ad1a03 100644
--- a/src/tint/writer/hlsl/generator_impl_array_accessor_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_array_accessor_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Expression = TestHelper;
@@ -34,6 +32,4 @@ TEST_F(HlslGeneratorImplTest_Expression, IndexAccessor) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_assign_test.cc b/src/tint/writer/hlsl/generator_impl_assign_test.cc
index 91f68d045f..6305dc0c09 100644
--- a/src/tint/writer/hlsl/generator_impl_assign_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_assign_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Assign = TestHelper;
@@ -206,6 +204,4 @@ void fn() {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_binary_test.cc b/src/tint/writer/hlsl/generator_impl_binary_test.cc
index 9d94a5a91a..f720db7a83 100644
--- a/src/tint/writer/hlsl/generator_impl_binary_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_binary_test.cc
@@ -16,9 +16,7 @@
 #include "src/tint/ast/variable_decl_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Binary = TestHelper;
@@ -823,6 +821,4 @@ void fn() {
 }  // namespace HlslGeneratorDivMod
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_bitcast_test.cc b/src/tint/writer/hlsl/generator_impl_bitcast_test.cc
index fcde73b33d..19c7ed78fb 100644
--- a/src/tint/writer/hlsl/generator_impl_bitcast_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_bitcast_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Bitcast = TestHelper;
@@ -55,6 +53,4 @@ TEST_F(HlslGeneratorImplTest_Bitcast, EmitExpression_Bitcast_Uint) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_block_test.cc b/src/tint/writer/hlsl/generator_impl_block_test.cc
index 9ad534fa24..2f6cd13fd7 100644
--- a/src/tint/writer/hlsl/generator_impl_block_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_block_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Block = TestHelper;
@@ -37,6 +35,4 @@ TEST_F(HlslGeneratorImplTest_Block, Emit_Block) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_break_test.cc b/src/tint/writer/hlsl/generator_impl_break_test.cc
index a3d6844e3d..4a2c038598 100644
--- a/src/tint/writer/hlsl/generator_impl_break_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_break_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Break = TestHelper;
@@ -34,6 +32,4 @@ TEST_F(HlslGeneratorImplTest_Break, Emit_Break) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_builtin_test.cc b/src/tint/writer/hlsl/generator_impl_builtin_test.cc
index 7e4150d070..95d59afa9d 100644
--- a/src/tint/writer/hlsl/generator_impl_builtin_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_builtin_test.cc
@@ -18,9 +18,7 @@
 #include "src/tint/sem/call.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using BuiltinType = sem::BuiltinType;
@@ -730,6 +728,4 @@ void main() {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_builtin_texture_test.cc b/src/tint/writer/hlsl/generator_impl_builtin_texture_test.cc
index e4e26b76f3..f11dd90879 100644
--- a/src/tint/writer/hlsl/generator_impl_builtin_texture_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_builtin_texture_test.cc
@@ -18,9 +18,7 @@
 #include "src/tint/ast/stage_attribute.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using ::testing::HasSubstr;
@@ -391,6 +389,4 @@ INSTANTIATE_TEST_SUITE_P(
     testing::ValuesIn(ast::builtin::test::TextureOverloadCase::ValidCases()));
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_call_test.cc b/src/tint/writer/hlsl/generator_impl_call_test.cc
index d1adc0ef4d..8a3289e9e6 100644
--- a/src/tint/writer/hlsl/generator_impl_call_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_call_test.cc
@@ -15,9 +15,7 @@
 #include "src/tint/ast/call_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Call = TestHelper;
@@ -76,6 +74,4 @@ TEST_F(HlslGeneratorImplTest_Call, EmitStatement_Call) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_case_test.cc b/src/tint/writer/hlsl/generator_impl_case_test.cc
index 56ac282d3a..004ba410b0 100644
--- a/src/tint/writer/hlsl/generator_impl_case_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_case_test.cc
@@ -15,9 +15,7 @@
 #include "src/tint/ast/fallthrough_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Case = TestHelper;
@@ -110,6 +108,4 @@ TEST_F(HlslGeneratorImplTest_Case, Emit_Case_Default) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_cast_test.cc b/src/tint/writer/hlsl/generator_impl_cast_test.cc
index f24b9d23dd..283c8590cd 100644
--- a/src/tint/writer/hlsl/generator_impl_cast_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_cast_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Cast = TestHelper;
@@ -44,6 +42,4 @@ TEST_F(HlslGeneratorImplTest_Cast, EmitExpression_Cast_Vector) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_constructor_test.cc b/src/tint/writer/hlsl/generator_impl_constructor_test.cc
index 4afcffe715..8801edd071 100644
--- a/src/tint/writer/hlsl/generator_impl_constructor_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_constructor_test.cc
@@ -15,9 +15,7 @@
 #include "gmock/gmock.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using ::testing::HasSubstr;
@@ -259,6 +257,4 @@ TEST_F(HlslGeneratorImplTest_Constructor, EmitConstructor_Type_Struct_Empty) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_continue_test.cc b/src/tint/writer/hlsl/generator_impl_continue_test.cc
index f487938495..5a9e07da63 100644
--- a/src/tint/writer/hlsl/generator_impl_continue_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_continue_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Continue = TestHelper;
@@ -41,6 +39,4 @@ TEST_F(HlslGeneratorImplTest_Continue, Emit_Continue) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_discard_test.cc b/src/tint/writer/hlsl/generator_impl_discard_test.cc
index 36322f5aa7..e8e52a9b5d 100644
--- a/src/tint/writer/hlsl/generator_impl_discard_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_discard_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Discard = TestHelper;
@@ -34,6 +32,4 @@ TEST_F(HlslGeneratorImplTest_Discard, Emit_Discard) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_function_test.cc b/src/tint/writer/hlsl/generator_impl_function_test.cc
index c3306efeed..15e9e86712 100644
--- a/src/tint/writer/hlsl/generator_impl_function_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_function_test.cc
@@ -20,9 +20,7 @@
 
 using ::testing::HasSubstr;
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Function = TestHelper;
@@ -912,6 +910,4 @@ void b() {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_identifier_test.cc b/src/tint/writer/hlsl/generator_impl_identifier_test.cc
index 56237f59af..d054bd8644 100644
--- a/src/tint/writer/hlsl/generator_impl_identifier_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_identifier_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Identifier = TestHelper;
@@ -35,6 +33,4 @@ TEST_F(HlslGeneratorImplTest_Identifier, EmitIdentifierExpression) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_if_test.cc b/src/tint/writer/hlsl/generator_impl_if_test.cc
index 63c551d261..f2e092cf9c 100644
--- a/src/tint/writer/hlsl/generator_impl_if_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_if_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_If = TestHelper;
@@ -130,6 +128,4 @@ TEST_F(HlslGeneratorImplTest_If, Emit_IfWithMultiple) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_import_test.cc b/src/tint/writer/hlsl/generator_impl_import_test.cc
index d80ba11dc6..ac415fe9e9 100644
--- a/src/tint/writer/hlsl/generator_impl_import_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_import_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Import = TestHelper;
@@ -278,6 +276,4 @@ TEST_F(HlslGeneratorImplTest_Import, HlslImportData_Determinant) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_loop_test.cc b/src/tint/writer/hlsl/generator_impl_loop_test.cc
index 82db0293a5..6932d3b7a3 100644
--- a/src/tint/writer/hlsl/generator_impl_loop_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_loop_test.cc
@@ -15,9 +15,7 @@
 #include "src/tint/ast/variable_decl_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Loop = TestHelper;
@@ -376,6 +374,4 @@ TEST_F(HlslGeneratorImplTest_Loop, Emit_ForLoopWithMultiStmtInitCondCont) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_member_accessor_test.cc b/src/tint/writer/hlsl/generator_impl_member_accessor_test.cc
index 79be125f5a..8244767461 100644
--- a/src/tint/writer/hlsl/generator_impl_member_accessor_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_member_accessor_test.cc
@@ -16,9 +16,7 @@
 #include "src/tint/ast/stage_attribute.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using ::testing::HasSubstr;
@@ -763,6 +761,4 @@ TEST_F(HlslGeneratorImplTest_MemberAccessor, Swizzle_gbr) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_module_constant_test.cc b/src/tint/writer/hlsl/generator_impl_module_constant_test.cc
index 1de71ec203..30b0b0c227 100644
--- a/src/tint/writer/hlsl/generator_impl_module_constant_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_module_constant_test.cc
@@ -15,9 +15,7 @@
 #include "src/tint/ast/id_attribute.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_ModuleConstant = TestHelper;
@@ -87,6 +85,4 @@ static const float b = WGSL_SPEC_CONSTANT_1;
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_return_test.cc b/src/tint/writer/hlsl/generator_impl_return_test.cc
index cb266f1356..3f839fc1bf 100644
--- a/src/tint/writer/hlsl/generator_impl_return_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_return_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Return = TestHelper;
@@ -46,6 +44,4 @@ TEST_F(HlslGeneratorImplTest_Return, Emit_ReturnWithValue) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_sanitizer_test.cc b/src/tint/writer/hlsl/generator_impl_sanitizer_test.cc
index 3a01bb5473..cb31f4d1d3 100644
--- a/src/tint/writer/hlsl/generator_impl_sanitizer_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_sanitizer_test.cc
@@ -17,9 +17,7 @@
 #include "src/tint/ast/variable_decl_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslSanitizerTest = TestHelper;
@@ -334,6 +332,4 @@ TEST_F(HlslSanitizerTest, InlinePtrLetsComplexChain) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_switch_test.cc b/src/tint/writer/hlsl/generator_impl_switch_test.cc
index 40310a5817..792b64be6d 100644
--- a/src/tint/writer/hlsl/generator_impl_switch_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_switch_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest_Switch = TestHelper;
@@ -66,6 +64,4 @@ TEST_F(HlslGeneratorImplTest_Switch, Emit_Switch_OnlyDefaultCase) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_test.cc b/src/tint/writer/hlsl/generator_impl_test.cc
index d97ed31d46..ea479e46aa 100644
--- a/src/tint/writer/hlsl/generator_impl_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslGeneratorImplTest = TestHelper;
@@ -67,6 +65,4 @@ INSTANTIATE_TEST_SUITE_P(
         HlslBuiltinData{ast::Builtin::kSampleMask, "SV_Coverage"}));
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_type_test.cc b/src/tint/writer/hlsl/generator_impl_type_test.cc
index ce179a9d63..bea99cefe2 100644
--- a/src/tint/writer/hlsl/generator_impl_type_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_type_test.cc
@@ -22,9 +22,7 @@
 #include "src/tint/sem/storage_texture_type.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using ::testing::HasSubstr;
@@ -566,6 +564,4 @@ INSTANTIATE_TEST_SUITE_P(
             "RWTexture1D<int4> tex : register(u1, space2);"}));
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_unary_op_test.cc b/src/tint/writer/hlsl/generator_impl_unary_op_test.cc
index 2b376c01aa..3217a0194b 100644
--- a/src/tint/writer/hlsl/generator_impl_unary_op_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_unary_op_test.cc
@@ -14,9 +14,7 @@
 
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using HlslUnaryOpTest = TestHelper;
@@ -88,6 +86,4 @@ TEST_F(HlslUnaryOpTest, Negation) {
   EXPECT_EQ(out.str(), "-(expr)");
 }
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_variable_decl_statement_test.cc b/src/tint/writer/hlsl/generator_impl_variable_decl_statement_test.cc
index 7f16121a04..1188aed88b 100644
--- a/src/tint/writer/hlsl/generator_impl_variable_decl_statement_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_variable_decl_statement_test.cc
@@ -16,9 +16,7 @@
 #include "src/tint/ast/variable_decl_statement.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 
 using ::testing::HasSubstr;
@@ -122,6 +120,4 @@ TEST_F(HlslGeneratorImplTest_VariableDecl,
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/generator_impl_workgroup_var_test.cc b/src/tint/writer/hlsl/generator_impl_workgroup_var_test.cc
index f59c71fbc6..641b8f1890 100644
--- a/src/tint/writer/hlsl/generator_impl_workgroup_var_test.cc
+++ b/src/tint/writer/hlsl/generator_impl_workgroup_var_test.cc
@@ -17,9 +17,7 @@
 #include "src/tint/ast/stage_attribute.h"
 #include "src/tint/writer/hlsl/test_helper.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 namespace {
 using ::testing::HasSubstr;
 
@@ -56,6 +54,4 @@ TEST_F(HlslGeneratorImplTest_WorkgroupVar, Aliased) {
 }
 
 }  // namespace
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
diff --git a/src/tint/writer/hlsl/test_helper.h b/src/tint/writer/hlsl/test_helper.h
index cac464506d..2fc800d191 100644
--- a/src/tint/writer/hlsl/test_helper.h
+++ b/src/tint/writer/hlsl/test_helper.h
@@ -25,9 +25,7 @@
 #include "src/tint/writer/hlsl/generator.h"
 #include "src/tint/writer/hlsl/generator_impl.h"
 
-namespace tint {
-namespace writer {
-namespace hlsl {
+namespace tint::writer::hlsl {
 
 /// Helper class for testing
 template <typename BODY>
@@ -116,8 +114,6 @@ using TestHelper = TestHelperBase<testing::Test>;
 template <typename T>
 using TestParamHelper = TestHelperBase<testing::TestWithParam<T>>;
 
-}  // namespace hlsl
-}  // namespace writer
-}  // namespace tint
+}  // namespace tint::writer::hlsl
 
 #endif  // SRC_TINT_WRITER_HLSL_TEST_HELPER_H_