Index: clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
===================================================================
--- clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
+++ clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.h
@@ -44,7 +44,8 @@
     CT_UpperCase,
     CT_CamelCase,
     CT_CamelSnakeCase,
-    CT_CamelSnakeBack
+    CT_CamelSnakeBack,
+    CT_LeadingUpperSnakeCase
   };
 
   enum HungarianPrefixType {
Index: clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
===================================================================
--- clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
+++ clang-tools-extra/clang-tidy/readability/IdentifierNamingCheck.cpp
@@ -46,7 +46,9 @@
           {readability::IdentifierNamingCheck::CT_CamelSnakeCase,
            "Camel_Snake_Case"},
           {readability::IdentifierNamingCheck::CT_CamelSnakeBack,
-           "camel_Snake_Back"}};
+           "camel_Snake_Back"},
+          {readability::IdentifierNamingCheck::CT_LeadingUpperSnakeCase,
+           "Leading_upper_snake_case"}};
   return llvm::ArrayRef(Mapping);
 }
 
@@ -871,6 +873,7 @@
       llvm::Regex("^[A-Z][a-zA-Z0-9]*$"),
       llvm::Regex("^[A-Z]([a-z0-9]*(_[A-Z])?)*"),
       llvm::Regex("^[a-z]([a-z0-9]*(_[A-Z])?)*"),
+      llvm::Regex("^[A-Z]([a-z0-9_]*[a-z])*$"),
   };
 
   if (!Name.consume_front(Style.Prefix))
@@ -993,6 +996,18 @@
       Fixup += Word.substr(1).lower();
     }
     break;
+
+  case IdentifierNamingCheck::CT_LeadingUpperSnakeCase:
+    for (auto const &Word : Words) {
+      if (&Word != &Words.front()) {
+        Fixup += "_";
+        Fixup += Word.lower();
+      } else {
+        Fixup += toupper(Word.front());
+        Fixup += Word.substr(1).lower();
+      }
+    }
+    break;
   }
 
   return Fixup.str().str();
Index: clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming-case-violation.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming-case-violation.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming-case-violation.cpp
@@ -5,6 +5,7 @@
 // RUN:   readability-identifier-naming.ClassCase: UUPER_CASE, \
 // RUN:   readability-identifier-naming.StructCase: CAMEL, \
 // RUN:   readability-identifier-naming.EnumCase: AnY_cASe, \
+// RUN:   readability-identifier-naming.VirtualMethodCase: lEaDiNg_upper_SNAKE_CaSe, \
 // RUN:   }}" -- 2>&1 | FileCheck %s --implicit-check-not="{{warning|error}}:"
 
 // CHECK-DAG: warning: invalid configuration value 'camelback' for option 'readability-identifier-naming.FunctionCase'; did you mean 'camelBack'? [clang-tidy-config]
@@ -13,3 +14,4 @@
 // CHECK-DAG: warning: invalid configuration value 'CAMEL' for option 'readability-identifier-naming.StructCase' [clang-tidy-config]
 // This fails on the EditDistance, but as it matches ignoring case suggest the correct value
 // CHECK-DAG: warning: invalid configuration value 'AnY_cASe' for option 'readability-identifier-naming.EnumCase'; did you mean 'aNy_CasE'? [clang-tidy-config]
+// CHECK-DAG: warning: invalid configuration value 'lEaDiNg_upper_SNAKE_CaSe' for option 'readability-identifier-naming.VirtualMethodCase'; did you mean 'Leading_upper_snake_case'? [clang-tidy-config]
Index: clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming.cpp
===================================================================
--- clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming.cpp
+++ clang-tools-extra/test/clang-tidy/checkers/readability/identifier-naming.cpp
@@ -49,7 +49,7 @@
 // RUN:     readability-identifier-naming.StaticConstantCase: UPPER_CASE, \
 // RUN:     readability-identifier-naming.StaticVariableCase: camelBack, \
 // RUN:     readability-identifier-naming.StaticVariablePrefix: 's_', \
-// RUN:     readability-identifier-naming.StructCase: lower_case, \
+// RUN:     readability-identifier-naming.StructCase: Leading_upper_snake_case, \
 // RUN:     readability-identifier-naming.TemplateParameterCase: UPPER_CASE, \
 // RUN:     readability-identifier-naming.TemplateTemplateParameterCase: CamelCase, \
 // RUN:     readability-identifier-naming.TemplateUsingCase: lower_case, \
@@ -513,9 +513,9 @@
 
 struct THIS___Structure {
 // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: invalid case style for struct 'THIS___Structure'
-// CHECK-FIXES: {{^}}struct this_structure {{{$}}
+// CHECK-FIXES: {{^}}struct This_structure {{{$}}
     THIS___Structure();
-// CHECK-FIXES: {{^}}    this_structure();{{$}}
+// CHECK-FIXES: {{^}}    This_structure();{{$}}
 
   union __MyUnion_is_wonderful__ {};
 // CHECK-MESSAGES: :[[@LINE-1]]:9: warning: invalid case style for union '__MyUnion_is_wonderful__'
@@ -524,7 +524,7 @@
 
 typedef THIS___Structure struct_type;
 // CHECK-MESSAGES: :[[@LINE-1]]:26: warning: invalid case style for typedef 'struct_type'
-// CHECK-FIXES: {{^}}typedef this_structure struct_type_t;{{$}}
+// CHECK-FIXES: {{^}}typedef This_structure struct_type_t;{{$}}
 
 struct_type GlobalTypedefTestFunction(struct_type a_argument1) {
 // CHECK-FIXES: {{^}}struct_type_t GlobalTypedefTestFunction(struct_type_t a_argument1) {
@@ -534,7 +534,7 @@
 
 using my_struct_type = THIS___Structure;
 // CHECK-MESSAGES: :[[@LINE-1]]:7: warning: invalid case style for type alias 'my_struct_type'
-// CHECK-FIXES: {{^}}using my_Struct_Type_t = this_structure;{{$}}
+// CHECK-FIXES: {{^}}using my_Struct_Type_t = This_structure;{{$}}
 
 template<typename t_t>
 using SomeOtherTemplate = my_other_templated_class  <:: FOO_NS  ::my_class>;
@@ -596,6 +596,8 @@
 }
 
 template <typename t_t> struct a {
+// CHECK-MESSAGES: :[[@LINE-1]]:32: warning: invalid case style for struct 'a'
+// CHECK-FIXES: {{^}}template <typename t_t> struct A {{{$}}
   typename t_t::template b<> c;
 
   char const MY_ConstMember_string[4] = "123";
@@ -609,9 +611,11 @@
 
 template<typename t_t>
 char const a<t_t>::MyConstClass_string[] = "123";
-// CHECK-FIXES: {{^}}char const a<t_t>::kMyConstClassString[] = "123";{{$}}
+// CHECK-FIXES: {{^}}char const A<t_t>::kMyConstClassString[] = "123";{{$}}
 
 template <template <typename> class A> struct b { A<int> c; };
+// CHECK-MESSAGES: :[[@LINE-1]]:47: warning: invalid case style for struct 'b'
+// CHECK-FIXES:template <template <typename> class A> struct B { A<int> c; };{{$}}
 
 unsigned MY_GLOBAL_array[] = {1,2,3};
 // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: invalid case style for global variable 'MY_GLOBAL_array'
@@ -645,17 +649,17 @@
 // CHECK-FIXES: {{^}}using namespace foo_ns::inline_namespace;
 
 void QualifiedTypeLocTest(THIS___Structure);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(this_structure);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(This_structure);{{$}}
 void QualifiedTypeLocTest(THIS___Structure &);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(this_structure &);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(This_structure &);{{$}}
 void QualifiedTypeLocTest(THIS___Structure &&);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(this_structure &&);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(This_structure &&);{{$}}
 void QualifiedTypeLocTest(const THIS___Structure);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(const this_structure);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(const This_structure);{{$}}
 void QualifiedTypeLocTest(const THIS___Structure &);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(const this_structure &);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(const This_structure &);{{$}}
 void QualifiedTypeLocTest(volatile THIS___Structure &);
-// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(volatile this_structure &);{{$}}
+// CHECK-FIXES: {{^}}void QualifiedTypeLocTest(volatile This_structure &);{{$}}
 
 namespace redecls {
 // We only want the warning to show up once here for the first decl.
@@ -700,6 +704,8 @@
 // Check implicit declarations in coroutines
 
 struct async_obj {
+// CHECK-MESSAGES: :[[@LINE-1]]:8: warning: invalid case style for struct 'async_obj'
+// CHECK-FIXES: {{^}}struct Async_obj {{{$}}
 public:
   never_suspend operator co_await() const noexcept;
 };
@@ -711,8 +717,8 @@
 // Test scenario when canonical declaration will be a forward declaration
 struct ForwardDeclStruct;
 // CHECK-MESSAGES: :[[@LINE-1]]:8: warning: invalid case style for struct 'ForwardDeclStruct' [readability-identifier-naming]
-// CHECK-FIXES: {{^}}struct forward_decl_struct;
-// CHECK-FIXES: {{^}}struct forward_decl_struct {
+// CHECK-FIXES: {{^}}struct Forward_decl_struct;
+// CHECK-FIXES: {{^}}struct Forward_decl_struct {
 struct ForwardDeclStruct {
 };