[clang] fix comment lexing of command names with underscore (#152943)

Comment lexer fails to parse non-alphanumeric names.

fixes #33296

---------

Co-authored-by: Brock Denson <[email protected]>

Author: mdenson

clang/docs/ReleaseNotes.rst

@@ -216,6 +216,7 @@ Bug Fixes to AST Handling
 - Fix incorrect name qualifiers applied to alias CTAD. (#GH136624)
 - Fixed ElaboratedTypes appearing within NestedNameSpecifier, which was not a
   legal representation. This is fixed because ElaboratedTypes don't exist anymore. (#GH43179) (#GH68670) (#GH92757)
+- Fix comment lexing of special command names (#GH152943)
 
 Miscellaneous Bug Fixes
 ^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/AST/CommentLexer.cpp

@@ -214,7 +214,7 @@ bool isCommandNameStartCharacter(char C) {
 }
 
 bool isCommandNameCharacter(char C) {
-  return isAlphanumeric(C);
+  return isAsciiIdentifierContinue(C, false);
 }
 
 const char *skipCommandName(const char *BufferPtr, const char *BufferEnd) {

clang/test/AST/ast-dump-comment.cpp

@@ -131,3 +131,9 @@ void Test_TemplatedFunctionVariadic(int arg, ...);
 // CHECK:        ParamCommandComment{{.*}} [in] implicitly Param="..."
 // CHECK-NEXT:     ParagraphComment
 // CHECK-NEXT:       TextComment{{.*}} Text=" More arguments"
+
+/// \thread_safe test for underscore in special command
+int Test_UnderscoreInSpecialCommand;
+// CHECK:      VarDecl{{.*}}Test_UnderscoreInSpecialCommand 'int'
+// CHECK:        InlineCommandComment{{.*}} Name="thread_safe" RenderNormal
+// CHECK-NEXT:     TextComment{{.*}} Text=" test for underscore in special command"