[clang] unrecognized html tag causing undesirable comment lexing. fixes llvm#32680

Author: Brock Denson

clang/include/clang/AST/CommentHTMLTags.td

@@ -51,6 +51,7 @@ def Col     : Tag<"col"> { let EndTagForbidden = 1; }
 def Tr      : Tag<"tr"> { let EndTagOptional = 1; }
 def Th      : Tag<"th"> { let EndTagOptional = 1; }
 def Td      : Tag<"td"> { let EndTagOptional = 1; }
+def Summary : Tag<"summary">;
 
 // Define a list of attributes that are not safe to pass through to HTML
 // output if the input is untrusted.

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

@@ -131,3 +131,12 @@ void Test_TemplatedFunctionVariadic(int arg, ...);
 // CHECK:        ParamCommandComment{{.*}} [in] implicitly Param="..."
 // CHECK-NEXT:     ParagraphComment
 // CHECK-NEXT:       TextComment{{.*}} Text=" More arguments"
+
+/// \param[out] Aaa <summary>Short summary</summary>
+int Test_HTMLSummaryTag(int Aaa);
+// CHECK:     FunctionDecl{{.*}}Test_HTMLSummaryTag
+// CHECK:       ParamCommandComment{{.*}} [out] explicitly Param="Aaa"
+// CHECK-NEXT:    ParagraphComment
+// CHECK:           HTMLStartTagComment{{.*}} Name="summary"
+// CHECK-NEXT:        TextComment{{.*}} Text="Short summary"
+// CHECK-NEXT:        HTMLEndTagComment{{.*}} Name="summary"