Update the description of the checks behavior to be more accurate

in the documentation, release notes and a test file.

Author: tigbr

clang-tools-extra/docs/ReleaseNotes.rst

@@ -112,8 +112,8 @@ Changes in existing checks
 
 - Improved :doc:`bugprone-tagged-union-member-count
   <clang-tidy/checks/bugprone/tagged-union-member-count>` by fixing a false
-  positive when typedefed enums or unions from system header files or the
-  ``std`` namespace are treated as the tag or the data part of a user-defined
+  positive when enums or unions from system header files or the ``std``
+  namespace are treated as the tag or the data part of a user-defined
   tagged union respectively.
 
 - Improved :doc:`bugprone-unchecked-optional-access

clang-tools-extra/docs/clang-tidy/checks/bugprone/tagged-union-member-count.rst

@@ -9,9 +9,8 @@ different from the number of data members inside the union.
 A struct or a class is considered to be a tagged union if it has
 exactly one union data member and exactly one enum data member and
 any number of other data members that are neither unions or enums.
-The union and enum data members that are from system header files or
-the ``std`` namespace are not considered to make up the tagged union part
-of a user-defined tagged union type.
+Furthermore, the types of the union and the enum members must 
+not come from a system header files or the ``std`` namespace
 
 Example:
 
@@ -45,7 +44,7 @@ system header files and the ``std`` namespace.
 
 The ``pthread_mutex_t`` type may be defined as a union behind a ``typedef``,
 in which case the check could mistake this type as a user-defined tagged union.
-After all it has exactly one enum data member and exactly one union data member.
+After all, it has exactly one enum data member and exactly one union data member.
 To avoid false-positive cases originating from this, unions and enums from
 system headers and the ``std`` namespace are ignored when pinpointing the
 union part and the enum part of a potential user-defined tagged union.

clang-tools-extra/test/clang-tidy/checkers/bugprone/tagged-union-member-count.c

@@ -149,12 +149,12 @@ struct Name {\
 // CHECK-MESSAGES: :[[@LINE+1]]:44: warning: tagged union has more data members (4) than tags (3)
 DECLARE_TAGGED_UNION_STRUCT(Tags3, Union4, TaggedUnionStructFromMacro);
 
-// Typedefed unions from system header files should be ignored when
+// Unions from system header files should be ignored when
 // we are trying to pinpoint the union part in a user-defined tagged union.
 #include <pthread.h>
 
 // This should not be analyzed as a user-defined tagged union,
-// even though pthread_mutex_t may be declared as a typedefed union.
+// even though pthread_mutex_t could be a union.
 struct SystemTypedefedUnionDataMemberShouldBeIgnored {
   pthread_mutex_t Mutex;
   enum {