setCopy[k] = v
	}
	return setCopy
}

// add - adds TargetID to the set.
func (set TargetIDSet) add(targetID TargetID) {
	set[targetID] = struct{}{}
}

// Union - returns union with given set as new set.
func (set TargetIDSet) Union(sset TargetIDSet) TargetIDSet {
	nset := set.Clone()

	for k := range sset {
		nset.add(k)
	}

	return nset
}

	rules := make(Rules)
	rules.Add(pattern, targetID)

	for _, eventName := range eventNames {
		for _, name := range eventName.Expand() {
			rulesMap[name] = rulesMap[name].Union(rules)
		}
	}
}

// Clone - returns copy of this rules map.
func (rulesMap RulesMap) Clone() RulesMap {
	rulesMapCopy := make(RulesMap)

	for eventName, rules := range rulesMap {

// struct_foo becomes "struct foo", and similarly for
// union and enum.
func cname(s string) string {
	if t, ok := nameToC[s]; ok {
		return t
	}

	if strings.HasPrefix(s, "struct_") {
		return "struct " + s[len("struct_"):]
	}
	if strings.HasPrefix(s, "union_") {
		return "union " + s[len("union_"):]
	}
	if strings.HasPrefix(s, "enum_") {
		return "enum " + s[len("enum_"):]
	}

		for _, p := range policiesToUpdate.ToSlice() {
			if _, found := cache.iamPolicyDocsMap[p]; !found {
				err = errNoSuchPolicy
				return
			}
		}
		newPolicySet = existingPolicySet.Union(policiesToUpdate)
	} else {
		// policies to detach => inputPolicies ∩ existing (intersection)
		policiesToUpdate = policiesToUpdate.Intersection(existingPolicySet)

	jt := JoinTable{UserID: 1, FriendID: 2}
	err := DB.Create(&jt).Error
	if err != nil {
		t.Errorf("No error should happen when create a record without a GORM primary key. But in the database this primary key exists and is the union of 2 or more fields\n But got: %s", err)
	}
}

func TestSelectWithCreate(t *testing.T) {

	if wantFormat := h.Format; wantFormat != FormatUnknown {
		if wantFormat.has(FormatPAX) && !preferPAX {
			wantFormat.mayBe(FormatUSTAR) // PAX implies USTAR allowed too
		}
		format.mayOnlyBe(wantFormat) // Set union of formats allowed and format wanted
	}
	if format == FormatUnknown {
		switch h.Format {
		case FormatUSTAR:
			err = headerError{"Format specifies USTAR", whyNoUSTAR, whyOnlyPAX, whyOnlyGNU}
		case FormatPAX:

		setCopy[k] = v
	}
	return setCopy
}

// add - adds TargetID to the set.
func (set TargetIDSet) add(targetID TargetID) {
	set[targetID] = struct{}{}
}

// Union - returns union with given set as new set.
func (set TargetIDSet) Union(sset TargetIDSet) TargetIDSet {
	nset := set.Clone()

	for k := range sset {
		nset.add(k)
	}

	return nset
}

		{NewTargetIDSet(TargetID{"1", "webhook"}), NewTargetIDSet(TargetID{"1", "webhook"}), NewTargetIDSet(TargetID{"1", "webhook"})},
	}

	for i, testCase := range testCases {
		result := testCase.set.Union(testCase.setToAdd)

		if !reflect.DeepEqual(testCase.expectedResult, result) {
			t.Fatalf("test %v: result: expected: %v, got: %v", i+1, testCase.expectedResult, result)
		}
	}
}

		{NewTargetIDSet(TargetID{"1", "webhook"}), NewTargetIDSet(TargetID{"1", "webhook"}), NewTargetIDSet(TargetID{"1", "webhook"})},
	}

	for i, testCase := range testCases {
		result := testCase.set.Union(testCase.setToAdd)

		if !reflect.DeepEqual(testCase.expectedResult, result) {
			t.Fatalf("test %v: result: expected: %v, got: %v", i+1, testCase.expectedResult, result)
		}
	}
}

a Go translation.  C arithmetic types translate to precisely-sized Go
arithmetic types.  A C struct translates to a Go struct, field by
field; unrepresentable fields are replaced with opaque byte arrays.  A
C union translates into a struct containing the first union member and
perhaps additional padding.  C arrays become Go arrays.  C pointers
become Go pointers.  C function pointers become Go's uintptr.
C void pointers become Go's unsafe.Pointer.