Revert "Fix compare package for reference types"

This reverts commit 033175b.

These changes cause differences to be reported for identical
structures under certain circumstances.

core/data/compare/comparator.go

@@ -18,19 +18,23 @@ import (
 	"reflect"
 	"unicode"
 	"unicode/utf8"
-	"unsafe"
 )
 
 // Comparator is passed to custom comparison functions holding the current comparison context.
 type Comparator struct {
 	Path    Path
 	Handler Handler
-	seenRef seen // mapping of seen 'reference' pointers to corresponding 'value' pointers
-	seenVal seen // inverse of the seenRef map
+	seen    seen
 	custom  *Custom
 }
 
-type seen map[unsafe.Pointer]unsafe.Pointer
+type seen map[seenKey]struct{}
+
+type seenKey struct {
+	typ   reflect.Type
+	addr1 uintptr
+	addr2 uintptr
+}
 
 func toValue(v reflect.Value, wasPointer bool) interface{} {
 	if wasPointer {
@@ -66,28 +70,22 @@ func (t Comparator) AddDiff(reference, value interface{}) {
 func (t Comparator) compareValues(v1, v2 reflect.Value, ptr bool) {
 	// First see if we have seen this comparison already
 	switch v1.Kind() {
-	case reflect.Map, reflect.Slice, reflect.Ptr:
-		if v1.Kind() == v2.Kind() {
-			addr1 := unsafe.Pointer(v1.Pointer())
-			addr2 := unsafe.Pointer(v2.Pointer())
-			if addr1 != unsafe.Pointer(uintptr(0)) && addr2 != unsafe.Pointer(uintptr(0)) {
-				if seen, ok := t.seenRef[addr1]; ok {
-					if seen != addr2 {
-						// Two identical v1 objects are being compared to two distinct v2 objects.
-						t.Handler(t.Path.Diff(v1.Interface(), v2.Interface()))
-					}
-					return // The contents was already compared before.
-				}
-				if seen, ok := t.seenVal[addr2]; ok {
-					if seen != addr1 {
-						// Two distinct v1 objects are being compared to two identical v2 objects.
-						t.Handler(t.Path.Diff(v1.Interface(), v2.Interface()))
-					}
-					return // The contents was already compared before.
-				}
-				t.seenRef[addr1] = addr2
-				t.seenVal[addr2] = addr1
+	case reflect.Array, reflect.Map, reflect.Slice, reflect.Struct:
+		if v1.CanAddr() && v2.CanAddr() {
+			key := seenKey{
+				typ:   v1.Type(),
+				addr1: v1.UnsafeAddr(),
+				addr2: v2.UnsafeAddr(),
+			}
+			if key.addr1 > key.addr2 {
+				// swap for stable ordering
+				key.addr1, key.addr2 = key.addr2, key.addr1
+			}
+			if _, seen := t.seen[key]; seen {
+				// Already seen, no need to traverse again
+				return
 			}
+			t.seen[key] = struct{}{}
 		}
 	}
 

core/data/compare/compare.go

@@ -65,7 +65,7 @@ func compare(reference, value interface{}, handler Handler, custom *Custom) {
 			}
 		}
 	}()
-	t := Comparator{Path: Path{}, Handler: handler, seenRef: seen{}, seenVal: seen{}, custom: custom}
+	t := Comparator{Path: Path{}, Handler: handler, seen: seen{}, custom: custom}
 	t.Compare(reference, value)
 }
 

core/data/compare/compare_test.go

@@ -30,12 +30,11 @@ var (
 	funcNotNil = func() { funcNil1() } // Not nil.
 
 	leafBase      = &Object{0, nil}
-	leafBase2     = &Object{0, nil}
 	leafEqual     = &Object{0, nil}
 	leafDifferent = &Object{2, nil}
 
-	objectBase       = &Object{0, []interface{}{leafBase, leafBase2}}
-	objectEqual1     = &Object{0, []interface{}{leafBase, leafBase2}}
+	objectBase       = &Object{0, []interface{}{leafBase, leafBase}}
+	objectEqual1     = &Object{0, []interface{}{leafBase, leafBase}}
 	objectEqual2     = &Object{0, []interface{}{leafEqual, leafBase}}
 	objectDifferent  = &Object{0, []interface{}{leafDifferent, leafBase}}
 	objectInverse    = &Object{0, []interface{}{leafBase, leafEqual}}
@@ -76,14 +75,6 @@ var (
 	mapDifferentLength = map[int]string{1: "one"}
 	mapUint            = map[uint]string{1: "one", 2: "two"}
 
-	intBase               = 42
-	pointerArrayBase      = [2]*int{&intBase, &intBase}
-	intEqual              = 42
-	pointerArrayEqual     = [2]*int{&intEqual, &intEqual}
-	intDifferent1         = 42
-	intDifferent2         = 42
-	pointerArrayDifferent = [2]*int{&intDifferent1, &intDifferent2}
-
 	hidden1 = compare.Hidden{Value: Hide{1}}
 	hidden2 = compare.Hidden{Value: Hide{2}}
 
@@ -121,7 +112,6 @@ var (
 		{"custom 3", Special(1), Special(3), noDiff},
 		{"special struct custom 1", SpecialStruct{false, 1}, SpecialStruct{false, 1}, noDiff},
 		{"special struct custom 3", SpecialStruct{false, 1}, SpecialStruct{false, 3}, noDiff},
-		{"pointer array ==", pointerArrayBase, pointerArrayEqual, noDiff},
 
 		// Inequalities
 		{"int !=", 1, 2, []compare.Path{root.Diff(1, 2)}},
@@ -221,12 +211,6 @@ var (
 			root.Member("Value", SpecialStruct{true, 1}, SpecialStruct{true, 3}).
 				Diff(Special(1), Special(3)),
 		}},
-		{"pointer array !=", pointerArrayBase, pointerArrayDifferent, []compare.Path{
-			root.Index(1, pointerArrayBase, pointerArrayDifferent).Diff(pointerArrayBase[1], pointerArrayDifferent[1]),
-		}},
-		{"pointer array != (reversed)", pointerArrayDifferent, pointerArrayBase, []compare.Path{
-			root.Index(1, pointerArrayDifferent, pointerArrayBase).Diff(pointerArrayDifferent[1], pointerArrayBase[1]),
-		}},
 
 		// Mismatched types
 		{"int != float64", 1, 1.0, []compare.Path{