Fix incorrect jsontext docs (#154)

In #65, we always track the StackPointer regardless of whether
AllowDuplicateNames is enabled or not.
Fix stale documentation comments.

Author: dsnet

jsontext/decode.go

@@ -1143,8 +1143,6 @@ func (d *Decoder) StackIndex(i int) (Kind, int64) {
 }
 
 // StackPointer returns a JSON Pointer (RFC 6901) to the most recently read value.
-// Object names are only present if [AllowDuplicateNames] is false, otherwise
-// object members are represented using their index within the object.
 func (d *Decoder) StackPointer() Pointer {
 	return Pointer(d.s.AppendStackPointer(nil, -1))
 }

jsontext/encode.go

@@ -947,8 +947,6 @@ func (e *Encoder) StackIndex(i int) (Kind, int64) {
 }
 
 // StackPointer returns a JSON Pointer (RFC 6901) to the most recently written value.
-// Object names are only present if [AllowDuplicateNames] is false, otherwise
-// object members are represented using their index within the object.
 func (e *Encoder) StackPointer() Pointer {
 	return Pointer(e.s.AppendStackPointer(nil, -1))
 }

jsontext/state.go

@@ -55,7 +55,6 @@ type state struct {
 	Tokens stateMachine
 
 	// Names is a stack of object names.
-	// Not used if AllowDuplicateNames is true.
 	Names objectNameStack
 
 	// Namespaces is a stack of object namespaces.
@@ -107,11 +106,11 @@ func (p Pointer) IsValid() bool {
 	return len(p) == 0 || p[0] == '/'
 }
 
-// Contains reports whether the JSON value that p1 points to
-// is equal to or contains the JSON value that p2 points to.
-func (p1 Pointer) Contains(p2 Pointer) bool {
-	// Invariant: len(p1) <= len(p2) if p1.Contains(p2)
-	suffix, ok := strings.CutPrefix(string(p2), string(p1))
+// Contains reports whether the JSON value that p points to
+// is equal to or contains the JSON value that pc points to.
+func (p Pointer) Contains(pc Pointer) bool {
+	// Invariant: len(p) <= len(pc) if p.Contains(pc)
+	suffix, ok := strings.CutPrefix(string(pc), string(p))
 	return ok && (suffix == "" || suffix[0] == '/')
 }