diff --git a/internal/addrs/map.go b/internal/addrs/map.go
new file mode 100644
index 0000000000..87b1aae266
--- /dev/null
+++ b/internal/addrs/map.go
@@ -0,0 +1,128 @@
+package addrs
+
+// Map represents a mapping whose keys are address types that implement
+// UniqueKeyer.
+//
+// Since not all address types are comparable in the Go language sense, this
+// type cannot work with the typical Go map access syntax, and so instead has
+// a method-based syntax. Use this type only for situations where the key
+// type isn't guaranteed to always be a valid key for a standard Go map.
+type Map[K UniqueKeyer, V any] struct {
+	// Elems is the internal data structure of the map.
+	//
+	// This is exported to allow for comparisons during tests and other similar
+	// careful read operations, but callers MUST NOT modify this map directly.
+	// Use only the methods of Map to modify the contents of this structure,
+	// to ensure that it remains correct and consistent.
+	Elems map[UniqueKey]MapElem[K, V]
+}
+
+type MapElem[K UniqueKeyer, V any] struct {
+	Key   K
+	Value V
+}
+
+func MakeMap[K UniqueKeyer, V any](initialElems ...MapElem[K, V]) Map[K, V] {
+	inner := make(map[UniqueKey]MapElem[K, V], len(initialElems))
+	ret := Map[K, V]{inner}
+	for _, elem := range initialElems {
+		ret.Put(elem.Key, elem.Value)
+	}
+	return ret
+}
+
+func MakeMapElem[K UniqueKeyer, V any](key K, value V) MapElem[K, V] {
+	return MapElem[K, V]{key, value}
+}
+
+// Put inserts a new element into the map, or replaces an existing element
+// which has an equivalent key.
+func (m Map[K, V]) Put(key K, value V) {
+	realKey := key.UniqueKey()
+	m.Elems[realKey] = MapElem[K, V]{key, value}
+}
+
+// PutElement is like Put but takes the key and value from the given MapElement
+// structure instead of as individual arguments.
+func (m Map[K, V]) PutElement(elem MapElem[K, V]) {
+	m.Put(elem.Key, elem.Value)
+}
+
+// Remove deletes the element with the given key from the map, or does nothing
+// if there is no such element.
+func (m Map[K, V]) Remove(key K) {
+	realKey := key.UniqueKey()
+	delete(m.Elems, realKey)
+}
+
+// Get returns the value of the element with the given key, or the zero value
+// of V if there is no such element.
+func (m Map[K, V]) Get(key K) V {
+	realKey := key.UniqueKey()
+	return m.Elems[realKey].Value
+}
+
+// GetOk is like Get but additionally returns a flag for whether there was an
+// element with the given key present in the map.
+func (m Map[K, V]) GetOk(key K) (V, bool) {
+	realKey := key.UniqueKey()
+	elem, ok := m.Elems[realKey]
+	return elem.Value, ok
+}
+
+// Has returns true if and only if there is an element in the map which has the
+// given key.
+func (m Map[K, V]) Has(key K) bool {
+	realKey := key.UniqueKey()
+	_, ok := m.Elems[realKey]
+	return ok
+}
+
+// Len returns the number of elements in the map.
+func (m Map[K, V]) Len() int {
+	return len(m.Elems)
+}
+
+// Elements returns a slice containing a snapshot of the current elements of
+// the map, in an unpredictable order.
+func (m Map[K, V]) Elements() []MapElem[K, V] {
+	if len(m.Elems) == 0 {
+		return nil
+	}
+	ret := make([]MapElem[K, V], 0, len(m.Elems))
+	for _, elem := range m.Elems {
+		ret = append(ret, elem)
+	}
+	return ret
+}
+
+// Keys returns a Set[K] containing a snapshot of the current keys of elements
+// of the map.
+func (m Map[K, V]) Keys() Set[K] {
+	if len(m.Elems) == 0 {
+		return nil
+	}
+	ret := make(Set[K], len(m.Elems))
+
+	// We mess with the internals of Set here, rather than going through its
+	// public interface, because that means we can avoid re-calling UniqueKey
+	// on all of the elements when we know that our own Put method would have
+	// already done the same thing.
+	for realKey, elem := range m.Elems {
+		ret[realKey] = elem.Key
+	}
+	return ret
+}
+
+// Values returns a slice containing a snapshot of the current values of
+// elements of the map, in an unpredictable order.
+func (m Map[K, V]) Values() []V {
+	if len(m.Elems) == 0 {
+		return nil
+	}
+	ret := make([]V, 0, len(m.Elems))
+	for _, elem := range m.Elems {
+		ret = append(ret, elem.Value)
+	}
+	return ret
+}
diff --git a/internal/addrs/map_test.go b/internal/addrs/map_test.go
new file mode 100644
index 0000000000..e5a84f03d9
--- /dev/null
+++ b/internal/addrs/map_test.go
@@ -0,0 +1,83 @@
+package addrs
+
+import (
+	"testing"
+)
+
+func TestMap(t *testing.T) {
+	variableName := InputVariable{Name: "name"}
+	localHello := LocalValue{Name: "hello"}
+	pathModule := PathAttr{Name: "module"}
+	moduleBeep := ModuleCall{Name: "beep"}
+	eachKey := ForEachAttr{Name: "key"} // intentionally not in the map
+
+	m := MakeMap(
+		MakeMapElem[Referenceable](variableName, "Aisling"),
+	)
+
+	m.Put(localHello, "hello")
+	m.Put(pathModule, "boop")
+	m.Put(moduleBeep, "unrealistic")
+
+	keySet := m.Keys()
+	if want := variableName; !m.Has(want) {
+		t.Errorf("map does not include %s", want)
+	}
+	if want := variableName; !keySet.Has(want) {
+		t.Errorf("key set does not include %s", want)
+	}
+	if want := localHello; !m.Has(want) {
+		t.Errorf("map does not include %s", want)
+	}
+	if want := localHello; !keySet.Has(want) {
+		t.Errorf("key set does not include %s", want)
+	}
+	if want := pathModule; !keySet.Has(want) {
+		t.Errorf("key set does not include %s", want)
+	}
+	if want := moduleBeep; !keySet.Has(want) {
+		t.Errorf("key set does not include %s", want)
+	}
+	if doNotWant := eachKey; m.Has(doNotWant) {
+		t.Errorf("map includes rogue element %s", doNotWant)
+	}
+	if doNotWant := eachKey; keySet.Has(doNotWant) {
+		t.Errorf("key set includes rogue element %s", doNotWant)
+	}
+
+	if got, want := m.Get(variableName), "Aisling"; got != want {
+		t.Errorf("unexpected value %q for %s; want %q", got, variableName, want)
+	}
+	if got, want := m.Get(localHello), "hello"; got != want {
+		t.Errorf("unexpected value %q for %s; want %q", got, localHello, want)
+	}
+	if got, want := m.Get(pathModule), "boop"; got != want {
+		t.Errorf("unexpected value %q for %s; want %q", got, pathModule, want)
+	}
+	if got, want := m.Get(moduleBeep), "unrealistic"; got != want {
+		t.Errorf("unexpected value %q for %s; want %q", got, moduleBeep, want)
+	}
+	if got, want := m.Get(eachKey), ""; got != want {
+		// eachKey isn't in the map, so Get returns the zero value of string
+		t.Errorf("unexpected value %q for %s; want %q", got, eachKey, want)
+	}
+
+	if v, ok := m.GetOk(variableName); v != "Aisling" || !ok {
+		t.Errorf("GetOk for %q returned incorrect result (%q, %#v)", variableName, v, ok)
+	}
+	if v, ok := m.GetOk(eachKey); v != "" || ok {
+		t.Errorf("GetOk for %q returned incorrect result (%q, %#v)", eachKey, v, ok)
+	}
+
+	m.Remove(moduleBeep)
+	if doNotWant := moduleBeep; m.Has(doNotWant) {
+		t.Errorf("map still includes %s after removing it", doNotWant)
+	}
+	if want := moduleBeep; !keySet.Has(want) {
+		t.Errorf("key set no longer includes %s after removing it from the map; key set is supposed to be a snapshot at the time of call", want)
+	}
+	keySet = m.Keys()
+	if doNotWant := moduleBeep; keySet.Has(doNotWant) {
+		t.Errorf("key set still includes %s after a second call after removing it from the map", doNotWant)
+	}
+}
diff --git a/internal/addrs/set.go b/internal/addrs/set.go
index ef82c59158..724df420ef 100644
--- a/internal/addrs/set.go
+++ b/internal/addrs/set.go
@@ -1,23 +1,37 @@
 package addrs
 
 // Set represents a set of addresses of types that implement UniqueKeyer.
-type Set map[UniqueKey]UniqueKeyer
+//
+// Modify the set only by the methods on this type. This type exposes its
+// internals for convenience during reading, such as iterating over set elements
+// by ranging over the map values, but making direct modifications could
+// potentially make the set data invalid or inconsistent, leading to undefined
+// behavior elsewhere.
+type Set[T UniqueKeyer] map[UniqueKey]UniqueKeyer
 
-func (s Set) Has(addr UniqueKeyer) bool {
+// Has returns true if and only if the set includes the given address.
+func (s Set[T]) Has(addr UniqueKeyer) bool {
 	_, exists := s[addr.UniqueKey()]
 	return exists
 }
 
-func (s Set) Add(addr UniqueKeyer) {
+// Add inserts the given address into the set, if not already present. If
+// an equivalent address is already in the set, this replaces that address
+// with the new value.
+func (s Set[T]) Add(addr UniqueKeyer) {
 	s[addr.UniqueKey()] = addr
 }
 
-func (s Set) Remove(addr UniqueKeyer) {
+// Remove deletes the given address from the set, if present. If not present,
+// this is a no-op.
+func (s Set[T]) Remove(addr UniqueKeyer) {
 	delete(s, addr.UniqueKey())
 }
 
-func (s Set) Union(other Set) Set {
-	ret := make(Set)
+// Union returns a new set which contains the union of all of the elements
+// of both the reciever and the given other set.
+func (s Set[T]) Union(other Set[T]) Set[T] {
+	ret := make(Set[T])
 	for k, addr := range s {
 		ret[k] = addr
 	}
@@ -27,8 +41,10 @@ func (s Set) Union(other Set) Set {
 	return ret
 }
 
-func (s Set) Intersection(other Set) Set {
-	ret := make(Set)
+// Intersection returns a new set which contains the intersection of all of the
+// elements of both the reciever and the given other set.
+func (s Set[T]) Intersection(other Set[T]) Set[T] {
+	ret := make(Set[T])
 	for k, addr := range s {
 		if _, exists := other[k]; exists {
 			ret[k] = addr
diff --git a/internal/addrs/unique_key.go b/internal/addrs/unique_key.go
index c3321a298b..f57e884f7b 100644
--- a/internal/addrs/unique_key.go
+++ b/internal/addrs/unique_key.go
@@ -21,3 +21,7 @@ type UniqueKey interface {
 type UniqueKeyer interface {
 	UniqueKey() UniqueKey
 }
+
+func Equivalent[T UniqueKeyer](a, b T) bool {
+	return a.UniqueKey() == b.UniqueKey()
+}