assert: fix TypeError on deepStrictEqual with null Map key or Set member

deepStrictEqual() and util.isDeepStrictEqual() threw "Cannot read
properties of null (reading 'constructor')" instead of comparing when
a Map key or Set member was null/undefined (or another primitive) and
lined up against object-only keys/members in the other collection with
an equal count. The primitive/null handling was gated behind an
optimization that is skipped when the counts match, letting such keys
reach objectComparisonStart, which dereferences `.constructor`.

Resolve primitive and null keys/members directly in every case.

Signed-off-by: semx <7532921+semx@users.noreply.github.com>

Author: semx

lib/internal/util/comparisons.js

@@ -686,16 +686,18 @@ function setObjectEquiv(array, a, b, mode, memo) {
   const comparator = mode !== kLoose ? objectComparisonStart : innerDeepEqual;
   const extraChecks = mode === kLoose || array.length !== a.size;
   for (const val1 of a) {
-    if (extraChecks) {
-      if (typeof val1 === 'object') {
-        if (b.has(val1)) {
-          continue;
-        }
-      } else if (b.has(val1)) {
+    // Primitive and null members can only match by identity, and must never
+    // reach objectComparisonStart (which throws on `val.constructor` for
+    // null/undefined). Resolve them directly for every such member.
+    if (typeof val1 !== 'object' || val1 === null) {
+      if (b.has(val1)) {
         continue;
-      } else if (mode !== kLoose) {
+      }
+      if (mode !== kLoose) {
         return false;
       }
+    } else if (extraChecks && b.has(val1)) {
+      continue;
     }
 
     let innerStart = start;

test/parallel/test-assert-deep.js

@@ -278,6 +278,10 @@ test('es6 Maps and Sets', () => {
   assertDeepAndStrictEqual(new Set([[1, 2], [3, 4]]), new Set([[3, 4], [1, 2]]));
   assertNotDeepOrStrict(new Set([{ a: 0 }]), new Set([{ a: 1 }]));
   assertNotDeepOrStrict(new Set([Symbol()]), new Set([Symbol()]));
+  // A null/primitive member lined up against object-only members in the other
+  // set must report inequality, not throw on `member.constructor`.
+  assertNotDeepOrStrict(new Set([null, {}, {}]), new Set([{}, {}, {}]));
+  assertNotDeepOrStrict(new Set([undefined, {}, {}]), new Set([{}, {}, {}]));
 
   {
     const a = [ 1, 2 ];
@@ -298,6 +302,17 @@ test('es6 Maps and Sets', () => {
     new Map([[[1], 1], [{}, 2]]),
     new Map([[[1], 2], [{}, 1]])
   );
+  // A null/primitive key that lines up with object-only keys in the other map
+  // must report inequality, not throw on `key.constructor`. Refs: object keys
+  // of `b` equal in count to `a.size` used to skip the primitive-key handling.
+  assertNotDeepOrStrict(
+    new Map([[null, 1], [{}, 2]]),
+    new Map([[{}, 9], [{}, 9]])
+  );
+  assertNotDeepOrStrict(
+    new Map([[undefined, 1], [{}, 2]]),
+    new Map([[{}, 9], [{}, 9]])
+  );
 
   assertNotDeepOrStrict(new Set([1]), [1]);
   assertNotDeepOrStrict(new Set(), []);