From d04f4c888c3ff8e355ec3c2ea0cda4d3c60b2bf7 Mon Sep 17 00:00:00 2001
From: Bart Veneman <bartveneman@gmail.com>
Date: Thu, 1 Oct 2026 11:47:06 +0200
Subject: [PATCH 1/2] chore: add tests for `::part()` and `::highlight()`

---
 test/index.js | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/test/index.js b/test/index.js
index 6d32d1f..fbf2adc 100644
--- a/test/index.js
+++ b/test/index.js
@@ -77,6 +77,24 @@ describe('CALCULATE', () => {
         it('::first-letter', () => {
             deepEqual(Specificity.calculate('::first-letter')[0].toObject(), { a: 0, b: 0, c: 1 });
         });
+        it('::part(my-ident)', () => {
+            deepEqual(Specificity.calculate('::part(my-ident)')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
+        it('::part(first-ident second-ident)', () => {
+            deepEqual(Specificity.calculate('::part(first-ident second-ident)')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
+        it('::highlight & do not crash', () => {
+            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
+        it('::highlight() & do not crash', () => {
+            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
+        it('::highlight(my-ident)', () => {
+            deepEqual(Specificity.calculate('::highlight(my-ident)')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
+        it('::highlight(*)', () => {
+            deepEqual(Specificity.calculate('::highlight(*)')[0].toObject(), { a: 0, b: 0, c: 1 });
+        });
     });
 
     describe('Pseudo-Element Selector ::slotted', () => {

From 139c19b084b47a1b8a00fefca91a5637aaa28a73 Mon Sep 17 00:00:00 2001
From: Bart Veneman <bartveneman@gmail.com>
Date: Mon, 5 Oct 2026 11:27:03 +0200
Subject: [PATCH 2/2] fix specificity of `::highlight`, `::highlight(*)` and
 `::highlight(my-ident)`

---
 src/core/calculate.js | 12 ++++++++++++
 test/index.js         |  6 +++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/core/calculate.js b/src/core/calculate.js
index f05b1ae..70510e5 100644
--- a/src/core/calculate.js
+++ b/src/core/calculate.js
@@ -161,6 +161,18 @@ const calculateForAST = (selectorAST) => {
                         c += 1;
                         break;
 
+                    case 'highlight':
+                        if (child.children?.size > 0) {
+                            // The specificity of a ::highlight() selector with a * argument is zero.
+                            if (child.children.first?.value === '*') {
+                                break;
+                            }
+                            // The specificity of a ::highlight() selector with a <custom-ident> argument
+                            // is equivalent to a type selector.
+                            c += 1;
+                        }
+                        break;
+
                     default:
                         c += 1;
                         break;
diff --git a/test/index.js b/test/index.js
index fbf2adc..57ec6bb 100644
--- a/test/index.js
+++ b/test/index.js
@@ -84,16 +84,16 @@ describe('CALCULATE', () => {
             deepEqual(Specificity.calculate('::part(first-ident second-ident)')[0].toObject(), { a: 0, b: 0, c: 1 });
         });
         it('::highlight & do not crash', () => {
-            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 1 });
+            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 0 });
         });
         it('::highlight() & do not crash', () => {
-            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 1 });
+            deepEqual(Specificity.calculate('::highlight')[0].toObject(), { a: 0, b: 0, c: 0 });
         });
         it('::highlight(my-ident)', () => {
             deepEqual(Specificity.calculate('::highlight(my-ident)')[0].toObject(), { a: 0, b: 0, c: 1 });
         });
         it('::highlight(*)', () => {
-            deepEqual(Specificity.calculate('::highlight(*)')[0].toObject(), { a: 0, b: 0, c: 1 });
+            deepEqual(Specificity.calculate('::highlight(*)')[0].toObject(), { a: 0, b: 0, c: 0 });
         });
     });