Added BorderRadius.copyWith (#75340)

packages/flutter/lib/src/painting/border_radius.dart

@@ -327,6 +327,22 @@ class BorderRadius extends BorderRadiusGeometry {
     this.bottomRight = Radius.zero,
   });
 
+  /// Returns a copy of this BorderRadius with the given fields replaced with
+  /// the new values.
+  BorderRadius copyWith({
+    Radius? topLeft,
+    Radius? topRight,
+    Radius? bottomLeft,
+    Radius? bottomRight,
+  }) {
+    return BorderRadius.only(
+      topLeft: topLeft ?? this.topLeft,
+      topRight: topRight ?? this.topRight,
+      bottomLeft: bottomLeft ?? this.bottomLeft,
+      bottomRight: bottomRight ?? this.bottomRight,
+    );
+  }
+
   /// A border radius with all zero radii.
   static const BorderRadius zero = BorderRadius.all(Radius.zero);
 

packages/flutter/test/painting/border_radius_test.dart

@@ -536,4 +536,24 @@ void main() {
     expect((a.add(b.subtract(a) * 0.0)).resolve(TextDirection.ltr), a);
     expect((a.add(b.subtract(a) * 1.0)).resolve(TextDirection.rtl), b.resolve(TextDirection.rtl));
   });
+
+  test('BorderRadius copyWith, merge, ==, hashCode basics', () {
+    const BorderRadius firstRadius = BorderRadius.all(Radius.circular(5.0));
+    final BorderRadius secondRadius = firstRadius.copyWith();
+    expect(firstRadius, secondRadius);
+    expect(firstRadius.hashCode, secondRadius.hashCode);
+  });
+
+  test('BorderRadius copyWith parameters', () {
+    const Radius radius = Radius.circular(10);
+    const BorderRadius borderRadius = BorderRadius.all(radius);
+    expect(borderRadius.copyWith(topLeft: Radius.zero).topLeft, Radius.zero);
+    expect(borderRadius.copyWith(topLeft: Radius.zero).copyWith(topLeft: radius), borderRadius);
+    expect(borderRadius.copyWith(topRight: Radius.zero).topRight, Radius.zero);
+    expect(borderRadius.copyWith(topRight: Radius.zero).copyWith(topRight: radius), borderRadius);
+    expect(borderRadius.copyWith(bottomLeft: Radius.zero).bottomLeft, Radius.zero);
+    expect(borderRadius.copyWith(bottomLeft: Radius.zero).copyWith(bottomLeft: radius), borderRadius);
+    expect(borderRadius.copyWith(bottomRight: Radius.zero).bottomRight, Radius.zero);
+    expect(borderRadius.copyWith(bottomRight: Radius.zero).copyWith(bottomRight: radius), borderRadius);
+  });
 }