fix(math): correctly validate second point in isLineSegment (#11007)

Co-authored-by: Mark Tolmacs <mark@lazycat.hu>

packages/math/src/segment.ts

@@ -40,7 +40,7 @@ export const isLineSegment = <Point extends GlobalPoint | LocalPoint>(
   Array.isArray(segment) &&
   segment.length === 2 &&
   isPoint(segment[0]) &&
-  isPoint(segment[0]);
+  isPoint(segment[1]);
 
 /**
  * Return the coordinates resulting from rotating the given line about an origin by an angle in radians

packages/math/tests/segment.test.ts

@@ -1,5 +1,9 @@
 import { pointFrom } from "../src/point";
-import { lineSegment, lineSegmentIntersectionPoints } from "../src/segment";
+import {
+  lineSegment,
+  lineSegmentIntersectionPoints,
+  isLineSegment,
+} from "../src/segment";
 
 describe("line-segment intersections", () => {
   it("should correctly detect intersection", () => {
@@ -19,3 +23,23 @@ describe("line-segment intersections", () => {
     ).toEqual(null);
   });
 });
+describe("isLineSegment validation", () => {
+  it("should return true for a valid segment", () => {
+    expect(
+      isLineSegment([
+        [0, 0],
+        [1, 1],
+      ]),
+    ).toBe(true);
+  });
+
+  it("should return false if second element is not a point", () => {
+    const invalidSegment = [[0, 0], "not-a-point"] as any;
+
+    expect(isLineSegment(invalidSegment)).toBe(false);
+  });
+
+  it("should return false for wrong length", () => {
+    expect(isLineSegment([[0, 0]])).toBe(false);
+  });
+});