fix: skip pcb pad overlap check for elements on different layers

lib/check-pcb-components-overlap/doPcbElementsOverlap.ts

@@ -1,13 +1,31 @@
 import { getBoundsOfPcbElements } from "@tscircuit/circuit-json-util"
 import { doBoundsOverlap } from "@tscircuit/math-utils"
 import type { PcbHole, PcbPlatedHole, PcbSmtPad } from "circuit-json"
+import { getLayersOfPcbElement } from "lib/util/getLayersOfPcbElement"
 
 export type OverlappableElement = PcbSmtPad | PcbPlatedHole | PcbHole
 
+function getElementLayers(elem: OverlappableElement): string[] {
+  return getLayersOfPcbElement(elem as any)
+}
+
+function doLayersOverlap(
+  layers1: string[],
+  layers2: string[],
+): boolean {
+  if (layers1.length === 0 || layers2.length === 0) return true
+  return layers1.some((l) => layers2.includes(l))
+}
+
 export function doPcbElementsOverlap(
   elem1: OverlappableElement,
   elem2: OverlappableElement,
 ): boolean {
+  // If the elements are on completely different layers they cannot overlap
+  const layers1 = getElementLayers(elem1)
+  const layers2 = getElementLayers(elem2)
+  if (!doLayersOverlap(layers1, layers2)) return false
+
   const bounds1 = getBoundsOfPcbElements([elem1])
   const bounds2 = getBoundsOfPcbElements([elem2])
   return doBoundsOverlap(bounds1, bounds2)

tests/lib/check-pcb-component-overlap/different-layer-pads-no-overlap.test.ts

@@ -0,0 +1,47 @@
+import { expect, test } from "bun:test"
+import { convertCircuitJsonToPcbSvg } from "circuit-to-svg"
+import type { AnyCircuitElement } from "circuit-json"
+import { checkPcbComponentOverlap } from "lib/check-pcb-components-overlap/checkPcbComponentOverlap"
+
+test("SMT pads on different layers at the same position should NOT be flagged as overlapping", () => {
+  const soup: AnyCircuitElement[] = [
+    {
+      type: "pcb_board",
+      pcb_board_id: "board1",
+      center: { x: 0, y: 0 },
+      width: 10,
+      height: 10,
+      thickness: 1.6,
+      num_layers: 2,
+      material: "fr4" as const,
+    },
+    {
+      type: "pcb_smtpad",
+      pcb_smtpad_id: "pad_top",
+      shape: "rect",
+      x: 0.5,
+      y: 0,
+      width: 2,
+      height: 2,
+      layer: "top",
+    },
+    {
+      type: "pcb_smtpad",
+      pcb_smtpad_id: "pad_bottom",
+      shape: "rect",
+      x: -0.5,
+      y: 0,
+      width: 2,
+      height: 2,
+      layer: "bottom",
+    },
+  ]
+
+  const errors = checkPcbComponentOverlap(soup)
+  expect(errors).toHaveLength(0)
+
+  soup.push(...errors)
+  expect(
+    convertCircuitJsonToPcbSvg(soup, { shouldDrawErrors: true }),
+  ).toMatchSvgSnapshot(import.meta.path)
+})