fix(static-paths): improve error message for invalid path type in getStaticPaths

packages/next/src/build/static-paths/pages.ts

@@ -129,7 +129,15 @@ export async function buildPagesStaticPaths({
     }
     // For the object-provided path, we must make sure it specifies all
     // required keys.
-    else {
+    else if (typeof entry !== 'object' || entry === null || Array.isArray(entry)) {
+    throw new Error(
+      `Invalid path "${String(entry)}" returned from \`getStaticPaths\` in ${page}.\n` +
+      `Each path must be a string or an object of shape { params: { [key: string]: string } }.\n` +
+      `Received: ${typeof entry}${entry !== null ? ` (${JSON.stringify(entry)})` : ''}.\n` +
+      `Did you forget to convert a number to a string? e.g. params: { id: String(id) }`
+    )
+  } 
+  else {
       const invalidKeys = Object.keys(entry).filter(
         (key) => key !== 'params' && key !== 'locale'
       )