chore: made SpanId opaque to prevent type coersion

Author: aryanjassal

src/tracer/Tracer.ts

@@ -13,7 +13,7 @@ class Tracer {
     if (result.done || result.value == null) {
       throw new Error('Unexpected end of id generator');
     }
-    return result.value.toMultibase('base32hex');
+    return result.value.toMultibase('base32hex') as SpanId;
   }
 
   protected queueSpanEvent(evt: SpanEvent) {
@@ -46,7 +46,7 @@ class Tracer {
 
   public async traced<T>(
     name: string,
-    parentSpanId: string | undefined,
+    parentSpanId: SpanId | undefined,
     fn: () => T | Promise<T>,
   ): Promise<T> {
     const fnProm = async () => {

src/tracer/types.ts

@@ -1,4 +1,4 @@
-type SpanId = string;
+type SpanId = string & { readonly brand: unique symbol };
 
 /**
  * A span is a virtual concept, not an actual object. A span is made up of

tests/asciinemaTest.ts

@@ -1,10 +1,11 @@
+import type { SpanId } from '#tracer/index.js';
 import fs from 'fs';
 import * as fc from 'fast-check';
 import tracer from '#tracer/index.js';
 
 let parentIndex = 0;
 let step = 0;
-let nestedIds: Array<string> = [];
+let nestedIds: Array<SpanId> = [];
 
 type Flags = {
   hasForkA: boolean;
@@ -18,9 +19,9 @@ type Flags = {
 };
 
 const current: {
-  parentId?: string;
-  forkAId?: string;
-  forkBId?: string;
+  parentId?: SpanId;
+  forkAId?: SpanId;
+  forkBId?: SpanId;
   flags: Flags;
 } = {
   flags: {