Add warning when TypeScript version is out of sync

Author: MasterKale

packages/types/extract-dom-types.ts

@@ -6,6 +6,7 @@
  */
 import { DenoDir } from '@deno/cache-dir';
 import { join } from '@std/path';
+import { lessThan, parse } from '@std/semver';
 // n.b. ts-morph is a sibling devDependency of typescript, so that the module
 // loader will resolve our project's typescript package, not the transient
 // dependency of ts-morph. We only want to reference our typescript dependency
@@ -21,6 +22,18 @@ import {
 } from 'ts-morph';
 import { version as npmVersion } from 'typescript';
 
+// Warn if the NPM "typescript" package is behind Deno's bundled TypeScript
+const denoTSVersion = Deno.version.typescript;
+const npmTS = parse(npmVersion);
+const denoTS = parse(denoTSVersion);
+
+// Compare only major.minor (ignore patch) by zeroing it out before comparing
+if (lessThan({ ...npmTS, patch: 0 }, { ...denoTS, patch: 0 })) {
+  console.warn(
+    `⚠️ Types Mismatch: Extracting types from TypeScript ${npmVersion}, but Deno v${Deno.version.deno} is using TypeScript ${denoTSVersion}`,
+  );
+}
+
 // List of types we directly reference from the dom lib. Only interface and type
 // alias identifiers are valid, since other syntax types (class, function, var)
 // are implementations, which will not be available outside of the browser.