Use babel and closure without bundler for type checking

tasks/typecheck.js

@@ -0,0 +1,28 @@
+const Compiler = require('google-closure-compiler').compiler;
+
+const compiler = new Compiler({
+  js: [
+    './build/src-closure/**.js',
+    './node_modules/pbf/package.json', './node_modules/pbf/**.js', './node_modules/ieee754/**.js',
+    './node_modules/pixelworks/package.json', './node_modules/pixelworks/**.js',
+    './node_modules/rbush/package.json', './node_modules/rbush/**.js', 'node_modules/quickselect/**.js'
+  ],
+  entry_point: './build/src-closure/index.js',
+  module_resolution: 'NODE',
+  dependency_mode: 'STRICT',
+  process_common_js_modules: true,
+  checks_only: true,
+  //FIXME Change newCheckTypes to jscomp_error when we have path types everywhere
+  jscomp_warning: ['newCheckTypes'],
+  // Options to make dependencies work
+  hide_warnings_for: 'node_modules'
+});
+
+compiler.run((exit, out, err) => {
+  if (exit) {
+    process.stderr.write(err, () => process.exit(exit));
+  } else {
+    process.stderr.write(err);
+    process.stdout.write(out);
+  }
+});