- The dart:io library uses Uri from dart:uri.

bin/main.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 
 #include "include/dart_api.h"
 #include "include/dart_debugger_api.h"
@@ skipping 373 matching lines @@
   Dart_EnterScope();
 
   if (snapshot_buffer != NULL) {
     // Setup the native resolver as the snapshot does not carry it.
     Builtin::SetNativeResolver(Builtin::kBuiltinLibrary);
     Builtin::SetNativeResolver(Builtin::kIOLibrary);
   }
 
   // Prepare builtin and its dependent libraries for use to resolve URIs.
   Dart_Handle uri_lib = Builtin::LoadLibrary(Builtin::kUriLibrary);
+  if (Dart_IsError(uri_lib)) {
+    *error = strdup(Dart_GetError(uri_lib));
+    return false;
+  }
   Dart_Handle builtin_lib = Builtin::LoadLibrary(Builtin::kBuiltinLibrary);
-  Dart_LibraryImportLibrary(builtin_lib, uri_lib);
+  if (Dart_IsError(builtin_lib)) {
+    *error = strdup(Dart_GetError(builtin_lib));
+    return false;
+  }
+  Dart_Handle library = Dart_LibraryImportLibrary(builtin_lib, uri_lib);
+  if (Dart_IsError(library)) {
+    *error = strdup(Dart_GetError(library));
+    return false;
+  }
 
   // Load the specified application script into the newly created isolate.
-  Dart_Handle library = LoadScript(builtin_lib, import_map_options);
+  library = LoadScript(builtin_lib, import_map_options);
   if (Dart_IsError(library)) {
     *error = strdup(Dart_GetError(library));
     Dart_ExitScope();
     Dart_ShutdownIsolate();
     return false;
   }
   if (!Dart_IsLibrary(library)) {
     char errbuf[256];
     snprintf(errbuf, sizeof(errbuf),
              "Expected a library when loading script: %s",
@@ skipping 193 matching lines @@
   EventHandler::Terminate();
   // Terminate process exit-code handler.
   Process::TerminateExitCodeHandler();
 
   free(const_cast<char*>(original_script_name));
   free(const_cast<char*>(original_working_directory));
   free(const_cast<char*>(original_script_url));
 
   return 0;
 }