Question: The offending line in my index.html file reads 

```
<script src="main.dart" type="application/dart"></script>

```

The error report is:

```
Build error:
Transform polymer (PolymerBootstrapTransformer) on myproj_frontend|web/index.html threw error: Invalid argument(s): Illegal character in path
dart:core/uri.dart 855                               Uri._checkWindowsPathReservedCharacters
dart:core/uri.dart 956                               Uri._makeWindowsFileUrl

```

The entire path to the project is

`D:\Projects\MyProj\MyProj_Project`

I'm building from command line on Windows 7 using Dart VM version: 1.16.0

I honestly have no idea how to continue diagnosing or fixing this. *Any* help would be greatly appreciated.

Answer: 
I have the same problem. Looks like it is an issue with the `analyzer` package `0.27.0` and later.

I solved it by pinning the version in `pubspec.yaml` to `<0.27.0`.
I found that analyzer 0.27.2 is ok, but analyzer 0.27.3 will cause exception “Invalid argument(s): Illegal character in path” on my Win 10.

ps. I use Dart 1.16.0