<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylVMuO2zgQ_Br5QkTQyCN7fNAhDwywh70kAXKmpJbUCUUqfNjrfP1WU_ZMHsfAhs1nd1V1NTs3XNuPPM1RWXdRxaH6NOuVhs_XlTBRHJRWvXGBBhWxpsI1RFpUnHVUq6dBRwpKTqt_bCQ_6h7zon7SfUzamGtRv1cc1UUjkFXO88RWG7W4yGcd2Vk1Ov9HgC7hCilLZ_JqclFp75IFBKc8Re9GjpHthMhFfSrV5xk4e08ZjFY2LR3uuRH5Jm35R06ErBxCkhOIdCH2g2LbkwUSLLIFKQIn95X6KLBpHDHCprmqRX-TfNpe1cDaYP1NWKnnkftNlyzIRdsYBCQLFbeqjgAnUO-QsTc6YHOWOEESiy69tlboDW6NOf-r_FCx5rskGN9oahOcmnXIpzeIwnTwfJbIAiZDkG1UsEtsIJXU8gY8C26dcjjhIacOTqhru3HA6hXCUxY743-FVBbVh6J6u_3-y5aXe4lRrDC7ZHAreYnEoigiIOwLiSz8vX4b_v84xF9gb0pwLNUnWrVHRX9PYJz7pgB0cZkwmEWywXkM5CD-Flo8jbe55MTwDOb5zE0bFupSQinwXZrs3MvM_YyVQUllMkK16aIiL5QN944gIq65XMyE81rwkCSMgDnNv2Ke9VmUvEMnPznrFu6DlA62oKWDyRBzCcX-bW6YfA_6G8quER0HEg-PEpfsgAqlVSJn_dxmw0z6YROkfNFFSR9dL6j37yWcoPArBzQokopiqePviaNLQaEK2WEiANvRazGtIOtdiECN1CmQD6X68sI3EAlQcRhtb8hF55OD27yRrbaIg_gHCj9w8GnNzwGyF_UzLIpOPINyyKpv1tBrLHdDux9O-5Pe6QSpfYv3yBg4pe9x2sZd8qadY1xFSUTCd-I4p67s3YKJMef735uXZn_eXgYMmn1VVbu5PR4fnx6bh-PhNB7H0-NwarrDcT_Uhz0dqqe62xndkQlt0bxDb1q6bI8LxkXzYff3CLitq7quHqoGn32zL_tDo5tDhUU60MPYFY8VLZpNKXFKPHQ73-aQXZoCNg18G143YTKe0NY3wB_hen-sjje8kaOh9llLj_z8BP3RwrsMs80Y_wcRKCqu>53000</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Factor ShapedType into an interface
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
            River707
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          stellaraccident
      </td>
    </tr>
</table>

<pre>
    Right now `ShapedType` is a closed type system that predates Type Interfaces (actually, it was an original motivation for Type Interfaces but we never got around to retrofitting it). This creates a number of organizational issues and weird incentives in the project, effectively making any dialect-specific type that wants to interop be a second class thing since it cannot adopt the ShapedType "interface". This also has the effect of driving types to the `builtin` dialect for no other reason than that they need to be a ShapedType.

Minimally, we should turn this into an interface and retrofit the existing types to adopt it. Separately, we should look at moving `tensor`, `memref`, and `vector` to their respective dialects (which did not exist at the time). Before doing such a move, though, we should have a look at ergonomics of assembly forms: it would be less than ideal if we ended up having to type `!tensor.tensor` everywhere.

Migrating such an old and ubiquitous part of the infra can be costly to users. We should see if there is a way to do this that minimizes disruption and/or provides time to adapt.
</pre>
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