Can't describe `required [EnforceRange] typename attributeName`

[padenot]

This stems from https://github.com/w3c/webcodecs/pull/488

STR

• Have a fragment like this:

<xmp class='idl'>
dictionary PlaneLayout {
  required [EnforceRange] unsigned long offset;
  required [EnforceRange] unsigned long stride;
};
</xmp>

: <dfn dict-member for=PlaneLayout>offset</dfn>
:: The offset in bytes where the given plane begins within a {{BufferSource}}.

: <dfn dict-member for=PlaneLayout>stride</dfn>
:: The number of bytes, including padding, used by each row of the plane within
    a {{BufferSource}}.

Expected

• it works, everything is linked appropriately

Actual

$ bikeshed --die-on=warning spec index.src.html index.html
LINK ERROR: No 'idl-name' refs found for '[EnforceRange] unsigned long'.
<a data-link-type="idl-name" data-lt="[EnforceRange] unsigned long">[EnforceRange] unsigned long</a>
 ✘  Did not generate, due to errors exceeding the allowed error level.
make: *** [index.html] Error 2

bikeshed attempts to reference a type that's [EnforceRange] unsigned long and that's not a thing.

Instead, we have to write:

<xmp class='idl'>
dictionary PlaneLayout {
  [EnforceRange] required unsigned long offset;
  [EnforceRange] required unsigned long stride;
};
</xmp>

: <dfn dict-member for=PlaneLayout>offset</dfn>
:: The offset in bytes where the given plane begins within a {{BufferSource}}.

: <dfn dict-member for=PlaneLayout>stride</dfn>
:: The number of bytes, including padding, used by each row of the plane within
    a {{BufferSource}}.

with [EnforceRange] and required swapped, which is incorrect WebIDL.