[m-rev.] for post-commit review: make diagnostic about coerce fails give the reason

[Zoltan Somogyi]

For review by Peter.

Zoltan.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Log.cdu
Type: application/octet-stream
Size: 314 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20240527/d985ba2c/attachment.obj>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: DIFF.cdu
Type: application/octet-stream
Size: 7882 bytes
Desc: not available
URL: <http://lists.mercurylang.org/archives/reviews/attachments/20240527/d985ba2c/attachment-0001.obj>