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| author | Ryan Scott <ryan.gl.scott@gmail.com> | 2018-06-17 12:28:23 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-06-17 12:42:56 -0400 |
| commit | c63754118cf6c3d0947d0c611f1db39c78acf1b7 (patch) | |
| tree | 07572deedcf1a73fda2cd540426dcf14666587a4 /includes | |
| parent | 793902e6891c30150fd3ac1e0e471269a4766780 (diff) | |
| download | haskell-c63754118cf6c3d0947d0c611f1db39c78acf1b7.tar.gz | |
Provide a better error message for unpromotable data constructor contexts
Trac #14845 brought to light a corner case where a data
constructor could not be promoted (even with `-XTypeInType`) due to
an unpromotable constraint in its context. However, the error message
was less than helpful, so this patch adds an additional check to
`tcTyVar` catch unpromotable data constructors like these //before//
they're promoted, and to give a sensible error message in such cases.
Test Plan: make test TEST="T13895 T14845"
Reviewers: simonpj, goldfire, bgamari
Reviewed By: bgamari
Subscribers: rwbarton, thomie, carter
GHC Trac Issues: #13895, #14845
Differential Revision: https://phabricator.haskell.org/D4728
Diffstat (limited to 'includes')
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