Don't deeply expand insolubles
authorSimon Peyton Jones <simonpj@microsoft.com>
Tue, 17 Oct 2017 15:30:33 +0000 (16:30 +0100)
committerSimon Peyton Jones <simonpj@microsoft.com>
Wed, 18 Oct 2017 07:31:01 +0000 (08:31 +0100)
commit74cd1be0b2778ad99566cde085328bde2090294a
tree7b82f1fb202bbdebf4679db7d057e2426101bf25
parent317aa966b3d89e45227a5870feba339e34d77a18
Don't deeply expand insolubles

Trac #13450 went bananas if we expand insoluble constraints.
Better just to leave them un-expanded.

I'm not sure in detail about why it goes so badly wrong; but
regardless, the less we mess around with insoluble contraints
the better the error messages will be.
compiler/typecheck/TcCanonical.hs
testsuite/tests/typecheck/should_fail/T14350.hs [new file with mode: 0644]
testsuite/tests/typecheck/should_fail/all.T