[commit: ghc] master: Fix #16002 by moving a validity check to the renamer (28f41f1)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/28f41f1a7a0ebae7b50ca41dbf78c04ee5b8b5b7/ghc

>---------------------------------------------------------------

commit 28f41f1a7a0ebae7b50ca41dbf78c04ee5b8b5b7
Author: Ryan Scott <ryan.gl.scott at gmail.com>
Date:   Thu Dec 20 23:00:21 2018 -0500

    Fix #16002 by moving a validity check to the renamer
    
    Summary:
    The validity check which rejected things like:
    
    ```lang=haskell
    type family B x where
      A x = x
    ```
    
    Used to live in the typechecker. But it turns out that this validity
    check was //only// being run on closed type families without CUSKs!
    This meant that GHC would silently accept something like this:
    
    ```lang=haskell
    type family B (x :: *) :: * where
      A x = x
    ```
    
    This patch fixes the issue by moving this validity check to the
    renamer, where we can be sure that the check will //always// be run.
    
    Test Plan: make test TEST=T16002
    
    Reviewers: simonpj, bgamari
    
    Reviewed By: simonpj
    
    Subscribers: goldfire, rwbarton, carter
    
    GHC Trac Issues: #16002
    
    Differential Revision: https://phabricator.haskell.org/D5420


>---------------------------------------------------------------

28f41f1a7a0ebae7b50ca41dbf78c04ee5b8b5b7
 compiler/rename/RnSource.hs                        | 57 ++++++++++++++++------
 compiler/typecheck/TcTyClsDecls.hs                 |  9 ----
 .../indexed-types/should_fail/Overlap5.stderr      |  4 +-
 testsuite/tests/rename/should_fail/T16002.hs       |  6 +++
 testsuite/tests/rename/should_fail/T16002.stderr   |  6 +++
 testsuite/tests/rename/should_fail/all.T           |  1 +
 .../tests/typecheck/should_fail/T11623.stderr      |  8 +--
 7 files changed, 62 insertions(+), 29 deletions(-)

Diff suppressed because of size. To see it, use:

    git diff-tree --root --patch-with-stat --no-color --find-copies-harder --ignore-space-at-eol --cc 28f41f1a7a0ebae7b50ca41dbf78c04ee5b8b5b7