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| author | HE, Tao <sighingnow@gmail.com> | 2018-06-15 13:45:42 -0400 |
|---|---|---|
| committer | Ben Gamari <ben@smart-cactus.org> | 2018-06-15 13:47:42 -0400 |
| commit | 91822e4eee295a42f69489c7e9e878b296e897bc (patch) | |
| tree | f601b1c1f052da905ea7ff3134a8f32a409a3ffe /testsuite/tests/deriving | |
| parent | b67b971740e77ba5e9e2892ac0f668d41c38381f (diff) | |
| download | haskell-91822e4eee295a42f69489c7e9e878b296e897bc.tar.gz | |
Add "quantified constraint" context in error message, fix #15231.
This patch adds "quantified constraint" context in error message when
UndecidableInstances checking fails for quantified constraints.
See Trac #15231:comment#1.
This patch also pretty-prints the instance head for better error messages.
Test Plan: make test TEST="T15231"
Reviewers: bgamari, simonpj
Reviewed By: simonpj
Subscribers: simonpj, rwbarton, thomie, carter
GHC Trac Issues: #15231
Differential Revision: https://phabricator.haskell.org/D4819
Diffstat (limited to 'testsuite/tests/deriving')
| -rw-r--r-- | testsuite/tests/deriving/should_fail/T8165_fail2.stderr | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/testsuite/tests/deriving/should_fail/T8165_fail2.stderr b/testsuite/tests/deriving/should_fail/T8165_fail2.stderr index 5e19173a33..c0ceabf920 100644 --- a/testsuite/tests/deriving/should_fail/T8165_fail2.stderr +++ b/testsuite/tests/deriving/should_fail/T8165_fail2.stderr @@ -1,6 +1,6 @@ T8165_fail2.hs:9:12: error: • The type family application ‘T Loop’ - is no smaller than the instance head + is no smaller than the instance head ‘T Loop’ (Use UndecidableInstances to permit this) • In the instance declaration for ‘C Loop’ |