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| author | Chaitanya Koparkar <ckoparkar@gmail.com> | 2019-01-14 14:36:29 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2019-01-20 05:24:59 -0500 |
| commit | 800d77e882f24066a7f6d818b2606ad8a0e79e02 (patch) | |
| tree | 6e7d9b4673499c1cb29214641571f27e8c32a2e8 | |
| parent | b137ab75ab269e043e0783e41ac704d1be5570c6 (diff) | |
| download | haskell-800d77e882f24066a7f6d818b2606ad8a0e79e02.tar.gz | |
Mention DerivingStrategies in the warning when DAC and GND are both enabled
Summary:
When DeriveAnyClass and GeneralizedNewtypeDeriving are both enabled,
GHC prints out a warning that specifies the strategy it used to
derive a class. This patch updates the warning to mention that users
may pick a particular strategy by using DerivingStrategies.
Test plan: make test TEST=T16179
| -rw-r--r-- | compiler/typecheck/TcDeriv.hs | 5 | ||||
| -rw-r--r-- | testsuite/tests/deriving/should_compile/T16179.hs | 7 | ||||
| -rw-r--r-- | testsuite/tests/deriving/should_compile/T16179.stderr | 5 | ||||
| -rw-r--r-- | testsuite/tests/deriving/should_compile/all.T | 1 |
4 files changed, 17 insertions, 1 deletions
diff --git a/compiler/typecheck/TcDeriv.hs b/compiler/typecheck/TcDeriv.hs index 90b230a972..6078a7a7ff 100644 --- a/compiler/typecheck/TcDeriv.hs +++ b/compiler/typecheck/TcDeriv.hs @@ -1640,7 +1640,10 @@ mkNewTypeEqn [ text "Both DeriveAnyClass and" <+> text "GeneralizedNewtypeDeriving are enabled" , text "Defaulting to the DeriveAnyClass strategy" - <+> text "for instantiating" <+> ppr cls ] + <+> text "for instantiating" <+> ppr cls + , text "Use DerivingStrategies to pick" + <+> text "a different strategy" + ] mk_originative_eqn DerivSpecAnyClass -- CanDeriveStock CanDeriveStock gen_fn -> mk_originative_eqn $ diff --git a/testsuite/tests/deriving/should_compile/T16179.hs b/testsuite/tests/deriving/should_compile/T16179.hs new file mode 100644 index 0000000000..5873f8913e --- /dev/null +++ b/testsuite/tests/deriving/should_compile/T16179.hs @@ -0,0 +1,7 @@ +{-# LANGUAGE DeriveAnyClass #-} +{-# LANGUAGE GeneralizedNewtypeDeriving #-} + +module T16179 where + +class C a +newtype T a = MkT a deriving C diff --git a/testsuite/tests/deriving/should_compile/T16179.stderr b/testsuite/tests/deriving/should_compile/T16179.stderr new file mode 100644 index 0000000000..c3815d138f --- /dev/null +++ b/testsuite/tests/deriving/should_compile/T16179.stderr @@ -0,0 +1,5 @@ +T16179.hs:7:30: warning: + Both DeriveAnyClass and GeneralizedNewtypeDeriving are enabled + Defaulting to the DeriveAnyClass strategy for instantiating C + Use DerivingStrategies to pick a different strategy + In the newtype declaration for âTâ diff --git a/testsuite/tests/deriving/should_compile/all.T b/testsuite/tests/deriving/should_compile/all.T index 8c84bcc31a..ef6259df54 100644 --- a/testsuite/tests/deriving/should_compile/all.T +++ b/testsuite/tests/deriving/should_compile/all.T @@ -114,3 +114,4 @@ test('T15290c', normal, compile, ['']) test('T15290d', normal, compile, ['']) test('T15398', normal, compile, ['']) test('T15637', normal, compile, ['']) +test('T16179', normal, compile, ['']) |