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sweirich
Failed deriving for GADT
[Reported by Hongbo Zhang]
I rolled back my compiler to 7.2.1
tried to derive such data type
data MyExp a where
A :: Int -> MyExp Int
B :: Char -> MyExp Char
F :: MyExp Int -> MyExp Char -> MyExp (Int,Char)
C :: MyExp a -> MyExp b -> MyExp (a,b)
D :: a -> MyExp a
data MyFoo a where
Bar :: Int -> MyFoo Int
Bar2 :: MyFoo b -> MyFoo [b]
Bar3 :: MyFoo c -> MyFoo d -> MyFoo (c,d)
data Test b where
Foo1 :: Test a -> Test (a,b)
Foo2 :: Char -> Test Char
Only the last succeed,
I have attached the source file, and error information.
Can you help me to make it compile? Many thanks
The first gives out error messages like this
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1:
Could not deduce (b1 ~ Char)
from the context (Rep a)
bound by the type signature for rMyExp :: Rep a => R (MyExp a)
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
or from (Rep b, Rep b1)
bound by a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV
b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2
c_a2HT a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
`b1' is a rigid type variable bound by
a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2 c_a2HT
a_a2HU,
in a case alternative
at
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
Expected type: a :=: (Int, Char)
Actual type: a :=: (b, b1)
In the pattern: Refl :: :=: a_a2H4 (Int, Char)
In the pattern: Result2 (Refl :: :=: a_a2H4 (Int, Char))
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1:
Could not deduce (b ~ Int)
from the context (Rep a)
bound by the type signature for rMyExp :: Rep a => R (MyExp a)
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
or from (Rep b, Rep b1)
bound by a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV
b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2
c_a2HT a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
`b' is a rigid type variable bound by
a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2 c_a2HT
a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
Expected type: a :=: (Int, Char)
Actual type: a :=: (b, b1)
In the pattern: Refl :: :=: a_a2H4 (Int, Char)
In the pattern: Result2 (Refl :: :=: a_a2H4 (Int, Char))
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1:
Could not deduce (b1 ~ Char)
from the context (Rep a)
bound by the type signature for
rMyExp1 :: Rep a =>
ctx Int
-> ctx Char
-> (ctx (MyExp Int), ctx (MyExp Char))
-> R1 ctx (MyExp a)
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
or from (Rep b, Rep b1)
bound by a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV
b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2
c_a2HT a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
`b1' is a rigid type variable bound by
a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2 c_a2HT
a_a2HU,
in a case alternative
at
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
Expected type: a :=: (Int, Char)
Actual type: a :=: (b, b1)
In the pattern: Refl :: :=: a_a2H4 (Int, Char)
In the pattern: Result2 (Refl :: :=: a_a2H4 (Int, Char))
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1:
Could not deduce (b ~ Int)
from the context (Rep a)
bound by the type signature for
rMyExp1 :: Rep a =>
ctx Int
-> ctx Char
-> (ctx (MyExp Int), ctx (MyExp Char))
-> R1 ctx (MyExp a)
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
or from (Rep b, Rep b1)
bound by a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV
b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2
c_a2HT a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1-18
`b' is a rigid type variable bound by
a pattern with constructor
Result2 :: forall (c_a2HT :: * -> * -> *) a_a2HU b_a2HV b_a2HW.
(Rep b_a2HV, Rep b_a2HW) =>
(a_a2HU :=: c_a2HT b_a2HV b_a2HW) -> Res2 c_a2HT
a_a2HU,
in a case alternative
at /Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
Expected type: a :=: (Int, Char)
Actual type: a :=: (b, b1)
In the pattern: Refl :: :=: a_a2H4 (Int, Char)
In the pattern: Result2 (Refl :: :=: a_a2H4 (Int, Char))
Failed, modules loaded: none.
The second gives out error messages like this:
Multiple declarations of `Generics.RepLib.RepExperiment.dict'
Declared at:
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1:
Multiple declarations of `Generics.RepLib.RepExperiment.Sat'
Declared at:
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
/Users/bob/SourceCode/course/is/expriment/RepExperiment.hs:41:1
Failed, modules loaded: none.
Original issue reported on code.google.com by [email protected] on 19 Sep 2012 at 4:06
