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authorTom Smeding <tom@tomsmeding.com>2024-10-10 22:33:21 +0200
committerTom Smeding <tom@tomsmeding.com>2024-10-10 22:33:21 +0200
commit62d0b4a515e807e15e8438fbe2f9ee87ccf5d911 (patch)
treeb3775510561d2919f55de8ff108e44b9670ce0b5 /src/Data/Array/Nested
parent7ea4ab011d0c63b0f284ae20f780fe8675a2d90c (diff)
Better error message in IsList(ListR)
Diffstat (limited to 'src/Data/Array/Nested')
-rw-r--r--src/Data/Array/Nested/Internal/Shape.hs6
1 files changed, 4 insertions, 2 deletions
diff --git a/src/Data/Array/Nested/Internal/Shape.hs b/src/Data/Array/Nested/Internal/Shape.hs
index a7797a7..b7bbf4c 100644
--- a/src/Data/Array/Nested/Internal/Shape.hs
+++ b/src/Data/Array/Nested/Internal/Shape.hs
@@ -273,12 +273,14 @@ shrPermutePrefix = coerce (listrPermutePrefix @i)
-- | Untyped: length is checked at runtime.
instance KnownNat n => IsList (ListR n i) where
type Item (ListR n i) = i
- fromList = go (SNat @n)
+ fromList topl = go (SNat @n) topl
where
go :: SNat n' -> [i] -> ListR n' i
go SZ [] = ZR
go (SS n) (i : is) = i ::: go n is
- go _ _ = error "IsList(ListR): Mismatched list length"
+ go _ _ = error $ "IsList(ListR): Mismatched list length (type says "
+ ++ show (fromSNat (SNat @n)) ++ ", list has length "
+ ++ show (length topl) ++ ")"
toList = Foldable.toList
-- | Untyped: length is checked at runtime.