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Diffstat (limited to 'testsuite/tests/eyeball/dmd-on-polymorphic-floatouts.hs')
| -rw-r--r-- | testsuite/tests/eyeball/dmd-on-polymorphic-floatouts.hs | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/testsuite/tests/eyeball/dmd-on-polymorphic-floatouts.hs b/testsuite/tests/eyeball/dmd-on-polymorphic-floatouts.hs new file mode 100644 index 0000000000..fa411e23f2 --- /dev/null +++ b/testsuite/tests/eyeball/dmd-on-polymorphic-floatouts.hs @@ -0,0 +1,23 @@ +{-# OPTIONS_GHC -fglasgow-exts -O -ddump-prep #-} +module Max(result) where + +foo ys = foldr (\x xs -> x : reverse xs) [] ys + +result xs = + let stuff = [1, 1, 1, 1, 1, 1] + in foo (reverse stuff) + +-- What used to happen is that foldr got expanded by main simplification +-- and the resulting "go" function got floated out but because we manufactured +-- a new binder for it in newPolyBndrs we would lose its demand signature! +-- This means that the later application of it in result did not use call by value :-( + +-- Eyeball test: +-- Ensure that Max.poly_go has a demand signature +-- Ensure that we use call by value to call Max.poly_go in result +-- i.e. the call to Max.poly_go inside Max.result looks like this: +-- +-- case GHC.List.poly_rev @ t1_a6x sat_seb (GHC.Base.[] @ t1_a6x) +-- of sat_sed { __DEFAULT -> +-- Max.poly_go @ t1_a6x sat_sed +-- } } in |