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tcfail103.hs:15:13: error:
• Couldn't match type ‘s’ with ‘t’
Expected: ST s Int
Actual: ST t Int
‘s’ is a rigid type variable bound by
the type signature for:
g :: forall s. ST s Int
at tcfail103.hs:13:9-21
‘t’ is a rigid type variable bound by
the type signature for:
f :: forall t. ST t Int
at tcfail103.hs:10:1-12
• In the expression: readSTRef v
In an equation for ‘g’: g = readSTRef v
In the expression:
do v <- newSTRef 5
let g :: ST s Int
g = readSTRef v
g
• Relevant bindings include
g :: ST s Int (bound at tcfail103.hs:15:9)
v :: STRef t Int (bound at tcfail103.hs:12:5)
f :: ST t Int (bound at tcfail103.hs:11:1)
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