only use generic info when ty var belong it in orphan check #132904
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Fixes #132826
This issue is caused by incorrect usage of a type variable. I will use the following example to illustrate:
When we check the orphan rule for
impl#1
, we create two type variables:ty_var(K)
andty_var(M)
, which come fromimpl#1
andimpl#0
respectively. After normalizing<ForeignType<K> as MyTrait>::Item
, it returnsty_var(M)
, which is then used to find the generics information ofimpl#1
, causing a panic due to it not being found.So naturally, I think there are three ways to solve this issue:
ty_var(M)
intoty_var(K)
since their relationship is similar to that of a parameter and an argument. And then we can usety_var(K)
as the correct key for the generic.r? @fmease