Auto merge of #153869 - ShoyuVanilla:issue-153816, r=lcnr

Do not shallow resolve to root var while fudging



Fixes rust-lang/rust#153816 and fixes rust-lang/rust#153849

In rust-lang/rust#151380, I thought that whether shallow resolve to root var or not wouldn't affect the actual type inferencing, but it isn't true for the fudge, in which we discard all newly created relationships between unresolved inference variables 😅

r? lcnr

Author: bors