E.g. when there's a type mismatch on the return value of a function. To
fix this, we have to return the expected type as the type of the block
when there's a mismatch. That meant some IDE code that expected
otherwise had to be adapted, in particular the "add return type" assist.
For the "wrap in Ok/Some" quickfix, this sadly means it usually can't be applied
in all branches of an if expression at the same time anymore, because
there's a type mismatch for each branch that has the wrong type.
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