Fix mutating method calls on class existentials #9573
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slavapestov
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May 13, 2017
lib/SILGen/SILGenLValue.cpp
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| @@ -223,6 +223,63 @@ ManagedValue LogicalPathComponent::getMaterialized(SILGenFunction &SGF, | |||
| SILLocation loc, | |||
| ManagedValue base, | |||
| AccessKind kind) && { | |||
| if (getTypeOfRValue().getSwiftRValueType()->hasOpenedExistential()) { | |||
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@jckarter @gottesmm This part is really awkward because it's mostly duplicating the code below. I don't really have a good feel for how to write idiomatic code with Initializations and the FormalEvaluationScope (which seems new, haven't seen it before). Can you think of a better way to address this problem?
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FormalEvaluationScope is just a writeback scope that can also handle borrows.
Now that SILGen can correctly lower lvalue accesses of class existential payloads, remove a hack in Sema that was simply doing the wrong thing. Fixes <rdar://problem/31858378>.
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This builds upon #9625 and #9637 to address miscompiles and assertions with a peculiar corner case -- performing a mutating method call on a class existential.
This can manifest in one of two ways:
The root cause is that mutating methods take the opened
selfvalue as an inout parameter, but we had no way to model an inout access of the payload inside a class existential at the SIL level. I've decided to model it as a logical lvalue component where the "get" strips the existential witness tables to produce a reference, and the "set" adds the witness tables back to the reference to form a new existential.Note that this miscompile was occurring irrespective of whether the mutating method was defined in an extension, or in the class itself. The problem was that incorrect code was being generated at the call site, where it is not known how the method is implemented, and
selfhas to be passed as an inout value.Fixes rdar://problem/31858378.