SIL verifier: Fix polarity of consuming check through (unchecked_addr_cast (open_existential_addr)).

This was looking for a single non-consuming use instead of checking for the absence of any consuming
uses, leading to false-positives when there were multiple non-consuming uses.
Fixes rdar://problem/44116763.

Author: jckarter

lib/SIL/SILVerifier.cpp

@@ -2840,35 +2840,23 @@ class SILVerifier : public SILVerifierBase<SILVerifier> {
         case SILInstructionKind::DestroyAddrInst:
           return true;
         case SILInstructionKind::UncheckedAddrCastInst: {
-          // Don't be too conservative here, we have a new case:
-          // sil-combine producing a new code pattern for devirtualizer
-          // open_existential_addr immutable_access -> witness_method
-          // witness_method gets transformed into unchecked_addr_cast
-          // we are "OK" If one of the new users is an non-consuming apply
-          // we are also "OK" if we have a single non-consuming user
           auto isCastToNonConsuming = [=](UncheckedAddrCastInst *I) -> bool {
             for (auto *use : I->getUses()) {
               auto *inst = use->getUser();
               switch (inst->getKind()) {
               case SILInstructionKind::ApplyInst:
               case SILInstructionKind::TryApplyInst:
               case SILInstructionKind::PartialApplyInst:
-                if (!isConsumingOrMutatingApplyUse(use))
-                  return true;
-                break;
-              case SILInstructionKind::StructElementAddrInst:
-              case SILInstructionKind::LoadInst:
-              case SILInstructionKind::DebugValueAddrInst:
-                if (I->hasOneUse())
-                  return true;
-                break;
+                if (isConsumingOrMutatingApplyUse(use))
+                  return false;
+                continue;
               default:
-                break;
+                continue;
               }
             }
-            return false;
+            return true;
           };
-          if (isCastToNonConsuming(dyn_cast<UncheckedAddrCastInst>(inst))) {
+          if (isCastToNonConsuming(cast<UncheckedAddrCastInst>(inst))) {
             break;
           }
           return true;