[SILGen] TypeWrappers: force emission of wrapper initializer

Make sure that wrapper's initializer is always emitted because
it could be used by DI and IRGen later on to aid in `_storage`
initialization.

Author: xedin

lib/SILGen/SILGenType.cpp

@@ -1115,6 +1115,14 @@ class SILGenType : public TypeMemberVisitor<SILGenType> {
       if (auto *normal = dyn_cast<NormalProtocolConformance>(conformance))
         SGM.getWitnessTable(normal);
     }
+
+    // Emit `init(for:storage)` initializer as it would be used
+    // by DI and IRGen later on.
+    if (auto typeWrapperInfo = theType->getTypeWrapper()) {
+      auto *ctor = typeWrapperInfo->Wrapper->getTypeWrapperInitializer();
+      assert(ctor);
+      (void)SGM.getFunction(SILDeclRef(ctor), NotForDefinition);
+    }
   }
 
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