[5.10][Runtime] Handle different types for src and dest in existentialAssig…

stdlib/public/runtime/BytecodeLayouts.cpp

@@ -1435,14 +1435,32 @@ static void existentialAssignWithCopy(const Metadata *metadata,
                                uint8_t *dest,
                                uint8_t *src) {
   uintptr_t _addrOffset = addrOffset;
-  auto *type = getExistentialTypeMetadata((OpaqueValue*)(src + _addrOffset));
+  auto *srcType = getExistentialTypeMetadata((OpaqueValue*)(src + _addrOffset));
+  auto *destType = getExistentialTypeMetadata((OpaqueValue*)(dest + _addrOffset));
   auto *destObject = (OpaqueValue *)(dest + _addrOffset);
   auto *srcObject = (OpaqueValue *)(src + _addrOffset);
   addrOffset = _addrOffset + (sizeof(uintptr_t) * NumWords_ValueBuffer);
-  if (type->getValueWitnesses()->isValueInline()) {
-    type->vw_assignWithCopy(destObject, srcObject);
+
+  if (srcType == destType) {
+    if (srcType->getValueWitnesses()->isValueInline()) {
+      srcType->vw_assignWithCopy(destObject, srcObject);
+    } else {
+      swift_release(*(HeapObject**)destObject);
+      memcpy(destObject, srcObject, sizeof(uintptr_t));
+      swift_retain(*(HeapObject**)srcObject);
+    }
+    return;
+  }
+
+  if (destType->getValueWitnesses()->isValueInline()) {
+      destType->vw_destroy(destObject);
   } else {
     swift_release(*(HeapObject**)destObject);
+  }
+
+  if (srcType->getValueWitnesses()->isValueInline()) {
+    srcType->vw_initializeWithCopy(destObject, srcObject);
+  } else {
     memcpy(destObject, srcObject, sizeof(uintptr_t));
     swift_retain(*(HeapObject**)srcObject);
   }

test/Interpreter/layout_string_witnesses_static.swift

@@ -308,6 +308,12 @@ struct StructWithSomeProtocolInline: SomeProtocol {
     let x: SimpleClass
 }
 
+struct StructWithSomeProtocolInlineShifted: SomeProtocol {
+    let y: Int = 0
+    let y2: Int = 0
+    let x: SimpleClass
+}
+
 func testExistentialStructInline() {
     let ptr = UnsafeMutablePointer<ExistentialWrapper>.allocate(capacity: 1)
 
@@ -396,6 +402,47 @@ func testExistentialStructBox() {
 
 testExistentialStructBox()
 
+func testExistentialStructTypeChange() {
+    let ptr = UnsafeMutablePointer<ExistentialWrapper>.allocate(capacity: 1)
+
+    do {
+        let x = StructWithSomeProtocolInline(x: SimpleClass(x: 23))
+        testInit(ptr, to: createExistentialWrapper(x))
+    }
+
+    do {
+        let y = StructWithSomeProtocolInlineShifted(x: SimpleClass(x: 32))
+
+        // CHECK: Before deinit
+        print("Before deinit")
+
+        // CHECK-NEXT: SimpleClass deinitialized!
+        var wrapper = createExistentialWrapper(y)
+        testAssignCopy(ptr, from: &wrapper)
+    }
+
+    do {
+        let z = StructWithSomeProtocolBox(x: SimpleClass(x: 32))
+
+        // CHECK-NEXT: Before deinit
+        print("Before deinit")
+
+        // CHECK-NEXT: SimpleClass deinitialized!
+        var wrapper = createExistentialWrapper(z)
+        testAssignCopy(ptr, from: &wrapper)
+    }
+
+    // CHECK-NEXT: Before deinit
+    print("Before deinit")
+
+    // CHECK-NEXT: SimpleClass deinitialized!
+    testDestroy(ptr)
+
+    ptr.deallocate()
+}
+
+testExistentialStructTypeChange()
+
 func testAnyWrapper() {
     let ptr = UnsafeMutablePointer<AnyWrapper>.allocate(capacity: 1)