Require converting empty set T{} to T

runtime/stdlib/cadence_v0.42_to_v1_contract_upgrade_validation_test.go

@@ -817,7 +817,7 @@ func TestContractUpgradeIntersectionFieldType(t *testing.T) {
 		assertFieldTypeMismatchError(t, cause, "Test", "a", "R", "{I}")
 	})
 
-	t.Run("change field type AnyResource restricted type", func(t *testing.T) {
+	t.Run("AnyResource restricted type, with restrictions", func(t *testing.T) {
 
 		t.Parallel()
 
@@ -849,6 +849,36 @@ func TestContractUpgradeIntersectionFieldType(t *testing.T) {
 		require.NoError(t, err)
 	})
 
+	t.Run("AnyResource restricted type, without restrictions", func(t *testing.T) {
+
+		t.Parallel()
+
+		const oldCode = `
+            pub contract Test {
+                pub resource R {}
+
+                pub var a: @AnyResource{}
+                init() {
+                    self.a <- create R()
+                }
+            }
+        `
+
+		const newCode = `
+            access(all) contract Test {
+                access(all) resource R {}
+
+                access(all) var a: @AnyResource
+                init() {
+                    self.a <- create R()
+                }
+            }
+        `
+
+		err := testContractUpdate(t, oldCode, newCode)
+		require.NoError(t, err)
+	})
+
 	t.Run("change field type restricted type variable sized", func(t *testing.T) {
 
 		t.Parallel()

runtime/stdlib/cadence_v0.42_to_v1_contract_upgrade_validator.go

@@ -285,17 +285,22 @@ typeSwitch:
 		validator.currentRestrictedTypeUpgradeRestrictions = oldType.Types
 
 		// If the old restricted type is for AnyStruct/AnyResource,
-		// require them to drop the "restricted type".
-		// e.g: `T{I} -> {I}`
+		// and if there are atleast one restriction, require them to drop the "restricted type".
+		// e.g-1: `AnyStruct{I} -> {I}`
+		// e.g-2: `AnyResource{I} -> {I}`
+		// See: https://github.com/onflow/cadence/issues/3112
 		if restrictedNominalType, isNominal := oldType.LegacyRestrictedType.(*ast.NominalType); isNominal {
 			switch restrictedNominalType.Identifier.Identifier {
 			case "AnyStruct", "AnyResource":
-				break typeSwitch
+				if len(oldType.Types) > 0 {
+					break typeSwitch
+				}
 			}
 		}
 
-		// Otherwise require them to drop the "restriction".
-		// e.g: `T{I} -> T`
+		// Otherwise require them to drop the "restrictions".
+		// e.g-1: `T{I} -> T`
+		// e.g-2: `AnyStruct{} -> AnyStruct`
 		return validator.checkTypeUpgradability(oldType.LegacyRestrictedType, newType)
 
 	case *ast.VariableSizedType: