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import org.checkerframework.checker.nullness.qual.*;
import org.checkerframework.dataflow.qual.*;
public class AssertIfClient {
@RequiresNonNull("#1.rpcResponse()")
void rpcResponseNonNull(Proxy proxy) {
@NonNull Object response = proxy.rpcResponse();
}
void rpcResponseNullable(Proxy proxy) {
@Nullable Object response = proxy.rpcResponse();
}
void rpcResponseTypestate() {
Proxy proxy = new Proxy();
// :: error: (assignment.type.incompatible)
@NonNull Object response1 = proxy.rpcResponse();
// :: error: (contracts.precondition.not.satisfied)
rpcResponseNonNull(proxy);
rpcResponseNullable(proxy);
proxy.issueRpc();
@NonNull Object response2 = proxy.rpcResponse();
@NonNull Object response3 = proxy.rpcResponse();
rpcResponseNonNull(proxy);
rpcResponseNullable(proxy);
}
}
class Proxy {
// the RPC response, or null if not yet received
@MonotonicNonNull Object response = null;
@SuppressWarnings("contracts.postcondition.not.satisfied")
@EnsuresNonNull({"response", "rpcResponse()"})
void issueRpc() {
response = new Object();
}
// If this method returns true,
// then response is non-null and rpcResponse() returns non-null
@SuppressWarnings("contracts.conditional.postcondition.not.satisfied")
@EnsuresNonNullIf(
expression = {"response", "rpcResponse()"},
result = true)
boolean rpcResponseReceived() {
return response != null;
}
// Returns non-null if the response has been received, null otherwise;
// but an @AssertNonNullIfNonNull annotation would states the converse,
// that if the result is non-null then the response hs been received.
// See rpcResponseReceived.
@Pure
@Nullable Object rpcResponse() {
return response;
}
}
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