Truffle: Improved support for "probing" AST nodes: - Node.isSafelyReplacaeableBy(Node) checks in advance if Node.replace(Node) would be unsafe (crash the VM). - Hoist Probe() from language imlementations into Node; now completely language agnostic. - Language implementations support probing by implementing Node.isInstrumentable() and Node.createWrapperNode() - Node.Probe() throws ProbeException (without side effects) if the probe fails. -- ProbeException contains an instance of ProbeFailure that diagnoses the failure in detail - Additional measures to prevent instrumentation from being applied to internal InstrumentationNodes. - Promote ProbeListener to top level interface and add a default implementation

/* 
 * Test recursive calls do not get inlined and do not crash.
 */
function fib(a) { 
    if (a == 2 || a == 1) {
        return 1;
    }
    return fib(a-1) + fib(a-2);
}

function test() {
    i = 0;
    sum = 0;
    while (i < 100) {
        sum = sum + fib(7);
        i = i + 1;
    }
    return sum;
}

function main() {
    callUntilOptimized(test);
    assertTrue(isInlined(test, test, fib), "fib is not inlined");
    assertFalse(isInlined(test, fib, fib), "fib -> fib is not inlined");
}