How trustworthy and robust is GHC?

Is “very” a trustworthy and robust answer? I suppose that trustworthiness and robustness of software are currently very vague. Common proxies are: * Number of automated tests. * Amount of human scrutiny received (correlates with size of community, anticorrelates with size and complexity of the code). * Severity of bugs that have been discovered (correlates with number of automated tests, anticorrelates with human scrutiny). One issue with individual bugs is that testing can only show the presence of bugs, never their absence. Discovering severe bugs may be due to increased testing, not due to poorer code.