code: func sanityCheck(fn *Function, reporter io.Writer) bool {
  	if reporter == nil {
  		reporter = os.Stderr
  	}
  	return (&sanity{reporter: reporter}).checkFunction(fn)
  }
docs: // sanityCheck performs integrity checking of the SSA representation
  // of the function fn and returns true if it was valid.  Diagnostics
  // are written to reporter if non-nil, os.Stderr otherwise.  Some
  // diagnostics are only warnings and do not imply a negative result.
  //
  // Sanity-checking is intended to facilitate the debugging of code
  // transformation passes.
  //