fail package:cabal-install-solver

We failed to find a solution in this path through the tree

O(1). Create a log with one message before a failure.

indicates program failure with an exit code. The exact interpretation of the code is operating-system dependent. In particular, some values may be prohibited (e.g. 0 on a POSIX-compliant system).

When a value is bound in do-notation, the pattern on the left hand side of <- might not match. In this case, this class provides a function to recover. A Monad without a MonadFail instance may only be used in conjunction with pattern that always match, such as newtypes, tuples, data types with only a single data constructor, and irrefutable patterns (~pat). Instances of MonadFail should satisfy the following law: fail s should be a left zero for >>=,

fail s >>= f  =  fail s

If your Monad is also MonadPlus, a popular definition is

fail _ = mzero

fail s should be an action that runs in the monad itself, not an exception (except in instances of MonadIO). In particular, fail should not be implemented in terms of error.

The computation exitFailure is equivalent to exitWith (ExitFailure exitfail), where exitfail is implementation-dependent.

Information about a dependency solver failure.

O(1). Apply a function to the failure value in a log.