compiler/modecheck_unify.m:
User-written lambdas always include a mode declaration. However,
the compiler can also construct lambdas from curried calls, and these
do not have a mode declaration. These converted, non-mode-declared
lambdas always start out containing *only* the curried call, but
the polymorphism transformation can insert other code before this call,
e.g. to pick up the typeinfos and/or typeclass infos to be passed
to that call from other typeclass infos, so don't abort if the lambda
contains calls to the builtin predicates that do these things besides
the original call.
tests/valid/undetermined_mode_lambda.m:
A regression test for the bug.
tests/valid/Mmakefile:
Enable the new test case.
