swift234

Now that the top level "diagnoseConstraintFailure" engine can handle multiple 
constraints of each kind, enhance FailureDiagnosis::diagnoseGeneralConversionFailure to 
ignore conversion constraints that are either trivially resolvable (like Int conforming
to IntegerLiteralConvertible) or constraints that cannot be resolved because a type 
variable is ambiguous.

This eliminates the last (known to me at least!) source of diagnostics that end up
complaining about obviously incorrect issues.


Swift SVN r31065