These traits are only implemented for Lambda<FN> and anything that implements FnMut of the various arities.
First of all, to nudge users in the direction of maintaining functional purity, the bound should probably be Fn not FnMut.
I believe the purpose is to allow using either a FnMut with no dependency information, or a Lambda that contains a function and also has dependency information.
It's not clear to me that this is actually serving a useful purpose, are Lambdas actually supposed to be constructed by the user? Does internal code pass Lambdas to the public API functions that take IsLambda?
These traits are only implemented for
Lambda<FN>and anything that implementsFnMutof the various arities.First of all, to nudge users in the direction of maintaining functional purity, the bound should probably be
FnnotFnMut.I believe the purpose is to allow using either a
FnMutwith no dependency information, or aLambdathat contains a function and also has dependency information.It's not clear to me that this is actually serving a useful purpose, are
Lambdas actually supposed to be constructed by the user? Does internal code passLambdas to the public API functions that takeIsLambda?