Static convertability testing?

[Chris Williams via Digitalmars-d-learn]

I have a template function that gets values out of a tree of 
variant types. My goal is to be able to write code like;

node.get!string("path", "to", "leaf");

Inside get(), I would like to use std.conv to dynamically convert 
(where able) to the target type (T) or, if that is not possible, 
to return T.init.

If I wanted to force the user to request the correct type as is 
stored in the structure, I could write code like:

switch (leafType) {
case STRING:
    static if (is(T : string)) {
       return leftValue;
    }
    else {
       return T.init
    }
break;
...

But since I want to allow all possiblities that std.conv 
supports, I want something like:

static if (isConvertible!(T, string)) {
    return leftValue.to!T;
}
else {
    return T.init;
}

Is there something like isConvertible() in the library somewhere?