Use Target-typing for expressions

Expressions now, via the parameter, variable or field declaration, allow fully generic types which is great.

However it would be helpful for these types to be used to condition how the expression is parsed.

It is often useful to add local 'functions' to the report as variables (or more often parameters). For example, currently you could declare a local function as a param (say of type java.util.function.BiFunction) with:

(java.util.function.BiFunction) ((a, b) -> {

... statements, possibly with control flow, to declare and compute foo

return foo;

})

Such that it can be invoked in another expression with $P{myFunction}.apply($F{field1}, $F{field2})

With target typing the expression becomes...

(a, b) -> {

... statements, possibly with control flow

return foo;

}

It's possible that this could be implemented purely by wrapping the expression in a cast using the parameter type information but you may not want to always do so a property may be desirable.