@Override
    public <R,C> R accept(Visitor<R,C> v, C context) {
        return getValue().accept(v, context);
    }
{@code Coalesce} defines a coalesce function invocation. The coalesce function
returns null if all arguments are null and the first non-null argument
otherwise

<p>Coalesce doesn't provide the full interface for comparable expressions. To get an immutable
copy with the full expressiveness of Comparable expressions, call getValue().</p>

@author tiwe

@param <T> expression type
querydsl-core/src/main/java/com/querydsl/core/types/dsl/Coalesce.java