On 10.03.2018 20:33, MG wrote:
Hi Jochen,

I was not aware that Groovy is so sophisticated in its expression analysis, that it actually uses intersection types

you actually do not have much of a choice. It is an AST-only representation only though.

 3. It would, on the other hand, allow to introduce var support not
    based on var === def to dynamic Groovy later on, without breaking
    backwards compatibility (becauseĀ  var x = new Foo(); x = 123
    suddenly does not work any more)

what exactly is the advantage of not having var === def? Only to disallow the reassignment in some cases at runtime? I do not see much gain in that actually

Just food for thought - I personally would prefer to see the "90% solution" I talked about in an earlier post for dynamic Groovy:
Support var x = RHS -> typeof(RHS) x = RHS for simple cases, such as:
var x = new Foo(...)
var x = (Foo) ...
var x = foo(...) // use the explicit return type of method foo(), CTE on return type == def ("'var' not supported for 'def' as return type - use Object as return type of method or define variable using 'def'.") throw CTE in all other cases (least surprise - "'Type for variable defined with 'var' cannot be deduced in dynamic Groovy. Annotate the method/class with @CompileStatic to switch to static compilation, or replace 'var' with 'def'."

there is almost no expressions consisting of multiple expression, that we can tell the type of in dynamic mode. Even something simple as 1+1 can in theory return a ComplexNumber suddenly.

From the view of my framework code that goes even more so for the related case of final x = RHS -> final typeof(RHS) x = RHS I therefore keep going on about - if dynamic Groovy does not pick up the RHS type for final, I need to keep my current code, or force framework users to use @CompileStatic on all Table derived classes, if they want to define table columns in the most elegant and concise way... :-)

for "final x = ..." the exact type of x is in dynamic mode actually totally not relevant. There is no reassignment, so that problem is out here. But if we forget about that, then there is no difference between "final x" and "def x". I know cases where it could make a difference, but they do not exist in Groovy yet. so what exactly is final x supposed to do different than def x besides the reassignment?

bye Jochen

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