On 04/02/2018 02:47 PM, Marco Leise wrote:
Am Mon, 2 Apr 2018 11:57:55 -0400
schrieb Andrei Alexandrescu <[email protected]>:
Problem is we don't have head-mutable in the language. Yes, for built-in
slices the mechanism is simple - just change qualifier(T[]) to
qualifier(T)[]. For a struct S, there is no way to convert from
qualifier(S) to tailqualifier(S).
I plan to attack this directly in the DIP - provide a way for structs to
express "here's what implicit conversion should be applied when doing
template matching".
Andrei
You are hitting a prominent type system flaw here. What may
look like a hurdle on the path to fix this(this) is also at
the core of getting "shared" into a good shape and probably
affects how we will discuss "immutable destructors" and their
kin in the future. The question is "How transitive is a
qualifier when we strip it top-level on an aggregate?"
Roger. My hope is to solve that for primitive types, then use that to
typecheck constructors and destructors, then use the signatures of
(typechecked) constructors and destructors to address composition.
Ideally we'd get away without defining another kind of qualifier -
@tail(const) or whatever. That would complicate the language a great deal.
Andrei
