On Monday, 19 February 2018 at 15:58:57 UTC, Joakim wrote:
17. Allow multiple selective imports from different modules in a single import statement

Let me hopefully conclude this discussion :).

We have an existing ambiguity in the language since at least dmd 1.0. This is unfortunate but seems costly to remove and minor in impact (after learning this behavior).

    import trees, fruits : apple, birds;

A newcomer to D could rightfully conclude that comma is a module separator and the following is the correct syntax to import multiple symbols.

    import std.stdio, std.conv : to, std.conv : parse;

Embracing that existing ambiguity to support multi-module selective imports wasn't well received, partly because it amplifies the ambiguity and partly because multi-module imports are frowned upon.

On the plus side, we've understood that the actual wish for that syntax arised from scripting and example contexts, which might be better addressed by https://dlang.org/changelog/2.079.0.html#std-experimental-scripting, lazy import resolution by the compiler or a library, or automatic imports (https://github.com/CyberShadow/AutoFix).

Furthermore there remain various ideas that would avoid the original ambiguity. Whether such changes are worthwhile is up for discussion and would benefit from someone taking the lead.

I still think that local imports are nice for being explicit and toolable but have the downside of being brittle. Something like bash style expansion could help to hit a sweet spot IMHO.

    import std.{algorithm : {find, findSplit}, stdio : writeln};
import std.experimental.allocator.building_blocks.{free_list, region};

But certainly anything in that direction requires time and research, which I don't have for that topic.

In hindsight the voting experiment on https://github.com/dlang/dmd/pull/6589 might have prevented useful early feedback and thinking.

Given the effort required for a language change, it's seductive to streamline seemingly small changes, but it certainly increases the risk of design mistakes, thanks for appealing against this one.


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