[RFC] [Discussion] Bound-Erased Generic Types

Hi Daniil,

Thanks for the support. That matters a lot.

1. Turbofish at callsite: this was already brought up before, while I understand the precedence issues that led to this choice, having written some rust myself, I still don’t like the syntax, and would very much prefer normal diamond syntax at callsite, like for declarations.

I personally like Turbofish; however, I understand that some people
might not find it "pretty". But the reason it has to stay as turbofish
is parser-level: [A(D)] is ambiguous between a single-element
array calling generic A and a two-element array of comparisons, and
there's no context-sensitive disambiguation that works inside
attributes, array expressions, and ternaries without introducing rules
that bite at exactly the worst places. Forcing parentheses around the
call ([(A(D))]) was suggested earlier in the thread and is
uglier than turbofish; it also closes the door on tuple syntax I'd
like to keep open for a future RFC. Turbofish costs two characters and
keeps the parser non-context-sensitive, which is the trade I'd rather
take.

The [self::foo::(1), self::foo::(2)] case genuinely looks
the worst. The same call without turbofish ([self::foo(1), self::foo(2)]) reads fine and is what the vast majority of call sites
will look like, since turbofish is opt-in for ambiguity resolution
(because inference is hard), and most calls won't need it.

2. -/+ for variant bounds: also brought up before, while it can be somewhat mnemonic (- consumes for input params, + produces for output params), in/out would indeed be much more descriptive IMO (or at the very least, both options could be provided at the same time).

Secondary vote added on this. +T/-T vs in T/out T. I have no
strong preference; the vote will decide.

I will implement support for this RFC in Psalm immediately after the RFC is approved

Side note: I'm optimistic ;)
https://github.com/carthage-software/mago/pull/1826

Thanks again for the careful read.

Cheers,
Seifeddine.

Leaving-the-door-open-for-tuples is a good additional argument for using the turbofish syntax; I'd say it's important enough to mention in the RFC.