On Fri, Oct 14, 2022 at 09:51:54PM +0000, WhatMeWorry via Digitalmars-d-learn wrote:
> 
> I lost about a half an hour troubleshooting some code of mine which as it turned out to be resolved with just one line.
> 
> 
> // paths.remove(i);   // compiles fine but does nothing
> 
> paths = paths.remove(i);  // works - what I erroneously thought the previous
> line was doing
> 
> Is the first line nonsensical and should the compiler have at least issued a warning?

Depending on what your range type was, it may not necessarily do *nothing* (it may mutate the range).  But as Andrei put it, "range mutation functions change content, not topology". It *returns* the new "topology", i.e., the new range after the removal; so you need to assign it to the original range in order to keep it up-to-date.

Given that this particular trap crops up regularly, perhaps some sort of warning ought to be added. Once the @nodiscard DIP is accepted & implemented this should be easy to do.


T

-- 
"I'm running Windows '98." "Yes." "My computer isn't working now." "Yes, you already said that." -- User-Friendly

On Sat, Oct 15, 2022 at 12:47:02AM +0000, Mike Parker via Digitalmars-d-learn wrote:
> On Friday, 14 October 2022 at 22:17:52 UTC, H. S. Teoh wrote:
> 
> > Given that this particular trap crops up regularly, perhaps some sort of warning ought to be added. Once the @nodiscard DIP is accepted & implemented this should be easy to do.
> > 
> 
> Seems like you're behind the times! The DIP was accepted and implemented with some changes:
> 
> https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1038.md#final-review

Has it really been implemented?  I tested the latest git master, the following code doesn't compile:

------
@mustUse int fun() { return 455; }

void main() {
	fun();
}
------

Compiler output:

------
/tmp/test.d(1): Error: undefined identifier `mustUse`
------

I tried @mustuse, @nodiscard, @noDiscard, no good.  What am I missing?


T

-- 
This is not a sentence.

https://github.com/dlang/dmd/blob/master/druntime/src/core/attribute.d#L292

On Wednesday, 19 October 2022 at 00:57:31 UTC, H. S. Teoh wrote:
> Has it really been implemented?  I tested the latest git master, the following code doesn't compile:

it only applies to types, not to functions.

On Wed, Oct 19, 2022 at 01:15:37AM +0000, Adam D Ruppe via Digitalmars-d-learn wrote:
> On Wednesday, 19 October 2022 at 00:57:31 UTC, H. S. Teoh wrote:
> > Has it really been implemented?  I tested the latest git master, the following code doesn't compile:
> 
> it only applies to types, not to functions.

Wat... so what's the use of it then?  So it's not possible to mark the return value of an int function @mustUse without making, in theory, *all* ints @mustUse?

I must confess I'm baffled as to the purpose of this strange design.


T

-- 
Doubt is a self-fulfilling prophecy.

On Wednesday, 19 October 2022 at 01:30:23 UTC, H. S. Teoh wrote:
> On Wed, Oct 19, 2022 at 01:15:37AM +0000, Adam D Ruppe via
>> 
>> it only applies to types, not to functions.
>
> Wat... so what's the use of it then?  So it's not possible to mark the return value of an int function @mustUse without making, in theory, *all* ints @mustUse?
>
> I must confess I'm baffled as to the purpose of this strange design.
>

Same, can't believe it.

Is there any (design) doc about this?

On 19/10/2022 2:30 PM, H. S. Teoh wrote:
> On Wed, Oct 19, 2022 at 01:15:37AM +0000, Adam D Ruppe via Digitalmars-d-learn wrote:
>> On Wednesday, 19 October 2022 at 00:57:31 UTC, H. S. Teoh wrote:
>>> Has it really been implemented?  I tested the latest git master, the
>>> following code doesn't compile:
>>
>> it only applies to types, not to functions.
> 
> Wat... so what's the use of it then?  So it's not possible to mark the
> return value of an int function @mustUse without making, in theory,
> *all* ints @mustUse?
> 
> I must confess I'm baffled as to the purpose of this strange design.

Oh but it gets better:

From C23 draft:

The nodiscard attribute shall be applied to the identifier in a function declaration or to the definition
of a structure, union, or enumeration type. If an attribute argument clause is present, it shall have
the form:
( string-literal )