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digitalmars.D.bugs - [Issue 2716] New: Confusion of auto and scope as the class attribute

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2716

           Summary: Confusion of auto and scope as the class attribute
           Product: D
           Version: unspecified
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: rayerd.wiz gmail.com


auto class B {}
void main()
{
        B x;
}
a.d(4): variable a.main.x reference to scope class must be scope


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Mar 07 2009
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=2716


smjg iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |smjg iname.com
             Status|NEW                         |RESOLVED
         Resolution|                            |INVALID





An auto class and a scope class are the same thing.  What do you think auto
means in this context?


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Mar 08 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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braddr puremagic.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |
            Version|unspecified                 |2.000





That use of auto is supposed to be going away.  I've reopened and assigned to
2.x.


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Mar 08 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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What is this different something that auto in this context means now?  I can't
find it by a quick look through the docs.


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Mar 08 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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The old concept of 'auto' meaning 'scope' should be dead.  It's death started
before the 1.0 release (if I remember my history correctly, don't feel like
searching the changelogs).  It appears that it isn't in this case.  'auto
class' should be either an error or a no-op depending on your philosophy of
redundant type prefixes.


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Mar 08 2009
prev sibling next sibling parent reply d-bugmail puremagic.com writes:
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smjg iname.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|rejects-valid               |diagnostic





No redundant type prefix here.  auto either
(a) still means the same as scope, IWC this whole bug report is nonsense
(b) makes no sense here at all, IWC the rejects-valid keyword here is nonsense
- it's diagnostic here, possibly accepts-invalid

But there's something wrong - auto is still given on attribute.html, but the
way it's used there it doesn't seem to be an attribute.

Brad, while I have your ear, are you planning to catch up on the issues filed
here against puremagic.com itself any time soon?


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Mar 08 2009
parent Sean Kelly <sean invisibleduck.org> writes:
d-bugmail puremagic.com wrote:

 
 But there's something wrong - auto is still given on attribute.html, but the
 way it's used there it doesn't seem to be an attribute.


'auto' was originally and continues to be a storage class.  It's the 
default storage class if another one isn't specified, so the following 
are equivalent:

auto int x = 5;
int x = 5;

Type inference happens via the omission of a type specifier, so auto is 
mostly used in this context, ie:

auto x = 5; // int variable with a storage class of 'auto'
const x = 5; // int variable with a storage class of 'const'
Mar 10 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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2009-07-12 08:23:17 PDT ---
Created an attachment (id=421)
 --> (http://d.puremagic.com/issues/attachment.cgi?id=421)
Do not consider auto to mean scope.

This is a patch against LDC's DMDFE. It removes the remaining instances of auto
meaning scope and makes 'auto class C { ... }' and 'auto C c;' an 'Error:
storage class has no effect: auto'. See also bug 3118 .

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Jul 12 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 Created an attachment (id=421)


 --> (http://d.puremagic.com/issues/attachment.cgi?id=421) [details]

 Do not consider auto to mean scope.
 
 This is a patch against LDC's DMDFE. It removes the remaining instances of auto
 meaning scope and makes 'auto class C { ... }' and 'auto C c;' an 'Error:
 storage class has no effect: auto'. See also bug 3118 .


"storage class has no effect" seems to be the wrong wording.  Firstly, it'll be
a case of doesn't make sense rather than has no effect; secondly, this is
making it not a storage class at all.

Moreover, should we get rid of it straight off, or deprecate it first?

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Jul 13 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Christian Kamm <kamm-removethis incasoftware.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kamm-removethis incasoftwar
                   |                            |e.de





2009-07-13 09:41:53 PDT ---

 "storage class has no effect" seems to be the wrong wording.


I'll change it if you come up with a nicer error message. "cannot be auto"
would've been consistent with other error messages of this kind, but I thought
the "has no effect" one was nicer.


 Firstly, it'll be a case of doesn't make sense rather than has no effect;
 secondly, this is making it not a storage class at all.


That's arguable. My reasoning was that as a do-nothing storage class, auto
makes sense everywhere. Its only 'effect' is to allow type inference in the
absence of another storage class.


 Moreover, should we get rid of it straight off, or deprecate it first?


I would've if it had ever been in the D1 spec, but as far as I remember it's
around purely as a holdover from pre-D1.

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Jul 13 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 "storage class has no effect" seems to be the wrong wording.


 
 I'll change it if you come up with a nicer error message. "cannot be auto"
 would've been consistent with other error messages of this kind, but I thought
 the "has no effect" one was nicer.


But "has no effect" reads to me to the effect that the compiler is supposed to
just ignore it, rendering the fact that the error is generated confusing to the
user.  How about "both auto and explicit type given"?


 Firstly, it'll be a case of doesn't make sense rather than has no effect;
 secondly, this is making it not a storage class at all.


 
 That's arguable. My reasoning was that as a do-nothing storage class, auto
 makes sense everywhere. Its only 'effect' is to allow type inference in the
 absence of another storage class.


The treatment of auto in this context as a storage class seems to be a hack to
simplify parsing of declarations, which is useful only because of auto's
ambiguity.  If we get rid of auto's ambiguity as is being suggested, we should
get rid of this hack while we're at it.

More logical is to handle auto as a placeholder for a type in auto-typed
declarations, as a direct part of the AutoDeclaration syntax (as I must've OUAT
thought it already was).  Something like (using * and + with their regexp
meanings)

AutoDeclaration:
    Attribute* auto Identifier = AssignExpression ;
    Attribute+ Identifier = AssignExpression ;
    Attribute* auto Attribute+ Identifier = AssignExpression ;

(this last form is for backward compatibility, but could be removed or
deprecated one day)

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Jul 14 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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---


 How about "both auto and explicit type given"?


Or even "both auto and explicit type given, use scope for RAII" for the benefit
of returning D programmers and those otherwise trying to update legacy code.

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Jul 14 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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2009-07-14 09:35:40 PDT ---
I've switched the error message to "both auto and explicit type given". auto
class C {} will still trigger the "storage class has no effect" one though. I
don't think error messages of this kind are avoidable if you want to make
directly applying inapplicable storage classes an error.

By the way, bug 3118 would benefit from having a list of attributes and
declarations that should trigger an error if combined via direct application. I
can't guarantee I'll find the time to work on it though.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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---


 I've switched the error message to "both auto and explicit type given". auto
 class C {} will still trigger the "storage class has no effect" one though. I
 don't think error messages of this kind are avoidable if you want to make
 directly applying inapplicable storage classes an error.


Probably 99% of poorly written error messages can be improved if only one stops
to think about it.

How about "auto cannot be applied to classes" or "auto can only be applied to
variable declarations"?  We could use the same format for all illegal uses of
attributes.

Of course, the relevance of this to auto'll change when/if the grammar change
proposed in comment 9 is implemented....

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Jul 14 2009
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Haruki Shigemori <rayerd.wiz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Platform|x86                         |All
         OS/Version|Windows                     |All



20:53:16 PST ---


 An auto class and a scope class are the same thing.  What do you think auto
 means in this context?


I think "auto class" must be an error, because a scoped class is "scope class"
already.

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Jan 01 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 An auto class and a scope class are the same thing.  What do you think auto
 means in this context?


 
 I think "auto class" must be an error, because a scoped class is "scope class"
 already.


This as a meaning of auto may have been removed from the spec, but AIUI it was
never the intention to withdraw it the moment scope was introduced.

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Jan 02 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Brad Roberts <braddr puremagic.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------

           obsolete|                            |



PDT ---
Created an attachment (id=636)
Update previous patch to tip of svn

I've updated this diff to the the current tip of svn 493.

I altered the error messages to point suggest that the user probably wants to
use the scope storage class when it finds the deprecated use of auto.

I've also run this through the dmd test suite (which needs some corresponding
changes that I'll send to Walter privately).

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May 18 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED



00:16:49 PDT ---
http://www.dsource.org/projects/dmd/changeset/639

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Aug 28 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Haruki Shigemori <rayerd.wiz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |



01:09:13 PDT ---
Thank you for your great job!
However, this invalid code is accepted yet.

auto class A{} // <-- not "scope"
void main()
{
    scope a = new A();
}

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Aug 28 2010
prev sibling parent d-bugmail puremagic.com writes:
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Haruki Shigemori <rayerd.wiz gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|                            |FIXED



01:52:44 PDT ---
Oh! Sorry...
This issue is already fixed.

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Aug 28 2010