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digitalmars.D.bugs - [Issue 6415] New: Placement of pure and nothrow for invariant()

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6415

           Summary: Placement of pure and nothrow for invariant()
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



This code shows a problem with placement of pure and nothrow:


class Foo {
    pure nothrow invariant() {} // OK
    invariant() pure nothrow {} // Error
}
void main() {}


DMD 2.054 gives:

test.d(3): statement expected to be { }, not pure
test.d(3): basic type expected, not {
test.d(3): no identifier for declarator int
test.d(3): semicolon expected, not '{'
test.d(3): Declaration expected, not '{'
test.d(5): } expected following member declarations in aggregate

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Jul 30 2011
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6415


Henning Pohl <henning still-hidden.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull
                 CC|                            |henning still-hidden.de



PDT ---
https://github.com/D-Programming-Language/dmd/pull/2156

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Jun 09 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 This code shows a problem with placement of pure and nothrow:
 
 class Foo {
     pure nothrow invariant() {} // OK
     invariant() pure nothrow {} // Error
 }
 void main() {}


Today `invariant {}` is parsed same as `immutable {}` (=
`AttributeDeclaration`), because in early D2 age `invariant` had been reused
for `immutable` meaning.
So `invariant` block requires following `()` to keep backward compatibility.
But, eventually the redundant parenthesis would be unnecessary, and you can
write invariant block as same as unittest block.

And, currently unittest block does not accept postfix attributes.

```d
invariant()  pure safe nothrow {}   // allwed by this change
invariant  pure safe nothrow {}     // eventually allowed?

unittest  pure safe nothrow {}      // currently not allowed
```

Therefore, just only fixing invariant syntax will introduce future
inconsistency. So we should consider unittest block syntax at the same time.

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Jun 09 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6415


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla digitalmars.com



10:33:41 PDT ---
I'm not convinced anything needs fixing. Why should:

   invariant() pure nothrow { }

be accepted? After all, as Kenji mentioned, the () is to support old code and
will eventually go away anyway.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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brian-schott cox.net changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |brian-schott cox.net



So this means that ideally the grammar would be:

invariant:
    'invariant' blockStatement
    ;

correct?

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Jun 10 2013
prev sibling next sibling parent d-bugmail puremagic.com writes:
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 After all, as Kenji mentioned, the () is to support old code and
 will eventually go away anyway.


OK. dmd 2.064 is a good moment for that "eventually" to be, see Issue 10326

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prev sibling parent d-bugmail puremagic.com writes:
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bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |WONTFIX





 https://github.com/D-Programming-Language/dmd/pull/2156


Given the recent comments by Walter and Kenji, the two years of Walter's total
silence passed since this proposal, and the changes proposed in Issue 10326 ,
then maybe this whole issue becomes useless.

Do we want to write code like this?


class Foo {
    invariant pure nothrow {}
}
unittest pure nothrow {}
void main() {}


It's not a good change. So please let me close this issue down. If someone
wants to press the issue further then please reopen this issue.

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