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digitalmars.D.bugs - [Issue 664] New: is(func T == return) ignores variadic arguments

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=664

           Summary: is(func T == return) ignores variadic arguments
           Product: D
           Version: 0.176
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla digitalmars.com
        ReportedBy: thomas-dloop kuehne.cn


according to is(... == return) all the functions below have the same argument
types:

void foo(int);
void foo(int ...);
void foo(int, ...);


-- 
Dec 09 2006
next sibling parent Bruno Medeiros <brunodomedeiros+spam com.gmail> writes:
d-bugmail puremagic.com wrote:
 http://d.puremagic.com/issues/show_bug.cgi?id=664
 
            Summary: is(func T == return) ignores variadic arguments
            Product: D
            Version: 0.176
           Platform: PC
         OS/Version: Linux
             Status: NEW
           Severity: normal
           Priority: P2
          Component: DMD
         AssignedTo: bugzilla digitalmars.com
         ReportedBy: thomas-dloop kuehne.cn
 
 
 according to is(... == return) all the functions below have the same argument
 types:
 
 void foo(int);
 void foo(int ...);
 void foo(int, ...);
 
 
perhaps you mean '== function' and not '== return' ? -- Bruno Medeiros - MSc in CS/E student http://www.prowiki.org/wiki4d/wiki.cgi?BrunoMedeiros#D
Dec 09 2006
prev sibling next sibling parent reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=664


thomas-dloop kuehne.cn changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|is(func T == return) ignores|is(func T == function)
                   |variadic arguments          |ignores variadic arguments




------- Comment #1 from thomas-dloop kuehne.cn  2006-12-10 07:03 -------
"is(... == function)" instead of "is(... == return)"

Thanks to Bruno Medeiros for catching this.


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Dec 10 2006
parent Thomas Kuehne <thomas-dloop kuehne.cn> writes:
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

d-bugmail puremagic.com schrieb am 2006-12-10:
 http://d.puremagic.com/issues/show_bug.cgi?id=664
 ------- Comment #1 from thomas-dloop kuehne.cn  2006-12-10 07:03 -------
 "is(... == function)" instead of "is(... == return)"

 Thanks to Bruno Medeiros for catching this.
Added to DStress as http://dsrtess.kuehne.cn/compile/i/is_16_A.d http://dsrtess.kuehne.cn/compile/i/is_16_B.d http://dsrtess.kuehne.cn/compile/i/is_16_C.d Thomas -----BEGIN PGP SIGNATURE----- iD8DBQFFfDcsLK5blCcjpWoRAnN5AJ9MX1ROgSUULtT47D1xu8IcdwzOIACeKzG7 snwZR9B8j4jhAOIp5NTs6Fs= =yZ/9 -----END PGP SIGNATURE-----
Dec 10 2006
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=664


Andrei Alexandrescu <andrei metalanguage.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |andrei metalanguage.com
         AssignedTo|nobody puremagic.com        |bugzilla digitalmars.com


--- Comment #3 from Andrei Alexandrescu <andrei metalanguage.com> 2010-11-26
13:22:37 PST ---
Fixed URLs:

http://dstress.kuehne.cn/compile/i/is_16_A.d
http://dstress.kuehne.cn/compile/i/is_16_B.d
http://dstress.kuehne.cn/compile/i/is_16_C.d

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Nov 26 2010
prev sibling next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=664


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au


--- Comment #4 from Don <clugdbug yahoo.com.au> 2011-12-07 02:29:39 PST ---
There are two ways to fix this:
(1) Change the spec to define that (is == function) returns the non-variadic
parameters.
(2) Create a '...' object inside the compiler, and allow it to be a member of a
tuple. Variadics are neither types nor expressions, nor symbols. Creates lots
of special cases all through the compiler.There are tricky examples like:

template baa(T...) {
    alias void function(T) a;  // OK, params are (char, ...)
    alias void function(T, ...) b; // illegal: (char, ..., ...)
    alias void function(T, int) c; // illegal: (char, ..., int)
}

alias baa!( is ( void function(char, ...) == function)).b baz;


And if we fix those problems, maybe we should allow this syntax:
alias baa!(char, ...).a foo;
because otherwise I don't know what to print when you do:
pragma(msg, T);
but then we have to make sure we can always distinguish variadic function
parameters from template variadics.

Is this issue important enough to justify (2) ?

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Dec 07 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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--- Comment #5 from Stewart Gordon <smjg iname.com> 2011-12-17 18:27:18 PST ---
(3) Have function(char, ...) just not matching function(T) for any value of T. 
... is a fundamentally different kind of thing from a type, so it doesn't seem
to make sense to allow it as an element of a type tuple.

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Dec 17 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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--- Comment #6 from Don <clugdbug yahoo.com.au> 2011-12-19 04:59:44 PST ---
(In reply to comment #5)
 (3) Have function(char, ...) just not matching function(T) for any value of T. 
 ... is a fundamentally different kind of thing from a type, so it doesn't seem
 to make sense to allow it as an element of a type tuple.
How does that solve the problem? The root cause is that is( ==function) assumes that all of the function parameters can be returned in a tuple, but that isn't true for ... Or do you mean that is( x==function) should be an error if x has a variadic parameter? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 19 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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--- Comment #7 from Stewart Gordon <smjg iname.com> 2011-12-19 05:23:40 PST ---
(In reply to comment #6)
 How does that solve the problem? The root cause is that is( ==function) assumes
 that all of the function parameters can be returned in a tuple, but that isn't
 true for ...
In what way does it make that assumption?
 Or do you mean that is( x==function) should be an error if x has a variadic
 parameter?
Of course not. What would be the point of that? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 19 2011
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--- Comment #8 from Don <clugdbug yahoo.com.au> 2011-12-19 22:34:00 PST ---
(In reply to comment #7)
 (In reply to comment #6)
 How does that solve the problem? The root cause is that is( ==function) assumes
 that all of the function parameters can be returned in a tuple, but that isn't
 true for ...
In what way does it make that assumption?
It declares T as a tuple containing all of the function arguments. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 19 2011
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Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |spec


--- Comment #9 from Don <clugdbug yahoo.com.au> 2011-12-19 22:44:37 PST ---
(In reply to comment #8)
 (In reply to comment #7)
 (In reply to comment #6)
 How does that solve the problem? The root cause is that is( ==function) assumes
 that all of the function parameters can be returned in a tuple, but that isn't
 true for ...
In what way does it make that assumption?
It declares T as a tuple containing all of the function arguments.
Complete section of the spec: ------ 6. is ( Type Identifier == TypeSpecialization ) The condition is satisfied if Type is semantically correct and is the same as TypeSpecialization. The Identifier is declared to be either an alias of the TypeSpecialization or, if TypeSpecialization is dependent on Identifier, the deduced type. If TypeSpecialization is one of typedef struct union class interface enum function delegate then the condition is satisifed if Type is one of those. Furthermore, Identifier is set to be an alias of the type: keyword alias type for Identifier function TypeTuple of the function parameter types ------ This is impossible if the function has a C-style variadic parameter. Although solution (2) would allow it to be a Tuple, it wouldnt be a TypeTuple. So a change to the spec is inevitable. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 19 2011
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--- Comment #10 from Stewart Gordon <smjg iname.com> 2011-12-20 03:54:21 PST ---
(In reply to comment #9)
 Complete section of the spec:
 ------
 6. is ( Type Identifier == TypeSpecialization )
You were suggesting in comment 6 that is(x == function), not is(x T == function), should fail if x is variadic.
 keyword     alias type for Identifier
 function     TypeTuple of the function parameter types
 ------
 This is impossible if the function has a C-style variadic parameter. Although
 solution (2) would allow it to be a Tuple, it wouldnt be a TypeTuple. So a
 change to the spec is inevitable.
I see now. So I suppose what we need is distinct syntaxes for extracting variadic and non-variadic parameter lists. So maybe: is ( Type == function ) passes iff Type is a function type, variadic or not is ( Type Identifier == function ) passes iff Identifier is a non-variadic function type, and binds Identifier to a tuple of the parameter types is ( Type Identifier , ... == function ) passes iff Identifier is a variadic function type, and binds Identifier to a tuple of the fixed parameter types -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Dec 20 2011
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--- Comment #11 from Don <clugdbug yahoo.com.au> 2011-12-20 05:22:56 PST ---
(In reply to comment #10)
 (In reply to comment #9)
 Complete section of the spec:
 ------
 6. is ( Type Identifier == TypeSpecialization )
You were suggesting in comment 6 that is(x == function), not is(x T == function), should fail if x is variadic.
I didn't intend to. All discussion has been about is(Type Identifier == function). Sorry that that wasn't clear.
 keyword     alias type for Identifier
 function     TypeTuple of the function parameter types
 ------
 This is impossible if the function has a C-style variadic parameter. Although
 solution (2) would allow it to be a Tuple, it wouldnt be a TypeTuple. So a
 change to the spec is inevitable.
I see now. So I suppose what we need is distinct syntaxes for extracting variadic and non-variadic parameter lists. So maybe: is ( Type == function ) passes iff Type is a function type, variadic or not is ( Type Identifier == function ) passes iff Identifier is a non-variadic function type, and binds Identifier to a tuple of the parameter types is ( Type Identifier , ... == function ) passes iff Identifier is a variadic function type, and binds Identifier to a tuple of the fixed parameter types
Yeah, that would work. But it's far more complicated than (1), changing one line of the spec to match the compiler, namely that: is(Type Identifier == function) binds Identifier to: -TypeTuple of the function parameter types +TypeTuple of the function parameter types. For C-style variadic functions, only the non-variadic parameters are included. and then (possibly*) provide some other mechanism for identifying if a function is C-style variadic. is() expressions are just about the ugliest thing in the language already, I'm loathe to recommend making them even uglier. * I say possibly, because I think that given a tuple T and return type R, you can check if typeof(f) == extern(C) R function (T, ...) So I'm not sure that any compiler changes are required. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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--- Comment #12 from Stewart Gordon <smjg iname.com> 2011-12-20 06:00:39 PST ---
(In reply to comment #11)
 and then (possibly*) provide some other mechanism for identifying 
 if a function is C-style variadic.  is() expressions are just about 
 the ugliest thing in the language already, I'm loathe to recommend 
 making them even uglier.
Why only C-style variadics? D-style variadics with typeinfo just as well need to be considered. Of course, with typesafe variadics we can feasibly just keep the type and just discard the ... .... -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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--- Comment #13 from Don <clugdbug yahoo.com.au> 2011-12-20 06:42:22 PST ---
(In reply to comment #12)
 (In reply to comment #11)
 and then (possibly*) provide some other mechanism for identifying 
 if a function is C-style variadic.  is() expressions are just about 
 the ugliest thing in the language already, I'm loathe to recommend 
 making them even uglier.
Why only C-style variadics? D-style variadics with typeinfo just as well need to be considered. Of course, with typesafe variadics we can feasibly just keep the type and just discard the ... ....
You're right. Fortunately, I don't think it's any different. -TypeTuple of the function parameter types +TypeTuple of the function parameter types. For C- and D-style variadic functions, only the non-variadic parameters are included. For typesafe variadic functions, the ... is ignored. Can you improve on that? -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
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--- Comment #14 from github-bugzilla puremagic.com 2012-01-21 11:24:41 PST ---
Commit pushed to
https://github.com/D-Programming-Language/d-programming-language.org

https://github.com/D-Programming-Language/d-programming-language.org/commit/e3ff6bd4a8c6d368a64d6a81af565868f6067c74
fix Issue 664 - is(func T == function) ignores variadic arguments

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Jan 21 2012
prev sibling parent d-bugmail puremagic.com writes:
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Walter Bright <bugzilla digitalmars.com> changed:

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


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