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digitalmars.D.bugs - [Issue 6408] New: string[].init gives a wrong type

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6408

           Summary: string[].init gives a wrong type
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: wrong-code
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc


--- Comment #0 from bearophile_hugs eml.cc 2011-07-30 06:56:07 PDT ---
I think this D2 code shows an error:

import std.stdio;
void main() {
    writeln(typeid(typeof(string[].init)));
    writeln(typeid(typeof(string[][].init)));
    writeln(typeid(typeof(string[][][].init)));
    writeln(typeid(typeof((string[]).init)));
}


Output, DMD 2.054:
immutable(char)[]
immutable(char)[]
immutable(char)[]
immutable(char)[][]

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6408


kennytm gmail.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|wrong-code                  |accepts-invalid
                 CC|                            |kennytm gmail.com


--- Comment #1 from kennytm gmail.com 2011-07-30 08:44:22 PDT ---
Apparently DMD shouldn't accept string[].init at all, e.g. int[].init is a
parser error:

--------------------------
alias int[] F;
//enum f = int[].init;  // error (as expected)
enum g = F[].init;      // no error, return 'null' of type F.
--------------------------

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--- Comment #2 from bearophile_hugs eml.cc 2011-07-30 09:13:40 PDT ---
(In reply to comment #1)

 Apparently DMD shouldn't accept string[].init at all, e.g. int[].init is a
 parser error:


Isn't it better to modify DMD to accept both string[].init and int[].init, and
return the correct results in both cases?

Because the alternative idiom to create an empty array is to use cast(int[])[],
and it's better to avoid casts where possible.

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--- Comment #3 from kennytm gmail.com 2011-07-30 12:03:14 PDT ---
(In reply to comment #2)

 (In reply to comment #1)

 Apparently DMD shouldn't accept string[].init at all, e.g. int[].init is a
 parser error:


 
 Isn't it better to modify DMD to accept both string[].init and int[].init, and
 return the correct results in both cases?
 
 Because the alternative idiom to create an empty array is to use cast(int[])[],
 and it's better to avoid casts where possible.


You could also just add a pair of parenthesis:

    (string[]).init
    (int[]).init

And (X[]).init returns 'null', not '[]'.


I'm not sure about allowing `S[].prop`. If this is allowed, we should also
allow `S[3].prop` and `S[T].prop` and maybe even `S*.prop`. Maybe let's have a
rejects-valid or enhancement request.

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--- Comment #4 from bearophile_hugs eml.cc 2011-07-30 12:37:31 PDT ---
(In reply to comment #3)


 You could also just add a pair of parenthesis:
 
     (string[]).init
     (int[]).init


This was my last example.



 I'm not sure about allowing `S[].prop`. If this is allowed, we should also
 allow `S[3].prop` and `S[T].prop` and maybe even `S*.prop`. Maybe let's have a
 rejects-valid or enhancement request.


Beside returning the correctly typed value, as alternative I accept this:

string[].init

to produce a syntax error that suggests the programmer to use (string[]).init
instead. What I don't accept it silently returning a value of the "wrong" type.

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--- Comment #5 from kennytm gmail.com 2011-07-30 13:41:25 PDT ---
(In reply to comment #4)

 (In reply to comment #3)
 

 You could also just add a pair of parenthesis:
 
     (string[]).init
     (int[]).init


 
 This was my last example.
 


Right.


 I'm not sure about allowing `S[].prop`. If this is allowed, we should also
 allow `S[3].prop` and `S[T].prop` and maybe even `S*.prop`. Maybe let's have a
 rejects-valid or enhancement request.


 
 Beside returning the correctly typed value, as alternative I accept this:
 
 string[].init
 
 to produce a syntax error that suggests the programmer to use (string[]).init
 instead. What I don't accept it silently returning a value of the "wrong" type.


I agree.

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yebblies <yebblies gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull
                 CC|                            |yebblies gmail.com
           Platform|x86                         |All
         AssignedTo|nobody puremagic.com        |yebblies gmail.com
         OS/Version|Windows                     |All


--- Comment #6 from yebblies <yebblies gmail.com> 2013-01-17 01:00:26 EST ---
T[], T[T] and T[N]

I'm not sure T* can be done like this, but it also produces an error instead of
being ignored silently.

https://github.com/D-Programming-Language/dmd/pull/1495

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--- Comment #7 from bearophile_hugs eml.cc 2013-01-16 09:58:21 PST ---
(In reply to comment #6)


 I'm not sure T* can be done like this, but it also produces an error instead of
 being ignored silently.


Thank you.
In the unittests have you added a test case that shows such error message?

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--- Comment #8 from yebblies <yebblies gmail.com> 2013-01-17 11:35:14 EST ---
(In reply to comment #7)

 (In reply to comment #6)
 

 I'm not sure T* can be done like this, but it also produces an error instead of
 being ignored silently.


 
 Thank you.
 In the unittests have you added a test case that shows such error message?


For:

auto x = string*.init;

You get:

testx.d(3): Error: undefined identifier 'init'

Because it is parsed as (string) * (.init).  To me it is much more clear that
string*.init is invalid code compared to string[].init.

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--- Comment #9 from github-bugzilla puremagic.com 2013-01-20 23:00:22 PST ---
Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/064b0419f8956a76f3d7cabeacd0861cff802923
Fix Issue 6408 - string[].init gives a wrong type

Allow reinterpreting a slice or index expression as a dynamic array, static
array, or associative array

https://github.com/D-Programming-Language/dmd/commit/cd9ef35c402dbeb177343c7cea5b9ed4a5e6b94f
Merge pull request #1495 from yebblies/issue6408

Fix Issue 6408 - string[].init gives a wrong type

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prev sibling parent d-bugmail puremagic.com writes:
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Kenji Hara <k.hara.pg gmail.com> changed:

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


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