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digitalmars.D.bugs - [Issue 6982] New: immutability isn't respected on array assignment

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6982

           Summary: immutability isn't respected on array assignment
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: accepts-invalid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: mrmocool gmx.de


--- Comment #0 from Trass3r <mrmocool gmx.de> 2011-11-21 08:04:48 PST ---
//struct Bla {}
alias int Bla;

import std.stdio;

void main()
{
        immutable(Bla[]) _a;
        writeln(_a.length); // prints 0
//        _a.length = 5; // Error: variable _a cannot modify immutable
        immutable(Bla)[] a = _a;
        a.length = 5;  // compiles, but:
        writeln(_a.length); // prints 0

        immutable(Bla[string]) _files;
        immutable(Bla)[string] files = _files;
}

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=6982


timon.gehr gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |timon.gehr gmx.ch
         Resolution|                            |INVALID


--- Comment #1 from timon.gehr gmx.ch 2011-11-21 08:30:21 PST ---
That works as designed. I do not understand what you would expect it to do.

immutable(Bla[]) _a; // this is an array that cannot be changed
immutable(Bla)[] a; // this is an array whose elements cannot be changed

a = _a; // fine. a is now a slice to _a's data

a.length = 5; // reallocate storage for a.
assert(_a.length == 0); // length of _a does not change as it is a different
variable

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--- Comment #2 from Trass3r <mrmocool gmx.de> 2011-11-21 08:43:41 PST ---
Yeah, was a subtle error in reasoning.

But what about the assoc. array case?

        immutable(Bla[string]) _files = ["a":1, "b":2, "c":3];
        immutable(Bla)[string] files = _files; // works
        files["d"] = 5; // Error: files["d"] isn't mutable
        writeln(_files);
        writeln(files);

gdc rejects the assignment.

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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Trass3r <mrmocool gmx.de> changed:

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


--- Comment #3 from Trass3r <mrmocool gmx.de> 2011-11-21 08:51:18 PST ---
Yep, it breaks immutability:

        immutable(Bla[string]) _files = ["a":1, "b":2, "c":3];
        immutable(Bla)[string] files = _files;
        files.remove ("a");
        writeln(_files);
        writeln(files);

prints:

["b":2, "c":3]
["b":2, "c":3]

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prev sibling next sibling parent d-bugmail puremagic.com writes:
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timon.gehr gmx.ch changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|immutability isn't          |immutability isn't
                   |respected on array          |respected on associative
                   |assignment                  |array assignment


--- Comment #4 from timon.gehr gmx.ch 2011-11-21 12:06:10 PST ---
Ok, I see. I change the title to reflect the actual bug.

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--- Comment #5 from Kenji Hara <k.hara.pg gmail.com> 2011-12-18 06:30:45 PST ---
I think there are at least two issues.

void main()
{
    alias int Bla;
    immutable(Bla[string]) ifiles = ["a":1, "b":2, "c":3];
    immutable(Bla)[string] files = ifiles;  // (1)
    ifiles.remove ("a");                    // (2)
}

1. Implicitly conversion from immutable to mutable AA reference.
2. Call 'remove' from immutable AA reference.

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bearophile_hugs eml.cc


--- Comment #6 from bearophile_hugs eml.cc 2011-12-18 07:39:16 PST ---
A related problem (I think I have already put this in Bugzilla, but I don't
remember the issue number):


void main() {
    int[char[]] aa; // line 2
    char[] a1 = "hello".dup;
    aa[a1] = 1; // line 4
}


It's stupid for D language to accept the line 2 and then refuse line 4 with:

test.d(4): Error: associative arrays can only be assigned values with immutable
keys, not char[]

Line 2 too needs to become an error.

So a better error message is something like:

test.d(2): Error: built-in associative arrays accept only immutable keys, not
char[]

Or alternatively:

test.d(2): Error: built-in associative arrays can be defined only with
immutable keys, not char[]

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Kenji Hara <k.hara.pg gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |pull


--- Comment #7 from Kenji Hara <k.hara.pg gmail.com> 2012-03-11 06:35:43 PDT ---
https://github.com/D-Programming-Language/dmd/pull/799

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--- Comment #8 from github-bugzilla puremagic.com 2012-03-11 18:08:03 PDT ---
Commit pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/229a37a1ae0766a54cbe64fc3995847aa17f17fb
Merge pull request #799 from 9rnsr/fix6982

Issue 6982 - immutability isn't respected on associative array assignment

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prev 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


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