[Issue 4832] New: Functions external to class break immutability

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4832

           Summary: Functions external to class break immutability
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: andrej.mitrovich at gmail.com


--- Comment #0 from Andrej Mitrovic <andrej.mitrovich at gmail.com> 2010-09-06 13:37:14 PDT ---
Code:

import std.stdio : writeln;

void foo(ref int x)
{
    x = 10;
}

class Bar
{
    immutable int x;

    this()
    {
        x = 5;
    }

    void printMe()
    {
        writeln(this.x);
    }

    void change()
    {
        //~ this.x = 20;    // illegal, errors out
    }
}

void main()
{
    Bar bar = new Bar;
    bar.printMe();  // prints 5

    //~ bar.x = 10;  // illegal, errors out

    foo(bar.x);     // no error!
    bar.printMe();  // prints 10
}

The commented out code would error out at compile time, which is expected. But
the function bar() is breaking immutability of x.

A relevant bug is bug 4416 , and my comment:
http://d.puremagic.com/issues/show_bug.cgi?id=4416#c1

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