http://d.puremagic.com/issues/show_bug.cgi?id=780

           Summary: The assignment of 'this' is allowed
           Product: D
           Version: 0.178
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Keywords: accepts-invalid
          Severity: major
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: brunodomedeiros+bugz@gmail.com


The compiler allows assignment of the 'this' special reference. Instead 'this' should be final (i.e., non assignable). In some cases, like in a class constructor, 'this' is treated as if an inout reference, changing a variable in another scope:

--------  --------
import std.stdio;

class Foo {
  static bool first = true;

  this() {
    if(first){
      first = false;
      this = new Foo();
      writefln("this= ", cast(void *)this);
    }
  }

}


void main(char[][] args) {

        Foo foo = new Foo();
        writefln("foo= ", cast(void *)foo);
}

--------  outputs:  --------
this before= 8B0FE0
this after= 8B0FD0
foo= 8B0FD0


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http://d.puremagic.com/issues/show_bug.cgi?id=780





------- Comment #1 from thomas-dloop@kuehne.cn  2007-02-27 10:47 -------
http://www.digitalmars.com/d/class.html#constructors
# Constructors are defined with a function name of this and having no return
value

However the compiler implements class constructors as returning the this
pointer
#
# module wood;
# class Tree{
#    this(){
#    }
# }
#

dmd -c wood.d && nm wood.o | grep _ctor | sed "s:.* ::" _D4wood4Tree5_ctorMFZC4wood4Tree

demangled: wood.Tree wood.Tree.this(this)


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http://d.puremagic.com/issues/show_bug.cgi?id=780


Andrei Alexandrescu <andrei@metalanguage.com> changed:

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


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--- Comment #2 from Andrei Alexandrescu <andrei@metalanguage.com> 2011-01-08 14:10:50 PST ---
Before and after return the same thing in 2.051. Nevertheless, assigning to this should be syntactically disallowed.

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Walter Bright <bugzilla@digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Platform|x86                         |All
            Version|0.178                       |D1 & D2
         OS/Version|Windows                     |All
           Severity|major                       |normal


--- Comment #3 from Walter Bright <bugzilla@digitalmars.com> 2012-01-22 13:40:09 PST ---
The spec now disallows assignment to this and super, but the compiler still allows it. Since code like gtkd relies on allowing it, the progression should be:

1. spec change
2. make it a warning
3. deprecate it
4. remove from compiler

This will take time. We're at (1). So the bug stays open for now.

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yebblies <yebblies@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jemandy@earthlink.net


--- Comment #4 from yebblies <yebblies@gmail.com> 2012-01-29 22:44:26 EST ---
*** Issue 4819 has been marked as a duplicate of this issue. ***

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           See Also|                            |http://d.puremagic.com/issu
                   |                            |es/show_bug.cgi?id=4596


--- Comment #5 from Kenji Hara <k.hara.pg@gmail.com> 2012-01-29 04:15:55 PST ---
After fixing bug 4596, this will be an issue for only D1.

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Denis Shelomovskij <verylonglogin.reg@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |verylonglogin.reg@gmail.com
            Version|D1 & D2                     |D1


--- Comment #6 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2012-10-30 16:29:54 MSK ---
(In reply to comment #5)
> After fixing bug 4596, this will be an issue for only D1.

Bug 4596 is fixed.

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