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Issue 3787 - clarification: assigment to 'this'
Summary: clarification: assigment to 'this'
Status: RESOLVED FIXED
Alias: None
Product: D
Classification: Unclassified
Component: dmd (show other issues)
Version: D2
Hardware: All All
: P3 normal
Assignee: No Owner
URL:
Keywords: spec
Depends on:
Blocks:
 
Reported: 2010-02-09 08:02 UTC by Johannes Pfau
Modified: 2015-06-09 05:14 UTC (History)
3 users (show)

See Also:

Attachments
Example of assignment to this (825 bytes, application/octet-stream)
2010-02-09 08:02 UTC, Johannes Pfau 		Details
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Description Johannes Pfau 2010-02-09 08:02:26 UTC 
Created attachment 564 [details]
Example of assignment to this

Assigning to 'this' is currently not documented anywhere. Still assigning to
this, at least in constructors, works and is used by some code (gtkd, for
example). I think assigning to this should either work in constructors as it
does right now, but it then should be documented, or it should be disallowed.
If it will stay implementation specific, that should still be noted in the
docs.

see also: http://d.puremagic.com/issues/show_bug.cgi?id=780 The assignment of
'this' is allowed
Comment 1 Andrei Alexandrescu 2010-02-09 08:42:34 UTC 
This doesn't look major.
Comment 2 Johannes Pfau 2010-02-09 10:54:37 UTC 
I just thought if you'd disallow assignment to this completely as the poster in bug 780 suggests, you might want to discuss that in the newsgroup. As this is quite late for d2 I flagged it major. Also I think completely undocumented and undefined features being already used in production code (gtkd) is a bad thing.
However, I hadn't seen the bugzilla fields explanation, sorry. I'll change the priority.

Btw, what is most likely to happen in the end?
1: make current behavior part of specification
2: disallow assignment to this completely
3: leave this as implementation specific behavior
Comment 3 Walter Bright 2012-01-22 13:34:48 UTC 
Assignment to this and super should not be allowed.

The gtkd code can be fixed by making a 'factory' method to create a new object. However, this is not a trivial fix, and so having the compiler disallow the current code should be a long time in coming.

In the meantime, I've updated the spec.