http://d.puremagic.com/issues/show_bug.cgi?id=4407

           Summary: Catch wrong argument<->attribute assignments in
                    methods
           Product: D
           Version: D1 & D2
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: diagnostic
          Severity: enhancement
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: bearophile_hugs@eml.cc


--- Comment #0 from bearophile_hugs@eml.cc 2010-06-29 18:15:53 PDT ---
This is related to bug 3878 , but it is meant to catch a different kind of bug. In my code I have seen two times bugs like:


class Foo {
    int x, y;
    this(int x_, int y_) {
        this.x = x;
        y = y;

    }
}
void main() {}


In D.learn Byron Heads has found this bug: http://www.digitalmars.com/webnews/newsgroups.php?art_group=digitalmars.D.learn&article_id=20354

this(string name, string id) {
    this._name = _name;
    this._id  = id;
}


So I think the D compiler has to catch such bugs, and refuse such assignments in class/struct member functions.

Automatic code generation can sometimes generate useless assignments, but catching common human bugs is more important. It's much simpler to fix code generators than humans.

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--- Comment #1 from bearophile_hugs@eml.cc 2010-09-20 17:32:46 PDT ---
To keep the language semantics more uniform (instead of special-casing just in methods), all redundant assignments may be flagged as errors:


void main() {
    int x;
    x = x; // error, redundant assignment
}

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--- Comment #2 from bearophile_hugs@eml.cc 2010-09-20 17:47:19 PDT ---
It's present among the Semantic Errors of Java code in the Google Web Toolkit too:

http://code.google.com/intl/en-EN/webtoolkit/tools/codepro/doc/features/audit/audit_rules_com.instantiations.assist.eclipse.auditGroup.semanticErrors.html#com.instantiations.assist.eclipse.audit.redundantAssignment

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--- Comment #3 from bearophile_hugs@eml.cc 2010-10-01 16:57:39 PDT ---
Another similar class of bugs, suggested by JimBob:


class Foo {
   int m_x;
   this(int x) {
       int m_x = x;
   }
}

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--- Comment #4 from bearophile_hugs@eml.cc 2011-07-11 10:03:16 PDT ---
One example of bug related to  x=x;  found inside the good QT libs:


PassRefPtr<Structure>
Structure::getterSetterTransition(Structure* structure)
{
  ...
  RefPtr<Structure> transition = create(
    structure->storedPrototype(), structure->typeInfo());
  transition->m_propertyStorageCapacity =
    structure->m_propertyStorageCapacity;
  transition->m_hasGetterSetterProperties =
    transition->m_hasGetterSetterProperties;
  transition->m_hasNonEnumerableProperties =
    structure->m_hasNonEnumerableProperties;
  transition->m_specificFunctionThrashCount =
    structure->m_specificFunctionThrashCount;
  ...
}

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dimitri.sabadie@gmail.com


--- Comment #5 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2012-12-20 15:03:53 PST ---
*** Issue 9080 has been marked as a duplicate of this issue. ***

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |andrej.mitrovich@gmail.com
         Resolution|                            |WONTFIX


--- Comment #6 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2013-01-09 17:41:19 PST ---
Denied by Walter. A shame because this is a common user bug.

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |verylonglogin.reg@gmail.com


--- Comment #7 from Denis Shelomovskij <verylonglogin.reg@gmail.com> 2013-06-29 19:13:27 MSD ---
(In reply to comment #6)
> Denied by Walter. A shame because this is a common user bug.

Any comments about the reason?

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--- Comment #8 from bearophile_hugs@eml.cc 2013-06-29 10:04:25 PDT ---
(In reply to comment #7)

> Any comments about the reason?

If you don't receive answers here in a day or two, then you probably have to ask again in the main D newsgroup...

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