[Issue 2192] New: Returning element in an AA of AAs during nested foreach generates compiler error

[Issue 2192] Returning from inside foreach body delegate only returns from inner delegate

Feb 03, 2012

yebblies

Feb 03, 2012

Kenji Hara

Feb 03, 2012

yebblies

July 04, 2008

[Issue 2192] New: Returning element in an AA of AAs during nested foreach generates compiler error

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http://d.puremagic.com/issues/show_bug.cgi?id=2192

           Summary: Returning element in an AA of AAs during nested foreach
                    generates compiler error
           Product: D
           Version: 1.029
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla@digitalmars.com
        ReportedBy: business3@twistedpairgaming.com


The following code generates a rather curious compiler error:

BEGIN CODE
class Foo { }
Foo[char][char] jaggedArray;

Foo Bar()
{
        foreach(Foo[char] array; jaggedArray)
        {
                foreach(Foo f; array)
                {
                        return null; // Error
                }
        }
}
END CODE

Compiler output from both DMD 1.029 and DMD 1.031:
testb1.d(10): Error: cannot implicitly convert expression (null) of type void*
to int
testb1.d(10): Error: cannot implicitly convert expression (cast(int)null) of
type int to testb1.Foo

Changes that DO NOT eliminate the error:
- Changing "jaggedArray" to "Foo[char[]][char[]]"
- Adding "return null;" to the end of the function
- Changing "return null;" to "return f;"

That last change (returning "f" instead of "null") generates the following
error:
testb1.d(10): Error: cannot implicitly convert expression (f) of type
testb1.Foo to int
testb1.d(10): Error: cannot implicitly convert expression (cast(int)f) of type
int to testb1.Foo

So, that means: The function Bar() is declared to return a Foo, and it tries to return a Foo. But the compiler tries to turn the Foo into an int...and then back into a Foo again.

Changes that DO cause the code to compile:
- Changing "jaggedArray" to any of the following: "Foo[][char]" "Foo[char][]"
"int[char][char]"
- Eliminating the inner foreach
- Eliminating the outer foreach and iterating over "jaggedAray['a']"

The following change also causes the code to compile:

class Foo { int var; }
Foo[char][char] jaggedArray;

Foo Bar()
{
        foreach(Foo[char] array; jaggedArray)
        {
                foreach(Foo f; array)
                {
                        f.var = 5;
                }
        }

        return null;
}


--

http://d.puremagic.com/issues/show_bug.cgi?id=2192 ------- Comment #1 from business3@twistedpairgaming.com 2008-07-04 02:22 ------- Changing the function's return type to something else, like 'bool' also eliminates the problem. Making the return statement conditional (ex "if(f.var == 1) return null;") does NOT solve to problem. If you need to return f, the following workaround does work (although it will result in extra unnecessary iterations): Foo Bar() { Foo ret = null; foreach(Foo[char] array; jaggedArray) { foreach(Foo f; array) { if( /* whatever you need */ ) { if(ret == null) ret = f; break; } } } return ret; } --

http://d.puremagic.com/issues/show_bug.cgi?id=2192 ------- Comment #2 from business3@twistedpairgaming.com 2008-07-04 02:25 ------- Erm...that should be "is null" in the workaround, not "== null". Must be tired... --

http://d.puremagic.com/issues/show_bug.cgi?id=2192 --- Comment #3 from Serg Kovrov <kovrov+puremagic@gmail.com> 2009-07-09 07:55:32 PDT --- Same error is issued on returning from nested foreach over opApply/delegates. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=2192 --- Comment #5 from Kenji Hara <k.hara.pg@gmail.com> 2012-02-03 04:48:55 PST --- I think the original issue titled "Returning element in an AA of AAs during nested foreach generates compiler error" is a dup of bug 3187, and today it works as expected. So, I can't understand why yebblies changed the title and switched the importance to an enhancement. -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

http://d.puremagic.com/issues/show_bug.cgi?id=2192 yebblies <yebblies@gmail.com> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords| |wrong-code Status|NEW |RESOLVED Resolution| |DUPLICATE Severity|enhancement |normal --- Comment #6 from yebblies <yebblies@gmail.com> 2012-02-04 00:25:24 EST --- (In reply to comment #5) > I think the original issue titled "Returning element in an AA of AAs during nested foreach generates compiler error" is a dup of bug 3187, and today it works as expected. > > So, I can't understand why yebblies changed the title and switched the importance to an enhancement. I had no idea that it worked, or that it had been fixed! My compiler's broken for the moment, so I can't test it, but I'll take your comment to mean this works and close it as a duplicate. *** This issue has been marked as a duplicate of issue 3187 *** -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------

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