digitalmars.D.bugs - [Issue 693] New: 'this' can't be used as an alias parameter for a mixin
- d-bugmail puremagic.com (43/43) Dec 16 2006 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (16/16) Nov 26 2010 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (18/18) Apr 12 2011 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (32/32) Apr 12 2011 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (10/10) May 07 2011 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (12/12) Jul 01 2011 http://d.puremagic.com/issues/show_bug.cgi?id=693
- d-bugmail puremagic.com (12/12) Jan 21 2013 http://d.puremagic.com/issues/show_bug.cgi?id=693
http://d.puremagic.com/issues/show_bug.cgi?id=693
Summary: 'this' can't be used as an alias parameter for a mixin
Product: D
Version: 0.177
Platform: All
OS/Version: All
Status: NEW
Severity: minor
Priority: P2
Component: DMD
AssignedTo: bugzilla digitalmars.com
ReportedBy: wbaxter gmail.com
This may not be a bug for some technical reason unbeknownst to me that the spec
mentions (if so downgrade it to enhancement please), but I found it unexpected.
You can't use 'this' as an alias paramter to a mixin in a class member
function. The workaround is pretty easy, you just assign it to a local dummy
variable, and use that instead.
import std.stdio : writefln;
template printer_mix(alias T)
{
void print() {
writefln(T);
}
}
class Foo
{
void dump() {
// Error: mixin printer_mix!(this) does not match any template
declaration
mixin printer_mix!(this);
// this version ok:
//Foo x = this;
//mixin printer_mix!(x);
print();
}
char[] toString() { return "I'm Batman"; }
}
void main()
{
Foo f = new Foo();
f.dump();
}
--
Dec 16 2006
d-bugmail puremagic.com
http://d.puremagic.com/issues/show_bug.cgi?id=693
Andrei Alexandrescu <andrei metalanguage.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
CC| |andrei metalanguage.com
AssignedTo|nobody puremagic.com |bugzilla digitalmars.com
13:33:57 PST ---
Bug present in 1.065 and 2.050 with different error messages. 1.065:
test.d(14): Error: mixin printer_mix!(this) does not match template declaration
printer_mix(alias T)
2.050:
test.d(14): Error: expression this is not a valid template value argument
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Nov 26 2010
http://d.puremagic.com/issues/show_bug.cgi?id=693
Simen Kjaeraas <simen.kjaras gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |simen.kjaras gmail.com
PDT ---
This also a problem for non-mixin templates:
struct MyCallable {
int opCall( int n ) {
return n;
}
auto mapthis( int[] arr ) {
return map!this( arr );
}
}
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Apr 12 2011
http://d.puremagic.com/issues/show_bug.cgi?id=693
PDT ---
Thinking about this some more, fixing this bug could lead to safer array
indexing for one, through a limited system of dependent types:
struct SafeArray( T ) {
T[] data;
struct Index( alias arr ) {
size_t idx;
// Add safety checks, overflow handling, etc.
}
Index!this makeIndex( size_t n ) {
typeof( return ) result;
result.idx = n;
return result;
}
T opIndex( Index!this idx ) {
return data[idx.idx];
}
}
unittest {
SafeArray!int arr;
arr.data = [1,2,3,4,5,6,7,8,9,0];
auto idx = arr.makeIndex( 3 );
writeln( arr[idx] ); // Completely safe indexing of array, enforced by type
system.
}
There may be a problem in that compiler considers 'this' a local parameter to a
non-global template, which is currently illegal. Not sure how much of a problem
this might be in practice.
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Apr 12 2011
http://d.puremagic.com/issues/show_bug.cgi?id=693
Kenji Hara <k.hara.pg gmail.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |zan77137 nifty.com
*** Issue 4799 has been marked as a duplicate of this issue. ***
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May 07 2011
http://d.puremagic.com/issues/show_bug.cgi?id=693
Walter Bright <bugzilla digitalmars.com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|ASSIGNED |RESOLVED
Resolution| |FIXED
00:31:09 PDT ---
https://github.com/D-Programming-Language/dmd/commit/5a1f396e915e083ce30c5f09f4e1ef1a9e704fda
https://github.com/D-Programming-Language/dmd/commit/c9e26681a834beb6b211f41234163707453f4ff1
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Jul 01 2011
http://d.puremagic.com/issues/show_bug.cgi?id=693 Commits pushed to master at https://github.com/D-Programming-Language/d-programming-language.org https://github.com/D-Programming-Language/d-programming-language.org/commit/9e84dccf6286dd7e718f247bf1a623cd50f68553 fix Issue 693 - 'this' can't be used as an alias parameter for a mixin https://github.com/D-Programming-Language/d-programming-language.org/commit/0cf09c6b06c13345024772864f6654002904244c Issue 693 - 'this' can't be used as an alias parameter for a mixin -- Configure issuemail: http://d.puremagic.com/issues/userprefs.cgi?tab=email ------- You are receiving this mail because: -------
Jan 21 2013