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digitalmars.D.learn - template cannot use local as parameter to non-global template

reply "simendsjo" <simendsjo gmail.com> writes:
I get a lot of these errors, and they can be quite tricky to get 
around and hurts my API.. Is this a temporary restriction in DMD, 
or is it another reason why this doesn't work?

Error: template instance template!local cannot use local 'local' 
as parameter to non-global template innerTemplate(alias T)
Mar 17 2013
next sibling parent "John Colvin" <john.loughran.colvin gmail.com> writes:
On Sunday, 17 March 2013 at 12:54:24 UTC, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to 
 get around and hurts my API.. Is this a temporary restriction 
 in DMD, or is it another reason why this doesn't work?

 Error: template instance template!local cannot use local 
 'local' as parameter to non-global template innerTemplate(alias 
 T)


A small code example that generates that error would be very 
useful in helping you.
Mar 17 2013
prev sibling parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 03/17/2013 01:54 PM, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to get around
 and hurts my API.. Is this a temporary restriction in DMD, or is it
 another reason why this doesn't work?

 Error: template instance template!local cannot use local 'local' as
 parameter to non-global template innerTemplate(alias T)


http://d.puremagic.com/issues/show_bug.cgi?id=5710
Mar 17 2013
parent reply "simendsjo" <simendsjo gmail.com> writes:
On Sunday, 17 March 2013 at 15:45:54 UTC, Timon Gehr wrote:

 On 03/17/2013 01:54 PM, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to 
 get around
 and hurts my API.. Is this a temporary restriction in DMD, or 
 is it
 another reason why this doesn't work?

 Error: template instance template!local cannot use local 
 'local' as
 parameter to non-global template innerTemplate(alias T)


 http://d.puremagic.com/issues/show_bug.cgi?id=5710


Looks like the same issue. For me the use-case was a bit 
different though..
I want to access struct members at CT only to look for UDAs, it's 
type etc.
It works with workarounds, but the code gets ugly, and much 
convenience is lost..

Too bad it looks like a wont-fix.
Mar 17 2013
parent reply Timon Gehr <timon.gehr gmx.ch> writes:
On 03/17/2013 05:15 PM, simendsjo wrote:

 On Sunday, 17 March 2013 at 15:45:54 UTC, Timon Gehr wrote:

 On 03/17/2013 01:54 PM, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to get around
 and hurts my API.. Is this a temporary restriction in DMD, or is it
 another reason why this doesn't work?

 Error: template instance template!local cannot use local 'local' as
 parameter to non-global template innerTemplate(alias T)


 http://d.puremagic.com/issues/show_bug.cgi?id=5710


 Looks like the same issue. For me the use-case was a bit different though..
 I want to access struct members at CT only to look for UDAs, it's type etc.
 It works with workarounds, but the code gets ugly, and much convenience
 is lost..

 Too bad it looks like a wont-fix.


It is not a wont-fix, and it actually should work.
Mar 17 2013
parent reply "simendsjo" <simendsjo gmail.com> writes:
On Sunday, 17 March 2013 at 16:21:25 UTC, Timon Gehr wrote:

 On 03/17/2013 05:15 PM, simendsjo wrote:

 On Sunday, 17 March 2013 at 15:45:54 UTC, Timon Gehr wrote:

 On 03/17/2013 01:54 PM, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to 
 get around
 and hurts my API.. Is this a temporary restriction in DMD, 
 or is it
 another reason why this doesn't work?

 Error: template instance template!local cannot use local 
 'local' as
 parameter to non-global template innerTemplate(alias T)


 http://d.puremagic.com/issues/show_bug.cgi?id=5710


 Looks like the same issue. For me the use-case was a bit 
 different though..
 I want to access struct members at CT only to look for UDAs, 
 it's type etc.
 It works with workarounds, but the code gets ugly, and much 
 convenience
 is lost..

 Too bad it looks like a wont-fix.


 It is not a wont-fix, and it actually should work.


All the talk there looks to be around delegates. Would the same 
fix work for my struct members?
Mar 17 2013
parent Timon Gehr <timon.gehr gmx.ch> writes:
On 03/17/2013 05:36 PM, simendsjo wrote:

 On Sunday, 17 March 2013 at 16:21:25 UTC, Timon Gehr wrote:

 On 03/17/2013 05:15 PM, simendsjo wrote:

 On Sunday, 17 March 2013 at 15:45:54 UTC, Timon Gehr wrote:

 On 03/17/2013 01:54 PM, simendsjo wrote:

 I get a lot of these errors, and they can be quite tricky to get
 around
 and hurts my API.. Is this a temporary restriction in DMD, or is it
 another reason why this doesn't work?

 Error: template instance template!local cannot use local 'local' as
 parameter to non-global template innerTemplate(alias T)


 http://d.puremagic.com/issues/show_bug.cgi?id=5710


 Looks like the same issue. For me the use-case was a bit different
 though..
 I want to access struct members at CT only to look for UDAs, it's
 type etc.
 It works with workarounds, but the code gets ugly, and much convenience
 is lost..

 Too bad it looks like a wont-fix.


 It is not a wont-fix, and it actually should work.


 All the talk there looks to be around delegates. Would the same fix work
 for my struct members?


Of course. It is exactly the same issue. In D, if any kind of local 
symbol is passed to a templated function, the templated function 
requires a context pointer to access the local symbol. Non-static member 
functions require a 'this' reference.

Only one additional implicit pointer can be passed to a non-static 
member function at a time, since every member function must be able to 
provide delegates. Therefore, there must be an additional indirection 
somewhere. (Eg. pass the 'this' pointer as a local variable inside the 
delegate context.)
Mar 17 2013