• =?UTF-8?Q?Ali_=c3=87ehreli?= (24/24) Sep 27 2021 We talked about template instantiation problems hiding valuable
• Steven Schveighoffer (4/6) Sep 27 2021 I recently asked the same question, got mostly crickets:
• =?UTF-8?Q?Ali_=c3=87ehreli?= (3/11) Sep 27 2021 Oh! Ok, then... See you again next month... :)
• Nicholas Wilson (12/35) Sep 27 2021 I couldn't figure out how to recreate the failed expression to

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

We talked about template instantiation problems hiding valuable 
information before. Here is one:

struct S {
   auto opDispatch(string symbol)() {
     static assert(symbol == "foo", "Invalid symbol.");
   }
}

void main() {
   S().bar;
}

Error: no property `bar` for type `deneme.S`
        potentially malformed `opDispatch`. Use an explicit 
instantiation to get a better error message

opDispatch fails to compile because of my 'static assert' but my message 
"Invalid symbol." is lost. Granted, the compiler recommends me to do the 
following:

   S().opDispatch!"bar";  // Ok, now I get my error message

1) Can't we display my message in the first place?

2) If we can't, can the compiler itself instantiate explicitly to show 
the error message?

3) If not even that, can we really expect a newcomer to figure out what 
to do? At least we should apologize and provide the expression for the 
programmer to try again with. :)

Ali

Steven Schveighoffer <schveiguy gmail.com> writes:

On 9/27/21 3:33 PM, Ali Çehreli wrote:
 We talked about template instantiation problems hiding valuable 
 information before. Here is one:

I recently asked the same question, got mostly crickets: 
https://forum.dlang.org/post/sgb2m5$2eai$1 digitalmars.com

-Steve

=?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:

On 9/27/21 12:45 PM, Steven Schveighoffer wrote:
 On 9/27/21 3:33 PM, Ali =C3=87ehreli wrote:
 We talked about template instantiation problems hiding valuable=20
 information before. Here is one:

=20
 I recently asked the same question, got mostly crickets:=20
 https://forum.dlang.org/post/sgb2m5$2eai$1 digitalmars.com
=20
 -Steve

Oh! Ok, then... See you again next month... :)

Ali

Nicholas Wilson <iamthewilsonator hotmail.com> writes:

On Monday, 27 September 2021 at 19:33:19 UTC, Ali Çehreli wrote:
 We talked about template instantiation problems hiding valuable 
 information before. Here is one:

 struct S {
   auto opDispatch(string symbol)() {
     static assert(symbol == "foo", "Invalid symbol.");
   }
 }

 void main() {
   S().bar;
 }

 Error: no property `bar` for type `deneme.S`
        potentially malformed `opDispatch`. Use an explicit 
 instantiation to get a better error message

 opDispatch fails to compile because of my 'static assert' but 
 my message "Invalid symbol." is lost. Granted, the compiler 
 recommends me to do the following:

   S().opDispatch!"bar";  // Ok, now I get my error message

 1) Can't we display my message in the first place?

I couldn't figure out how to recreate the failed expression to 
issue the underlying error. See [this 
pr](https://github.com/dlang/dmd/pull/12288)

 2) If we can't, can the compiler itself instantiate explicitly 
 to show the error message?

It might be possible, [this bit of 
code](https://github.com/dlang/dmd/blob/58653722e2be7abe61517505c06edf7680c933d1/src/dmd/ty
esem.d#L3602-L3629) looks like it does something similar.

 3) If not even that, can we really expect a newcomer to figure 
 out what to do? At least we should apologize and provide the 
 expression for the programmer to try again with. :)

That should be possible by formatting [this 
string](https://github.com/dlang/dmd/blob/d396a9e89c9e2a7ae687616231ba392c9ba7859d/src/
md/typesem.d#L2429) with:
     "...(rest of 
message)...`%s.opDispatch!\"%s\"`",mt.toPrettyChars(), 
ident.toChars()

PRs welcome!