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digitalmars.D - Need clear error msg. (template instantiating)

reply CLXX <kk_tnr hotmail.com> writes:
I need clear error-messages of compiling.
See this code.

// example.d
import std.conv: to;
void main( ){
    S s;
    to!( int )( s ); // 'to' does not support struct-argument.
}
struct S{
}

'to' cannot convert 'S' to 'int', so that this is error.
Then I got mysterious messages.

"src\phobos\std\conv.d(344): Error: cannot implicitly convert expression
(value) of type S to int"
"src\phobos\std\conv.d(206): template instance std.conv.toImpl!(S,int) error
instantiating"
"src\phobos\std\conv.d(4): template instance std.conv.to!(int).to!(S) error
instantiating"

We know 'std.conv.d' has no error, and assume 'example.d' has some.
The problem is 'std.conv.d' seems to have errors.

The message should be as follows.

"example.d(5): template instance to!(S)(int,S) does not match template
declaration."

Thank you for your reading.
Feb 28 2009
next sibling parent reply Moritz Warning <moritzwarning web.de> writes:
On Sat, 28 Feb 2009 13:36:25 -0500, CLXX wrote:


 I need clear error-messages of compiling. See this code.
 
 // example.d
 import std.conv: to;
 void main( ){
     S s;
     to!( int )( s ); // 'to' does not support struct-argument.
 }
 struct S{
 }
 
 'to' cannot convert 'S' to 'int', so that this is error. Then I got
 mysterious messages.
 
 "src\phobos\std\conv.d(344): Error: cannot implicitly convert expression
 (value) of type S to int" "src\phobos\std\conv.d(206): template instance
 std.conv.toImpl!(S,int) error instantiating" "src\phobos\std\conv.d(4):
 template instance std.conv.to!(int).to!(S) error instantiating"
 
 We know 'std.conv.d' has no error, and assume 'example.d' has some. The
 problem is 'std.conv.d' seems to have errors.
 
 The message should be as follows.
 
 "example.d(5): template instance to!(S)(int,S) does not match template
 declaration."
 
 Thank you for your reading.



What do you expect the integer from such a struct to be?
What you are trying to do makes no sense to me.
The compiler tells you the same.
Feb 28 2009
next sibling parent Moritz Warning <moritzwarning web.de> writes:
On Sat, 28 Feb 2009 19:41:59 +0000, Moritz Warning wrote:


 On Sat, 28 Feb 2009 13:36:25 -0500, CLXX wrote:
 

 I need clear error-messages of compiling. See this code.
 
 // example.d
 import std.conv: to;
 void main( ){
     S s;
     to!( int )( s ); // 'to' does not support struct-argument.
 }
 struct S{
 }
 
 'to' cannot convert 'S' to 'int', so that this is error. Then I got
 mysterious messages.
 
 "src\phobos\std\conv.d(344): Error: cannot implicitly convert
 expression (value) of type S to int" "src\phobos\std\conv.d(206):
 template instance std.conv.toImpl!(S,int) error instantiating"
 "src\phobos\std\conv.d(4): template instance std.conv.to!(int).to!(S)
 error instantiating"
 
 We know 'std.conv.d' has no error, and assume 'example.d' has some. The
 problem is 'std.conv.d' seems to have errors.
 
 The message should be as follows.
 
 "example.d(5): template instance to!(S)(int,S) does not match template
 declaration."
 
 Thank you for your reading.



 What do you expect the integer from such a struct to be? What you are
 trying to do makes no sense to me. The compiler tells you the same.



Nvm, I'm too tired today.
Feb 28 2009
prev sibling parent CLXX <kk_tnr hotmail.com> writes:
Moritz Warning Wrote:


 What do you expect the integer from such a struct to be?
 What you are trying to do makes no sense to me.
 The compiler tells you the same.



What is important is, compilier should show correct messages when we wrote
illegal code.

Thank you.
Feb 28 2009
prev sibling parent Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:
CLXX wrote:

 I need clear error-messages of compiling.
 See this code.
 
 // example.d
 import std.conv: to;
 void main( ){
     S s;
     to!( int )( s ); // 'to' does not support struct-argument.
 }
 struct S{
 }
 
 'to' cannot convert 'S' to 'int', so that this is error.
 Then I got mysterious messages.
 
 "src\phobos\std\conv.d(344): Error: cannot implicitly convert expression
(value) of type S to int"
 "src\phobos\std\conv.d(206): template instance std.conv.toImpl!(S,int) error
instantiating"
 "src\phobos\std\conv.d(4): template instance std.conv.to!(int).to!(S) error
instantiating"
 
 We know 'std.conv.d' has no error, and assume 'example.d' has some.
 The problem is 'std.conv.d' seems to have errors.
 
 The message should be as follows.
 
 "example.d(5): template instance to!(S)(int,S) does not match template
declaration."
 
 Thank you for your reading.



Thanks, that's a good point. We need to make a few changes to the way 
the compiler and static assert work to get to that point. Phobos in my 
tree (i.e., as of two releases from now) already points at your file and 
line, however with not such a clear message:

./example.d(5): template std.conv.to(T,S) if (!implicitlyConverts!(S,T) 
&& isSomeString!(T) && isSomeString!(S)) does not match any function 
template declaration
./example.d(5): template std.conv.to(T,S) if (!implicitlyConverts!(S,T) 
&& isSomeString!(T) && isSomeString!(S)) cannot deduce template function 
from argument types!(int)(S)

Showing the if clause is completely superfluous (I just filed a bug 
report about that, see 
http://d.puremagic.com/issues/show_bug.cgi?id=2696) so at least you'll 
see something like:

./example.d(5): template std.conv.to(T,S) does not match any function 
template declaration
./example.d(5): template std.conv.to(T,S) cannot deduce template 
function from argument types!(int)(S)

which is rather passable.


Andrei
Feb 28 2009