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digitalmars.D - Compiler bug?

reply IM <3di gm.com> writes:
The following code:

   int guess;
   readln().formattedRead!"%d"(guess);

produces the following compiler error:

Error: template std.format.formattedRead cannot deduce function 
from argument types !("%s")(string, int), candidates are:
/usr/include/dmd/phobos/std/format.d(635):        
std.format.formattedRead(alias fmt, R, S...)(ref R r, auto ref S 
args) if (isSomeString!(typeof(fmt)))
/usr/include/dmd/phobos/std/format.d(644):        
std.format.formattedRead(R, Char, S...)(ref R r, const(Char)[] 
fmt, auto ref S args)

That is odd! I expected this to match:

   uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S args)

However, the following works!!!

   int guess;
   string line = readln();
   line.formattedRead!"%d"(guess);


This definitely looks like a bug, but I want to confirm first 
before filing one.
Dec 28 2017
next sibling parent Daniel Kozak <kozzi11 gmail.com> writes:
No it is not a bug, because
 uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S args)
could not match (there is a ref R r) so in your first example you dont have
lvalue but rvalue


On Fri, Dec 29, 2017 at 8:30 AM, IM via Digitalmars-d <
digitalmars-d puremagic.com> wrote:


 The following code:

   int guess;
   readln().formattedRead!"%d"(guess);

 produces the following compiler error:

 Error: template std.format.formattedRead cannot deduce function from
 argument types !("%s")(string, int), candidates are:
 /usr/include/dmd/phobos/std/format.d(635):
 std.format.formattedRead(alias fmt, R, S...)(ref R r, auto ref S args) if
 (isSomeString!(typeof(fmt)))
 /usr/include/dmd/phobos/std/format.d(644):
 std.format.formattedRead(R, Char, S...)(ref R r, const(Char)[] fmt, auto
 ref S args)

 That is odd! I expected this to match:

   uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S args)

 However, the following works!!!

   int guess;
   string line = readln();
   line.formattedRead!"%d"(guess);


 This definitely looks like a bug, but I want to confirm first before
 filing one.
Dec 28 2017
prev sibling parent reply Daniel Kozak <kozzi11 gmail.com> writes:
But maybe you can propose cjange from ref R r to auto ref R r

https://dlang.org/spec/template.html#auto-ref-parameters

On Fri, Dec 29, 2017 at 8:50 AM, Daniel Kozak <kozzi11 gmail.com> wrote:


 No it is not a bug, because
  uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S args)
 could not match (there is a ref R r) so in your first example you dont
 have lvalue but rvalue


 On Fri, Dec 29, 2017 at 8:30 AM, IM via Digitalmars-d <
 digitalmars-d puremagic.com> wrote:


 The following code:

   int guess;
   readln().formattedRead!"%d"(guess);

 produces the following compiler error:

 Error: template std.format.formattedRead cannot deduce function from
 argument types !("%s")(string, int), candidates are:
 /usr/include/dmd/phobos/std/format.d(635):
 std.format.formattedRead(alias fmt, R, S...)(ref R r, auto ref S args) if
 (isSomeString!(typeof(fmt)))
 /usr/include/dmd/phobos/std/format.d(644):
 std.format.formattedRead(R, Char, S...)(ref R r, const(Char)[] fmt, auto
 ref S args)

 That is odd! I expected this to match:

   uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S args)

 However, the following works!!!

   int guess;
   string line = readln();
   line.formattedRead!"%d"(guess);


 This definitely looks like a bug, but I want to confirm first before
 filing one.
Dec 28 2017
parent reply IM <3di gm.com> writes:
On Friday, 29 December 2017 at 07:55:08 UTC, Daniel Kozak wrote:

 But maybe you can propose cjange from ref R r to auto ref R r


If this will make it work with both lvalues and rvalues, then 
yes, this would be a nice fix. No need to force users to cache 
string line = readln(); first and then use it with 
formattedRead().


 https://dlang.org/spec/template.html#auto-ref-parameters

 On Fri, Dec 29, 2017 at 8:50 AM, Daniel Kozak 
 <kozzi11 gmail.com> wrote:


 No it is not a bug, because
  uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S 
 args)
 could not match (there is a ref R r) so in your first example 
 you dont
 have lvalue but rvalue
Dec 29 2017
parent Daniel Kozak <kozzi11 gmail.com> writes:
On Friday, 29 December 2017 at 08:02:36 UTC, IM wrote:

 On Friday, 29 December 2017 at 07:55:08 UTC, Daniel Kozak wrote:

 But maybe you can propose cjange from ref R r to auto ref R r


 If this will make it work with both lvalues and rvalues, then 
 yes, this would be a nice fix. No need to force users to cache 
 string line = readln(); first and then use it with 
 formattedRead().


 https://dlang.org/spec/template.html#auto-ref-parameters

 On Fri, Dec 29, 2017 at 8:50 AM, Daniel Kozak 
 <kozzi11 gmail.com> wrote:


 No it is not a bug, because
  uint formattedRead(alias fmt, R, S...)(ref R r, auto ref S 
 args)
 could not match (there is a ref R r) so in your first example 
 you dont
 have lvalue but rvalue






https://github.com/dlang/phobos/pull/5971
Dec 29 2017