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digitalmars.D.learn - errnoEnforce: which imports?

reply kdevel <kdevel vogtner.de> writes:
In https://dlang.org/phobos/std_exception.html#errnoEnforce this 
example is shown:

---
auto f = errnoEnforce(fopen("data.txt"));
auto line = readln(f);
enforce(line.length); // expect a non-empty line
---

I added

    import std.stdio;
    import std.exception;

and get an error message which reminds me of C++:

zz.d(8): Deprecation: std.stdio.fopen(R1, R2)(R1 name, R2 mode = 
"r") if ((isInputRange!R1 && isSomeChar!(ElementEncodingType!R1) 
|| isSomeString!R1) && (isInputRange!R2 && 
isSomeChar!(ElementEncodingType!R2) || isSomeString!R2)) is not 
visible from module zz
zz.d(8): Error: function std.stdio.fopen!(string, string).fopen 
is not accessible from module zz
zz.d(9): Error: template std.stdio.readln cannot deduce function 
from argument types !()(shared(_IO_FILE)*), candidates are:
[...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4068):        
std.stdio.readln(S = string)(dchar terminator = '\x0a') if 
(isSomeString!S)
[...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4102):        
std.stdio.readln(C)(ref C[] buf, dchar terminator = '\x0a') if 
(isSomeChar!C && is(Unqual!C == C) && !is(C == enum))
[...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4109):        
std.stdio.readln(C, R)(ref C[] buf, R terminator) if 
(isSomeChar!C && is(Unqual!C == C) && !is(C == enum) && 
isBidirectionalRange!R && is(typeof(terminator.front == 
(dchar).init)))
make: *** [zz.o] Error 1

What's wrong here?
Jun 28 2018
parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Friday, June 29, 2018 01:25:39 kdevel via Digitalmars-d-learn wrote:

 In https://dlang.org/phobos/std_exception.html#errnoEnforce this
 example is shown:

 ---
 auto f = errnoEnforce(fopen("data.txt"));
 auto line = readln(f);
 enforce(line.length); // expect a non-empty line
 ---

 I added

     import std.stdio;
     import std.exception;

 and get an error message which reminds me of C++:

 zz.d(8): Deprecation: std.stdio.fopen(R1, R2)(R1 name, R2 mode =
 "r") if ((isInputRange!R1 && isSomeChar!(ElementEncodingType!R1)

 || isSomeString!R1) && (isInputRange!R2 &&

 isSomeChar!(ElementEncodingType!R2) || isSomeString!R2)) is not
 visible from module zz
 zz.d(8): Error: function std.stdio.fopen!(string, string).fopen
 is not accessible from module zz
 zz.d(9): Error: template std.stdio.readln cannot deduce function
 from argument types !()(shared(_IO_FILE)*), candidates are:
 [...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4068):
 std.stdio.readln(S = string)(dchar terminator = '\x0a') if
 (isSomeString!S)
 [...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4102):
 std.stdio.readln(C)(ref C[] buf, dchar terminator = '\x0a') if
 (isSomeChar!C && is(Unqual!C == C) && !is(C == enum))
 [...]/dmd2/linux/bin64/../../src/phobos/std/stdio.d(4109):
 std.stdio.readln(C, R)(ref C[] buf, R terminator) if
 (isSomeChar!C && is(Unqual!C == C) && !is(C == enum) &&
 isBidirectionalRange!R && is(typeof(terminator.front ==
 (dchar).init)))
 make: *** [zz.o] Error 1

 What's wrong here?


It looks like that example is using a private function from std.stdio which
wraps core.stdc.stdio.fopen. It also passes a FILE* to readln, which is
completely wrong. readln as a free function works with std.stdio.stdin and
does not accept a FILE*, whereas readln on std.stdio.File obviously operates
on File, since it's a member function on File. You could use
core.stdc.stdio.fopen to get a FILE and pass it to File's constructor, and
then call readln on the file, but really, that example needs to be
completely redone.

The error message for fopen stems from the fact that it's private, and that
message is longer than it would be otherwise because of an import bug that
was previously fixed but generates a deprecation message for now so as not
to immediately break code. The error messages after that have to do with the
compiler showing you the various overloads of readln that don't match FILE*.

- Jonathan M Davis
Jun 28 2018
parent reply kdevel <kdevel vogtner.de> writes:
On Friday, 29 June 2018 at 02:28:04 UTC, Jonathan M Davis wrote:

 [...] really, that example needs to be completely redone.


Shall I create a bug report?
Jun 29 2018
parent reply Jonathan M Davis <newsgroup.d jmdavisprog.com> writes:
On Friday, June 29, 2018 09:08:40 kdevel via Digitalmars-d-learn wrote:

 On Friday, 29 June 2018 at 02:28:04 UTC, Jonathan M Davis wrote:

 [...] really, that example needs to be completely redone.


 Shall I create a bug report?


Yes. Aside from someone trying it out and complaining about it, it probably
wouldn't be noticed or fixed, since it's one of the few tests that doesn't
work as a ddoc-ed unit test.

- Jonathan M Davis
Jun 29 2018
parent kdevel <kdevel vogtner.de> writes:
On Friday, 29 June 2018 at 09:22:03 UTC, Jonathan M Davis wrote:

 Shall I create a bug report?


 Yes. Aside from someone trying it out and complaining about it, 
 it probably wouldn't be noticed or fixed, since it's one of the 
 few tests that doesn't work as a ddoc-ed unit test.


Issue 19041 - errnoEnforce: example does not compile
Jun 29 2018