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digitalmars.D.bugs - [Issue 8063] New: Purity of assert's second parameter

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8063

           Summary: Purity of assert's second parameter
           Product: D
           Version: D2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: dransic gmail.com


--- Comment #0 from Nicolas Sicard <dransic gmail.com> 2012-05-08 02:39:16 PDT
---
Calling impure functions in the second parameter of an assert statement within
the body of a pure pure is an error, even in release mode. Since such a call is
just about displaying an error message, should purity be checked here? Idem for
static asserts.  Maybe it is the same for 'nothrowness' (I didn't try).

Example:
---
import std.conv : text; // text is not pure

pure int foo(int value) {
    assert(value <= 10, text(value, " is greater than ", 10)); // Error: pure
function 'foo' cannot call impure function 'text'
    return value;
}

pure int foo2(int value) {
    debug assert(value <= 10, text(value, " is greater than ", 10)); // OK
    return value;
}

pure T bar(T)(T value) {
    static assert(T.sizeof == 4, text("Bad type size: ", T.sizeof)); // Error:
pure function 'bar' cannot call impure function 'text'
    return value;
}

void main() {
    int f = foo(42);
    int f2 = foo2(42);
    auto b = bar(42L);
}
---

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parent reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=8063


bearophile_hugs eml.cc changed:

           What    |Removed                     |Added
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                 CC|                            |bearophile_hugs eml.cc


--- Comment #1 from bearophile_hugs eml.cc 2012-05-08 04:12:12 PDT ---
(In reply to comment #0)

 Calling impure functions in the second parameter of an assert statement within
 the body of a pure pure is an error, even in release mode.


This is good.



 Idem for static asserts.


For static arrays I think it will be OK to call impure functions in the message
part.




     assert(value <= 10, text(value, " is greater than ", 10)); // Error: pure
 function 'foo' cannot call impure function 'text'


The solution is to have a pure text(), not to compromise on purity.

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May 08 2012
parent reply "Nicolas Sicard" <dransic gmail.com> writes:
 --- Comment #1 from bearophile_hugs eml.cc 2012-05-08 04:12:12 
 PDT ---
 (In reply to comment #0)

 Calling impure functions in the second parameter of an assert 
 statement within
 the body of a pure pure is an error, even in release mode.


 This is good.


Since it is allowed to call impure functions in debug blocks 
inside pure functions, I thought it would be coherent that assert 
could do the same.
May 08 2012
parent "Jonathan M Davis" <jmdavisProg gmx.com> writes:
On Tuesday, May 08, 2012 15:08:42 Nicolas Sicard wrote:

 --- Comment #1 from bearophile_hugs eml.cc 2012-05-08 04:12:12
 PDT ---
 (In reply to comment #0)
 

 Calling impure functions in the second parameter of an assert
 statement within
 the body of a pure pure is an error, even in release mode.


 
 This is good.


 
 Since it is allowed to call impure functions in debug blocks
 inside pure functions, I thought it would be coherent that assert
 could do the same.


Please don't post directly to the bug list. Respond in bugzilla please. The 
buglist if for receiving reports from bugzilla not for posting to directly.

- Jonathan M Davis
May 08 2012