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digitalmars.D.bugs - [Issue 5671] New: CTFE string concat problem

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5671

           Summary: CTFE string concat problem
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Windows
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody puremagic.com
        ReportedBy: bearophile_hugs eml.cc



A problem found by Peter Lundgren and David Nadlinger.

Reduced D2 code:


import std.conv: to;
string foo() {
    // return to!string(10); // OK
    return to!string(10) ~ "";
}
string s = foo();
void main() {}


DMD 2.052 gives the errors:
test.d(4): Error: to(10) ~ "" cannot be interpreted at compile time
test.d(6): Error: cannot evaluate foo() at compile time
test.d(6): Error: cannot evaluate foo() at compile time


I think it's not a problem of to!() because this alternative version works
correctly:


import std.conv: to;
string foo() {
    return to!string(10);
}
string s = foo();
void main() {}

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Mar 01 2011
next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5671


Don <clugdbug yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug yahoo.com.au



Reduced test case shows it is a constant folding problem.
['a', 'b'] ~ "c" doesn't get constant folded.

string foo5671() {
    return ['a', 'b'];
}

string bug5671() {
    return foo5671() ~ "c";
}

static assert(bug5671() == "abc");

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Mar 01 2011
prev sibling next sibling parent d-bugmail puremagic.com writes:
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Can be reduced even further, showing CTFE isn't involved at all:

static assert( ['a', 'b'] ~ "c" == "abc" );

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Mar 05 2011
prev sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5671


Walter Bright <bugzilla digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla digitalmars.com
         Resolution|                            |FIXED



16:02:31 PDT ---
https://github.com/D-Programming-Language/dmd/commit/316ba0a77e3934bfc8091940444f706e82aecc72

https://github.com/D-Programming-Language/dmd/commit/5c7c6b51e27d9cd394ddda4f7940cdf9c1610953

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Apr 18 2011