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digitalmars.D.bugs - [Issue 5406] New: [patch] Major regressions in std.algorithm for functions relying on is(typeof(binaryFun!... due to a static assert in binaryFunImpl

reply d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5406

           Summary: [patch] Major regressions in std.algorithm for
                    functions relying on is(typeof(binaryFun!... due to a
                    static assert in binaryFunImpl
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Keywords: patch
          Severity: regression
          Priority: P2
         Component: Phobos
        AssignedTo: nobody puremagic.com
        ReportedBy: sandford jhu.edu


--- Comment #0 from Rob Jacques <sandford jhu.edu> 2011-01-03 21:18:21 PST ---
This is a regression between DMD 2.050 and 2.051.
Several routines in std.algorithm rely on template constraints of the form:
is(typeof(binaryFun!... However, since binaryFun triggers a static assert and
stops compilation, there is a logical error here and causes
find("goodbye","bye"), etc to not compile. This might be rooted in a change to
how DMD handles is statements / static asserts, but there is a simple patch to
Phobos that seems to work around this issue by adding a template constraint to
binaryFunImpl in std.functional:

template binaryFunImpl(alias fun, string parm1Name, string parm2Name) {
    static if (is(typeof(fun) : string)) {
        enum testAsExpression = "{ ElementType1 "
            ~parm1Name~"; ElementType2 "
            ~parm2Name~"; return ("~fun~");}()";

        typeof(mixin(testAsExpression))
        result(ElementType1, ElementType2)(ElementType1 __a, ElementType2 __b)
            if(__traits(compiles, mixin(testAsExpression)))
        {
            mixin("alias __a "~parm1Name~";");
            mixin("alias __b "~parm2Name~";");
            mixin("return (" ~ fun ~ ");");
        }
    } else {
        alias fun result;
    }
}

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next sibling parent d-bugmail puremagic.com writes:
http://d.puremagic.com/issues/show_bug.cgi?id=5406


Lars T. Kyllingstad <bugzilla kyllingen.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bugzilla kyllingen.net


--- Comment #1 from Lars T. Kyllingstad <bugzilla kyllingen.net> 2011-02-03
00:23:39 PST ---
Do you have a test case?  I tried your example

    find("goodbye", "bye");

and it works for me.

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--- Comment #2 from Rob Jacques <sandford jhu.edu> 2011-02-03 09:46:11 PST ---
I apologize for the bad test case. In retrospect, I believe I didn't try to
reduce it, I simply extrapolated the issue from the error message reported.
Here is a properly test case:

import std.string;
pragma(msg, replace(int.stringof,"int","real"));

Which generates the error:

C:\dmd2\src\phobos\std\functional.d(177): Error: static assert  "Bad binary
function q{a == b}. You need to use a valid D expression using symbols a of
type dchar and b of type const(char)[]."
C:\dmd2\src\phobos\std\functional.d(180):        instantiated from here:
Body!(dchar,const(char)[])
C:\dmd2\src\phobos\std\algorithm.d(2149):        instantiated from here:
result!(dchar,const(char)[])

What got me was that algorithm.d(2149) turns out to be:

2147: R find(alias pred = "a == b", R, E)(R haystack, E needle)
2148: if (isInputRange!R &&
2149:         is(typeof(binaryFun!pred(haystack.front, needle)) : bool))

However, this only seems to generate a bug in certain compile-time contexts.
For example, enum bug = replace(int.stringof,"int","real"); compiles, while:
import std.typetuple;
mixin( "alias TypeTuple!("~replace(int.stringof,"int","real")~")
This2Algebraic;");
doesn't.

Although I don't know how/why find is called.

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prev sibling parent d-bugmail puremagic.com writes:
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Rob Jacques <sandford jhu.edu> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


--- Comment #3 from Rob Jacques <sandford jhu.edu> 2011-02-03 14:58:35 PST ---
As identified by soul8o8 gmail.com, this appears to be identical to Issue 5373
- Regression (2.051) CTFE and std.string.replace() causes "Bad binary function
q{a == b}...

*** This issue has been marked as a duplicate of issue 5373 ***

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