http://d.puremagic.com/issues/show_bug.cgi?id=4430

           Summary: erroneous matching on specialized template function
           Product: D
           Version: D2
          Platform: Other
        OS/Version: Windows
            Status: NEW
          Severity: regression
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: s.d.hammett@googlemail.com


--- Comment #0 from simon <s.d.hammett@googlemail.com> 2010-07-06 02:13:12 PDT ---
A bug has been introduced in 2.037 which in some circumstances causes a specialized template function to be considered a match even when though it isn't.

I tried to cut it down to a small test case but I didn't succeed,
it must be something to do with a specific instantiation which is causing the
bug.

FWIW:

http://www.sstk.co.uk/spiritd.zip

Compiles fine w/ 2.036

If I can make a smaller test case, I'll update this bug report.

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Richard Webb <webby@beardmouse.org.uk> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |webby@beardmouse.org.uk


--- Comment #1 from Richard Webb <webby@beardmouse.org.uk> 2010-07-06 06:25:42 PDT ---
You can repro the compile error in the spiritd test app by doing:

/////////
import spiritd.match, spiritd.nil;

void main(string[] args)
{
    Match!(nilT) temp;
    conv!(Match!(char))(temp);
}
/////////

(you only need the match bits to see the problem, rather than the whole thing).

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |clugdbug@yahoo.com.au
            Summary|erroneous matching on       |Regression(2.037) erroneous
                   |specialized template        |matching on specialized
                   |function                    |template function


--- Comment #2 from Don <clugdbug@yahoo.com.au> 2010-07-26 11:33:07 PDT ---
Reduced test case:

struct Ghost(T) {}

void bug4430(T)(Ghost!(T) x) {}
void bug4430(T)(Ghost!(int) x)    {}

void spirit4430()
{
    Ghost!(int) temp;
    bug4430!(Ghost!(char))( temp );
}

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--- Comment #3 from Don <clugdbug@yahoo.com.au> 2010-09-01 00:19:06 PDT ---
Even further reduced, shows that a class template is not required.
---
struct Ghost {}

void bug4430(T)(int x)   {}
void bug4430(T)(Ghost x) {}

void spirit4430()
{
    bug4430!(char)( 777 );
}
----
bad.d(53): Error: template instance bug4430!(char) matches more than one
templat
e declaration, bad.d(48):bug4430(T) and bad.d(49):bug4430(T)

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Don <clugdbug@yahoo.com.au> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |patch, rejects-valid


--- Comment #4 from Don <clugdbug@yahoo.com.au> 2010-09-01 11:57:33 PDT ---
This bug was triggered by svn commit 273, which was related to opDispatch.
The immediate change was in CallExp::semantic(). Previously, it attempted full
explicit instantiation, and if that failed, it tried partial explicit
instantiation. In this case, the full explicit instantiation was failing
(because there were two candidate templates), and then partial instantiation
succeeded.
After svn 273, it calls needsTypeInference(). If that returns true, it does
partial instantiation, otherwise does full instantiation. In this example, it's
returning false.

There is a situation missing from needsTypeInference(). If there is more than one candidate template, and they are ALL function templates, and they are ALL potentially explicitly instantiated, we need to do partial instantiation.

Template.c, needsTypeInference(), around line 4625.


Index: template.c ===================================================================
--- template.c    (revision 655)
+++ template.c    (working copy)
@@ -4622,6 +4622,7 @@
     //printf("TemplateInstance::needsTypeInference() %s\n", toChars());
     if (!tempdecl)
         tempdecl = findTemplateDeclaration(sc);
+    int multipleMatches = FALSE;
     for (TemplateDeclaration *td = tempdecl; td; td = td->overnext)
     {
         /* If any of the overloaded template declarations need inference,
@@ -4647,9 +4648,14 @@
         if (Parameter::dim(fdtype->parameters) &&
             (tp || tiargs->dim < td->parameters->dim))
             return TRUE;
+        /* If there is more than one function template which matches, we may
need type inference
+         */
+        if (td != tempdecl)
+            multipleMatches = TRUE;
     }
     //printf("false\n");
-    return FALSE;
+    return multipleMatches;
 }

 void TemplateInstance::semantic2(Scope *sc)

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Walter Bright <bugzilla@digitalmars.com> changed:

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


--- Comment #5 from Walter Bright <bugzilla@digitalmars.com> 2010-09-11 16:47:38 PDT ---
http://www.dsource.org/projects/dmd/changeset/674

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