[Issue 2287] New: to!(string)(struct) should work if struct has toString() function

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=2287

           Summary: to!(string)(struct) should work if struct has toString()
                    function
           Product: D
           Version: 2.018
          Platform: PC
        OS/Version: Windows
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: dsimcha at yahoo.com


import std.stdio, std.conv;

struct Foo {
    string toString() {
        return "test";
    }
}

void main() {
    Foo test;
    //Doesn't work.  std.conv unaware of foo.toString().
    writefln(to!(string)(test));
}

Obviously, this is a very simplified test case, but when writing generic code,
it can become a legitimate issue.  Also note that the following test case,
which just changes Foo to a class, actually works.

import std.stdio, std.conv;

class Foo {

    this(){}

    string toString() {
        return "test";
    }
}

void main() {
    Foo test = new Foo;
    writefln(to!(string)(test));
}

I've found the bug and the fix is a dead simple two-liner.  I'll attach the
diffs against conv.d.


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