[Issue 4617] New: Alias this'ed symbols cannot be passed to templates

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=4617

           Summary: Alias this'ed symbols cannot be passed to templates
           Product: D
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody at puremagic.com
        ReportedBy: rsinfu at gmail.com


--- Comment #0 from Shin Fujishiro <rsinfu at gmail.com> 2010-08-10 22:38:03 PDT ---
DMD tries to evaluate alias this'ed symbols.  It causes a compile error on
instantiating templates with alias this'ed symbols.

-------------------- test1.d
alias Test!(S.square) test;

struct S
{
    struct F
    {
        int  square(int  n) { return n*n; }
        real square(real n) { return n*n; }
    }
    F forward;

    alias forward this;
}

template Test(alias k) {}
--------------------
% dmd -o- -c test1.d
test1.d(1): Error: function test1.S.F.square (int n) is not callable using
argument types ()
test1.d(1): Error: expected 1 function arguments, not 0
% _
--------------------

TemplateInstance::semanticTiargs() (or TypeQualified::resolveHelper()) resolves
forwarded symbols as dotvar expressions and tries to evaluate them at compile
time.  Apparently, it causes the problem.

The error does not occur if the symbol is forwarded directly:
-------------------- test2.d
alias Test!(S.square) test;

struct S
{
    struct F
    {
        int  square(int  n) { return n*n; }
        real square(real n) { return n*n; }
    }
    F forward;

    alias forward.square square;    // okay
}

template Test(alias k) {}
--------------------
% dmd -o- -c test2.d
% _
--------------------

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