Unable to invoke macros on file private classes

[spalladino]

See #3858, by @makenowjust. This issue is here to keep track of the problem.

On Crystal 0.20.3, for instance:

private class Foo
end

Foo.new.dup

this code causes an error:

Error in foo.cr:4: instantiating 'Foo#dup()'

Foo.new.dup
        ^~~

in /.../src/reference.cr:40: expanding macro

    {% if @type.abstract? %}
    ^

in macro 'macro_XXX' /.../src/reference.cr:40, line 2:

   1.
>  2.       dup = Foo.allocate
   3.       dup.as(Void*).copy_from(self.as(Void*), instance_sizeof(Foo))
   4.       dup
   5.

[david50407]

This is a simple patch to get Reference#dup work without changing macro: (But we still need to improve the macro system)

From 2b74a5a99eea3e7da6c62646ef609db5e7a6875e Mon Sep 17 00:00:00 2001
From: David Kuo <s50407s@gmail.com>
Date: Fri, 13 Jan 2017 21:42:00 +0800
Subject: [PATCH] Allow Reference#dup in private type

---
 src/reference.cr | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/reference.cr b/src/reference.cr
index 35e26d2..a09a8e5 100644
--- a/src/reference.cr
+++ b/src/reference.cr
@@ -44,8 +44,8 @@ class Reference
       # but we need to avoid the allocate invocation below
       raise "can't dup {{@type}}"
     {% else %}
-      dup = {{@type}}.allocate
-      dup.as(Void*).copy_from(self.as(Void*), instance_sizeof({{@type}}))
+      dup = self.class.allocate
+      dup.as(Void*).copy_from(self.as(Void*), instance_sizeof(self))
       dup
     {% end %}
   end
--
2.7.4

tested with:

private class Foo
  property a = 1
end

f = Foo.new
p f.a

p f.a = 2
b = f.dup
p b.a

[asterite]

@david50407 Doesn't work with:

class Foo
  property a = 1
end

class Bar < Foo
end

[Foo.new, Bar.new].map &.dup

This needs a compiler fix, there's no way to do it without changing the compiler.

[david50407]

@asterite oops, I think I know why that fails

Should we create a macro system central-discussing issue like this #2665 ?