Spec $*ARGFILES in MAIN in 6.d to be fed by $*IN

- Even when @*ARGS has stuff
- Rakudo impl: rakudo/rakudo@84d45f07fb

MISC/misc-6.d.t

@@ -1,11 +1,13 @@
 use v6.d.PREVIEW;
+use lib $?FILE.IO.parent(2).add: 'packages';
 use Test;
+use Test::Util;
 
 # This file is for various 6.d-specific tests that require the use of `v6.d.PREVIEW` pragma.
 # They might be rearranged into other files in the future, but for now, keeping them in this
 # file avoids creating a ton of `-6.d.t` files for the sake of single tests.
 
-plan 1;
+plan 2;
 
 subtest ':sym<> colonpair on subroutine names is reserved' => {
     plan 6;
@@ -21,4 +23,60 @@ subtest ':sym<> colonpair on subroutine names is reserved' => {
         ':sym«...»:foo<bar>';
 }
 
+subtest '$*ARGFILES is set to $*IN inside sub MAIN' => {
+    plan 5;
+    my @args = <THE FILES CONTENT>.map: {make-temp-file :$^content}
+
+    is_run ｢
+        use v6.c;
+        sub MAIN(*@args) {
+            .say for lines;
+        }
+    ｣,
+    "blah\nbleh\nbloh", :@args, {
+        :err(''), :0status, :out("THE\nFILES\nCONTENT\n"),
+    }, 'inside MAIN in 6.c language (with @*ARGS content)';
+
+    is_run ｢
+        use v6.c;
+        sub MAIN(*@args) {
+            .say for lines;
+        }
+    ｣,
+    "blah\nbleh\nbloh", {
+        :err(''), :0status, :out("blah\nbleh\nbloh\n"),
+    }, 'inside MAIN in 6.c language (without @*ARGS content)';
+
+    is_run ｢
+        use v6.d.PREVIEW;
+        .say for lines;
+        sub MAIN(*@args) {
+            .say for lines;
+        }
+    ｣,
+    "blah\nbleh\nbloh", :@args, {
+        :err(''), :0status, :out("THE\nFILES\nCONTENT\nblah\nbleh\nbloh\n"),
+    }, 'MAIN is an only sub';
+
+    is_run ｢
+        use v6.d.PREVIEW;
+        .say for lines;
+        multi MAIN($, $, $) {
+            .say for lines;
+        }
+        multi MAIN(|) { die }
+    ｣,
+    "blah\nbleh\nbloh", :@args, {
+        :err(''), :0status, :out("THE\nFILES\nCONTENT\nblah\nbleh\nbloh\n"),
+    }, 'MAIN is a multi sub';
+
+    is_run ｢
+        use v6.d.PREVIEW;
+        .say for lines;
+    ｣,
+    "blah\nbleh\nbloh", :@args, {
+        :err(''), :0status, :out("THE\nFILES\nCONTENT\n"),
+    }, 'no MAIN';
+}
+
 # vim: expandtab shiftwidth=4 ft=perl6