[t] move lazy.t to spec/

git-svn-id: http://svn.pugscode.org/pugs@22121 c213334d-75ef-0310-aa23-eaa082d1ae64

S04-statements/lazy.t

@@ -0,0 +1,76 @@
+use v6;
+
+use Test;
+
+=begin pod
+=head1 DESCRIPTION
+
+This test tests nothingmuch's C<lazy> proposal.
+
+This proposal was accepted on 2005-08-23 in a p6l post by Larry
+L<"http://www.nntp.perl.org/group/perl.perl6.language/22890">:
+
+  > Which already seems to be there with
+  > 
+  >     lazy {...}
+  > 
+  > which is, I presume, mostly syntactic sugar for something like:
+  > 
+  >     sub is cached {...}
+
+=end pod
+
+plan 15;
+
+{
+  my $was_in_lazy;
+
+  my $var = lazy { $was_in_lazy++; 42 };
+
+  ok !$was_in_lazy,     'our lazy block wasn\'t yet executed (1)';
+
+  is $var,          42, 'our lazy var has the correct value';
+  ok $was_in_lazy,      'our lazy block was executed';
+
+  is $var,          42, 'our lazy var still has the correct value';
+  is $was_in_lazy,   1, 'our lazy block was not executed again';
+}
+
+# Same, but passing the lazy value around before accessing it:
+{
+  my $was_in_lazy;
+
+  my $var = lazy { $was_in_lazy++; 42 };
+  my $sub = -> Num $v, Bool $access { $access and +$v };
+
+  ok !$was_in_lazy,         'our lazy block wasn\'t yet executed (2)';
+  $sub($var, 0);  
+  ok !$was_in_lazy,         'our lazy block has still not been executed';
+  $sub($var, 1);
+  ok $was_in_lazy,          'our lazy block has been executed now';
+}
+
+# dies_ok/lives_ok tests:
+{
+  my $was_in_lazy;
+  my $lazy = lazy { $was_in_lazy++; 42 };
+  lives_ok { $lazy = 23 }, "reassigning our var containing a lazy worked (1)";
+  is $lazy, 23,            "reassigning our var containing a lazy worked (2)";
+  ok !$was_in_lazy,        "reassigning our var containing a lazy worked (3)";
+}
+
+{
+  my $was_in_lazy;
+  my $lazy = lazy { $was_in_lazy++; 42 };
+  lives_ok { $lazy := 23 }, "rebinding our var containing a lazy worked (1)";
+  is $lazy, 23,             "rebinding our var containing a lazy worked (2)";
+  ok !$was_in_lazy,         "rebinding our var containing a lazy worked (3)";
+}
+
+{
+  dies_ok { (lazy { 42 }) = 23 },
+    "directly assigning to a lazy var does not work";
+}
+
+# Arguably, we should remove the $was_in_lazy tests, as it doesn't really
+# matter when the lazy {...} block is actually executed.