t/class/accessor.t - add additional :reader and :writer tests

The :reader tests are not really needed at present, as `pp_leavesub` makes
the necessary copies, but exploring some fast accessor ideas which bypass
that logic has shown the usefulness of having these tests present.

A test for :writer on an array field already exists in a separate file.
A comment pointing to that file has been added, and a test for the hash
case added next to the pre-existing test.

Author: richardleach

t/class/accessor.t

@@ -19,7 +19,10 @@ no warnings 'experimental::class';
         field @a :reader = qw( the array );
 
         # Present-but-empty parens counts as default
+
         field %h :reader() = qw( the hash );
+
+        field $empty :reader;
     }
 
     my $o = Testcase1->new;
@@ -35,12 +38,24 @@ no warnings 'experimental::class';
         'Reader accessor fails with argument');
     like($@, qr/^Too many arguments for subroutine \'Testcase1::s\' \(got 2; expected 1\) at /,
         'Failure from argument to accessor');
+
+    # Reading an undefined value has predictable behaviour
+    is(scalar $o->empty, undef, 'scalar :reader on uninitialized field is undef');
+    my ($empty) = $o->empty;
+    is($empty, undef, 'list :reader on uninitialized field is undef');
+
+    # :reader returns value copies, not the internal SVs
+    map { $_ = 99 } $o->s, $o->a, $o->h;
+    is($o->s, "the scalar", ':reader does not expose internal SVs');
+    ok(eq_array([$o->a], [qw( the array )]), ':reader does not expose internal AVs');
+    ok(eq_hash({$o->h}, {qw( the hash )}), ':reader does not expose internal HVs');
 }
 
 # writer accessors on scalars
 {
     class Testcase2 {
         field $s :reader :writer = "initial";
+        field $xno :param :reader = "Eh-ehhh";
     }
 
     my $o = Testcase2->new;
@@ -57,6 +72,12 @@ no warnings 'experimental::class';
         'Writer accessor fails with 2 arguments');
     like($@, qr/^Too many arguments for subroutine \'Testcase2::set_s\' \(got 3; expected 2\) at /,
         'Failure from argument to accessor');
+
+    # Should not be able to write without the :writer attribute
+    ok(!eval { $o->set_xno(77) },
+        'Cannot write without :writer attribute');
+    like($@, qr/^Can\'t locate object method \"set_xno\" via package \"Testcase2\"/,
+        'Failure from writing without :writer');
 }
 
 # Alternative names
@@ -76,4 +97,6 @@ no warnings 'experimental::class';
        'Failure from lack of original name accessor');
 }
 
+# Note: see t/lib/croak/class for testing :writer accessors on AVs or HVs
+
 done_testing;

t/lib/croak/class

@@ -175,7 +175,7 @@ class XXX {
 EXPECT
 "set-abc-def" is not a valid name for a generated method at - line 6.
 ########
-# Writer on non-scalar field
+# Writer on array field
 use v5.36;
 use feature 'class';
 no warnings 'experimental::class';
@@ -185,6 +185,16 @@ class XXX {
 EXPECT
 Cannot apply a :writer attribute to a non-scalar field at - line 6.
 ########
+# Writer on hash field
+use v5.36;
+use feature 'class';
+no warnings 'experimental::class';
+class XXX {
+  field %things :writer;
+}
+EXPECT
+Cannot apply a :writer attribute to a non-scalar field at - line 6.
+########
 use v5.36;
 use feature 'class';
 no warnings 'experimental::class';