Set first line numbers for empty iseqs.

* compile.c (iseq_compile_each): for empty method, block and so on,
  `last_line` is not set so that line number of `putnil` instruction
  will be zero. This patch set `first_lineno` for such `putnil`.

  Problem is reported by deivid-rodriguez via Yuichiro Kaneko.

* test/ruby/test_iseq.rb: add a test for this spec.


git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@61457 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

compile.c

@@ -5413,8 +5413,10 @@ iseq_compile_each(rb_iseq_t *iseq, LINK_ANCHOR *ret, const NODE *node, int poppe
 {
     if (node == 0) {
 	if (!popped) {
+	    int lineno = ISEQ_COMPILE_DATA(iseq)->last_line;
+	    if (lineno == 0) lineno = FIX2INT(rb_iseq_first_lineno(iseq));
 	    debugs("node: NODE_NIL(implicit)\n");
-	    ADD_INSN(ret, ISEQ_COMPILE_DATA(iseq)->last_line, putnil);
+	    ADD_INSN(ret, lineno, putnil);
 	}
 	return COMPILE_OK;
     }

test/ruby/test_iseq.rb

@@ -357,4 +357,37 @@ class TestISeq < Test::Unit::TestCase
                    [["<class:D>@17", [[17, :class],
                                       [18, :end]]]]], collect_iseq.call(sample_iseq)
   end
+
+  def test_empty_iseq_lineno
+    iseq = ISeq.compile(<<-EOS)
+    # 1
+    # 2
+    def foo   # line 3 empty method
+    end       # line 4
+    1.time do # line 5 empty block
+    end       # line 6
+    class C   # line 7 empty class
+    end
+    EOS
+
+    iseq.each_child{|ci|
+      ary = ci.to_a
+      type = ary[9]
+      name = ary[5]
+      line = ary[13].first
+      case ary[9]
+      when :method
+        assert_equal "foo", name
+        assert_equal 3, line
+      when :class
+        assert_equal '<class:C>', name
+        assert_equal 7, line
+      when :block
+        assert_equal 'block in <compiled>', name
+        assert_equal 5, line
+      else
+        raise "unknown ary: " + ary.inspect
+      end
+    }
+  end
 end