`RubyVM.keep_script_lines`

`RubyVM.keep_script_lines` enables to keep script lines
for each ISeq and AST. This feature is for debugger/REPL
support.

```ruby
RubyVM.keep_script_lines = true
RubyVM::keep_script_lines = true

eval("def foo = nil\ndef bar = nil")
pp RubyVM::InstructionSequence.of(method(:foo)).script_lines
```

1 files changed, 1 insertions, 1 deletions

diff --git a/compile.c b/compile.c
index 71e078d20c..055d4e85f5 100644
--- a/compile.c
+++ b/compile.c
@@ -1328,7 +1328,7 @@ new_child_iseq(rb_iseq_t *iseq, const NODE *const node,
 
     ast.root = node;
     ast.compile_option = 0;
-    ast.script_lines = INT2FIX(-1);
+    ast.script_lines = iseq->body->variable.script_lines;
 
     debugs("[new_child_iseq]> ---------------------------------------\n");
     int isolated_depth = ISEQ_COMPILE_DATA(iseq)->isolated_depth;