Reimplement `block_given?`; ref #3841

Make `block_given?` to search for the top of the scope first.
The top of the scope means either:

* the top method body
* the enclosing class body
* the top-level

The special case is the method defined by `define_method` with a
block as in #3841. In cases like this, the method body (given by
a block) is not considered as the top of the scope. You need to use
`&block` in the block parameter if you want to know if a block is
given to the method.

This commit also changes the behavior of `MRB_PROC_SCOPE` flag.
Now it is only set if the `proc` is either a class body or a method
body defined in Ruby. It is no longer set for a block that given to
`define_method`.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/class.c b/src/class.c
index 77a7050da..30faa85e9 100644
--- a/src/class.c
+++ b/src/class.c
@@ -436,7 +436,6 @@ mrb_define_method_raw(mrb_state *mrb, struct RClass *c, mrb_sym mid, struct RPro
   k = kh_put(mt, mrb, h, mid);
   kh_value(h, k) = p;
   if (p) {
-    p->flags |= MRB_PROC_SCOPE;
     p->c = NULL;
     mrb_field_write_barrier(mrb, (struct RBasic*)c, (struct RBasic*)p);
     MRB_PROC_SET_TARGET_CLASS(p, c);
@@ -453,6 +452,7 @@ mrb_define_method_id(mrb_state *mrb, struct RClass *c, mrb_sym mid, mrb_func_t f
 
   p = mrb_proc_new_cfunc(mrb, func);
   MRB_PROC_SET_TARGET_CLASS(p, c);
+  p->flags |= MRB_PROC_SCOPE;
   mrb_define_method_raw(mrb, c, mid, p);
   mrb_gc_arena_restore(mrb, ai);
 }