Fixed finding variables from `proc` in `binding.eval` failed

Previously the following code did not produce the expected results:
```ruby
bx = binding
block = bx.eval("a = 1; proc { a }")
bx.eval("a = 2")
p block.call  # Expect 2 but return 1 due to a bug
```

The previous implementation of `Binding#eval` evaluated the code and then merged the top layer variables.
This patch will parse and expand the variable space before making a call to `eval`.
This means that the call to `Binding#eval` will do the parsing twice.

In addition, the following changes will be made:
- Make `mrb_parser_foreach_top_variable()`, `mrb_binding_extract_proc()` and `mrb_binding_extract_env()` functions private global functions.
- Remove the `posthook` argument from `mrb_exec_irep()`.
  The `posthook` argument was introduced to implement the `binding` method.
  This patch is unnecessary because it uses a different implementation method.

ref #5362
fixed #5491

1 files changed, 2 insertions, 2 deletions

diff --git a/mrbgems/mruby-method/src/method.c b/mrbgems/mruby-method/src/method.c
index 7410f007e..02131050d 100644
--- a/mrbgems/mruby-method/src/method.c
+++ b/mrbgems/mruby-method/src/method.c
@@ -7,7 +7,7 @@
 #include "mruby/presym.h"
 
 mrb_noreturn void mrb_method_missing(mrb_state *mrb, mrb_sym name, mrb_value self, mrb_value args);
-mrb_value mrb_exec_irep(mrb_state *mrb, mrb_value self, struct RProc *p, mrb_func_t posthook);
+mrb_value mrb_exec_irep(mrb_state *mrb, mrb_value self, struct RProc *p);
 
 static mrb_value
 args_shift(mrb_state *mrb)
@@ -242,7 +242,7 @@ mcall(mrb_state *mrb, mrb_value self, mrb_value recv)
   mrb->c->ci->mid = mid;
   mrb->c->ci->u.target_class = tc;
 
-  return mrb_exec_irep(mrb, recv, proc, NULL);
+  return mrb_exec_irep(mrb, recv, proc);
 }
 
 static mrb_value