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

2 files changed, 32 insertions, 0 deletions

diff --git a/mrbgems/mruby-compiler/core/parse.y b/mrbgems/mruby-compiler/core/parse.y
index 8e68fa21a..b20dc1713 100644
--- a/mrbgems/mruby-compiler/core/parse.y
+++ b/mrbgems/mruby-compiler/core/parse.y
@@ -7758,3 +7758,19 @@ mrb_parser_dump(mrb_state *mrb, node *tree, int offset)
   }
 #endif
 }
+
+typedef mrb_bool mrb_parser_foreach_top_variable_func(mrb_state *mrb, mrb_sym sym, void *user);
+void mrb_parser_foreach_top_variable(mrb_state *mrb, struct mrb_parser_state *p, mrb_parser_foreach_top_variable_func *func, void *user);
+
+void
+mrb_parser_foreach_top_variable(mrb_state *mrb, struct mrb_parser_state *p, mrb_parser_foreach_top_variable_func *func, void *user)
+{
+  const mrb_ast_node *n = p->tree;
+  if ((intptr_t)n->car == NODE_SCOPE) {
+    n = n->cdr->car;
+    for (; n; n = n->cdr) {
+      mrb_sym sym = (intptr_t)n->car;
+      if (sym && !func(mrb, sym, user)) break;
+    }
+  }
+}
diff --git a/mrbgems/mruby-compiler/core/y.tab.c b/mrbgems/mruby-compiler/core/y.tab.c
index 22752e050..81f4efc26 100644
--- a/mrbgems/mruby-compiler/core/y.tab.c
+++ b/mrbgems/mruby-compiler/core/y.tab.c
@@ -13950,3 +13950,19 @@ mrb_parser_dump(mrb_state *mrb, node *tree, int offset)
   }
 #endif
 }
+
+typedef mrb_bool mrb_parser_foreach_top_variable_func(mrb_state *mrb, mrb_sym sym, void *user);
+void mrb_parser_foreach_top_variable(mrb_state *mrb, struct mrb_parser_state *p, mrb_parser_foreach_top_variable_func *func, void *user);
+
+void
+mrb_parser_foreach_top_variable(mrb_state *mrb, struct mrb_parser_state *p, mrb_parser_foreach_top_variable_func *func, void *user)
+{
+  const mrb_ast_node *n = p->tree;
+  if ((intptr_t)n->car == NODE_SCOPE) {
+    n = n->cdr->car;
+    for (; n; n = n->cdr) {
+      mrb_sym sym = (intptr_t)n->car;
+      if (sym && !func(mrb, sym, user)) break;
+    }
+  }
+}