Started implementation for private flags in rust (#7269)

Adds flag to the cpp to fix bad annotations in all the languages

Addresses comments to the PR, and fixes logic for leaking annotations

tests/private_annotation_test/annotations_generated.rs

@@ -0,0 +1,137 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+extern crate alloc;
+extern crate flatbuffers;
+use alloc::boxed::Box;
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
+use core::mem;
+use core::cmp::Ordering;
+use self::flatbuffers::{EndianScalar, Follow};
+use super::*;
+pub(crate) enum AnnotationsOffset {}
+#[derive(Copy, Clone, PartialEq)]
+
+pub(crate) struct Annotations<'a> {
+  pub _tab: flatbuffers::Table<'a>,
+}
+
+impl<'a> flatbuffers::Follow<'a> for Annotations<'a> {
+  type Inner = Annotations<'a>;
+  #[inline]
+  fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
+    Self { _tab: flatbuffers::Table { buf, loc } }
+  }
+}
+
+impl<'a> Annotations<'a> {
+  pub const VT_VALUE: flatbuffers::VOffsetT = 4;
+
+  pub const fn get_fully_qualified_name() -> &'static str {
+    "Annotations"
+  }
+
+  #[inline]
+  pub fn init_from_table(table: flatbuffers::Table<'a>) -> Self {
+    Annotations { _tab: table }
+  }
+  #[allow(unused_mut)]
+  pub fn create<'bldr: 'args, 'args: 'mut_bldr, 'mut_bldr>(
+    _fbb: &'mut_bldr mut flatbuffers::FlatBufferBuilder<'bldr>,
+    args: &'args AnnotationsArgs
+  ) -> flatbuffers::WIPOffset<Annotations<'bldr>> {
+    let mut builder = AnnotationsBuilder::new(_fbb);
+    builder.add_value(args.value);
+    builder.finish()
+  }
+
+  pub fn unpack(&self) -> AnnotationsT {
+    let value = self.value();
+    AnnotationsT {
+      value,
+    }
+  }
+
+  #[inline]
+  pub fn value(&self) -> i32 {
+    self._tab.get::<i32>(Annotations::VT_VALUE, Some(0)).unwrap()
+  }
+}
+
+impl flatbuffers::Verifiable for Annotations<'_> {
+  #[inline]
+  fn run_verifier(
+    v: &mut flatbuffers::Verifier, pos: usize
+  ) -> Result<(), flatbuffers::InvalidFlatbuffer> {
+    use self::flatbuffers::Verifiable;
+    v.visit_table(pos)?
+     .visit_field::<i32>("value", Self::VT_VALUE, false)?
+     .finish();
+    Ok(())
+  }
+}
+pub(crate) struct AnnotationsArgs {
+    pub value: i32,
+}
+impl<'a> Default for AnnotationsArgs {
+  #[inline]
+  fn default() -> Self {
+    AnnotationsArgs {
+      value: 0,
+    }
+  }
+}
+
+pub(crate) struct AnnotationsBuilder<'a: 'b, 'b> {
+  fbb_: &'b mut flatbuffers::FlatBufferBuilder<'a>,
+  start_: flatbuffers::WIPOffset<flatbuffers::TableUnfinishedWIPOffset>,
+}
+impl<'a: 'b, 'b> AnnotationsBuilder<'a, 'b> {
+  #[inline]
+  pub fn add_value(&mut self, value: i32) {
+    self.fbb_.push_slot::<i32>(Annotations::VT_VALUE, value, 0);
+  }
+  #[inline]
+  pub fn new(_fbb: &'b mut flatbuffers::FlatBufferBuilder<'a>) -> AnnotationsBuilder<'a, 'b> {
+    let start = _fbb.start_table();
+    AnnotationsBuilder {
+      fbb_: _fbb,
+      start_: start,
+    }
+  }
+  #[inline]
+  pub fn finish(self) -> flatbuffers::WIPOffset<Annotations<'a>> {
+    let o = self.fbb_.end_table(self.start_);
+    flatbuffers::WIPOffset::new(o.value())
+  }
+}
+
+impl core::fmt::Debug for Annotations<'_> {
+  fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
+    let mut ds = f.debug_struct("Annotations");
+      ds.field("value", &self.value());
+      ds.finish()
+  }
+}
+#[non_exhaustive]
+#[derive(Debug, Clone, PartialEq)]
+pub(crate) struct AnnotationsT {
+  pub value: i32,
+}
+impl Default for AnnotationsT {
+  fn default() -> Self {
+    Self {
+      value: 0,
+    }
+  }
+}
+impl AnnotationsT {
+  pub fn pack<'b>(
+    &self,
+    _fbb: &mut flatbuffers::FlatBufferBuilder<'b>
+  ) -> flatbuffers::WIPOffset<Annotations<'b>> {
+    let value = self.value;
+    Annotations::create(_fbb, &AnnotationsArgs{
+      value,
+    })
+  }
+}