Fix Rust keyword inconsistency (#6794)

* Make Rust keyword escaping more consistent

* fix comment

* git clang format

Co-authored-by: Casper Neo <cneo@google.com>

tests/keyword_test/keywords_in_union_generated.rs

@@ -0,0 +1,170 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+extern crate flatbuffers;
+use std::mem;
+use std::cmp::Ordering;
+use self::flatbuffers::{EndianScalar, Follow};
+use super::*;
+#[deprecated(since = "2.0.0", note = "Use associated constants instead. This will no longer be generated in 2021.")]
+pub const ENUM_MIN_KEYWORDS_IN_UNION: u8 = 0;
+#[deprecated(since = "2.0.0", note = "Use associated constants instead. This will no longer be generated in 2021.")]
+pub const ENUM_MAX_KEYWORDS_IN_UNION: u8 = 2;
+#[deprecated(since = "2.0.0", note = "Use associated constants instead. This will no longer be generated in 2021.")]
+#[allow(non_camel_case_types)]
+pub const ENUM_VALUES_KEYWORDS_IN_UNION: [KeywordsInUnion; 3] = [
+  KeywordsInUnion::NONE,
+  KeywordsInUnion::static_,
+  KeywordsInUnion::internal,
+];
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Default)]
+#[repr(transparent)]
+pub struct KeywordsInUnion(pub u8);
+#[allow(non_upper_case_globals)]
+impl KeywordsInUnion {
+  pub const NONE: Self = Self(0);
+  pub const static_: Self = Self(1);
+  pub const internal: Self = Self(2);
+
+  pub const ENUM_MIN: u8 = 0;
+  pub const ENUM_MAX: u8 = 2;
+  pub const ENUM_VALUES: &'static [Self] = &[
+    Self::NONE,
+    Self::static_,
+    Self::internal,
+  ];
+  /// Returns the variant's name or "" if unknown.
+  pub fn variant_name(self) -> Option<&'static str> {
+    match self {
+      Self::NONE => Some("NONE"),
+      Self::static_ => Some("static_"),
+      Self::internal => Some("internal"),
+      _ => None,
+    }
+  }
+}
+impl std::fmt::Debug for KeywordsInUnion {
+  fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+    if let Some(name) = self.variant_name() {
+      f.write_str(name)
+    } else {
+      f.write_fmt(format_args!("<UNKNOWN {:?}>", self.0))
+    }
+  }
+}
+impl<'a> flatbuffers::Follow<'a> for KeywordsInUnion {
+  type Inner = Self;
+  #[inline]
+  fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
+    let b = unsafe {
+      flatbuffers::read_scalar_at::<u8>(buf, loc)
+    };
+    Self(b)
+  }
+}
+
+impl flatbuffers::Push for KeywordsInUnion {
+    type Output = KeywordsInUnion;
+    #[inline]
+    fn push(&self, dst: &mut [u8], _rest: &[u8]) {
+        unsafe { flatbuffers::emplace_scalar::<u8>(dst, self.0); }
+    }
+}
+
+impl flatbuffers::EndianScalar for KeywordsInUnion {
+  #[inline]
+  fn to_little_endian(self) -> Self {
+    let b = u8::to_le(self.0);
+    Self(b)
+  }
+  #[inline]
+  #[allow(clippy::wrong_self_convention)]
+  fn from_little_endian(self) -> Self {
+    let b = u8::from_le(self.0);
+    Self(b)
+  }
+}
+
+impl<'a> flatbuffers::Verifiable for KeywordsInUnion {
+  #[inline]
+  fn run_verifier(
+    v: &mut flatbuffers::Verifier, pos: usize
+  ) -> Result<(), flatbuffers::InvalidFlatbuffer> {
+    use self::flatbuffers::Verifiable;
+    u8::run_verifier(v, pos)
+  }
+}
+
+impl flatbuffers::SimpleToVerifyInSlice for KeywordsInUnion {}
+pub struct KeywordsInUnionUnionTableOffset {}
+
+#[allow(clippy::upper_case_acronyms)]
+#[non_exhaustive]
+#[derive(Debug, Clone, PartialEq)]
+pub enum KeywordsInUnionT {
+  NONE,
+  Static_(Box<KeywordsInTableT>),
+  Internal(Box<KeywordsInTableT>),
+}
+impl Default for KeywordsInUnionT {
+  fn default() -> Self {
+    Self::NONE
+  }
+}
+impl KeywordsInUnionT {
+  pub fn keywords_in_union_type(&self) -> KeywordsInUnion {
+    match self {
+      Self::NONE => KeywordsInUnion::NONE,
+      Self::Static_(_) => KeywordsInUnion::static_,
+      Self::Internal(_) => KeywordsInUnion::internal,
+    }
+  }
+  pub fn pack(&self, fbb: &mut flatbuffers::FlatBufferBuilder) -> Option<flatbuffers::WIPOffset<flatbuffers::UnionWIPOffset>> {
+    match self {
+      Self::NONE => None,
+      Self::Static_(v) => Some(v.pack(fbb).as_union_value()),
+      Self::Internal(v) => Some(v.pack(fbb).as_union_value()),
+    }
+  }
+  /// If the union variant matches, return the owned KeywordsInTableT, setting the union to NONE.
+  pub fn take_static_(&mut self) -> Option<Box<KeywordsInTableT>> {
+    if let Self::Static_(_) = self {
+      let v = std::mem::replace(self, Self::NONE);
+      if let Self::Static_(w) = v {
+        Some(w)
+      } else {
+        unreachable!()
+      }
+    } else {
+      None
+    }
+  }
+  /// If the union variant matches, return a reference to the KeywordsInTableT.
+  pub fn as_static_(&self) -> Option<&KeywordsInTableT> {
+    if let Self::Static_(v) = self { Some(v.as_ref()) } else { None }
+  }
+  /// If the union variant matches, return a mutable reference to the KeywordsInTableT.
+  pub fn as_static__mut(&mut self) -> Option<&mut KeywordsInTableT> {
+    if let Self::Static_(v) = self { Some(v.as_mut()) } else { None }
+  }
+  /// If the union variant matches, return the owned KeywordsInTableT, setting the union to NONE.
+  pub fn take_internal(&mut self) -> Option<Box<KeywordsInTableT>> {
+    if let Self::Internal(_) = self {
+      let v = std::mem::replace(self, Self::NONE);
+      if let Self::Internal(w) = v {
+        Some(w)
+      } else {
+        unreachable!()
+      }
+    } else {
+      None
+    }
+  }
+  /// If the union variant matches, return a reference to the KeywordsInTableT.
+  pub fn as_internal(&self) -> Option<&KeywordsInTableT> {
+    if let Self::Internal(v) = self { Some(v.as_ref()) } else { None }
+  }
+  /// If the union variant matches, return a mutable reference to the KeywordsInTableT.
+  pub fn as_internal_mut(&mut self) -> Option<&mut KeywordsInTableT> {
+    if let Self::Internal(v) = self { Some(v.as_mut()) } else { None }
+  }
+}