Support Rust edition 2024 (#8638)

* Developers intro how to contribute

* Fix Rust code generation for Rust edition 2024

The errors look like:

```
warning[E0133]: call to unsafe function `fbs::flatbuffers::emplace_scalar` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::follow_cast_ref` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::Follow::follow` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::read_scalar_at` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::root_unchecked` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::size_prefixed_root_unchecked` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `fbs::flatbuffers::Table::<'a>::new` is unsafe and requires unsafe block
warning[E0133]: call to unsafe function `std::slice::from_raw_parts` is unsafe and requires unsafe block
```

* Update goldens

Ran `goldens/generate_goldens.py`

* Regenerate code files

Ran `scripts/generate_code.py`

Author: aleb

CONTRIBUTING.md

@@ -40,3 +40,26 @@ Some tips for good pull requests:
 # The small print
 Contributions made by corporations are covered by a different agreement than
 the one above, the Software Grant and Corporate Contributor License Agreement.
+
+# Code
+
+TL/DR
+
+See [how to build flatc](https://flatbuffers.dev/building/).
+
+When making changes, build `flatc` and then re-generate the goldens files to see the effect of your changes:
+
+```
+$ cp build/flatc .
+$ goldens/generate_goldens.py
+```
+
+Re-generate other code files to see the effects of the changes:
+
+```
+$ scripts/generate_code.py
+```
+
+Run tests with [TestAll.sh](tests/TestAll.sh) in [tests](tests), or directly any of the sub-scripts run by it.
+
+[Format the code](Formatters.md) before submitting a PR.

goldens/README.md

@@ -3,8 +3,8 @@
 This directory is a repository for the generated files of `flatc`.
 
 We check in the generated code so we can see, during a PR review, how the
-changes affect the generated output. Its also useful as a reference to point too
-as how things work across various languages.
+changes affect the generated output. It's also useful as a reference to show
+how things work across various languages.
 
 These files are **NOT** intended to be depended on by any code, such as tests or
 or compiled examples.

goldens/rust/basic_generated.rs

@@ -37,7 +37,7 @@ impl<'a> flatbuffers::Follow<'a> for Galaxy<'a> {
   type Inner = Galaxy<'a>;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    Self { _tab: flatbuffers::Table::new(buf, loc) }
+    Self { _tab: unsafe { flatbuffers::Table::new(buf, loc) } }
   }
 }
 
@@ -134,7 +134,7 @@ impl<'a> flatbuffers::Follow<'a> for Universe<'a> {
   type Inner = Universe<'a>;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    Self { _tab: flatbuffers::Table::new(buf, loc) }
+    Self { _tab: unsafe { flatbuffers::Table::new(buf, loc) } }
   }
 }
 
@@ -288,14 +288,14 @@ pub fn size_prefixed_root_as_universe_with_opts<'b, 'o>(
 /// # Safety
 /// Callers must trust the given bytes do indeed contain a valid `Universe`.
 pub unsafe fn root_as_universe_unchecked(buf: &[u8]) -> Universe {
-  flatbuffers::root_unchecked::<Universe>(buf)
+  unsafe { flatbuffers::root_unchecked::<Universe>(buf) }
 }
 #[inline]
 /// Assumes, without verification, that a buffer of bytes contains a size prefixed Universe and returns it.
 /// # Safety
 /// Callers must trust the given bytes do indeed contain a valid size prefixed `Universe`.
 pub unsafe fn size_prefixed_root_as_universe_unchecked(buf: &[u8]) -> Universe {
-  flatbuffers::size_prefixed_root_unchecked::<Universe>(buf)
+  unsafe { flatbuffers::size_prefixed_root_unchecked::<Universe>(buf) }
 }
 #[inline]
 pub fn finish_universe_buffer<'a, 'b, A: flatbuffers::Allocator + 'a>(

samples/rust_generated/my_game/sample/color_generated.rs

@@ -60,7 +60,7 @@ impl<'a> flatbuffers::Follow<'a> for Color {
   type Inner = Self;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    let b = flatbuffers::read_scalar_at::<i8>(buf, loc);
+    let b = unsafe { flatbuffers::read_scalar_at::<i8>(buf, loc) };
     Self(b)
   }
 }
@@ -69,7 +69,7 @@ impl flatbuffers::Push for Color {
     type Output = Color;
     #[inline]
     unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {
-        flatbuffers::emplace_scalar::<i8>(dst, self.0);
+        unsafe { flatbuffers::emplace_scalar::<i8>(dst, self.0); }
     }
 }
 

samples/rust_generated/my_game/sample/equipment_generated.rs

@@ -56,7 +56,7 @@ impl<'a> flatbuffers::Follow<'a> for Equipment {
   type Inner = Self;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    let b = flatbuffers::read_scalar_at::<u8>(buf, loc);
+    let b = unsafe { flatbuffers::read_scalar_at::<u8>(buf, loc) };
     Self(b)
   }
 }
@@ -65,7 +65,7 @@ impl flatbuffers::Push for Equipment {
     type Output = Equipment;
     #[inline]
     unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {
-        flatbuffers::emplace_scalar::<u8>(dst, self.0);
+        unsafe { flatbuffers::emplace_scalar::<u8>(dst, self.0); }
     }
 }
 

samples/rust_generated/my_game/sample/monster_generated.rs

@@ -20,7 +20,7 @@ impl<'a> flatbuffers::Follow<'a> for Monster<'a> {
   type Inner = Monster<'a>;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    Self { _tab: flatbuffers::Table::new(buf, loc) }
+    Self { _tab: unsafe { flatbuffers::Table::new(buf, loc) } }
   }
 }
 
@@ -451,14 +451,14 @@ pub fn size_prefixed_root_as_monster_with_opts<'b, 'o>(
 /// # Safety
 /// Callers must trust the given bytes do indeed contain a valid `Monster`.
 pub unsafe fn root_as_monster_unchecked(buf: &[u8]) -> Monster {
-  flatbuffers::root_unchecked::<Monster>(buf)
+  unsafe { flatbuffers::root_unchecked::<Monster>(buf) }
 }
 #[inline]
 /// Assumes, without verification, that a buffer of bytes contains a size prefixed Monster and returns it.
 /// # Safety
 /// Callers must trust the given bytes do indeed contain a valid size prefixed `Monster`.
 pub unsafe fn size_prefixed_root_as_monster_unchecked(buf: &[u8]) -> Monster {
-  flatbuffers::size_prefixed_root_unchecked::<Monster>(buf)
+  unsafe { flatbuffers::size_prefixed_root_unchecked::<Monster>(buf) }
 }
 #[inline]
 pub fn finish_monster_buffer<'a, 'b, A: flatbuffers::Allocator + 'a>(

samples/rust_generated/my_game/sample/vec_3_generated.rs

@@ -33,21 +33,21 @@ impl<'a> flatbuffers::Follow<'a> for Vec3 {
   type Inner = &'a Vec3;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    <&'a Vec3>::follow(buf, loc)
+    unsafe { <&'a Vec3>::follow(buf, loc) }
   }
 }
 impl<'a> flatbuffers::Follow<'a> for &'a Vec3 {
   type Inner = &'a Vec3;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    flatbuffers::follow_cast_ref::<Vec3>(buf, loc)
+    unsafe { flatbuffers::follow_cast_ref::<Vec3>(buf, loc) }
   }
 }
 impl<'b> flatbuffers::Push for Vec3 {
     type Output = Vec3;
     #[inline]
     unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {
-        let src = ::core::slice::from_raw_parts(self as *const Vec3 as *const u8, <Self as flatbuffers::Push>::size());
+        let src = unsafe { ::core::slice::from_raw_parts(self as *const Vec3 as *const u8, <Self as flatbuffers::Push>::size()) };
         dst.copy_from_slice(src);
     }
     #[inline]

samples/rust_generated/my_game/sample/weapon_generated.rs

@@ -20,7 +20,7 @@ impl<'a> flatbuffers::Follow<'a> for Weapon<'a> {
   type Inner = Weapon<'a>;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    Self { _tab: flatbuffers::Table::new(buf, loc) }
+    Self { _tab: unsafe { flatbuffers::Table::new(buf, loc) } }
   }
 }
 

src/idl_gen_rust.cpp

@@ -841,7 +841,7 @@ class RustGenerator : public BaseGenerator {
     code_ += "  #[inline]";
     code_ += "  unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {";
     code_ +=
-        "    let b = flatbuffers::read_scalar_at::<{{BASE_TYPE}}>(buf, loc);";
+        "    let b = unsafe { flatbuffers::read_scalar_at::<{{BASE_TYPE}}>(buf, loc) };";
     if (IsBitFlagsEnum(enum_def)) {
       code_ += "    Self::from_bits_retain(b)";
     } else {
@@ -855,8 +855,8 @@ class RustGenerator : public BaseGenerator {
     code_ += "    #[inline]";
     code_ += "    unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {";
     code_ +=
-        "        flatbuffers::emplace_scalar::<{{BASE_TYPE}}>(dst, "
-        "{{INTO_BASE}});";
+        "        unsafe { flatbuffers::emplace_scalar::<{{BASE_TYPE}}>(dst, "
+        "{{INTO_BASE}}); }";
     code_ += "    }";
     code_ += "}";
     code_ += "";
@@ -1658,7 +1658,7 @@ class RustGenerator : public BaseGenerator {
     code_ += "  type Inner = {{STRUCT_TY}}<'a>;";
     code_ += "  #[inline]";
     code_ += "  unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {";
-    code_ += "    Self { _tab: flatbuffers::Table::new(buf, loc) }";
+    code_ += "    Self { _tab: unsafe { flatbuffers::Table::new(buf, loc) } }";
     code_ += "  }";
     code_ += "}";
     code_ += "";
@@ -2481,7 +2481,7 @@ class RustGenerator : public BaseGenerator {
     code_ +=
         "pub unsafe fn root_as_{{STRUCT_FN}}_unchecked"
         "(buf: &[u8]) -> {{STRUCT_TY}} {";
-    code_ += "  flatbuffers::root_unchecked::<{{STRUCT_TY}}>(buf)";
+    code_ += "  unsafe { flatbuffers::root_unchecked::<{{STRUCT_TY}}>(buf) }";
     code_ += "}";
     code_ += "#[inline]";
     code_ +=
@@ -2495,8 +2495,8 @@ class RustGenerator : public BaseGenerator {
         "pub unsafe fn size_prefixed_root_as_{{STRUCT_FN}}"
         "_unchecked(buf: &[u8]) -> {{STRUCT_TY}} {";
     code_ +=
-        "  flatbuffers::size_prefixed_root_unchecked::<{{STRUCT_TY}}>"
-        "(buf)";
+        "  unsafe { flatbuffers::size_prefixed_root_unchecked::<{{STRUCT_TY}}>"
+        "(buf) }";
     code_ += "}";
 
     if (parser_.file_identifier_.length()) {
@@ -2656,23 +2656,23 @@ class RustGenerator : public BaseGenerator {
     code_ += "  type Inner = &'a {{STRUCT_TY}};";
     code_ += "  #[inline]";
     code_ += "  unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {";
-    code_ += "    <&'a {{STRUCT_TY}}>::follow(buf, loc)";
+    code_ += "    unsafe { <&'a {{STRUCT_TY}}>::follow(buf, loc) }";
     code_ += "  }";
     code_ += "}";
     code_ += "impl<'a> flatbuffers::Follow<'a> for &'a {{STRUCT_TY}} {";
     code_ += "  type Inner = &'a {{STRUCT_TY}};";
     code_ += "  #[inline]";
     code_ += "  unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {";
-    code_ += "    flatbuffers::follow_cast_ref::<{{STRUCT_TY}}>(buf, loc)";
+    code_ += "    unsafe { flatbuffers::follow_cast_ref::<{{STRUCT_TY}}>(buf, loc) }";
     code_ += "  }";
     code_ += "}";
     code_ += "impl<'b> flatbuffers::Push for {{STRUCT_TY}} {";
     code_ += "    type Output = {{STRUCT_TY}};";
     code_ += "    #[inline]";
     code_ += "    unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {";
     code_ +=
-        "        let src = ::core::slice::from_raw_parts(self as *const "
-        "{{STRUCT_TY}} as *const u8, <Self as flatbuffers::Push>::size());";
+        "        let src = unsafe { ::core::slice::from_raw_parts(self as *const "
+        "{{STRUCT_TY}} as *const u8, <Self as flatbuffers::Push>::size()) };";
     code_ += "        dst.copy_from_slice(src);";
     code_ += "    }";
     code_ += "    #[inline]";

tests/arrays_test/my_game/example/array_struct_generated.rs

@@ -36,21 +36,21 @@ impl<'a> flatbuffers::Follow<'a> for ArrayStruct {
   type Inner = &'a ArrayStruct;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    <&'a ArrayStruct>::follow(buf, loc)
+    unsafe { <&'a ArrayStruct>::follow(buf, loc) }
   }
 }
 impl<'a> flatbuffers::Follow<'a> for &'a ArrayStruct {
   type Inner = &'a ArrayStruct;
   #[inline]
   unsafe fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
-    flatbuffers::follow_cast_ref::<ArrayStruct>(buf, loc)
+    unsafe { flatbuffers::follow_cast_ref::<ArrayStruct>(buf, loc) }
   }
 }
 impl<'b> flatbuffers::Push for ArrayStruct {
     type Output = ArrayStruct;
     #[inline]
     unsafe fn push(&self, dst: &mut [u8], _written_len: usize) {
-        let src = ::core::slice::from_raw_parts(self as *const ArrayStruct as *const u8, <Self as flatbuffers::Push>::size());
+        let src = unsafe { ::core::slice::from_raw_parts(self as *const ArrayStruct as *const u8, <Self as flatbuffers::Push>::size()) };
         dst.copy_from_slice(src);
     }
     #[inline]