WIP stabilize simple offset_of

Author: GKFX

compiler/rustc_error_codes/src/error_codes/E0795.md

@@ -3,7 +3,7 @@ Invalid argument for the `offset_of!` macro.
 Erroneous code example:
 
 ```compile_fail,E0795
-#![feature(offset_of, offset_of_enum)]
+#![feature(offset_of_enum, offset_of_nested)]
 
 let x = std::mem::offset_of!(Option<u8>, Some);
 ```
@@ -16,7 +16,7 @@ The offset of the contained `u8` in the `Option<u8>` can be found by specifying
 the field name `0`:
 
 ```
-#![feature(offset_of, offset_of_enum)]
+#![feature(offset_of_enum, offset_of_nested)]
 
 let x: usize = std::mem::offset_of!(Option<u8>, Some.0);
 ```

compiler/rustc_feature/src/unstable.rs

@@ -541,6 +541,8 @@ declare_features! (
     (unstable, object_safe_for_dispatch, "1.40.0", Some(43561), None),
     /// Allows using enums in offset_of!
     (unstable, offset_of_enum, "1.75.0", Some(106655), None),
+    /// Allows using multiple nested field accesses in offset_of!
+    (unstable, offset_of_nested, "CURRENT_RUSTC_VERSION", Some(106655), None),
     /// Allows using `#[optimize(X)]`.
     (unstable, optimize_attribute, "1.34.0", Some(54882), None),
     /// Allows macro attributes on expressions, statements and non-inline modules.

compiler/rustc_hir_typeck/src/expr.rs

@@ -3261,6 +3261,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
     ) -> Ty<'tcx> {
         let container = self.to_ty(container).normalized;
 
+        if let Some(ident_2) = fields.get(1)
+            && !self.tcx.features().offset_of_nested
+        {
+            rustc_session::parse::feature_err(
+                &self.tcx.sess.parse_sess,
+                sym::offset_of_nested,
+                ident_2.span,
+                "only a single ident or integer is stable as the field in offset_of",
+            )
+            .emit();
+        }
+
         let mut field_indices = Vec::with_capacity(fields.len());
         let mut current_container = container;
         let mut fields = fields.into_iter();

compiler/rustc_span/src/symbol.rs

@@ -1137,6 +1137,7 @@ symbols! {
         offset,
         offset_of,
         offset_of_enum,
+        offset_of_nested,
         omit_gdb_pretty_printer_section,
         on,
         on_unimplemented,

library/core/src/lib.rs

@@ -111,6 +111,7 @@
 //
 // Library features:
 // tidy-alphabetical-start
+#![cfg_attr(not(bootstrap), feature(offset_of_nested))]
 #![feature(char_indices_offset)]
 #![feature(const_align_of_val)]
 #![feature(const_align_of_val_raw)]
@@ -178,7 +179,6 @@
 #![feature(isqrt)]
 #![feature(maybe_uninit_uninit_array)]
 #![feature(non_null_convenience)]
-#![feature(offset_of)]
 #![feature(offset_of_enum)]
 #![feature(ptr_alignment_type)]
 #![feature(ptr_metadata)]

library/core/src/mem/mod.rs

@@ -1303,11 +1303,12 @@ impl<T> SizedTypeProperties for T {}
 /// Enum variants may be traversed as if they were fields. Variants themselves do
 /// not have an offset.
 ///
+/// However, on stable only a single field name is supported, which blocks the use of
+/// enum support.
+///
 /// Visibility is respected - all types and fields must be visible to the call site:
 ///
 /// ```
-/// #![feature(offset_of)]
-///
 /// mod nested {
 ///     #[repr(C)]
 ///     pub struct Struct {
@@ -1330,8 +1331,6 @@ impl<T> SizedTypeProperties for T {}
 /// not *identical*, e.g.:
 ///
 /// ```
-/// #![feature(offset_of)]
-///
 /// struct Wrapper<T, U>(T, U);
 ///
 /// type A = Wrapper<u8, u8>;
@@ -1359,8 +1358,7 @@ impl<T> SizedTypeProperties for T {}
 /// # Examples
 ///
 /// ```
-/// #![feature(offset_of)]
-/// # #![feature(offset_of_enum)]
+/// #![feature(offset_of_enum, offset_of_nested)]
 ///
 /// use std::mem;
 /// #[repr(C)]
@@ -1395,7 +1393,7 @@ impl<T> SizedTypeProperties for T {}
 ///
 /// assert_eq!(mem::offset_of!(Option<&u8>, Some.0), 0);
 /// ```
-#[unstable(feature = "offset_of", issue = "106655")]
+#[stable(feature = "offset_of", since = "CURRENT_RUSTC_VERSION")]
 #[allow_internal_unstable(builtin_syntax, hint_must_use)]
 pub macro offset_of($Container:ty, $($fields:tt).+ $(,)?) {
     // The `{}` is for better error messages

library/core/tests/lib.rs

@@ -115,7 +115,6 @@
 #![feature(utf8_chunks)]
 #![feature(is_ascii_octdigit)]
 #![feature(get_many_mut)]
-#![feature(offset_of)]
 #![feature(iter_map_windows)]
 #![deny(unsafe_op_in_unsafe_fn)]
 #![deny(fuzzy_provenance_casts)]

library/std/src/lib.rs

@@ -329,7 +329,6 @@
 #![feature(maybe_uninit_slice)]
 #![feature(maybe_uninit_uninit_array)]
 #![feature(maybe_uninit_write_slice)]
-#![feature(offset_of)]
 #![feature(panic_can_unwind)]
 #![feature(panic_info_message)]
 #![feature(panic_internals)]

tests/ui/feature-gates/feature-gate-offset-of-enum.rs

@@ -1,4 +1,4 @@
-#![feature(offset_of)]
+#![feature(offset_of_nested)]
 
 use std::mem::offset_of;
 

tests/ui/feature-gates/feature-gate-offset-of-nested.rs

@@ -0,0 +1,28 @@
+#![feature(offset_of_enum)]
+
+use std::mem::offset_of;
+
+struct S {
+    a: u8,
+    b: (u8, u8),
+    c: T,
+}
+
+struct T {
+    t: &'static str,
+}
+
+enum Alpha {
+    One(u8),
+    Two(u8),
+}
+
+fn main() {
+    offset_of!(Alpha, Two.0); //~ ERROR only a single ident or integer is stable as the field in offset_of
+    offset_of!(S, a);
+    offset_of!((u8, S), 1);
+    offset_of!((u32, (S, T)), 1.1); //~ ERROR only a single ident or integer is stable as the field in offset_of
+    offset_of!(S, b.0); //~ ERROR only a single ident or integer is stable as the field in offset_of
+    offset_of!((S, ()), 0.c); //~ ERROR only a single ident or integer is stable as the field in offset_of
+    offset_of!(S, c.t); //~ ERROR only a single ident or integer is stable as the field in offset_of
+}

tests/ui/feature-gates/feature-gate-offset-of-nested.stderr

@@ -0,0 +1,48 @@
+error[E0658]: only a single ident or integer is stable as the field in offset_of
+  --> $DIR/feature-gate-offset-of-nested.rs:21:27
+   |
+LL |     offset_of!(Alpha, Two.0);
+   |                           ^
+   |
+   = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
+   = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable
+
+error[E0658]: only a single ident or integer is stable as the field in offset_of
+  --> $DIR/feature-gate-offset-of-nested.rs:24:33
+   |
+LL |     offset_of!((u32, (S, T)), 1.1);
+   |                                 ^
+   |
+   = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
+   = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable
+
+error[E0658]: only a single ident or integer is stable as the field in offset_of
+  --> $DIR/feature-gate-offset-of-nested.rs:25:21
+   |
+LL |     offset_of!(S, b.0);
+   |                     ^
+   |
+   = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
+   = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable
+
+error[E0658]: only a single ident or integer is stable as the field in offset_of
+  --> $DIR/feature-gate-offset-of-nested.rs:26:27
+   |
+LL |     offset_of!((S, ()), 0.c);
+   |                           ^
+   |
+   = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
+   = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable
+
+error[E0658]: only a single ident or integer is stable as the field in offset_of
+  --> $DIR/feature-gate-offset-of-nested.rs:27:21
+   |
+LL |     offset_of!(S, c.t);
+   |                     ^
+   |
+   = note: see issue #106655 <https://github.com/rust-lang/rust/issues/106655> for more information
+   = help: add `#![feature(offset_of_nested)]` to the crate attributes to enable
+
+error: aborting due to 5 previous errors
+
+For more information about this error, try `rustc --explain E0658`.

tests/ui/lint/dead-code/offset-of-correct-param-env.rs

@@ -1,6 +1,6 @@
 // check-pass
 
-#![feature(offset_of)]
+#![feature(offset_of_nested)]
 #![deny(dead_code)]
 
 // This struct contains a projection that can only be normalized after getting the field type.

tests/ui/lint/dead-code/offset-of.rs

@@ -1,4 +1,4 @@
-#![feature(offset_of)]
+#![feature(offset_of_nested)]
 #![deny(dead_code)]
 
 use std::mem::offset_of;

tests/ui/offset-of/offset-of-arg-count.rs

@@ -1,5 +1,3 @@
-#![feature(offset_of)]
-
 use std::mem::offset_of;
 
 fn main() {

tests/ui/offset-of/offset-of-arg-count.stderr

@@ -1,5 +1,5 @@
 error: unexpected end of macro invocation
-  --> $DIR/offset-of-arg-count.rs:6:34
+  --> $DIR/offset-of-arg-count.rs:4:34
    |
 LL |     offset_of!(NotEnoughArguments);
    |                                  ^ missing tokens in macro arguments
@@ -8,7 +8,7 @@ note: while trying to match `,`
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
 
 error: unexpected end of macro invocation
-  --> $DIR/offset-of-arg-count.rs:7:45
+  --> $DIR/offset-of-arg-count.rs:5:45
    |
 LL |     offset_of!(NotEnoughArgumentsWithAComma, );
    |                                             ^ missing tokens in macro arguments
@@ -17,15 +17,15 @@ note: while trying to match meta-variable `$fields:tt`
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
 
 error: no rules expected the token `too`
-  --> $DIR/offset-of-arg-count.rs:8:34
+  --> $DIR/offset-of-arg-count.rs:6:34
    |
 LL |     offset_of!(Container, field, too many arguments);
    |                                  ^^^ no rules expected this token in macro call
    |
    = note: while trying to match sequence end
 
 error: unexpected end of macro invocation
-  --> $DIR/offset-of-arg-count.rs:11:21
+  --> $DIR/offset-of-arg-count.rs:9:21
    |
 LL |     offset_of!(S, f.);
    |                     ^ missing tokens in macro arguments
@@ -34,21 +34,21 @@ note: while trying to match meta-variable `$fields:tt`
   --> $SRC_DIR/core/src/mem/mod.rs:LL:COL
 
 error: expected identifier, found `,`
-  --> $DIR/offset-of-arg-count.rs:12:21
+  --> $DIR/offset-of-arg-count.rs:10:21
    |
 LL |     offset_of!(S, f.,);
    |                     ^ expected identifier
 
 error: no rules expected the token `..`
-  --> $DIR/offset-of-arg-count.rs:13:20
+  --> $DIR/offset-of-arg-count.rs:11:20
    |
 LL |     offset_of!(S, f..);
    |                    ^^ no rules expected this token in macro call
    |
    = note: while trying to match sequence start
 
 error: no rules expected the token `..`
-  --> $DIR/offset-of-arg-count.rs:14:20
+  --> $DIR/offset-of-arg-count.rs:12:20
    |
 LL |     offset_of!(S, f..,);
    |                    ^^ no rules expected this token in macro call

tests/ui/offset-of/offset-of-dst-field.rs

@@ -1,4 +1,4 @@
-#![feature(offset_of, extern_types)]
+#![feature(extern_types)]
 
 use std::mem::offset_of;
 

tests/ui/offset-of/offset-of-enum.rs

@@ -1,4 +1,4 @@
-#![feature(offset_of, offset_of_enum)]
+#![feature(offset_of_enum, offset_of_nested)]
 
 use std::mem::offset_of;
 

tests/ui/offset-of/offset-of-inference.rs

@@ -1,7 +1,5 @@
 // Test that inference types in `offset_of!` don't ICE.
 
-#![feature(offset_of)]
-
 struct Foo<T> {
     x: T,
 }

tests/ui/offset-of/offset-of-inference.stderr

@@ -1,5 +1,5 @@
 error[E0282]: type annotations needed
-  --> $DIR/offset-of-inference.rs:10:35
+  --> $DIR/offset-of-inference.rs:8:35
    |
 LL |     let _ = core::mem::offset_of!(Foo<_>, x);
    |                                   ^^^^^^ cannot infer type

tests/ui/offset-of/offset-of-must-use.rs

@@ -1,6 +1,5 @@
 // check-pass
 
-#![feature(offset_of)]
 #![warn(unused)]
 
 fn main() {

tests/ui/offset-of/offset-of-must-use.stderr

@@ -1,11 +1,11 @@
 warning: unused return value of `must_use` that must be used
-  --> $DIR/offset-of-must-use.rs:7:5
+  --> $DIR/offset-of-must-use.rs:6:5
    |
 LL |     core::mem::offset_of!((String,), 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/offset-of-must-use.rs:4:9
+  --> $DIR/offset-of-must-use.rs:3:9
    |
 LL | #![warn(unused)]
    |         ^^^^^^

tests/ui/offset-of/offset-of-output-type.rs

@@ -1,5 +1,3 @@
-#![feature(offset_of)]
-
 use std::mem::offset_of;
 
 struct S {

tests/ui/offset-of/offset-of-output-type.stderr

@@ -1,45 +1,45 @@
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:12:17
+  --> $DIR/offset-of-output-type.rs:10:17
    |
 LL |     let _: u8 = offset_of!(S, v);
    |                 ^^^^^^^^^^^^^^^^ expected `u8`, found `usize`
    |
    = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:13:18
+  --> $DIR/offset-of-output-type.rs:11:18
    |
 LL |     let _: u16 = offset_of!(S, v);
    |                  ^^^^^^^^^^^^^^^^ expected `u16`, found `usize`
    |
    = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:14:18
+  --> $DIR/offset-of-output-type.rs:12:18
    |
 LL |     let _: u32 = offset_of!(S, v);
    |                  ^^^^^^^^^^^^^^^^ expected `u32`, found `usize`
    |
    = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:15:18
+  --> $DIR/offset-of-output-type.rs:13:18
    |
 LL |     let _: u64 = offset_of!(S, v);
    |                  ^^^^^^^^^^^^^^^^ expected `u64`, found `usize`
    |
    = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:16:20
+  --> $DIR/offset-of-output-type.rs:14:20
    |
 LL |     let _: isize = offset_of!(S, v);
    |                    ^^^^^^^^^^^^^^^^ expected `isize`, found `usize`
    |
    = note: this error originates in the macro `offset_of` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error[E0308]: mismatched types
-  --> $DIR/offset-of-output-type.rs:19:5
+  --> $DIR/offset-of-output-type.rs:17:5
    |
 LL | fn main() {
    |          - expected `()` because of default return type