Auto merge of rust-lang#97835 - Dylan-DPC:rollup-0ae3pwp, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - rust-lang#95948 (Improve the safety docs for `CStr`)
 - rust-lang#97325 (Fix precise field capture of univariant enums)
 - rust-lang#97817 (:arrow_up: rust-analyzer)
 - rust-lang#97821 (Remove confusing sentence from `Mutex` docs)
 - rust-lang#97826 (Add more information for rustdoc-gui tests)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_middle/src/thir.rs

@@ -317,9 +317,11 @@ pub enum ExprKind<'tcx> {
         lhs: ExprId,
         rhs: ExprId,
     },
-    /// Access to a struct or tuple field.
+    /// Access to a field of a struct, a tuple, an union, or an enum.
     Field {
         lhs: ExprId,
+        /// Variant containing the field.
+        variant_index: VariantIdx,
         /// This can be a named (`.foo`) or unnamed (`.0`) field.
         name: Field,
     },

compiler/rustc_middle/src/thir/visit.rs

@@ -80,7 +80,7 @@ pub fn walk_expr<'a, 'tcx: 'a, V: Visitor<'a, 'tcx>>(visitor: &mut V, expr: &Exp
             visitor.visit_expr(&visitor.thir()[lhs]);
             visitor.visit_expr(&visitor.thir()[rhs]);
         }
-        Field { lhs, name: _ } => visitor.visit_expr(&visitor.thir()[lhs]),
+        Field { lhs, variant_index: _, name: _ } => visitor.visit_expr(&visitor.thir()[lhs]),
         Index { lhs, index } => {
             visitor.visit_expr(&visitor.thir()[lhs]);
             visitor.visit_expr(&visitor.thir()[index]);

compiler/rustc_mir_build/src/build/expr/as_place.rs

@@ -5,6 +5,7 @@ use crate::build::ForGuard::{OutsideGuard, RefWithinGuard};
 use crate::build::{BlockAnd, BlockAndExtension, Builder};
 use rustc_hir::def_id::DefId;
 use rustc_hir::HirId;
+use rustc_middle::hir::place::Projection as HirProjection;
 use rustc_middle::hir::place::ProjectionKind as HirProjectionKind;
 use rustc_middle::middle::region;
 use rustc_middle::mir::AssertKind::BoundsCheck;
@@ -268,20 +269,52 @@ fn to_upvars_resolved_place_builder<'a, 'tcx>(
                 ty::UpvarCapture::ByValue => upvar_resolved_place_builder,
             };
 
-            let next_projection = capture.place.projections.len();
-            let mut curr_projections = from_builder.projection;
-
             // We used some of the projections to build the capture itself,
             // now we apply the remaining to the upvar resolved place.
-            upvar_resolved_place_builder
-                .projection
-                .extend(curr_projections.drain(next_projection..));
+            let remaining_projections = strip_prefix(
+                capture.place.base_ty,
+                from_builder.projection,
+                &capture.place.projections,
+            );
+            upvar_resolved_place_builder.projection.extend(remaining_projections);
 
             Ok(upvar_resolved_place_builder)
         }
     }
 }
 
+/// Returns projections remaining after stripping an initial prefix of HIR
+/// projections.
+///
+/// Supports only HIR projection kinds that represent a path that might be
+/// captured by a closure or a generator, i.e., an `Index` or a `Subslice`
+/// projection kinds are unsupported.
+fn strip_prefix<'tcx>(
+    mut base_ty: Ty<'tcx>,
+    projections: Vec<PlaceElem<'tcx>>,
+    prefix_projections: &[HirProjection<'tcx>],
+) -> impl Iterator<Item = PlaceElem<'tcx>> {
+    let mut iter = projections.into_iter();
+    for projection in prefix_projections {
+        match projection.kind {
+            HirProjectionKind::Deref => {
+                assert!(matches!(iter.next(), Some(ProjectionElem::Deref)));
+            }
+            HirProjectionKind::Field(..) => {
+                if base_ty.is_enum() {
+                    assert!(matches!(iter.next(), Some(ProjectionElem::Downcast(..))));
+                }
+                assert!(matches!(iter.next(), Some(ProjectionElem::Field(..))));
+            }
+            HirProjectionKind::Index | HirProjectionKind::Subslice => {
+                bug!("unexpected projection kind: {:?}", projection);
+            }
+        }
+        base_ty = projection.ty;
+    }
+    iter
+}
+
 impl<'tcx> PlaceBuilder<'tcx> {
     pub(crate) fn into_place<'a>(
         self,
@@ -438,11 +471,15 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     this.expr_as_place(block, &this.thir[value], mutability, fake_borrow_temps)
                 })
             }
-            ExprKind::Field { lhs, name } => {
-                let place_builder = unpack!(
-                    block =
-                        this.expr_as_place(block, &this.thir[lhs], mutability, fake_borrow_temps,)
-                );
+            ExprKind::Field { lhs, variant_index, name } => {
+                let lhs = &this.thir[lhs];
+                let mut place_builder =
+                    unpack!(block = this.expr_as_place(block, lhs, mutability, fake_borrow_temps,));
+                if let ty::Adt(adt_def, _) = lhs.ty.kind() {
+                    if adt_def.is_enum() {
+                        place_builder = place_builder.downcast(*adt_def, variant_index);
+                    }
+                }
                 block.and(place_builder.field(name, expr.ty))
             }
             ExprKind::Deref { arg } => {

compiler/rustc_mir_build/src/thir/cx/expr.rs

@@ -591,6 +591,7 @@ impl<'tcx> Cx<'tcx> {
             }
             hir::ExprKind::Field(ref source, ..) => ExprKind::Field {
                 lhs: self.mirror_expr(source),
+                variant_index: VariantIdx::new(0),
                 name: Field::new(tcx.field_index(expr.hir_id, self.typeck_results)),
             },
             hir::ExprKind::Cast(ref source, ref cast_ty) => {
@@ -994,14 +995,11 @@ impl<'tcx> Cx<'tcx> {
                 HirProjectionKind::Deref => {
                     ExprKind::Deref { arg: self.thir.exprs.push(captured_place_expr) }
                 }
-                HirProjectionKind::Field(field, ..) => {
-                    // Variant index will always be 0, because for multi-variant
-                    // enums, we capture the enum entirely.
-                    ExprKind::Field {
-                        lhs: self.thir.exprs.push(captured_place_expr),
-                        name: Field::new(field as usize),
-                    }
-                }
+                HirProjectionKind::Field(field, variant_index) => ExprKind::Field {
+                    lhs: self.thir.exprs.push(captured_place_expr),
+                    variant_index,
+                    name: Field::new(field as usize),
+                },
                 HirProjectionKind::Index | HirProjectionKind::Subslice => {
                     // We don't capture these projections, so we can ignore them here
                     continue;

library/core/src/ffi/c_str.rs

@@ -196,20 +196,32 @@ impl CStr {
     /// allows inspection and interoperation of non-owned C strings. The total
     /// size of the raw C string must be smaller than `isize::MAX` **bytes**
     /// in memory due to calling the `slice::from_raw_parts` function.
-    /// This method is unsafe for a number of reasons:
     ///
-    /// * There is no guarantee to the validity of `ptr`.
-    /// * The returned lifetime is not guaranteed to be the actual lifetime of
-    ///   `ptr`.
-    /// * There is no guarantee that the memory pointed to by `ptr` contains a
-    ///   valid nul terminator byte at the end of the string.
-    /// * It is not guaranteed that the memory pointed by `ptr` won't change
-    ///   before the `CStr` has been destroyed.
+    /// # Safety
+    ///
+    /// * The memory pointed to by `ptr` must contain a valid nul terminator at the
+    ///   end of the string.
+    ///
+    /// * `ptr` must be [valid] for reads of bytes up to and including the null terminator.
+    ///   This means in particular:
+    ///
+    ///     * The entire memory range of this `CStr` must be contained within a single allocated object!
+    ///     * `ptr` must be non-null even for a zero-length cstr.
+    ///
+    /// * The memory referenced by the returned `CStr` must not be mutated for
+    ///   the duration of lifetime `'a`.
     ///
     /// > **Note**: This operation is intended to be a 0-cost cast but it is
     /// > currently implemented with an up-front calculation of the length of
     /// > the string. This is not guaranteed to always be the case.
     ///
+    /// # Caveat
+    ///
+    /// The lifetime for the returned slice is inferred from its usage. To prevent accidental misuse,
+    /// it's suggested to tie the lifetime to whichever source lifetime is safe in the context,
+    /// such as by providing a helper function taking the lifetime of a host value for the slice,
+    /// or by explicit annotation.
+    ///
     /// # Examples
     ///
     /// ```ignore (extern-declaration)
@@ -227,6 +239,8 @@ impl CStr {
     /// }
     /// # }
     /// ```
+    ///
+    /// [valid]: core::ptr#safety
     #[inline]
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -349,8 +363,11 @@ impl CStr {
     /// Unsafely creates a C string wrapper from a byte slice.
     ///
     /// This function will cast the provided `bytes` to a `CStr` wrapper without
-    /// performing any sanity checks. The provided slice **must** be nul-terminated
-    /// and not contain any interior nul bytes.
+    /// performing any sanity checks.
+    ///
+    /// # Safety
+    /// The provided slice **must** be nul-terminated and not contain any interior
+    /// nul bytes.
     ///
     /// # Examples
     ///

library/std/src/sync/mutex.rs

@@ -10,11 +10,10 @@ use crate::sys_common::mutex as sys;
 /// A mutual exclusion primitive useful for protecting shared data
 ///
 /// This mutex will block threads waiting for the lock to become available. The
-/// mutex can also be statically initialized or created via a [`new`]
-/// constructor. Each mutex has a type parameter which represents the data that
-/// it is protecting. The data can only be accessed through the RAII guards
-/// returned from [`lock`] and [`try_lock`], which guarantees that the data is only
-/// ever accessed when the mutex is locked.
+/// mutex can be created via a [`new`] constructor. Each mutex has a type parameter
+/// which represents the data that it is protecting. The data can only be accessed
+/// through the RAII guards returned from [`lock`] and [`try_lock`], which
+/// guarantees that the data is only ever accessed when the mutex is locked.
 ///
 /// # Poisoning
 ///

src/test/rustdoc-gui/README.md

@@ -11,14 +11,24 @@ You can find more information and its documentation in its [repository][browser-
 If you need to have more information on the tests run, you can use `--test-args`:
 
 ```bash
-$ ./x.py test src/test/rustdoc-gui --stage 1 --jobs 8 --test-args --debug
+$ ./x.py test src/test/rustdoc-gui --stage 1 --test-args --debug
 ```
 
-There are three options supported:
+If you don't want to run in headless mode (helpful to debug sometimes), you can use
+`--no-headless`:
 
- * `--debug`: allows to see puppeteer commands.
- * `--no-headless`: disable headless mode so you can see what's going on.
- * `--show-text`: by default, text isn't rendered because of issues with fonts, it enables it back.
+```bash
+$ ./x.py test src/test/rustdoc-gui --stage 1 --test-args --no-headless
+```
+
+To see the supported options, use `--help`.
+
+Important to be noted: if the chromium instance crashes when you run it, you might need to
+use `--no-sandbox` to make it work:
+
+```bash
+$ ./x.py test src/test/rustdoc-gui --stage 1 --test-args --no-sandbox
+```
 
 [browser-ui-test]: https://github.com/GuillaumeGomez/browser-UI-test/
 [puppeteer]: https://pptr.dev/

src/test/ui/closures/2229_closure_analysis/capture-enum-field.rs

@@ -0,0 +1,27 @@
+// edition:2021
+// run-pass
+
+#[derive(Debug, PartialEq, Eq)]
+pub enum Color {
+    RGB(u8, u8, u8),
+}
+
+fn main() {
+    let mut color = Color::RGB(0, 0, 0);
+    let mut red = |v| {
+        let Color::RGB(ref mut r, _, _) = color;
+        *r = v;
+    };
+    let mut green = |v| {
+        let Color::RGB(_, ref mut g, _) = color;
+        *g = v;
+    };
+    let mut blue = |v| {
+        let Color::RGB(_, _, ref mut b) = color;
+        *b = v;
+    };
+    red(1);
+    green(2);
+    blue(3);
+    assert_eq!(Color::RGB(1, 2, 3), color);
+}

src/tools/rustdoc-gui/tester.js

@@ -16,6 +16,7 @@ function showHelp() {
     console.log("  --debug                    : show extra information about script run");
     console.log("  --show-text                : render font in pages");
     console.log("  --no-headless              : disable headless mode");
+    console.log("  --no-sandbox               : disable sandbox mode");
     console.log("  --help                     : show this message then quit");
     console.log("  --tests-folder [PATH]      : location of the .GOML tests folder");
     console.log("  --jobs [NUMBER]            : number of threads to run tests on");