Auto merge of #143627 - matthiaskrgr:rollup-3elo6xo, r=matthiaskrgr

Rollup of 6 pull requests

Successful merges:

 - #134628 (Make `Default` const and add some `const Default` impls)
 - #143555 (Don't mark `#[target_feature]` safe fns as unsafe in rustdoc JSON.)
 - #143600 (Update intro blurb in `wasm32-wasip1` docs)
 - #143603 (Clarify the meaning of `AttributeOrder::KeepFirst` and `AttributeOrder::KeepLast`)
 - #143620 (fix: Remove newline from multiple crate versions note)
 - #143622 (Add target maintainer information for mips64-unknown-linux-muslabi64)

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

Author: bors

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -217,7 +217,14 @@ impl<S: Stage> OnDuplicate<S> {
 // them will be merged in another PR
 #[allow(unused)]
 pub(crate) enum AttributeOrder {
-    /// Duplicates after the first attribute will be an error.
+    /// Duplicates after the first attribute will be an error. I.e. only keep the lowest attribute.
+    ///
+    /// Attributes are processed from bottom to top, so this raises an error on all the attributes
+    /// further above the lowest one:
+    /// ```
+    /// #[stable(since="1.0")] //~ WARNING duplicated attribute
+    /// #[stable(since="2.0")]
+    /// ```
     ///
     /// This should be used where duplicates would be ignored, but carry extra
     /// meaning that could cause confusion. For example, `#[stable(since="1.0")]
@@ -227,6 +234,13 @@ pub(crate) enum AttributeOrder {
     /// Duplicates preceding the last instance of the attribute will be a
     /// warning, with a note that this will be an error in the future.
     ///
+    /// Attributes are processed from bottom to top, so this raises a warning on all the attributes
+    /// below the higher one:
+    /// ```
+    /// #[path="foo.rs"]
+    /// #[path="bar.rs"] //~ WARNING duplicated attribute
+    /// ```
+    ///
     /// This is the same as `FutureWarnFollowing`, except the last attribute is
     /// the one that is "used". Ideally these can eventually migrate to
     /// `ErrorPreceding`.

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -1933,7 +1933,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
                     StringPart::highlighted("multiple different versions".to_string()),
                     StringPart::normal(" of crate `".to_string()),
                     StringPart::highlighted(format!("{crate_name}")),
-                    StringPart::normal("` in the dependency graph\n".to_string()),
+                    StringPart::normal("` in the dependency graph".to_string()),
                 ],
             );
             if points_at_type {

src/doc/rustc/src/SUMMARY.md

@@ -83,6 +83,7 @@
     - [m68k-unknown-linux-gnu](platform-support/m68k-unknown-linux-gnu.md)
     - [m68k-unknown-none-elf](platform-support/m68k-unknown-none-elf.md)
     - [mips64-openwrt-linux-musl](platform-support/mips64-openwrt-linux-musl.md)
+    - [mips64-unknown-linux-muslabi64](platform-support/mips64-unknown-linux-muslabi64.md)
     - [mipsel-sony-psx](platform-support/mipsel-sony-psx.md)
     - [mipsel-unknown-linux-gnu](platform-support/mipsel-unknown-linux-gnu.md)
     - [mips\*-mti-none-elf](platform-support/mips-mti-none-elf.md)

src/doc/rustc/src/platform-support.md

@@ -333,7 +333,7 @@ target | std | host | notes
 `mips-unknown-linux-uclibc` | ✓ |  | MIPS Linux with uClibc
 [`mips64-openwrt-linux-musl`](platform-support/mips64-openwrt-linux-musl.md) | ? |  | MIPS64 for OpenWrt Linux musl 1.2.3
 `mips64-unknown-linux-gnuabi64` | ✓ | ✓ | MIPS64 Linux, N64 ABI (kernel 4.4, glibc 2.23)
-`mips64-unknown-linux-muslabi64` | ✓ |  | MIPS64 Linux, N64 ABI, musl 1.2.3
+[`mips64-unknown-linux-muslabi64`](platform-support/mips64-unknown-linux-muslabi64.md) | ✓ | ✓ | MIPS64 Linux, N64 ABI, musl 1.2.3
 `mips64el-unknown-linux-gnuabi64` | ✓ | ✓ | MIPS64 (little endian) Linux, N64 ABI (kernel 4.4, glibc 2.23)
 `mips64el-unknown-linux-muslabi64` | ✓ |  | MIPS64 (little endian) Linux, N64 ABI, musl 1.2.3
 `mipsel-sony-psp` | * |  | MIPS (LE) Sony PlayStation Portable (PSP)

src/doc/rustc/src/platform-support/mips64-unknown-linux-muslabi64.md

@@ -0,0 +1,49 @@
+# mips64-unknown-linux-muslabi64
+
+**Tier: 3**
+
+Target for 64-bit big endian MIPS Linux programs using musl libc and the N64 ABI.
+
+## Target maintainers
+
+[@Gelbpunkt](https://github.com/Gelbpunkt)
+
+## Requirements
+
+Building the target itself requires a 64-bit big endian MIPS compiler that is
+supported by `cc-rs`.
+
+## Building the target
+
+The target can be built by enabling it for a `rustc` build.
+
+```toml
+[build]
+target = ["mips64-unknown-linux-muslabi64"]
+```
+
+Make sure your C compiler is included in `$PATH`, then add it to the
+`bootstrap.toml`:
+
+```toml
+[target.mips64-unknown-linux-muslabi64]
+cc = "mips64-linux-musl-gcc"
+cxx = "mips64-linux-musl-g++"
+ar = "mips64-linux-musl-ar"
+linker = "mips64-linux-musl-gcc"
+```
+
+## Building Rust programs
+
+Rust does not yet ship pre-compiled artifacts for this target. To compile for
+this target, you will first need to build Rust with the target enabled (see
+"Building the target" above).
+
+## Cross-compilation
+
+This target can be cross-compiled from any host.
+
+## Testing
+
+This target can be tested as normal with `x.py` on a 64-bit big endian MIPS
+host or via QEMU emulation.

src/doc/rustc/src/platform-support/wasm32-wasip1.md

@@ -4,37 +4,35 @@
 
 The `wasm32-wasip1` target is a WebAssembly compilation target which
 assumes that the [WASIp1] (aka "WASI preview1") set of "syscalls" are available
-for use in the standard library. Historically this target in the Rust compiler
-was one of the first for WebAssembly where Rust and C code are explicitly
-intended to interoperate as well.
-
-There's a bit of history to the target and current development which is also
-worth explaining before going much further. Historically this target was
-originally called `wasm32-wasi` in both rustc and Clang. This was first added
-to Rust in 2019. In the intervening years leading up to 2024 the WASI standard
-continued to be developed and was eventually "rebased" on top of the [Component
-Model]. This was a large change to the WASI specification and was released as
-0.2.0 ("WASIp2" colloquially) in January 2024. The previous target's name in
-rustc, `wasm32-wasi`, was then renamed to `wasm32-wasip1`, to avoid
-confusion with this new target to be added to rustc as `wasm32-wasip2`.
-Some more context can be found in these MCPs:
-
-* [Rename wasm32-wasi target to wasm32-wasip1](https://github.com/rust-lang/compiler-team/issues/607)
-* [Smooth the renaming transition of wasm32-wasi](https://github.com/rust-lang/compiler-team/issues/695)
-
-At this point the `wasm32-wasip1` target is intended for historical
-compatibility with the first version of the WASI standard. As of now (January
-2024) the 0.2.0 target of WASI ("WASIp2") is relatively new. The state of
-WASI will likely change in few years after which point this documentation will
-probably receive another update.
-
-[WASI Preview1]: https://github.com/WebAssembly/WASI/tree/main/legacy/preview1
+for use in the standard library. This target explicitly supports interop with
+non-Rust code such as C and C++.
+
+The [WASIp1] set of syscalls is standard insofar as it was written down once by
+a set of folks and has not changed since then. Additionally the [WASIp1]
+syscalls have been adapted and adopted into a number of runtimes and embeddings.
+It is not standard in the sense that there are no formal semantics for each
+syscall and APIs are no longer receiving any maintenance (e.g. no new APIs, no
+new documentation, etc). After [WASIp1] was originally developed in 2019 the
+WASI standard effort has since been "rebased" on top of the [Component Model].
+This was a large change to the WASI specification and was released as 0.2.0
+("WASIp2" colloquially) in January 2024. Current standardization efforts are
+focused on the Component Model-based definition of WASI. At this point the
+`wasm32-wasip1` Rust target is intended for historical compatibility with
+[WASIp1] set of syscalls.
+
+[WASIp1]: https://github.com/WebAssembly/WASI/tree/main/legacy/preview1
 [Component Model]: https://github.com/webassembly/component-model
 
 Today the `wasm32-wasip1` target will generate core WebAssembly modules
 which will import functions from the `wasi_snapshot_preview1` module for
 OS-related functionality (e.g. printing).
 
+> **Note**: Prior to March 2024 this target was known as `wasm32-wasi` with some
+> historical context found in old MCPs:
+>
+> * [Rename wasm32-wasi target to wasm32-wasip1](https://github.com/rust-lang/compiler-team/issues/607)
+> * [Smooth the renaming transition of wasm32-wasi](https://github.com/rust-lang/compiler-team/issues/695)
+
 ## Target maintainers
 
 When this target was added to the compiler platform-specific documentation here

src/librustdoc/json/conversions.rs

@@ -7,6 +7,7 @@ use rustc_ast::ast;
 use rustc_attr_data_structures::{self as attrs, DeprecatedSince};
 use rustc_hir::def::CtorKind;
 use rustc_hir::def_id::DefId;
+use rustc_hir::{HeaderSafety, Safety};
 use rustc_metadata::rendered_const;
 use rustc_middle::{bug, ty};
 use rustc_span::{Pos, kw, sym};
@@ -381,10 +382,22 @@ impl FromClean<clean::Union> for Union {
 
 impl FromClean<rustc_hir::FnHeader> for FunctionHeader {
     fn from_clean(header: &rustc_hir::FnHeader, renderer: &JsonRenderer<'_>) -> Self {
+        let is_unsafe = match header.safety {
+            HeaderSafety::SafeTargetFeatures => {
+                // The type system's internal implementation details consider
+                // safe functions with the `#[target_feature]` attribute to be analogous
+                // to unsafe functions: `header.is_unsafe()` returns `true` for them.
+                // For rustdoc, this isn't the right decision, so we explicitly return `false`.
+                // Context: https://github.com/rust-lang/rust/issues/142655
+                false
+            }
+            HeaderSafety::Normal(Safety::Safe) => false,
+            HeaderSafety::Normal(Safety::Unsafe) => true,
+        };
         FunctionHeader {
             is_async: header.is_async(),
             is_const: header.is_const(),
-            is_unsafe: header.is_unsafe(),
+            is_unsafe,
             abi: header.abi.into_json(renderer),
         }
     }

tests/rustdoc-json/attrs/target_feature.rs

@@ -1,17 +1,40 @@
 //@ only-x86_64
 
 //@ is "$.index[?(@.name=='test1')].attrs" '["#[target_feature(enable=\"avx\")]"]'
+//@ is "$.index[?(@.name=='test1')].inner.function.header.is_unsafe" false
 #[target_feature(enable = "avx")]
 pub fn test1() {}
 
 //@ is "$.index[?(@.name=='test2')].attrs" '["#[target_feature(enable=\"avx\", enable=\"avx2\")]"]'
+//@ is "$.index[?(@.name=='test1')].inner.function.header.is_unsafe" false
 #[target_feature(enable = "avx,avx2")]
 pub fn test2() {}
 
 //@ is "$.index[?(@.name=='test3')].attrs" '["#[target_feature(enable=\"avx\", enable=\"avx2\")]"]'
+//@ is "$.index[?(@.name=='test1')].inner.function.header.is_unsafe" false
 #[target_feature(enable = "avx", enable = "avx2")]
 pub fn test3() {}
 
 //@ is "$.index[?(@.name=='test4')].attrs" '["#[target_feature(enable=\"avx\", enable=\"avx2\", enable=\"avx512f\")]"]'
+//@ is "$.index[?(@.name=='test1')].inner.function.header.is_unsafe" false
 #[target_feature(enable = "avx", enable = "avx2,avx512f")]
 pub fn test4() {}
+
+//@ is "$.index[?(@.name=='test_unsafe_fn')].attrs" '["#[target_feature(enable=\"avx\")]"]'
+//@ is "$.index[?(@.name=='test_unsafe_fn')].inner.function.header.is_unsafe" true
+#[target_feature(enable = "avx")]
+pub unsafe fn test_unsafe_fn() {}
+
+pub struct Example;
+
+impl Example {
+    //@ is "$.index[?(@.name=='safe_assoc_fn')].attrs" '["#[target_feature(enable=\"avx\")]"]'
+    //@ is "$.index[?(@.name=='safe_assoc_fn')].inner.function.header.is_unsafe" false
+    #[target_feature(enable = "avx")]
+    pub fn safe_assoc_fn() {}
+
+    //@ is "$.index[?(@.name=='unsafe_assoc_fn')].attrs" '["#[target_feature(enable=\"avx\")]"]'
+    //@ is "$.index[?(@.name=='unsafe_assoc_fn')].inner.function.header.is_unsafe" true
+    #[target_feature(enable = "avx")]
+    pub unsafe fn unsafe_assoc_fn() {}
+}