Auto merge of #156140 - jhpratt:rollup-tW55BUD, r=jhpratt

Rollup of 6 pull requests

Successful merges:

 - #155543 (docs(unstable-book): Document const generics features)
 - #156043 (c-variadic: gate `va_arg` on `c_variadic_experimental_arch`)
 - #156082 (Move tests associated types)
 - #156092 (Clean up `TyCtxt::needs_crate_hash` usage and rename it to `needs_hir_hash`.)
 - #156104 (Relax `T: Sized` bound on `try_as_dyn` / `try_as_dyn_mut`)
 - #156128 (.mailmap: prefer matching just based on commit emails)

Author: bors

.mailmap

@@ -259,11 +259,9 @@ Gregor Peach <gregorpeach@gmail.com>
 Grzegorz Bartoszek <grzegorz.bartoszek@thaumatec.com>
 Guanqun Lu <guanqun.lu@gmail.com>
 Guillaume Gomez <contact@guillaume-gomez.fr>
-Guillaume Gomez <contact@guillaume-gomez.fr> Guillaume Gomez <guillaume1.gomez@gmail.com>
-Guillaume Gomez <contact@guillaume-gomez.fr> ggomez <guillaume1.gomez@gmail.com>
-Guillaume Gomez <contact@guillaume-gomez.fr> ggomez <ggomez@ggo.ifr.lan>
-Guillaume Gomez <contact@guillaume-gomez.fr> Guillaume Gomez <ggomez@ggo.ifr.lan>
-Guillaume Gomez <contact@guillaume-gomez.fr> Guillaume Gomez <guillaume.gomez@huawei.com>
+Guillaume Gomez <contact@guillaume-gomez.fr> <guillaume1.gomez@gmail.com>
+Guillaume Gomez <contact@guillaume-gomez.fr> <ggomez@ggo.ifr.lan>
+Guillaume Gomez <contact@guillaume-gomez.fr> <guillaume.gomez@huawei.com>
 gnzlbg <gonzalobg88@gmail.com> <gnzlbg@users.noreply.github.com>
 hamidreza kalbasi <hamidrezakalbasi@protonmail.com>
 Hanna Kruppe <hanna.kruppe@gmail.com> <robin.kruppe@gmail.com>

compiler/rustc_ast_lowering/src/lib.rs

@@ -562,7 +562,7 @@ pub fn lower_to_hir(tcx: TyCtxt<'_>, (): ()) -> mid_hir::Crate<'_> {
 
     // Don't hash unless necessary, because it's expensive.
     let opt_hir_hash =
-        if tcx.needs_crate_hash() { Some(compute_hir_hash(tcx, &owners)) } else { None };
+        if tcx.needs_hir_hash() { Some(compute_hir_hash(tcx, &owners)) } else { None };
 
     let delayed_resolver = Steal::new((resolver, krate));
     mid_hir::Crate::new(owners, delayed_ids, delayed_resolver, opt_hir_hash)

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -3,8 +3,8 @@ use std::ffi::c_uint;
 use std::{assert_matches, iter, ptr};
 
 use rustc_abi::{
-    AddressSpace, Align, BackendRepr, Float, HasDataLayout, Integer, NumScalableVectors, Primitive,
-    Size, WrappingRange,
+    AddressSpace, Align, BackendRepr, CVariadicStatus, Float, HasDataLayout, Integer,
+    NumScalableVectors, Primitive, Size, WrappingRange,
 };
 use rustc_codegen_ssa::base::{compare_simd_types, wants_msvc_seh, wants_wasm_eh};
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
@@ -23,6 +23,7 @@ use rustc_middle::ty::{
 };
 use rustc_middle::{bug, span_bug};
 use rustc_session::config::CrateType;
+use rustc_session::errors::feature_err;
 use rustc_session::lint::builtin::DEPRECATED_LLVM_INTRINSIC;
 use rustc_span::{Span, Symbol, sym};
 use rustc_symbol_mangling::{mangle_internal_symbol, symbol_name_for_instance_in_crate};
@@ -288,6 +289,16 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
             }
             sym::breakpoint => self.call_intrinsic("llvm.debugtrap", &[], &[]),
             sym::va_arg => {
+                let target = &self.cx.tcx.sess.target;
+                let stability = target.supports_c_variadic_definitions();
+                if let CVariadicStatus::Unstable { feature } = stability
+                    && !self.tcx.features().enabled(feature)
+                {
+                    let msg =
+                        format!("C-variadic function definitions on this target are unstable");
+                    feature_err(&*self.sess(), feature, span, msg).emit();
+                }
+
                 let BackendRepr::Scalar(scalar) = result.layout.backend_repr else {
                     bug!("the va_arg intrinsic does not support non-scalar types")
                 };

compiler/rustc_feature/src/unstable.rs

@@ -563,8 +563,9 @@ declare_features! (
     /// Allows defining gen blocks and `gen fn`.
     (unstable, gen_blocks, "1.75.0", Some(117078)),
     /// Allows using generics in more complex const expressions, based on definitional equality.
-    (unstable, generic_const_args, "1.95.0", Some(151972)),
-    /// Allows non-trivial generic constants which have to have wfness manually propagated to callers
+    (incomplete, generic_const_args, "1.95.0", Some(151972)),
+    /// Allows non-trivial generic constants which have to be shown to successfully evaluate
+    /// to a value by being part of an item signature.
     (incomplete, generic_const_exprs, "1.56.0", Some(76560)),
     /// Allows generic parameters and where-clauses on free & associated const items.
     (incomplete, generic_const_items, "1.73.0", Some(113521)),
@@ -626,7 +627,8 @@ declare_features! (
     /// Allows additional const parameter types, such as [u8; 10] or user defined types.
     /// User defined types must not have fields more private than the type itself.
     (unstable, min_adt_const_params, "1.96.0", Some(154042)),
-    /// Enables the generic const args MVP (only bare paths, not arbitrary computation).
+    /// Enables the generic const args MVP (paths to type const items and constructors
+    /// for ADTs and primitives).
     (incomplete, min_generic_const_args, "1.84.0", Some(132980)),
     /// A minimal, sound subset of specialization intended to be used by the
     /// standard library until the soundness issues with specialization

compiler/rustc_interface/src/queries.rs

@@ -36,7 +36,7 @@ impl Linker {
         Linker {
             dep_graph: tcx.dep_graph.clone(),
             output_filenames: Arc::clone(tcx.output_filenames(())),
-            crate_hash: if tcx.needs_crate_hash() {
+            crate_hash: if tcx.sess.opts.incremental.is_some() {
                 Some(tcx.crate_hash(LOCAL_CRATE))
             } else {
                 None

compiler/rustc_middle/src/hir/mod.rs

@@ -237,7 +237,7 @@ impl<'tcx> TyCtxt<'tcx> {
         attrs: &SortedMap<ItemLocalId, &[Attribute]>,
         define_opaque: Option<&[(Span, LocalDefId)]>,
     ) -> Hashes {
-        if !self.needs_crate_hash() {
+        if !self.needs_hir_hash() {
             return Hashes { opt_hash_including_bodies: None, attrs_hash: None };
         }
 

compiler/rustc_middle/src/ty/context.rs

@@ -1127,12 +1127,12 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn needs_crate_hash(self) -> bool {
-        // Why is the crate hash needed for these configurations?
+    pub fn needs_hir_hash(self) -> bool {
+        // Why is the hir hash needed for these configurations?
         // - debug_assertions: for the "fingerprint the result" check in
         //   `rustc_query_impl::execution::execute_job`.
         // - incremental: for query lookups.
-        // - needs_metadata: for putting into crate metadata.
+        // - needs_metadata: it is included in the crate metadata through the crate_hash query
         // - instrument_coverage: for putting into coverage data (see
         //   `hash_mir_source`).
         // - metrics_dir: metrics use the strict version hash in the filenames

library/core/src/any.rs

@@ -1007,18 +1007,23 @@ pub const fn type_name_of_val<T: ?Sized>(_val: &T) -> &'static str {
 #[must_use]
 #[unstable(feature = "try_as_dyn", issue = "144361")]
 pub const fn try_as_dyn<
-    T: Any + 'static,
+    T: Any + ?Sized + 'static,
     U: ptr::Pointee<Metadata = ptr::DynMetadata<U>> + ?Sized + 'static,
 >(
     t: &T,
 ) -> Option<&U> {
+    // For unsized `T`, `trait_info_of` always returns `None` (vtable lookup is
+    // only supported for sized types). The function therefore unconditionally
+    // returns `None` in that case.
     let vtable: Option<ptr::DynMetadata<U>> =
         const { TypeId::of::<T>().trait_info_of::<U>().as_ref().map(TraitImpl::get_vtable) };
     match vtable {
         Some(dyn_metadata) => {
-            let pointer = ptr::from_raw_parts(t, dyn_metadata);
+            let pointer = ptr::from_raw_parts(t as *const T as *const (), dyn_metadata);
             // SAFETY: `t` is a reference to a type, so we know it is valid.
             // `dyn_metadata` is a vtable for T, implementing the trait of `U`.
+            // `T` is sized here because `trait_info_of` only returns `Some` for sized types,
+            // so the thin data pointer fully describes the value.
             Some(unsafe { &*pointer })
         }
         None => None,
@@ -1061,18 +1066,23 @@ pub const fn try_as_dyn<
 #[must_use]
 #[unstable(feature = "try_as_dyn", issue = "144361")]
 pub const fn try_as_dyn_mut<
-    T: Any + 'static,
+    T: Any + ?Sized + 'static,
     U: ptr::Pointee<Metadata = ptr::DynMetadata<U>> + ?Sized + 'static,
 >(
     t: &mut T,
 ) -> Option<&mut U> {
+    // For unsized `T`, `trait_info_of` always returns `None` (vtable lookup is
+    // only supported for sized types). The function therefore unconditionally
+    // returns `None` in that case.
     let vtable: Option<ptr::DynMetadata<U>> =
         const { TypeId::of::<T>().trait_info_of::<U>().as_ref().map(TraitImpl::get_vtable) };
     match vtable {
         Some(dyn_metadata) => {
-            let pointer = ptr::from_raw_parts_mut(t, dyn_metadata);
+            let pointer = ptr::from_raw_parts_mut(t as *mut T as *mut (), dyn_metadata);
             // SAFETY: `t` is a reference to a type, so we know it is valid.
             // `dyn_metadata` is a vtable for T, implementing the trait of `U`.
+            // `T` is sized here because `trait_info_of` only returns `Some` for sized types,
+            // so the thin data pointer fully describes the value.
             Some(unsafe { &mut *pointer })
         }
         None => None,

src/doc/unstable-book/src/language-features/generic-const-args.md

@@ -0,0 +1,37 @@
+# generic_const_args
+
+Allows using generics in more complex const expressions, based on definitional equality.
+
+The tracking issue for this feature is: [#151972]
+
+[#151972]: https://github.com/rust-lang/rust/issues/151972
+
+------------------------
+
+Warning: This feature is incomplete; its design and syntax may change.
+
+This feature enables many of the same use cases supported by [generic_const_exprs],
+but based on the machinery developed for [min_generic_const_args]. In a way, it is
+meant to be an interim successor for GCE (though it might not currently support all
+the valid cases that supported by GCE).
+
+See also: [generic_const_items]
+
+[min_generic_const_args]: min-generic-const-args.md
+[generic_const_exprs]: generic-const-exprs.md
+[generic_const_items]: generic-const-items.md
+
+## Examples
+
+```rust
+#![feature(generic_const_items)]
+#![feature(min_generic_const_args)]
+#![feature(generic_const_args)]
+#![expect(incomplete_features)]
+
+type const ADD1<const N: usize>: usize = const { N + 1 };
+
+type const INC<const N: usize>: usize = ADD1::<N>;
+
+const ARR: [(); ADD1::<0>] = [(); INC::<0>];
+```

src/doc/unstable-book/src/language-features/generic-const-exprs.md

@@ -0,0 +1,73 @@
+# generic_const_exprs
+
+Allows non-trivial generic constants which have to be shown to successfully evaluate
+to a value by being part of an item signature.
+
+The tracking issue for this feature is: [#76560]
+
+
+[#76560]: https://github.com/rust-lang/rust/issues/76560
+
+------------------------
+
+Warning: This feature is incomplete; its design and syntax may change.
+
+See also: [min_generic_const_args], [generic_const_args]
+
+[min_generic_const_args]: min-generic-const-args.md
+[generic_const_args]: generic-const-args.md
+
+## Examples
+
+```rust
+#![allow(incomplete_features)]
+#![feature(generic_const_exprs)]
+
+// Use parameters that depend on a generic argument.
+struct Foo<const N: usize>
+where
+    [(); N + 1]:,
+{
+    array: [usize; N + 1],
+}
+
+// Use generic parameters in const operations.
+trait Bar {
+    const X: usize;
+    const Y: usize;
+}
+
+// Note `B::X * B::Y`.
+const fn baz<B: Bar>(x: [usize; B::X], y: [usize; B::Y]) -> [usize; B::X * B::Y] {
+    let mut out = [0; B::X * B::Y];
+    let mut i = 0;
+    while i < B::Y {
+        let mut j = 0;
+        while j < B::X {
+            out[i * B::X + j] = y[i].saturating_mul(x[j]);
+            j += 1;
+        }
+        i += 1;
+    }
+    out
+}
+
+
+// Create a new type based on a generic argument.
+pub struct Grow<const N: usize> {
+    arr: [usize; N],
+}
+
+impl<const N: usize> Grow<N> {
+    pub const fn grow(self, val: usize) -> Grow<{ N + 1 }> {
+        let mut new_arr = [0; { N + 1 }];
+        let mut idx = 0;
+        while idx < N {
+            new_arr[idx] = self.arr[idx];
+            idx += 1;
+        }
+        new_arr[N] = val;
+        Grow { arr: new_arr }
+    }
+}
+```