Auto merge of #101938 - Dylan-DPC:rollup-6vlohhs, r=Dylan-DPC

Rollup of 6 pull requests

Successful merges:

 - #93628 (Stabilize `let else`)
 - #98441 (Implement simd_as for pointers)
 - #101790 (Do not suggest a placeholder to const and static without a type)
 - #101807 (Disallow defaults on type GATs)
 - #101915 (doc: fix redirected link in `/index.html`)
 - #101931 (doc: Fix a typo in `Rc::make_mut` docstring)

Failed merges:

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

compiler/rustc_ast/src/lib.rs

@@ -15,7 +15,7 @@
 #![feature(if_let_guard)]
 #![cfg_attr(bootstrap, feature(label_break_value))]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(negative_impls)]
 #![feature(slice_internals)]

compiler/rustc_ast_lowering/src/block.rs

@@ -1,8 +1,6 @@
 use crate::{ImplTraitContext, ImplTraitPosition, LoweringContext};
 use rustc_ast::{Block, BlockCheckMode, Local, LocalKind, Stmt, StmtKind};
 use rustc_hir as hir;
-use rustc_session::parse::feature_err;
-use rustc_span::sym;
 
 use smallvec::SmallVec;
 
@@ -92,15 +90,6 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         let hir_id = self.lower_node_id(l.id);
         let pat = self.lower_pat(&l.pat);
         let els = if let LocalKind::InitElse(_, els) = &l.kind {
-            if !self.tcx.features().let_else {
-                feature_err(
-                    &self.tcx.sess.parse_sess,
-                    sym::let_else,
-                    l.span,
-                    "`let...else` statements are unstable",
-                )
-                .emit();
-            }
             Some(self.lower_block(els, false))
         } else {
             None

compiler/rustc_ast_lowering/src/lib.rs

@@ -32,7 +32,7 @@
 
 #![feature(box_patterns)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(never_type)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]

compiler/rustc_ast_passes/src/lib.rs

@@ -9,7 +9,7 @@
 #![feature(if_let_guard)]
 #![feature(iter_is_partitioned)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![recursion_limit = "256"]
 
 #[macro_use]

compiler/rustc_attr/src/lib.rs

@@ -5,7 +5,7 @@
 //! to this crate.
 
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![deny(rustc::untranslatable_diagnostic)]
 #![deny(rustc::diagnostic_outside_of_impl)]
 

compiler/rustc_borrowck/src/lib.rs

@@ -3,7 +3,7 @@
 #![allow(rustc::potential_query_instability)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(rustc_attrs)]

compiler/rustc_builtin_macros/src/lib.rs

@@ -9,7 +9,7 @@
 #![feature(if_let_guard)]
 #![feature(is_sorted)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(proc_macro_internals)]
 #![feature(proc_macro_quote)]
 #![recursion_limit = "256"]

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -1705,6 +1705,97 @@ unsupported {} from `{}` with element `{}` of size `{}` to `{}`"#,
     bitwise_red!(simd_reduce_all: vector_reduce_and, true);
     bitwise_red!(simd_reduce_any: vector_reduce_or, true);
 
+    if name == sym::simd_cast_ptr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::RawPtr(p) => {
+                let (metadata, check_sized) = p.ty.ptr_metadata_ty(bx.tcx, |ty| {
+                    bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
+                });
+                assert!(!check_sized); // we are in codegen, so we shouldn't see these types
+                require!(metadata.is_unit(), "cannot cast fat pointer `{}`", in_elem)
+            }
+            _ => return_error!("expected pointer, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::RawPtr(p) => {
+                let (metadata, check_sized) = p.ty.ptr_metadata_ty(bx.tcx, |ty| {
+                    bx.tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), ty)
+                });
+                assert!(!check_sized); // we are in codegen, so we shouldn't see these types
+                require!(metadata.is_unit(), "cannot cast to fat pointer `{}`", out_elem)
+            }
+            _ => return_error!("expected pointer, got `{}`", out_elem),
+        }
+
+        if in_elem == out_elem {
+            return Ok(args[0].immediate());
+        } else {
+            return Ok(bx.pointercast(args[0].immediate(), llret_ty));
+        }
+    }
+
+    if name == sym::simd_expose_addr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::RawPtr(_) => {}
+            _ => return_error!("expected pointer, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::Uint(ty::UintTy::Usize) => {}
+            _ => return_error!("expected `usize`, got `{}`", out_elem),
+        }
+
+        return Ok(bx.ptrtoint(args[0].immediate(), llret_ty));
+    }
+
+    if name == sym::simd_from_exposed_addr {
+        require_simd!(ret_ty, "return");
+        let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());
+        require!(
+            in_len == out_len,
+            "expected return type with length {} (same as input type `{}`), \
+                  found `{}` with length {}",
+            in_len,
+            in_ty,
+            ret_ty,
+            out_len
+        );
+
+        match in_elem.kind() {
+            ty::Uint(ty::UintTy::Usize) => {}
+            _ => return_error!("expected `usize`, got `{}`", in_elem),
+        }
+        match out_elem.kind() {
+            ty::RawPtr(_) => {}
+            _ => return_error!("expected pointer, got `{}`", out_elem),
+        }
+
+        return Ok(bx.inttoptr(args[0].immediate(), llret_ty));
+    }
+
     if name == sym::simd_cast || name == sym::simd_as {
         require_simd!(ret_ty, "return");
         let (out_len, out_elem) = ret_ty.simd_size_and_type(bx.tcx());

compiler/rustc_codegen_llvm/src/lib.rs

@@ -7,7 +7,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(hash_raw_entry)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(extern_types)]
 #![feature(once_cell)]
 #![feature(iter_intersperse)]

compiler/rustc_codegen_ssa/src/lib.rs

@@ -1,7 +1,7 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(box_patterns)]
 #![feature(try_blocks)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(once_cell)]
 #![feature(associated_type_bounds)]
 #![feature(strict_provenance)]

compiler/rustc_const_eval/src/lib.rs

@@ -10,7 +10,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(decl_macro)]
 #![feature(exact_size_is_empty)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(map_try_insert)]
 #![feature(min_specialization)]
 #![feature(slice_ptr_get)]

compiler/rustc_data_structures/src/lib.rs

@@ -13,7 +13,7 @@
 #![feature(cell_leak)]
 #![feature(control_flow_enum)]
 #![feature(extend_one)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(hash_raw_entry)]
 #![feature(hasher_prefixfree_extras)]
 #![feature(maybe_uninit_uninit_array)]

compiler/rustc_driver/src/lib.rs

@@ -5,7 +5,7 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(once_cell)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]

compiler/rustc_errors/src/lib.rs

@@ -7,7 +7,7 @@
 #![feature(if_let_guard)]
 #![feature(adt_const_params)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(never_type)]
 #![feature(result_option_inspect)]
 #![feature(rustc_attrs)]
@@ -635,6 +635,10 @@ impl Handler {
         inner.steal((span, key)).map(|diag| DiagnosticBuilder::new_diagnostic(self, diag))
     }
 
+    pub fn has_stashed_diagnostic(&self, span: Span, key: StashKey) -> bool {
+        self.inner.borrow().stashed_diagnostics.get(&(span, key)).is_some()
+    }
+
     /// Emit all stashed diagnostics.
     pub fn emit_stashed_diagnostics(&self) -> Option<ErrorGuaranteed> {
         self.inner.borrow_mut().emit_stashed_diagnostics()

compiler/rustc_expand/src/lib.rs

@@ -3,7 +3,7 @@
 #![feature(associated_type_defaults)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(macro_metavar_expr)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_internals)]

compiler/rustc_feature/src/accepted.rs

@@ -190,6 +190,8 @@ declare_features! (
     (accepted, item_like_imports, "1.15.0", Some(35120), None),
     /// Allows `'a: { break 'a; }`.
     (accepted, label_break_value, "CURRENT_RUSTC_VERSION", Some(48594), None),
+    /// Allows `let...else` statements.
+    (accepted, let_else, "CURRENT_RUSTC_VERSION", Some(87335), None),
     /// Allows `break {expr}` with a value inside `loop`s.
     (accepted, loop_break_value, "1.19.0", Some(37339), None),
     /// Allows use of `?` as the Kleene "at most one" operator in macros.

compiler/rustc_feature/src/active.rs

@@ -430,8 +430,6 @@ declare_features! (
     (active, large_assignments, "1.52.0", Some(83518), None),
     /// Allows `if/while p && let q = r && ...` chains.
     (active, let_chains, "1.37.0", Some(53667), None),
-    /// Allows `let...else` statements.
-    (active, let_else, "1.56.0", Some(87335), None),
     /// Allows `#[link(..., cfg(..))]`.
     (active, link_cfg, "1.14.0", Some(37406), None),
     /// Allows using `reason` in lint attributes and the `#[expect(lint)]` lint check.

compiler/rustc_hir/src/lib.rs

@@ -5,7 +5,7 @@
 #![feature(associated_type_defaults)]
 #![feature(closure_track_caller)]
 #![feature(const_btree_new)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(once_cell)]
 #![feature(min_specialization)]
 #![feature(never_type)]

compiler/rustc_incremental/src/lib.rs

@@ -2,7 +2,7 @@
 
 #![deny(missing_docs)]
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 

compiler/rustc_index/src/lib.rs

@@ -3,7 +3,7 @@
 #![feature(allow_internal_unstable)]
 #![feature(bench_black_box)]
 #![feature(extend_one)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(new_uninit)]
 #![feature(step_trait)]

compiler/rustc_infer/src/lib.rs

@@ -19,7 +19,7 @@
 #![feature(extend_one)]
 #![cfg_attr(bootstrap, feature(label_break_value))]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![feature(try_blocks)]

compiler/rustc_interface/src/lib.rs

@@ -1,5 +1,5 @@
 #![feature(box_patterns)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(internal_output_capture)]
 #![feature(thread_spawn_unchecked)]
 #![feature(once_cell)]

compiler/rustc_lint/src/lib.rs

@@ -34,7 +34,7 @@
 #![feature(iter_intersperse)]
 #![feature(iter_order_by)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(never_type)]
 #![recursion_limit = "256"]

compiler/rustc_macros/src/lib.rs

@@ -1,5 +1,5 @@
 #![feature(allow_internal_unstable)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(never_type)]
 #![feature(proc_macro_diagnostic)]
 #![feature(proc_macro_span)]

compiler/rustc_metadata/src/lib.rs

@@ -5,7 +5,7 @@
 #![cfg_attr(bootstrap, feature(generic_associated_types))]
 #![feature(iter_from_generator)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(once_cell)]
 #![feature(proc_macro_internals)]
 #![feature(macro_metavar_expr)]

compiler/rustc_middle/src/lib.rs

@@ -40,7 +40,7 @@
 #![feature(new_uninit)]
 #![feature(once_cell)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
 #![feature(type_alias_impl_trait)]

compiler/rustc_mir_build/src/lib.rs

@@ -6,7 +6,7 @@
 #![feature(control_flow_enum)]
 #![feature(if_let_guard)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(once_cell)]
 #![recursion_limit = "256"]

compiler/rustc_mir_build/src/thir/pattern/check_match.rs

@@ -491,8 +491,8 @@ impl<'p, 'tcx> MatchVisitor<'_, 'p, 'tcx> {
                     err.span_suggestion_verbose(
                         semi_span.shrink_to_lo(),
                         &format!(
-                            "alternatively, on nightly, you might want to use \
-                             `#![feature(let_else)]` to handle the variant{} that {} matched",
+                            "alternatively, you might want to use \
+                             let else to handle the variant{} that {} matched",
                             pluralize!(witnesses.len()),
                             match witnesses.len() {
                                 1 => "isn't",

compiler/rustc_mir_dataflow/src/lib.rs

@@ -1,7 +1,7 @@
 #![feature(associated_type_defaults)]
 #![feature(box_patterns)]
 #![feature(exact_size_is_empty)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(min_specialization)]
 #![feature(once_cell)]
 #![feature(stmt_expr_attributes)]

compiler/rustc_mir_transform/src/lib.rs

@@ -1,7 +1,7 @@
 #![allow(rustc::potential_query_instability)]
 #![feature(box_patterns)]
 #![feature(let_chains)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![feature(map_try_insert)]
 #![feature(min_specialization)]
 #![feature(never_type)]

compiler/rustc_monomorphize/src/lib.rs

@@ -1,6 +1,6 @@
 #![feature(array_windows)]
 #![feature(control_flow_enum)]
-#![feature(let_else)]
+#![cfg_attr(bootstrap, feature(let_else))]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]