Merge #9138

9138: feat: Implement hover for lints r=Veykril a=Veykril

fixes https://github.com/rust-analyzer/rust-analyzer/issues/8857, fixes https://github.com/rust-analyzer/rust-analyzer/issues/3941

![URXBanNxYe](https://user-images.githubusercontent.com/3757771/120830905-4bd8da80-c55f-11eb-9f55-ff5a321726fa.gif)

We also generate the default lints(and lint groups 🎉) instead now by invoking `rustc -W help` and parsing the output from that.


Co-authored-by: Lukas Wirth <[email protected]>

2 files changed, 6919 insertions, 0 deletions

diff --git a/crates/ide_db/src/helpers.rs b/crates/ide_db/src/helpers.rs
index 21b48237a..00900cdc2 100644
--- a/crates/ide_db/src/helpers.rs
+++ b/crates/ide_db/src/helpers.rs
@@ -3,6 +3,7 @@ pub mod import_assets;
 pub mod insert_use;
 pub mod merge_imports;
 pub mod rust_doc;
+pub mod generated_lints;
 
 use std::collections::VecDeque;
 
diff --git a/crates/ide_db/src/helpers/generated_lints.rs b/crates/ide_db/src/helpers/generated_lints.rs
new file mode 100644
index 000000000..6ccb0478e
--- /dev/null
+++ b/crates/ide_db/src/helpers/generated_lints.rs
@@ -0,0 +1,6918 @@
+//! Generated file, do not edit by hand, see `xtask/src/codegen`
+
+pub struct Lint {
+    pub label: &'static str,
+    pub description: &'static str,
+}
+
+pub const DEFAULT_LINTS: &[Lint] = &[
+    Lint {
+        label: "absolute_paths_not_starting_with_crate",
+        description: r##"fully qualified paths that start with a module name instead of `crate`, `self`, or an extern crate name"##,
+    },
+    Lint { label: "ambiguous_associated_items", description: r##"ambiguous associated items"## },
+    Lint { label: "anonymous_parameters", description: r##"detects anonymous parameters"## },
+    Lint { label: "arithmetic_overflow", description: r##"arithmetic operation overflows"## },
+    Lint { label: "array_into_iter", description: r##"detects calling `into_iter` on arrays"## },
+    Lint {
+        label: "asm_sub_register",
+        description: r##"using only a subset of a register for inline asm inputs"##,
+    },
+    Lint { label: "bad_asm_style", description: r##"incorrect use of inline assembly"## },
+    Lint {
+        label: "bare_trait_objects",
+        description: r##"suggest using `dyn Trait` for trait objects"##,
+    },
+    Lint {
+        label: "bindings_with_variant_name",
+        description: r##"detects pattern bindings with the same name as one of the matched variants"##,
+    },
+    Lint { label: "box_pointers", description: r##"use of owned (Box type) heap memory"## },
+    Lint {
+        label: "cenum_impl_drop_cast",
+        description: r##"a C-like enum implementing Drop is cast"##,
+    },
+    Lint {
+        label: "clashing_extern_declarations",
+        description: r##"detects when an extern fn has been declared with the same name but different types"##,
+    },
+    Lint {
+        label: "coherence_leak_check",
+        description: r##"distinct impls distinguished only by the leak-check code"##,
+    },
+    Lint {
+        label: "conflicting_repr_hints",
+        description: r##"conflicts between `#[repr(..)]` hints that were previously accepted and used in practice"##,
+    },
+    Lint {
+        label: "confusable_idents",
+        description: r##"detects visually confusable pairs between identifiers"##,
+    },
+    Lint {
+        label: "const_err",
+        description: r##"constant evaluation encountered erroneous expression"##,
+    },
+    Lint {
+        label: "const_evaluatable_unchecked",
+        description: r##"detects a generic constant is used in a type without a emitting a warning"##,
+    },
+    Lint {
+        label: "const_item_mutation",
+        description: r##"detects attempts to mutate a `const` item"##,
+    },
+    Lint { label: "dead_code", description: r##"detect unused, unexported items"## },
+    Lint { label: "deprecated", description: r##"detects use of deprecated items"## },
+    Lint {
+        label: "deprecated_in_future",
+        description: r##"detects use of items that will be deprecated in a future version"##,
+    },
+    Lint {
+        label: "deref_nullptr",
+        description: r##"detects when an null pointer is dereferenced"##,
+    },
+    Lint {
+        label: "disjoint_capture_migration",
+        description: r##"Drop reorder and auto traits error because of `capture_disjoint_fields`"##,
+    },
+    Lint { label: "drop_bounds", description: r##"bounds of the form `T: Drop` are useless"## },
+    Lint {
+        label: "elided_lifetimes_in_paths",
+        description: r##"hidden lifetime parameters in types are deprecated"##,
+    },
+    Lint {
+        label: "ellipsis_inclusive_range_patterns",
+        description: r##"`...` range patterns are deprecated"##,
+    },
+    Lint {
+        label: "explicit_outlives_requirements",
+        description: r##"outlives requirements can be inferred"##,
+    },
+    Lint {
+        label: "exported_private_dependencies",
+        description: r##"public interface leaks type from a private dependency"##,
+    },
+    Lint { label: "forbidden_lint_groups", description: r##"applying forbid to lint-groups"## },
+    Lint {
+        label: "function_item_references",
+        description: r##"suggest casting to a function pointer when attempting to take references to function items"##,
+    },
+    Lint {
+        label: "future_incompatible",
+        description: r##"lint group for: keyword-idents, anonymous-parameters, ellipsis-inclusive-range-patterns, forbidden-lint-groups, illegal-floating-point-literal-pattern, private-in-public, pub-use-of-private-extern-crate, invalid-type-param-default, const-err, unaligned-references, patterns-in-fns-without-body, missing-fragment-specifier, late-bound-lifetime-arguments, order-dependent-trait-objects, coherence-leak-check, tyvar-behind-raw-pointer, bare-trait-objects, absolute-paths-not-starting-with-crate, unstable-name-collisions, where-clauses-object-safety, proc-macro-derive-resolution-fallback, macro-expanded-macro-exports-accessed-by-absolute-paths, ill-formed-attribute-input, conflicting-repr-hints, ambiguous-associated-items, mutable-borrow-reservation-conflict, indirect-structural-match, pointer-structural-match, nontrivial-structural-match, soft-unstable, cenum-impl-drop-cast, const-evaluatable-unchecked, uninhabited-static, unsupported-naked-functions, semicolon-in-expressions-from-macros, legacy-derive-helpers, proc-macro-back-compat, array-into-iter"##,
+    },
+    Lint {
+        label: "ill_formed_attribute_input",
+        description: r##"ill-formed attribute inputs that were previously accepted and used in practice"##,
+    },
+    Lint {
+        label: "illegal_floating_point_literal_pattern",
+        description: r##"floating-point literals cannot be used in patterns"##,
+    },
+    Lint {
+        label: "improper_ctypes",
+        description: r##"proper use of libc types in foreign modules"##,
+    },
+    Lint {
+        label: "improper_ctypes_definitions",
+        description: r##"proper use of libc types in foreign item definitions"##,
+    },
+    Lint {
+        label: "incomplete_features",
+        description: r##"incomplete features that may function improperly in some or all cases"##,
+    },
+    Lint { label: "incomplete_include", description: r##"trailing content in included file"## },
+    Lint {
+        label: "indirect_structural_match",
+        description: r##"constant used in pattern contains value of non-structural-match type in a field or a variant"##,
+    },
+    Lint {
+        label: "ineffective_unstable_trait_impl",
+        description: r##"detects `#[unstable]` on stable trait implementations for stable types"##,
+    },
+    Lint {
+        label: "inline_no_sanitize",
+        description: r##"detects incompatible use of `#[inline(always)]` and `#[no_sanitize(...)]`"##,
+    },
+    Lint {
+        label: "invalid_type_param_default",
+        description: r##"type parameter default erroneously allowed in invalid location"##,
+    },
+    Lint {
+        label: "invalid_value",
+        description: r##"an invalid value is being created (such as a null reference)"##,
+    },
+    Lint {
+        label: "irrefutable_let_patterns",
+        description: r##"detects irrefutable patterns in `if let` and `while let` statements"##,
+    },
+    Lint {
+        label: "keyword_idents",
+        description: r##"detects edition keywords being used as an identifier"##,
+    },
+    Lint { label: "large_assignments", description: r##"detects large moves or copies"## },
+    Lint {
+        label: "late_bound_lifetime_arguments",
+        description: r##"detects generic lifetime arguments in path segments with late bound lifetime parameters"##,
+    },
+    Lint {
+        label: "legacy_derive_helpers",
+        description: r##"detects derive helper attributes that are used before they are introduced"##,
+    },
+    Lint {
+        label: "macro_expanded_macro_exports_accessed_by_absolute_paths",
+        description: r##"macro-expanded `macro_export` macros from the current crate cannot be referred to by absolute paths"##,
+    },
+    Lint {
+        label: "macro_use_extern_crate",
+        description: r##"the `#[macro_use]` attribute is now deprecated in favor of using macros via the module system"##,
+    },
+    Lint {
+        label: "meta_variable_misuse",
+        description: r##"possible meta-variable misuse at macro definition"##,
+    },
+    Lint { label: "missing_abi", description: r##"No declared ABI for extern declaration"## },
+    Lint {
+        label: "missing_copy_implementations",
+        description: r##"detects potentially-forgotten implementations of `Copy`"##,
+    },
+    Lint {
+        label: "missing_debug_implementations",
+        description: r##"detects missing implementations of Debug"##,
+    },
+    Lint {
+        label: "missing_docs",
+        description: r##"detects missing documentation for public members"##,
+    },
+    Lint {
+        label: "missing_fragment_specifier",
+        description: r##"detects missing fragment specifiers in unused `macro_rules!` patterns"##,
+    },
+    Lint {
+        label: "mixed_script_confusables",
+        description: r##"detects Unicode scripts whose mixed script confusables codepoints are solely used"##,
+    },
+    Lint {
+        label: "mutable_borrow_reservation_conflict",
+        description: r##"reservation of a two-phased borrow conflicts with other shared borrows"##,
+    },
+    Lint {
+        label: "mutable_transmutes",
+        description: r##"mutating transmuted &mut T from &T may cause undefined behavior"##,
+    },
+    Lint {
+        label: "no_mangle_const_items",
+        description: r##"const items will not have their symbols exported"##,
+    },
+    Lint { label: "no_mangle_generic_items", description: r##"generic items must be mangled"## },
+    Lint { label: "non_ascii_idents", description: r##"detects non-ASCII identifiers"## },
+    Lint {
+        label: "non_camel_case_types",
+        description: r##"types, variants, traits and type parameters should have camel case names"##,
+    },
+    Lint {
+        label: "non_fmt_panic",
+        description: r##"detect single-argument panic!() invocations in which the argument is not a format string"##,
+    },
+    Lint {
+        label: "non_shorthand_field_patterns",
+        description: r##"using `Struct { x: x }` instead of `Struct { x }` in a pattern"##,
+    },
+    Lint {
+        label: "non_snake_case",
+        description: r##"variables, methods, functions, lifetime parameters and modules should have snake case names"##,
+    },
+    Lint {
+        label: "non_upper_case_globals",
+        description: r##"static constants should have uppercase identifiers"##,
+    },
+    Lint {
+        label: "nonstandard_style",
+        description: r##"lint group for: non-camel-case-types, non-snake-case, non-upper-case-globals"##,
+    },
+    Lint {
+        label: "nontrivial_structural_match",
+        description: r##"constant used in pattern of non-structural-match type and the constant's initializer expression contains values of non-structural-match types"##,
+    },
+    Lint {
+        label: "noop_method_call",
+        description: r##"detects the use of well-known noop methods"##,
+    },
+    Lint {
+        label: "or_patterns_back_compat",
+        description: r##"detects usage of old versions of or-patterns"##,
+    },
+    Lint {
+        label: "order_dependent_trait_objects",
+        description: r##"trait-object types were treated as different depending on marker-trait order"##,
+    },
+    Lint { label: "overflowing_literals", description: r##"literal out of range for its type"## },
+    Lint {
+        label: "overlapping_range_endpoints",
+        description: r##"detects range patterns with overlapping endpoints"##,
+    },
+    Lint { label: "path_statements", description: r##"path statements with no effect"## },
+    Lint {
+        label: "patterns_in_fns_without_body",
+        description: r##"patterns in functions without body were erroneously allowed"##,
+    },
+    Lint {
+        label: "pointer_structural_match",
+        description: r##"pointers are not structural-match"##,
+    },
+    Lint {
+        label: "private_in_public",
+        description: r##"detect private items in public interfaces not caught by the old implementation"##,
+    },
+    Lint {
+        label: "proc_macro_back_compat",
+        description: r##"detects usage of old versions of certain proc-macro crates"##,
+    },
+    Lint {
+        label: "proc_macro_derive_resolution_fallback",
+        description: r##"detects proc macro derives using inaccessible names from parent modules"##,
+    },
+    Lint {
+        label: "pub_use_of_private_extern_crate",
+        description: r##"detect public re-exports of private extern crates"##,
+    },
+    Lint {
+        label: "redundant_semicolons",
+        description: r##"detects unnecessary trailing semicolons"##,
+    },
+    Lint {
+        label: "renamed_and_removed_lints",
+        description: r##"lints that have been renamed or removed"##,
+    },
+    Lint {
+        label: "rust_2018_compatibility",
+        description: r##"lint group for: keyword-idents, anonymous-parameters, tyvar-behind-raw-pointer, absolute-paths-not-starting-with-crate"##,
+    },
+    Lint {
+        label: "rust_2018_idioms",
+        description: r##"lint group for: bare-trait-objects, unused-extern-crates, ellipsis-inclusive-range-patterns, elided-lifetimes-in-paths, explicit-outlives-requirements"##,
+    },
+    Lint {
+        label: "rust_2021_compatibility",
+        description: r##"lint group for: ellipsis-inclusive-range-patterns, bare-trait-objects"##,
+    },
+    Lint {
+        label: "semicolon_in_expressions_from_macros",
+        description: r##"trailing semicolon in macro body used as expression"##,
+    },
+    Lint {
+        label: "single_use_lifetimes",
+        description: r##"detects lifetime parameters that are only used once"##,
+    },
+    Lint {
+        label: "soft_unstable",
+        description: r##"a feature gate that doesn't break dependent crates"##,
+    },
+    Lint {
+        label: "stable_features",
+        description: r##"stable features found in `#[feature]` directive"##,
+    },
+    Lint {
+        label: "temporary_cstring_as_ptr",
+        description: r##"detects getting the inner pointer of a temporary `CString`"##,
+    },
+    Lint {
+        label: "trivial_bounds",
+        description: r##"these bounds don't depend on an type parameters"##,
+    },
+    Lint {
+        label: "trivial_casts",
+        description: r##"detects trivial casts which could be removed"##,
+    },
+    Lint {
+        label: "trivial_numeric_casts",
+        description: r##"detects trivial casts of numeric types which could be removed"##,
+    },
+    Lint {
+        label: "type_alias_bounds",
+        description: r##"bounds in type aliases are not enforced"##,
+    },
+    Lint {
+        label: "tyvar_behind_raw_pointer",
+        description: r##"raw pointer to an inference variable"##,
+    },
+    Lint {
+        label: "unaligned_references",
+        description: r##"detects unaligned references to fields of packed structs"##,
+    },
+    Lint {
+        label: "uncommon_codepoints",
+        description: r##"detects uncommon Unicode codepoints in identifiers"##,
+    },
+    Lint {
+        label: "unconditional_panic",
+        description: r##"operation will cause a panic at runtime"##,
+    },
+    Lint {
+        label: "unconditional_recursion",
+        description: r##"functions that cannot return without calling themselves"##,
+    },
+    Lint { label: "uninhabited_static", description: r##"uninhabited static"## },
+    Lint {
+        label: "unknown_crate_types",
+        description: r##"unknown crate type found in `#[crate_type]` directive"##,
+    },
+    Lint { label: "unknown_lints", description: r##"unrecognized lint attribute"## },
+    Lint {
+        label: "unnameable_test_items",
+        description: r##"detects an item that cannot be named being marked as `#[test_case]`"##,
+    },
+    Lint { label: "unreachable_code", description: r##"detects unreachable code paths"## },
+    Lint { label: "unreachable_patterns", description: r##"detects unreachable patterns"## },
+    Lint {
+        label: "unreachable_pub",
+        description: r##"`pub` items not reachable from crate root"##,
+    },
+    Lint { label: "unsafe_code", description: r##"usage of `unsafe` code"## },
+    Lint {
+        label: "unsafe_op_in_unsafe_fn",
+        description: r##"unsafe operations in unsafe functions without an explicit unsafe block are deprecated"##,
+    },
+    Lint {
+        label: "unstable_features",
+        description: r##"enabling unstable features (deprecated. do not use)"##,
+    },
+    Lint {
+        label: "unstable_name_collisions",
+        description: r##"detects name collision with an existing but unstable method"##,
+    },
+    Lint {
+        label: "unsupported_naked_functions",
+        description: r##"unsupported naked function definitions"##,
+    },
+    Lint {
+        label: "unused",
+        description: r##"lint group for: unused-imports, unused-variables, unused-assignments, dead-code, unused-mut, unreachable-code, unreachable-patterns, unused-must-use, unused-unsafe, path-statements, unused-attributes, unused-macros, unused-allocation, unused-doc-comments, unused-extern-crates, unused-features, unused-labels, unused-parens, unused-braces, redundant-semicolons"##,
+    },
+    Lint {
+        label: "unused_allocation",
+        description: r##"detects unnecessary allocations that can be eliminated"##,
+    },
+    Lint {
+        label: "unused_assignments",
+        description: r##"detect assignments that will never be read"##,
+    },
+    Lint {
+        label: "unused_attributes",
+        description: r##"detects attributes that were not used by the compiler"##,
+    },
+    Lint { label: "unused_braces", description: r##"unnecessary braces around an expression"## },
+    Lint {
+        label: "unused_comparisons",
+        description: r##"comparisons made useless by limits of the types involved"##,
+    },
+    Lint {
+        label: "unused_crate_dependencies",
+        description: r##"crate dependencies that are never used"##,
+    },
+    Lint {
+        label: "unused_doc_comments",
+        description: r##"detects doc comments that aren't used by rustdoc"##,
+    },
+    Lint { label: "unused_extern_crates", description: r##"extern crates that are never used"## },
+    Lint {
+        label: "unused_features",
+        description: r##"unused features found in crate-level `#[feature]` directives"##,
+    },
+    Lint {
+        label: "unused_import_braces",
+        description: r##"unnecessary braces around an imported item"##,
+    },
+    Lint { label: "unused_imports", description: r##"imports that are never used"## },
+    Lint { label: "unused_labels", description: r##"detects labels that are never used"## },
+    Lint {
+        label: "unused_lifetimes",
+        description: r##"detects lifetime parameters that are never used"##,
+    },
+    Lint { label: "unused_macros", description: r##"detects macros that were not used"## },
+    Lint {
+        label: "unused_must_use",
+        description: r##"unused result of a type flagged as `#[must_use]`"##,
+    },
+    Lint {
+        label: "unused_mut",
+        description: r##"detect mut variables which don't need to be mutable"##,
+    },
+    Lint {
+        label: "unused_parens",
+        description: r##"`if`, `match`, `while` and `return` do not need parentheses"##,
+    },
+    Lint {
+        label: "unused_qualifications",
+        description: r##"detects unnecessarily qualified names"##,
+    },
+    Lint {
+        label: "unused_results",
+        description: r##"unused result of an expression in a statement"##,
+    },
+    Lint { label: "unused_unsafe", description: r##"unnecessary use of an `unsafe` block"## },
+    Lint {
+        label: "unused_variables",
+        description: r##"detect variables which are not used in any way"##,
+    },
+    Lint {
+        label: "useless_deprecated",
+        description: r##"detects deprecation attributes with no effect"##,
+    },
+    Lint {
+        label: "variant_size_differences",
+        description: r##"detects enums with widely varying variant sizes"##,
+    },
+    Lint {
+        label: "warnings",
+        description: r##"mass-change the level for lints which produce warnings"##,
+    },
+    Lint {
+        label: "warnings",
+        description: r##"lint group for: all lints that are set to issue warnings"##,
+    },
+    Lint {
+        label: "where_clauses_object_safety",
+        description: r##"checks the object safety of where clauses"##,
+    },
+    Lint {
+        label: "while_true",
+        description: r##"suggest using `loop { }` instead of `while true { }`"##,
+    },
+];
+
+pub const FEATURES: &[Lint] = &[
+    Lint {
+        label: "abi_c_cmse_nonsecure_call",
+        description: r##"# `abi_c_cmse_nonsecure_call`
+
+The tracking issue for this feature is: [#81391]
+
+[#81391]: https://github.com/rust-lang/rust/issues/81391
+
+------------------------
+
+The [TrustZone-M
+feature](https://developer.arm.com/documentation/100690/latest/) is available
+for targets with the Armv8-M architecture profile (`thumbv8m` in their target
+name).
+LLVM, the Rust compiler and the linker are providing
+[support](https://developer.arm.com/documentation/ecm0359818/latest/) for the
+TrustZone-M feature.
+
+One of the things provided, with this unstable feature, is the
+`C-cmse-nonsecure-call` function ABI. This ABI is used on function pointers to
+non-secure code to mark a non-secure function call (see [section
+5.5](https://developer.arm.com/documentation/ecm0359818/latest/) for details).
+
+With this ABI, the compiler will do the following to perform the call:
+* save registers needed after the call to Secure memory
+* clear all registers that might contain confidential information
+* clear the Least Significant Bit of the function address
+* branches using the BLXNS instruction
+
+To avoid using the non-secure stack, the compiler will constrain the number and
+type of parameters/return value.
+
+The `extern "C-cmse-nonsecure-call"` ABI is otherwise equivalent to the
+`extern "C"` ABI.
+
+<!-- NOTE(ignore) this example is specific to thumbv8m targets -->
+
+``` rust,ignore
+#![no_std]
+#![feature(abi_c_cmse_nonsecure_call)]
+
+#[no_mangle]
+pub fn call_nonsecure_function(addr: usize) -> u32 {
+    let non_secure_function =
+        unsafe { core::mem::transmute::<usize, extern "C-cmse-nonsecure-call" fn() -> u32>(addr) };
+    non_secure_function()
+}
+```
+
+``` text
+$ rustc --emit asm --crate-type lib --target thumbv8m.main-none-eabi function.rs
+
+call_nonsecure_function:
+        .fnstart
+        .save   {r7, lr}
+        push    {r7, lr}
+        .setfp  r7, sp
+        mov     r7, sp
+        .pad    #16
+        sub     sp, #16
+        str     r0, [sp, #12]
+        ldr     r0, [sp, #12]
+        str     r0, [sp, #8]
+        b       .LBB0_1
+.LBB0_1:
+        ldr     r0, [sp, #8]
+        push.w  {r4, r5, r6, r7, r8, r9, r10, r11}
+        bic     r0, r0, #1
+        mov     r1, r0
+        mov     r2, r0
+        mov     r3, r0
+        mov     r4, r0
+        mov     r5, r0
+        mov     r6, r0
+        mov     r7, r0
+        mov     r8, r0
+        mov     r9, r0
+        mov     r10, r0
+        mov     r11, r0
+        mov     r12, r0
+        msr     apsr_nzcvq, r0
+        blxns   r0
+        pop.w   {r4, r5, r6, r7, r8, r9, r10, r11}
+        str     r0, [sp, #4]
+        b       .LBB0_2
+.LBB0_2:
+        ldr     r0, [sp, #4]
+        add     sp, #16
+        pop     {r7, pc}
+```
+"##,
+    },
+    Lint {
+        label: "abi_msp430_interrupt",
+        description: r##"# `abi_msp430_interrupt`
+
+The tracking issue for this feature is: [#38487]
+
+[#38487]: https://github.com/rust-lang/rust/issues/38487
+
+------------------------
+
+In the MSP430 architecture, interrupt handlers have a special calling
+convention. You can use the `"msp430-interrupt"` ABI to make the compiler apply
+the right calling convention to the interrupt handlers you define.
+
+<!-- NOTE(ignore) this example is specific to the msp430 target -->
+
+``` rust,ignore
+#![feature(abi_msp430_interrupt)]
+#![no_std]
+
+// Place the interrupt handler at the appropriate memory address
+// (Alternatively, you can use `#[used]` and remove `pub` and `#[no_mangle]`)
+#[link_section = "__interrupt_vector_10"]
+#[no_mangle]
+pub static TIM0_VECTOR: extern "msp430-interrupt" fn() = tim0;
+
+// The interrupt handler
+extern "msp430-interrupt" fn tim0() {
+    // ..
+}
+```
+
+``` text
+$ msp430-elf-objdump -CD ./target/msp430/release/app
+Disassembly of section __interrupt_vector_10:
+
+0000fff2 <TIM0_VECTOR>:
+    fff2:       00 c0           interrupt service routine at 0xc000
+
+Disassembly of section .text:
+
+0000c000 <int::tim0>:
+    c000:       00 13           reti
+```
+"##,
+    },
+    Lint {
+        label: "abi_ptx",
+        description: r##"# `abi_ptx`
+
+The tracking issue for this feature is: [#38788]
+
+[#38788]: https://github.com/rust-lang/rust/issues/38788
+
+------------------------
+
+When emitting PTX code, all vanilla Rust functions (`fn`) get translated to
+"device" functions. These functions are *not* callable from the host via the
+CUDA API so a crate with only device functions is not too useful!
+
+OTOH, "global" functions *can* be called by the host; you can think of them
+as the real public API of your crate. To produce a global function use the
+`"ptx-kernel"` ABI.
+
+<!-- NOTE(ignore) this example is specific to the nvptx targets -->
+
+``` rust,ignore
+#![feature(abi_ptx)]
+#![no_std]
+
+pub unsafe extern "ptx-kernel" fn global_function() {
+    device_function();
+}
+
+pub fn device_function() {
+    // ..
+}
+```
+
+``` text
+$ xargo rustc --target nvptx64-nvidia-cuda --release -- --emit=asm
+
+$ cat $(find -name '*.s')
+//
+// Generated by LLVM NVPTX Back-End
+//
+
+.version 3.2
+.target sm_20
+.address_size 64
+
+        // .globl       _ZN6kernel15global_function17h46111ebe6516b382E
+
+.visible .entry _ZN6kernel15global_function17h46111ebe6516b382E()
+{
+
+
+        ret;
+}
+
+        // .globl       _ZN6kernel15device_function17hd6a0e4993bbf3f78E
+.visible .func _ZN6kernel15device_function17hd6a0e4993bbf3f78E()
+{
+
+
+        ret;
+}
+```
+"##,
+    },
+    Lint {
+        label: "abi_thiscall",
+        description: r##"# `abi_thiscall`
+
+The tracking issue for this feature is: [#42202]
+
+[#42202]: https://github.com/rust-lang/rust/issues/42202
+
+------------------------
+
+The MSVC ABI on x86 Windows uses the `thiscall` calling convention for C++
+instance methods by default; it is identical to the usual (C) calling
+convention on x86 Windows except that the first parameter of the method,
+the `this` pointer, is passed in the ECX register.
+"##,
+    },
+    Lint {
+        label: "allocator_api",
+        description: r##"# `allocator_api`
+
+The tracking issue for this feature is [#32838]
+
+[#32838]: https://github.com/rust-lang/rust/issues/32838
+
+------------------------
+
+Sometimes you want the memory for one collection to use a different
+allocator than the memory for another collection. In this case,
+replacing the global allocator is not a workable option. Instead,
+you need to pass in an instance of an `AllocRef` to each collection
+for which you want a custom allocator.
+
+TBD
+"##,
+    },
+    Lint {
+        label: "allocator_internals",
+        description: r##"# `allocator_internals`
+
+This feature does not have a tracking issue, it is an unstable implementation
+detail of the `global_allocator` feature not intended for use outside the
+compiler.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "arbitrary_enum_discriminant",
+        description: r##"# `arbitrary_enum_discriminant`
+
+The tracking issue for this feature is: [#60553]
+
+[#60553]: https://github.com/rust-lang/rust/issues/60553
+
+------------------------
+
+The `arbitrary_enum_discriminant` feature permits tuple-like and
+struct-like enum variants with `#[repr(<int-type>)]` to have explicit discriminants.
+
+## Examples
+
+```rust
+#![feature(arbitrary_enum_discriminant)]
+
+#[allow(dead_code)]
+#[repr(u8)]
+enum Enum {
+    Unit = 3,
+    Tuple(u16) = 2,
+    Struct {
+        a: u8,
+        b: u16,
+    } = 1,
+}
+
+impl Enum {
+    fn tag(&self) -> u8 {
+        unsafe { *(self as *const Self as *const u8) }
+    }
+}
+
+assert_eq!(3, Enum::Unit.tag());
+assert_eq!(2, Enum::Tuple(5).tag());
+assert_eq!(1, Enum::Struct{a: 7, b: 11}.tag());
+```
+"##,
+    },
+    Lint {
+        label: "asm",
+        description: r##"# `asm`
+
+The tracking issue for this feature is: [#72016]
+
+[#72016]: https://github.com/rust-lang/rust/issues/72016
+
+------------------------
+
+For extremely low-level manipulations and performance reasons, one
+might wish to control the CPU directly. Rust supports using inline
+assembly to do this via the `asm!` macro.
+
+# Guide-level explanation
+[guide-level-explanation]: #guide-level-explanation
+
+Rust provides support for inline assembly via the `asm!` macro.
+It can be used to embed handwritten assembly in the assembly output generated by the compiler.
+Generally this should not be necessary, but might be where the required performance or timing
+cannot be otherwise achieved. Accessing low level hardware primitives, e.g. in kernel code, may also demand this functionality.
+
+> **Note**: the examples here are given in x86/x86-64 assembly, but other architectures are also supported.
+
+Inline assembly is currently supported on the following architectures:
+- x86 and x86-64
+- ARM
+- AArch64
+- RISC-V
+- NVPTX
+- PowerPC
+- Hexagon
+- MIPS32r2 and MIPS64r2
+- wasm32
+
+## Basic usage
+
+Let us start with the simplest possible example:
+
+```rust,allow_fail
+#![feature(asm)]
+unsafe {
+    asm!("nop");
+}
+```
+
+This will insert a NOP (no operation) instruction into the assembly generated by the compiler.
+Note that all `asm!` invocations have to be inside an `unsafe` block, as they could insert
+arbitrary instructions and break various invariants. The instructions to be inserted are listed
+in the first argument of the `asm!` macro as a string literal.
+
+## Inputs and outputs
+
+Now inserting an instruction that does nothing is rather boring. Let us do something that
+actually acts on data:
+
+```rust,allow_fail
+#![feature(asm)]
+let x: u64;
+unsafe {
+    asm!("mov {}, 5", out(reg) x);
+}
+assert_eq!(x, 5);
+```
+
+This will write the value `5` into the `u64` variable `x`.
+You can see that the string literal we use to specify instructions is actually a template string.
+It is governed by the same rules as Rust [format strings][format-syntax].
+The arguments that are inserted into the template however look a bit different then you may
+be familiar with. First we need to specify if the variable is an input or an output of the
+inline assembly. In this case it is an output. We declared this by writing `out`.
+We also need to specify in what kind of register the assembly expects the variable.
+In this case we put it in an arbitrary general purpose register by specifying `reg`.
+The compiler will choose an appropriate register to insert into
+the template and will read the variable from there after the inline assembly finishes executing.
+
+Let us see another example that also uses an input:
+
+```rust,allow_fail
+#![feature(asm)]
+let i: u64 = 3;
+let o: u64;
+unsafe {
+    asm!(
+        "mov {0}, {1}",
+        "add {0}, {number}",
+        out(reg) o,
+        in(reg) i,
+        number = const 5,
+    );
+}
+assert_eq!(o, 8);
+```
+
+This will add `5` to the input in variable `i` and write the result to variable `o`.
+The particular way this assembly does this is first copying the value from `i` to the output,
+and then adding `5` to it.
+
+The example shows a few things:
+
+First, we can see that `asm!` allows multiple template string arguments; each
+one is treated as a separate line of assembly code, as if they were all joined
+together with newlines between them. This makes it easy to format assembly
+code.
+
+Second, we can see that inputs are declared by writing `in` instead of `out`.
+
+Third, one of our operands has a type we haven't seen yet, `const`.
+This tells the compiler to expand this argument to value directly inside the assembly template.
+This is only possible for constants and literals.
+
+Fourth, we can see that we can specify an argument number, or name as in any format string.
+For inline assembly templates this is particularly useful as arguments are often used more than once.
+For more complex inline assembly using this facility is generally recommended, as it improves
+readability, and allows reordering instructions without changing the argument order.
+
+We can further refine the above example to avoid the `mov` instruction:
+
+```rust,allow_fail
+#![feature(asm)]
+let mut x: u64 = 3;
+unsafe {
+    asm!("add {0}, {number}", inout(reg) x, number = const 5);
+}
+assert_eq!(x, 8);
+```
+
+We can see that `inout` is used to specify an argument that is both input and output.
+This is different from specifying an input and output separately in that it is guaranteed to assign both to the same register.
+
+It is also possible to specify different variables for the input and output parts of an `inout` operand:
+
+```rust,allow_fail
+#![feature(asm)]
+let x: u64 = 3;
+let y: u64;
+unsafe {
+    asm!("add {0}, {number}", inout(reg) x => y, number = const 5);
+}
+assert_eq!(y, 8);
+```
+
+## Late output operands
+
+The Rust compiler is conservative with its allocation of operands. It is assumed that an `out`
+can be written at any time, and can therefore not share its location with any other argument.
+However, to guarantee optimal performance it is important to use as few registers as possible,
+so they won't have to be saved and reloaded around the inline assembly block.
+To achieve this Rust provides a `lateout` specifier. This can be used on any output that is
+written only after all inputs have been consumed.
+There is also a `inlateout` variant of this specifier.
+
+Here is an example where `inlateout` *cannot* be used:
+
+```rust,allow_fail
+#![feature(asm)]
+let mut a: u64 = 4;
+let b: u64 = 4;
+let c: u64 = 4;
+unsafe {
+    asm!(
+        "add {0}, {1}",
+        "add {0}, {2}",
+        inout(reg) a,
+        in(reg) b,
+        in(reg) c,
+    );
+}
+assert_eq!(a, 12);
+```
+
+Here the compiler is free to allocate the same register for inputs `b` and `c` since it knows they have the same value. However it must allocate a separate register for `a` since it uses `inout` and not `inlateout`. If `inlateout` was used, then `a` and `c` could be allocated to the same register, in which case the first instruction to overwrite the value of `c` and cause the assembly code to produce the wrong result.
+
+However the following example can use `inlateout` since the output is only modified after all input registers have been read:
+
+```rust,allow_fail
+#![feature(asm)]
+let mut a: u64 = 4;
+let b: u64 = 4;
+unsafe {
+    asm!("add {0}, {1}", inlateout(reg) a, in(reg) b);
+}
+assert_eq!(a, 8);
+```
+
+As you can see, this assembly fragment will still work correctly if `a` and `b` are assigned to the same register.
+
+## Explicit register operands
+
+Some instructions require that the operands be in a specific register.
+Therefore, Rust inline assembly provides some more specific constraint specifiers.
+While `reg` is generally available on any architecture, these are highly architecture specific. E.g. for x86 the general purpose registers `eax`, `ebx`, `ecx`, `edx`, `ebp`, `esi`, and `edi`
+among others can be addressed by their name.
+
+```rust,allow_fail,no_run
+#![feature(asm)]
+let cmd = 0xd1;
+unsafe {
+    asm!("out 0x64, eax", in("eax") cmd);
+}
+```
+
+In this example we call the `out` instruction to output the content of the `cmd` variable
+to port `0x64`. Since the `out` instruction only accepts `eax` (and its sub registers) as operand
+we had to use the `eax` constraint specifier.
+
+Note that unlike other operand types, explicit register operands cannot be used in the template string: you can't use `{}` and should write the register name directly instead. Also, they must appear at the end of the operand list after all other operand types.
+
+Consider this example which uses the x86 `mul` instruction:
+
+```rust,allow_fail
+#![feature(asm)]
+fn mul(a: u64, b: u64) -> u128 {
+    let lo: u64;
+    let hi: u64;
+
+    unsafe {
+        asm!(
+            // The x86 mul instruction takes rax as an implicit input and writes
+            // the 128-bit result of the multiplication to rax:rdx.
+            "mul {}",
+            in(reg) a,
+            inlateout("rax") b => lo,
+            lateout("rdx") hi
+        );
+    }
+
+    ((hi as u128) << 64) + lo as u128
+}
+```
+
+This uses the `mul` instruction to multiply two 64-bit inputs with a 128-bit result.
+The only explicit operand is a register, that we fill from the variable `a`.
+The second operand is implicit, and must be the `rax` register, which we fill from the variable `b`.
+The lower 64 bits of the result are stored in `rax` from which we fill the variable `lo`.
+The higher 64 bits are stored in `rdx` from which we fill the variable `hi`.
+
+## Clobbered registers
+
+In many cases inline assembly will modify state that is not needed as an output.
+Usually this is either because we have to use a scratch register in the assembly,
+or instructions modify state that we don't need to further examine.
+This state is generally referred to as being "clobbered".
+We need to tell the compiler about this since it may need to save and restore this state
+around the inline assembly block.
+
+```rust,allow_fail
+#![feature(asm)]
+let ebx: u32;
+let ecx: u32;
+
+unsafe {
+    asm!(
+        "cpuid",
+        // EAX 4 selects the "Deterministic Cache Parameters" CPUID leaf
+        inout("eax") 4 => _,
+        // ECX 0 selects the L0 cache information.
+        inout("ecx") 0 => ecx,
+        lateout("ebx") ebx,
+        lateout("edx") _,
+    );
+}
+
+println!(
+    "L1 Cache: {}",
+    ((ebx >> 22) + 1) * (((ebx >> 12) & 0x3ff) + 1) * ((ebx & 0xfff) + 1) * (ecx + 1)
+);
+```
+
+In the example above we use the `cpuid` instruction to get the L1 cache size.
+This instruction writes to `eax`, `ebx`, `ecx`, and `edx`, but for the cache size we only care about the contents of `ebx` and `ecx`.
+
+However we still need to tell the compiler that `eax` and `edx` have been modified so that it can save any values that were in these registers before the asm. This is done by declaring these as outputs but with `_` instead of a variable name, which indicates that the output value is to be discarded.
+
+This can also be used with a general register class (e.g. `reg`) to obtain a scratch register for use inside the asm code:
+
+```rust,allow_fail
+#![feature(asm)]
+// Multiply x by 6 using shifts and adds
+let mut x: u64 = 4;
+unsafe {
+    asm!(
+        "mov {tmp}, {x}",
+        "shl {tmp}, 1",
+        "shl {x}, 2",
+        "add {x}, {tmp}",
+        x = inout(reg) x,
+        tmp = out(reg) _,
+    );
+}
+assert_eq!(x, 4 * 6);
+```
+
+## Symbol operands
+
+A special operand type, `sym`, allows you to use the symbol name of a `fn` or `static` in inline assembly code.
+This allows you to call a function or access a global variable without needing to keep its address in a register.
+
+```rust,allow_fail
+#![feature(asm)]
+extern "C" fn foo(arg: i32) {
+    println!("arg = {}", arg);
+}
+
+fn call_foo(arg: i32) {
+    unsafe {
+        asm!(
+            "call {}",
+            sym foo,
+            // 1st argument in rdi, which is caller-saved
+            inout("rdi") arg => _,
+            // All caller-saved registers must be marked as clobbered
+            out("rax") _, out("rcx") _, out("rdx") _, out("rsi") _,
+            out("r8") _, out("r9") _, out("r10") _, out("r11") _,
+            out("xmm0") _, out("xmm1") _, out("xmm2") _, out("xmm3") _,
+            out("xmm4") _, out("xmm5") _, out("xmm6") _, out("xmm7") _,
+            out("xmm8") _, out("xmm9") _, out("xmm10") _, out("xmm11") _,
+            out("xmm12") _, out("xmm13") _, out("xmm14") _, out("xmm15") _,
+            // Also mark AVX-512 registers as clobbered. This is accepted by the
+            // compiler even if AVX-512 is not enabled on the current target.
+            out("xmm16") _, out("xmm17") _, out("xmm18") _, out("xmm19") _,
+            out("xmm20") _, out("xmm21") _, out("xmm22") _, out("xmm23") _,
+            out("xmm24") _, out("xmm25") _, out("xmm26") _, out("xmm27") _,
+            out("xmm28") _, out("xmm29") _, out("xmm30") _, out("xmm31") _,
+        )
+    }
+}
+```
+
+Note that the `fn` or `static` item does not need to be public or `#[no_mangle]`:
+the compiler will automatically insert the appropriate mangled symbol name into the assembly code.
+
+## Register template modifiers
+
+In some cases, fine control is needed over the way a register name is formatted when inserted into the template string. This is needed when an architecture's assembly language has several names for the same register, each typically being a "view" over a subset of the register (e.g. the low 32 bits of a 64-bit register).
+
+By default the compiler will always choose the name that refers to the full register size (e.g. `rax` on x86-64, `eax` on x86, etc).
+
+This default can be overriden by using modifiers on the template string operands, just like you would with format strings:
+
+```rust,allow_fail
+#![feature(asm)]
+let mut x: u16 = 0xab;
+
+unsafe {
+    asm!("mov {0:h}, {0:l}", inout(reg_abcd) x);
+}
+
+assert_eq!(x, 0xabab);
+```
+
+In this example, we use the `reg_abcd` register class to restrict the register allocator to the 4 legacy x86 register (`ax`, `bx`, `cx`, `dx`) of which the first two bytes can be addressed independently.
+
+Let us assume that the register allocator has chosen to allocate `x` in the `ax` register.
+The `h` modifier will emit the register name for the high byte of that register and the `l` modifier will emit the register name for the low byte. The asm code will therefore be expanded as `mov ah, al` which copies the low byte of the value into the high byte.
+
+If you use a smaller data type (e.g. `u16`) with an operand and forget the use template modifiers, the compiler will emit a warning and suggest the correct modifier to use.
+
+## Memory address operands
+
+Sometimes assembly instructions require operands passed via memory addresses/memory locations.
+You have to manually use the memory address syntax specified by the respectively architectures.
+For example, in x86/x86_64 and intel assembly syntax, you should wrap inputs/outputs in `[]`
+to indicate they are memory operands:
+
+```rust,allow_fail
+#![feature(asm, llvm_asm)]
+# fn load_fpu_control_word(control: u16) {
+unsafe {
+    asm!("fldcw [{}]", in(reg) &control, options(nostack));
+
+    // Previously this would have been written with the deprecated `llvm_asm!` like this
+    llvm_asm!("fldcw $0" :: "m" (control) :: "volatile");
+}
+# }
+```
+
+## Labels
+
+The compiler is allowed to instantiate multiple copies an `asm!` block, for example when the function containing it is inlined in multiple places. As a consequence, you should only use GNU assembler [local labels] inside inline assembly code. Defining symbols in assembly code may lead to assembler and/or linker errors due to duplicate symbol definitions.
+
+Moreover, due to [an llvm bug], you shouldn't use labels exclusively made of `0` and `1` digits, e.g. `0`, `11` or `101010`, as they may end up being interpreted as binary values.
+
+```rust,allow_fail
+#![feature(asm)]
+
+let mut a = 0;
+unsafe {
+    asm!(
+        "mov {0}, 10",
+        "2:",
+        "sub {0}, 1",
+        "cmp {0}, 3",
+        "jle 2f",
+        "jmp 2b",
+        "2:",
+        "add {0}, 2",
+        out(reg) a
+    );
+}
+assert_eq!(a, 5);
+```
+
+This will decrement the `{0}` register value from 10 to 3, then add 2 and store it in `a`.
+
+This example show a few thing:
+
+First that the same number can be used as a label multiple times in the same inline block.
+
+Second, that when a numeric label is used as a reference (as an instruction operand, for example), the suffixes b (“backward”) or f (“forward”) should be added to the numeric label. It will then refer to the nearest label defined by this number in this direction.
+
+[local labels]: https://sourceware.org/binutils/docs/as/Symbol-Names.html#Local-Labels
+[an llvm bug]: https://bugs.llvm.org/show_bug.cgi?id=36144
+
+## Options
+
+By default, an inline assembly block is treated the same way as an external FFI function call with a custom calling convention: it may read/write memory, have observable side effects, etc. However in many cases, it is desirable to give the compiler more information about what the assembly code is actually doing so that it can optimize better.
+
+Let's take our previous example of an `add` instruction:
+
+```rust,allow_fail
+#![feature(asm)]
+let mut a: u64 = 4;
+let b: u64 = 4;
+unsafe {
+    asm!(
+        "add {0}, {1}",
+        inlateout(reg) a, in(reg) b,
+        options(pure, nomem, nostack),
+    );
+}
+assert_eq!(a, 8);
+```
+
+Options can be provided as an optional final argument to the `asm!` macro. We specified three options here:
+- `pure` means that the asm code has no observable side effects and that its output depends only on its inputs. This allows the compiler optimizer to call the inline asm fewer times or even eliminate it entirely.
+- `nomem` means that the asm code does not read or write to memory. By default the compiler will assume that inline assembly can read or write any memory address that is accessible to it (e.g. through a pointer passed as an operand, or a global).
+- `nostack` means that the asm code does not push any data onto the stack. This allows the compiler to use optimizations such as the stack red zone on x86-64 to avoid stack pointer adjustments.
+
+These allow the compiler to better optimize code using `asm!`, for example by eliminating pure `asm!` blocks whose outputs are not needed.
+
+See the reference for the full list of available options and their effects.
+
+# Reference-level explanation
+[reference-level-explanation]: #reference-level-explanation
+
+Inline assembler is implemented as an unsafe macro `asm!()`.
+The first argument to this macro is a template string literal used to build the final assembly.
+The following arguments specify input and output operands.
+When required, options are specified as the final argument.
+
+The following ABNF specifies the general syntax:
+
+```text
+dir_spec := "in" / "out" / "lateout" / "inout" / "inlateout"
+reg_spec := <register class> / "<explicit register>"
+operand_expr := expr / "_" / expr "=>" expr / expr "=>" "_"
+reg_operand := dir_spec "(" reg_spec ")" operand_expr
+operand := reg_operand / "const" const_expr / "sym" path
+option := "pure" / "nomem" / "readonly" / "preserves_flags" / "noreturn" / "nostack" / "att_syntax"
+options := "options(" option *["," option] [","] ")"
+asm := "asm!(" format_string *("," format_string) *("," [ident "="] operand) ["," options] [","] ")"
+```
+
+The macro will initially be supported only on ARM, AArch64, Hexagon, PowerPC, x86, x86-64 and RISC-V targets. Support for more targets may be added in the future. The compiler will emit an error if `asm!` is used on an unsupported target.
+
+[format-syntax]: https://doc.rust-lang.org/std/fmt/#syntax
+
+## Template string arguments
+
+The assembler template uses the same syntax as [format strings][format-syntax] (i.e. placeholders are specified by curly braces). The corresponding arguments are accessed in order, by index, or by name. However, implicit named arguments (introduced by [RFC #2795][rfc-2795]) are not supported.
+
+An `asm!` invocation may have one or more template string arguments; an `asm!` with multiple template string arguments is treated as if all the strings were concatenated with a `\n` between them. The expected usage is for each template string argument to correspond to a line of assembly code. All template string arguments must appear before any other arguments.
+
+As with format strings, named arguments must appear after positional arguments. Explicit register operands must appear at the end of the operand list, after named arguments if any.
+
+Explicit register operands cannot be used by placeholders in the template string. All other named and positional operands must appear at least once in the template string, otherwise a compiler error is generated.
+
+The exact assembly code syntax is target-specific and opaque to the compiler except for the way operands are substituted into the template string to form the code passed to the assembler.
+
+The 5 targets specified in this RFC (x86, ARM, AArch64, RISC-V, Hexagon) all use the assembly code syntax of the GNU assembler (GAS). On x86, the `.intel_syntax noprefix` mode of GAS is used by default. On ARM, the `.syntax unified` mode is used. These targets impose an additional restriction on the assembly code: any assembler state (e.g. the current section which can be changed with `.section`) must be restored to its original value at the end of the asm string. Assembly code that does not conform to the GAS syntax will result in assembler-specific behavior.
+
+[rfc-2795]: https://github.com/rust-lang/rfcs/pull/2795
+
+## Operand type
+
+Several types of operands are supported:
+
+* `in(<reg>) <expr>`
+  - `<reg>` can refer to a register class or an explicit register. The allocated register name is substituted into the asm template string.
+  - The allocated register will contain the value of `<expr>` at the start of the asm code.
+  - The allocated register must contain the same value at the end of the asm code (except if a `lateout` is allocated to the same register).
+* `out(<reg>) <expr>`
+  - `<reg>` can refer to a register class or an explicit register. The allocated register name is substituted into the asm template string.
+  - The allocated register will contain an undefined value at the start of the asm code.
+  - `<expr>` must be a (possibly uninitialized) place expression, to which the contents of the allocated register is written to at the end of the asm code.
+  - An underscore (`_`) may be specified instead of an expression, which will cause the contents of the register to be discarded at the end of the asm code (effectively acting as a clobber).
+* `lateout(<reg>) <expr>`
+  - Identical to `out` except that the register allocator can reuse a register allocated to an `in`.
+  - You should only write to the register after all inputs are read, otherwise you may clobber an input.
+* `inout(<reg>) <expr>`
+  - `<reg>` can refer to a register class or an explicit register. The allocated register name is substituted into the asm template string.
+  - The allocated register will contain the value of `<expr>` at the start of the asm code.
+  - `<expr>` must be a mutable initialized place expression, to which the contents of the allocated register is written to at the end of the asm code.
+* `inout(<reg>) <in expr> => <out expr>`
+  - Same as `inout` except that the initial value of the register is taken from the value of `<in expr>`.
+  - `<out expr>` must be a (possibly uninitialized) place expression, to which the contents of the allocated register is written to at the end of the asm code.
+  - An underscore (`_`) may be specified instead of an expression for `<out expr>`, which will cause the contents of the register to be discarded at the end of the asm code (effectively acting as a clobber).
+  - `<in expr>` and `<out expr>` may have different types.
+* `inlateout(<reg>) <expr>` / `inlateout(<reg>) <in expr> => <out expr>`
+  - Identical to `inout` except that the register allocator can reuse a register allocated to an `in` (this can happen if the compiler knows the `in` has the same initial value as the `inlateout`).
+  - You should only write to the register after all inputs are read, otherwise you may clobber an input.
+* `const <expr>`
+  - `<expr>` must be an integer constant expression.
+  - The value of the expression is formatted as a string and substituted directly into the asm template string.
+* `sym <path>`
+  - `<path>` must refer to a `fn` or `static`.
+  - A mangled symbol name referring to the item is substituted into the asm template string.
+  - The substituted string does not include any modifiers (e.g. GOT, PLT, relocations, etc).
+  - `<path>` is allowed to point to a `#[thread_local]` static, in which case the asm code can combine the symbol with relocations (e.g. `@plt`, `@TPOFF`) to read from thread-local data.
+
+Operand expressions are evaluated from left to right, just like function call arguments. After the `asm!` has executed, outputs are written to in left to right order. This is significant if two outputs point to the same place: that place will contain the value of the rightmost output.
+
+## Register operands
+
+Input and output operands can be specified either as an explicit register or as a register class from which the register allocator can select a register. Explicit registers are specified as string literals (e.g. `"eax"`) while register classes are specified as identifiers (e.g. `reg`). Using string literals for register names enables support for architectures that use special characters in register names, such as MIPS (`$0`, `$1`, etc).
+
+Note that explicit registers treat register aliases (e.g. `r14` vs `lr` on ARM) and smaller views of a register (e.g. `eax` vs `rax`) as equivalent to the base register. It is a compile-time error to use the same explicit register for two input operands or two output operands. Additionally, it is also a compile-time error to use overlapping registers (e.g. ARM VFP) in input operands or in output operands.
+
+Only the following types are allowed as operands for inline assembly:
+- Integers (signed and unsigned)
+- Floating-point numbers
+- Pointers (thin only)
+- Function pointers
+- SIMD vectors (structs defined with `#[repr(simd)]` and which implement `Copy`). This includes architecture-specific vector types defined in `std::arch` such as `__m128` (x86) or `int8x16_t` (ARM).
+
+Here is the list of currently supported register classes:
+
+| Architecture | Register class | Registers | LLVM constraint code |
+| ------------ | -------------- | --------- | -------------------- |
+| x86 | `reg` | `ax`, `bx`, `cx`, `dx`, `si`, `di`, `bp`, `r[8-15]` (x86-64 only) | `r` |
+| x86 | `reg_abcd` | `ax`, `bx`, `cx`, `dx` | `Q` |
+| x86-32 | `reg_byte` | `al`, `bl`, `cl`, `dl`, `ah`, `bh`, `ch`, `dh` | `q` |
+| x86-64 | `reg_byte`\* | `al`, `bl`, `cl`, `dl`, `sil`, `dil`, `bpl`, `r[8-15]b` | `q` |
+| x86 | `xmm_reg` | `xmm[0-7]` (x86) `xmm[0-15]` (x86-64) | `x` |
+| x86 | `ymm_reg` | `ymm[0-7]` (x86) `ymm[0-15]` (x86-64) | `x` |
+| x86 | `zmm_reg` | `zmm[0-7]` (x86) `zmm[0-31]` (x86-64) | `v` |
+| x86 | `kreg` | `k[1-7]` | `Yk` |
+| AArch64 | `reg` | `x[0-30]` | `r` |
+| AArch64 | `vreg` | `v[0-31]` | `w` |
+| AArch64 | `vreg_low16` | `v[0-15]` | `x` |
+| ARM | `reg` | `r[0-12]`, `r14` | `r` |
+| ARM (Thumb) | `reg_thumb` | `r[0-r7]` | `l` |
+| ARM (ARM) | `reg_thumb` | `r[0-r12]`, `r14` | `l` |
+| ARM | `sreg` | `s[0-31]` | `t` |
+| ARM | `sreg_low16` | `s[0-15]` | `x` |
+| ARM | `dreg` | `d[0-31]` | `w` |
+| ARM | `dreg_low16` | `d[0-15]` | `t` |
+| ARM | `dreg_low8` | `d[0-8]` | `x` |
+| ARM | `qreg` | `q[0-15]` | `w` |
+| ARM | `qreg_low8` | `q[0-7]` | `t` |
+| ARM | `qreg_low4` | `q[0-3]` | `x` |
+| MIPS | `reg` | `$[2-25]` | `r` |
+| MIPS | `freg` | `$f[0-31]` | `f` |
+| NVPTX | `reg16` | None\* | `h` |
+| NVPTX | `reg32` | None\* | `r` |
+| NVPTX | `reg64` | None\* | `l` |
+| RISC-V | `reg` | `x1`, `x[5-7]`, `x[9-15]`, `x[16-31]` (non-RV32E) | `r` |
+| RISC-V | `freg` | `f[0-31]` | `f` |
+| Hexagon | `reg` | `r[0-28]` | `r` |
+| PowerPC | `reg` | `r[0-31]` | `r` |
+| PowerPC | `reg_nonzero` | | `r[1-31]` | `b` |
+| PowerPC | `freg` | `f[0-31]` | `f` |
+| wasm32 | `local` | None\* | `r` |
+
+> **Note**: On x86 we treat `reg_byte` differently from `reg` because the compiler can allocate `al` and `ah` separately whereas `reg` reserves the whole register.
+>
+> Note #2: On x86-64 the high byte registers (e.g. `ah`) are not available in the `reg_byte` register class.
+>
+> Note #3: NVPTX doesn't have a fixed register set, so named registers are not supported.
+>
+> Note #4: WebAssembly doesn't have registers, so named registers are not supported.
+
+Additional register classes may be added in the future based on demand (e.g. MMX, x87, etc).
+
+Each register class has constraints on which value types they can be used with. This is necessary because the way a value is loaded into a register depends on its type. For example, on big-endian systems, loading a `i32x4` and a `i8x16` into a SIMD register may result in different register contents even if the byte-wise memory representation of both values is identical. The availability of supported types for a particular register class may depend on what target features are currently enabled.
+
+| Architecture | Register class | Target feature | Allowed types |
+| ------------ | -------------- | -------------- | ------------- |
+| x86-32 | `reg` | None | `i16`, `i32`, `f32` |
+| x86-64 | `reg` | None | `i16`, `i32`, `f32`, `i64`, `f64` |
+| x86 | `reg_byte` | None | `i8` |
+| x86 | `xmm_reg` | `sse` | `i32`, `f32`, `i64`, `f64`, <br> `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4`, `f64x2` |
+| x86 | `ymm_reg` | `avx` | `i32`, `f32`, `i64`, `f64`, <br> `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4`, `f64x2` <br> `i8x32`, `i16x16`, `i32x8`, `i64x4`, `f32x8`, `f64x4` |
+| x86 | `zmm_reg` | `avx512f` | `i32`, `f32`, `i64`, `f64`, <br> `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4`, `f64x2` <br> `i8x32`, `i16x16`, `i32x8`, `i64x4`, `f32x8`, `f64x4` <br> `i8x64`, `i16x32`, `i32x16`, `i64x8`, `f32x16`, `f64x8` |
+| x86 | `kreg` | `axv512f` | `i8`, `i16` |
+| x86 | `kreg` | `axv512bw` | `i32`, `i64` |
+| AArch64 | `reg` | None | `i8`, `i16`, `i32`, `f32`, `i64`, `f64` |
+| AArch64 | `vreg` | `fp` | `i8`, `i16`, `i32`, `f32`, `i64`, `f64`, <br> `i8x8`, `i16x4`, `i32x2`, `i64x1`, `f32x2`, `f64x1`, <br> `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4`, `f64x2` |
+| ARM | `reg` | None | `i8`, `i16`, `i32`, `f32` |
+| ARM | `sreg` | `vfp2` | `i32`, `f32` |
+| ARM | `dreg` | `vfp2` | `i64`, `f64`, `i8x8`, `i16x4`, `i32x2`, `i64x1`, `f32x2` |
+| ARM | `qreg` | `neon` | `i8x16`, `i16x8`, `i32x4`, `i64x2`, `f32x4` |
+| MIPS32 | `reg` | None | `i8`, `i16`, `i32`, `f32` |
+| MIPS32 | `freg` | None | `f32`, `f64` |
+| MIPS64 | `reg` | None | `i8`, `i16`, `i32`, `i64`, `f32`, `f64` |
+| MIPS64 | `freg` | None | `f32`, `f64` |
+| NVPTX | `reg16` | None | `i8`, `i16` |
+| NVPTX | `reg32` | None | `i8`, `i16`, `i32`, `f32` |
+| NVPTX | `reg64` | None | `i8`, `i16`, `i32`, `f32`, `i64`, `f64` |
+| RISC-V32 | `reg` | None | `i8`, `i16`, `i32`, `f32` |
+| RISC-V64 | `reg` | None | `i8`, `i16`, `i32`, `f32`, `i64`, `f64` |
+| RISC-V | `freg` | `f` | `f32` |
+| RISC-V | `freg` | `d` | `f64` |
+| Hexagon | `reg` | None | `i8`, `i16`, `i32`, `f32` |
+| PowerPC | `reg` | None | `i8`, `i16`, `i32` |
+| PowerPC | `reg_nonzero` | None | `i8`, `i16`, `i32` |
+| PowerPC | `freg` | None | `f32`, `f64` |
+| wasm32 | `local` | None | `i8` `i16` `i32` `i64` `f32` `f64` |
+
+> **Note**: For the purposes of the above table pointers, function pointers and `isize`/`usize` are treated as the equivalent integer type (`i16`/`i32`/`i64` depending on the target).
+
+If a value is of a smaller size than the register it is allocated in then the upper bits of that register will have an undefined value for inputs and will be ignored for outputs. The only exception is the `freg` register class on RISC-V where `f32` values are NaN-boxed in a `f64` as required by the RISC-V architecture.
+
+When separate input and output expressions are specified for an `inout` operand, both expressions must have the same type. The only exception is if both operands are pointers or integers, in which case they are only required to have the same size. This restriction exists because the register allocators in LLVM and GCC sometimes cannot handle tied operands with different types.
+
+## Register names
+
+Some registers have multiple names. These are all treated by the compiler as identical to the base register name. Here is the list of all supported register aliases:
+
+| Architecture | Base register | Aliases |
+| ------------ | ------------- | ------- |
+| x86 | `ax` | `eax`, `rax` |
+| x86 | `bx` | `ebx`, `rbx` |
+| x86 | `cx` | `ecx`, `rcx` |
+| x86 | `dx` | `edx`, `rdx` |
+| x86 | `si` | `esi`, `rsi` |
+| x86 | `di` | `edi`, `rdi` |
+| x86 | `bp` | `bpl`, `ebp`, `rbp` |
+| x86 | `sp` | `spl`, `esp`, `rsp` |
+| x86 | `ip` | `eip`, `rip` |
+| x86 | `st(0)` | `st` |
+| x86 | `r[8-15]` | `r[8-15]b`, `r[8-15]w`, `r[8-15]d` |
+| x86 | `xmm[0-31]` | `ymm[0-31]`, `zmm[0-31]` |
+| AArch64 | `x[0-30]` | `w[0-30]` |
+| AArch64 | `x29` | `fp` |
+| AArch64 | `x30` | `lr` |
+| AArch64 | `sp` | `wsp` |
+| AArch64 | `xzr` | `wzr` |
+| AArch64 | `v[0-31]` | `b[0-31]`, `h[0-31]`, `s[0-31]`, `d[0-31]`, `q[0-31]` |
+| ARM | `r[0-3]` | `a[1-4]` |
+| ARM | `r[4-9]` | `v[1-6]` |
+| ARM | `r9` | `rfp` |
+| ARM | `r10` | `sl` |
+| ARM | `r11` | `fp` |
+| ARM | `r12` | `ip` |
+| ARM | `r13` | `sp` |
+| ARM | `r14` | `lr` |
+| ARM | `r15` | `pc` |
+| RISC-V | `x0` | `zero` |
+| RISC-V | `x1` | `ra` |
+| RISC-V | `x2` | `sp` |
+| RISC-V | `x3` | `gp` |
+| RISC-V | `x4` | `tp` |
+| RISC-V | `x[5-7]` | `t[0-2]` |
+| RISC-V | `x8` | `fp`, `s0` |
+| RISC-V | `x9` | `s1` |
+| RISC-V | `x[10-17]` | `a[0-7]` |
+| RISC-V | `x[18-27]` | `s[2-11]` |
+| RISC-V | `x[28-31]` | `t[3-6]` |
+| RISC-V | `f[0-7]` | `ft[0-7]` |
+| RISC-V | `f[8-9]` | `fs[0-1]` |
+| RISC-V | `f[10-17]` | `fa[0-7]` |
+| RISC-V | `f[18-27]` | `fs[2-11]` |
+| RISC-V | `f[28-31]` | `ft[8-11]` |
+| Hexagon | `r29` | `sp` |
+| Hexagon | `r30` | `fr` |
+| Hexagon | `r31` | `lr` |
+
+Some registers cannot be used for input or output operands:
+
+| Architecture | Unsupported register | Reason |
+| ------------ | -------------------- | ------ |
+| All | `sp` | The stack pointer must be restored to its original value at the end of an asm code block. |
+| All | `bp` (x86), `x29` (AArch64), `x8` (RISC-V), `fr` (Hexagon), `$fp` (MIPS) | The frame pointer cannot be used as an input or output. |
+| ARM | `r7` or `r11` | On ARM the frame pointer can be either `r7` or `r11` depending on the target. The frame pointer cannot be used as an input or output. |
+| All | `si` (x86-32), `bx` (x86-64), `r6` (ARM), `x19` (AArch64), `r19` (Hexagon), `x9` (RISC-V) | This is used internally by LLVM as a "base pointer" for functions with complex stack frames. |
+| x86 | `k0` | This is a constant zero register which can't be modified. |
+| x86 | `ip` | This is the program counter, not a real register. |
+| x86 | `mm[0-7]` | MMX registers are not currently supported (but may be in the future). |
+| x86 | `st([0-7])` | x87 registers are not currently supported (but may be in the future). |
+| AArch64 | `xzr` | This is a constant zero register which can't be modified. |
+| ARM | `pc` | This is the program counter, not a real register. |
+| ARM | `r9` | This is a reserved register on some ARM targets. |
+| MIPS | `$0` or `$zero` | This is a constant zero register which can't be modified. |
+| MIPS | `$1` or `$at` | Reserved for assembler. |
+| MIPS | `$26`/`$k0`, `$27`/`$k1` | OS-reserved registers. |
+| MIPS | `$28`/`$gp` | Global pointer cannot be used as inputs or outputs. |
+| MIPS | `$ra` | Return address cannot be used as inputs or outputs. |
+| RISC-V | `x0` | This is a constant zero register which can't be modified. |
+| RISC-V | `gp`, `tp` | These registers are reserved and cannot be used as inputs or outputs. |
+| Hexagon | `lr` | This is the link register which cannot be used as an input or output. |
+
+In some cases LLVM will allocate a "reserved register" for `reg` operands even though this register cannot be explicitly specified. Assembly code making use of reserved registers should be careful since `reg` operands may alias with those registers. Reserved registers are the frame pointer and base pointer
+- The frame pointer and LLVM base pointer on all architectures.
+- `r9` on ARM.
+- `x18` on AArch64.
+
+## Template modifiers
+
+The placeholders can be augmented by modifiers which are specified after the `:` in the curly braces. These modifiers do not affect register allocation, but change the way operands are formatted when inserted into the template string. Only one modifier is allowed per template placeholder.
+
+The supported modifiers are a subset of LLVM's (and GCC's) [asm template argument modifiers][llvm-argmod], but do not use the same letter codes.
+
+| Architecture | Register class | Modifier | Example output | LLVM modifier |
+| ------------ | -------------- | -------- | -------------- | ------------- |
+| x86-32 | `reg` | None | `eax` | `k` |
+| x86-64 | `reg` | None | `rax` | `q` |
+| x86-32 | `reg_abcd` | `l` | `al` | `b` |
+| x86-64 | `reg` | `l` | `al` | `b` |
+| x86 | `reg_abcd` | `h` | `ah` | `h` |
+| x86 | `reg` | `x` | `ax` | `w` |
+| x86 | `reg` | `e` | `eax` | `k` |
+| x86-64 | `reg` | `r` | `rax` | `q` |
+| x86 | `reg_byte` | None | `al` / `ah` | None |
+| x86 | `xmm_reg` | None | `xmm0` | `x` |
+| x86 | `ymm_reg` | None | `ymm0` | `t` |
+| x86 | `zmm_reg` | None | `zmm0` | `g` |
+| x86 | `*mm_reg` | `x` | `xmm0` | `x` |
+| x86 | `*mm_reg` | `y` | `ymm0` | `t` |
+| x86 | `*mm_reg` | `z` | `zmm0` | `g` |
+| x86 | `kreg` | None | `k1` | None |
+| AArch64 | `reg` | None | `x0` | `x` |
+| AArch64 | `reg` | `w` | `w0` | `w` |
+| AArch64 | `reg` | `x` | `x0` | `x` |
+| AArch64 | `vreg` | None | `v0` | None |
+| AArch64 | `vreg` | `v` | `v0` | None |
+| AArch64 | `vreg` | `b` | `b0` | `b` |
+| AArch64 | `vreg` | `h` | `h0` | `h` |
+| AArch64 | `vreg` | `s` | `s0` | `s` |
+| AArch64 | `vreg` | `d` | `d0` | `d` |
+| AArch64 | `vreg` | `q` | `q0` | `q` |
+| ARM | `reg` | None | `r0` | None |
+| ARM | `sreg` | None | `s0` | None |
+| ARM | `dreg` | None | `d0` | `P` |
+| ARM | `qreg` | None | `q0` | `q` |
+| ARM | `qreg` | `e` / `f` | `d0` / `d1` | `e` / `f` |
+| MIPS | `reg` | None | `$2` | None |
+| MIPS | `freg` | None | `$f0` | None |
+| NVPTX | `reg16` | None | `rs0` | None |
+| NVPTX | `reg32` | None | `r0` | None |
+| NVPTX | `reg64` | None | `rd0` | None |
+| RISC-V | `reg` | None | `x1` | None |
+| RISC-V | `freg` | None | `f0` | None |
+| Hexagon | `reg` | None | `r0` | None |
+| PowerPC | `reg` | None | `0` | None |
+| PowerPC | `reg_nonzero` | None | `3` | `b` |
+| PowerPC | `freg` | None | `0` | None |
+
+> Notes:
+> - on ARM `e` / `f`: this prints the low or high doubleword register name of a NEON quad (128-bit) register.
+> - on x86: our behavior for `reg` with no modifiers differs from what GCC does. GCC will infer the modifier based on the operand value type, while we default to the full register size.
+> - on x86 `xmm_reg`: the `x`, `t` and `g` LLVM modifiers are not yet implemented in LLVM (they are supported by GCC only), but this should be a simple change.
+
+As stated in the previous section, passing an input value smaller than the register width will result in the upper bits of the register containing undefined values. This is not a problem if the inline asm only accesses the lower bits of the register, which can be done by using a template modifier to use a subregister name in the asm code (e.g. `ax` instead of `rax`). Since this an easy pitfall, the compiler will suggest a template modifier to use where appropriate given the input type. If all references to an operand already have modifiers then the warning is suppressed for that operand.
+
+[llvm-argmod]: http://llvm.org/docs/LangRef.html#asm-template-argument-modifiers
+
+## Options
+
+Flags are used to further influence the behavior of the inline assembly block.
+Currently the following options are defined:
+- `pure`: The `asm` block has no side effects, and its outputs depend only on its direct inputs (i.e. the values themselves, not what they point to) or values read from memory (unless the `nomem` options is also set). This allows the compiler to execute the `asm` block fewer times than specified in the program (e.g. by hoisting it out of a loop) or even eliminate it entirely if the outputs are not used.
+- `nomem`: The `asm` blocks does not read or write to any memory. This allows the compiler to cache the values of modified global variables in registers across the `asm` block since it knows that they are not read or written to by the `asm`.
+- `readonly`: The `asm` block does not write to any memory. This allows the compiler to cache the values of unmodified global variables in registers across the `asm` block since it knows that they are not written to by the `asm`.
+- `preserves_flags`: The `asm` block does not modify the flags register (defined in the rules below). This allows the compiler to avoid recomputing the condition flags after the `asm` block.
+- `noreturn`: The `asm` block never returns, and its return type is defined as `!` (never). Behavior is undefined if execution falls through past the end of the asm code. A `noreturn` asm block behaves just like a function which doesn't return; notably, local variables in scope are not dropped before it is invoked.
+- `nostack`: The `asm` block does not push data to the stack, or write to the stack red-zone (if supported by the target). If this option is *not* used then the stack pointer is guaranteed to be suitably aligned (according to the target ABI) for a function call.
+- `att_syntax`: This option is only valid on x86, and causes the assembler to use the `.att_syntax prefix` mode of the GNU assembler. Register operands are substituted in with a leading `%`.
+
+The compiler performs some additional checks on options:
+- The `nomem` and `readonly` options are mutually exclusive: it is a compile-time error to specify both.
+- The `pure` option must be combined with either the `nomem` or `readonly` options, otherwise a compile-time error is emitted.
+- It is a compile-time error to specify `pure` on an asm block with no outputs or only discarded outputs (`_`).
+- It is a compile-time error to specify `noreturn` on an asm block with outputs.
+
+## Rules for inline assembly
+
+- Any registers not specified as inputs will contain an undefined value on entry to the asm block.
+  - An "undefined value" in the context of inline assembly means that the register can (non-deterministically) have any one of the possible values allowed by the architecture. Notably it is not the same as an LLVM `undef` which can have a different value every time you read it (since such a concept does not exist in assembly code).
+- Any registers not specified as outputs must have the same value upon exiting the asm block as they had on entry, otherwise behavior is undefined.
+  - This only applies to registers which can be specified as an input or output. Other registers follow target-specific rules.
+  - Note that a `lateout` may be allocated to the same register as an `in`, in which case this rule does not apply. Code should not rely on this however since it depends on the results of register allocation.
+- Behavior is undefined if execution unwinds out of an asm block.
+  - This also applies if the assembly code calls a function which then unwinds.
+- The set of memory locations that assembly code is allowed the read and write are the same as those allowed for an FFI function.
+  - Refer to the unsafe code guidelines for the exact rules.
+  - If the `readonly` option is set, then only memory reads are allowed.
+  - If the `nomem` option is set then no reads or writes to memory are allowed.
+  - These rules do not apply to memory which is private to the asm code, such as stack space allocated within the asm block.
+- The compiler cannot assume that the instructions in the asm are the ones that will actually end up executed.
+  - This effectively means that the compiler must treat the `asm!` as a black box and only take the interface specification into account, not the instructions themselves.
+  - Runtime code patching is allowed, via target-specific mechanisms (outside the scope of this RFC).
+- Unless the `nostack` option is set, asm code is allowed to use stack space below the stack pointer.
+  - On entry to the asm block the stack pointer is guaranteed to be suitably aligned (according to the target ABI) for a function call.
+  - You are responsible for making sure you don't overflow the stack (e.g. use stack probing to ensure you hit a guard page).
+  - You should adjust the stack pointer when allocating stack memory as required by the target ABI.
+  - The stack pointer must be restored to its original value before leaving the asm block.
+- If the `noreturn` option is set then behavior is undefined if execution falls through to the end of the asm block.
+- If the `pure` option is set then behavior is undefined if the `asm` has side-effects other than its direct outputs. Behavior is also undefined if two executions of the `asm` code with the same inputs result in different outputs.
+  - When used with the `nomem` option, "inputs" are just the direct inputs of the `asm!`.
+  - When used with the `readonly` option, "inputs" comprise the direct inputs of the `asm!` and any memory that the `asm!` block is allowed to read.
+- These flags registers must be restored upon exiting the asm block if the `preserves_flags` option is set:
+  - x86
+    - Status flags in `EFLAGS` (CF, PF, AF, ZF, SF, OF).
+    - Floating-point status word (all).
+    - Floating-point exception flags in `MXCSR` (PE, UE, OE, ZE, DE, IE).
+  - ARM
+    - Condition flags in `CPSR` (N, Z, C, V)
+    - Saturation flag in `CPSR` (Q)
+    - Greater than or equal flags in `CPSR` (GE).
+    - Condition flags in `FPSCR` (N, Z, C, V)
+    - Saturation flag in `FPSCR` (QC)
+    - Floating-point exception flags in `FPSCR` (IDC, IXC, UFC, OFC, DZC, IOC).
+  - AArch64
+    - Condition flags (`NZCV` register).
+    - Floating-point status (`FPSR` register).
+  - RISC-V
+    - Floating-point exception flags in `fcsr` (`fflags`).
+- On x86, the direction flag (DF in `EFLAGS`) is clear on entry to an asm block and must be clear on exit.
+  - Behavior is undefined if the direction flag is set on exiting an asm block.
+- The requirement of restoring the stack pointer and non-output registers to their original value only applies when exiting an `asm!` block.
+  - This means that `asm!` blocks that never return (even if not marked `noreturn`) don't need to preserve these registers.
+  - When returning to a different `asm!` block than you entered (e.g. for context switching), these registers must contain the value they had upon entering the `asm!` block that you are *exiting*.
+    - You cannot exit an `asm!` block that has not been entered. Neither can you exit an `asm!` block that has already been exited.
+    - You are responsible for switching any target-specific state (e.g. thread-local storage, stack bounds).
+    - The set of memory locations that you may access is the intersection of those allowed by the `asm!` blocks you entered and exited.
+- You cannot assume that an `asm!` block will appear exactly once in the output binary. The compiler is allowed to instantiate multiple copies of the `asm!` block, for example when the function containing it is inlined in multiple places.
+
+> **Note**: As a general rule, the flags covered by `preserves_flags` are those which are *not* preserved when performing a function call.
+"##,
+    },
+    Lint {
+        label: "auto_traits",
+        description: r##"# `auto_traits`
+
+The tracking issue for this feature is [#13231]
+
+[#13231]: https://github.com/rust-lang/rust/issues/13231
+
+----
+
+The `auto_traits` feature gate allows you to define auto traits.
+
+Auto traits, like [`Send`] or [`Sync`] in the standard library, are marker traits
+that are automatically implemented for every type, unless the type, or a type it contains,
+has explicitly opted out via a negative impl. (Negative impls are separately controlled
+by the `negative_impls` feature.)
+
+[`Send`]: https://doc.rust-lang.org/std/marker/trait.Send.html
+[`Sync`]: https://doc.rust-lang.org/std/marker/trait.Sync.html
+
+```rust,ignore (partial-example)
+impl !Trait for Type {}
+```
+
+Example:
+
+```rust
+#![feature(negative_impls)]
+#![feature(auto_traits)]
+
+auto trait Valid {}
+
+struct True;
+struct False;
+
+impl !Valid for False {}
+
+struct MaybeValid<T>(T);
+
+fn must_be_valid<T: Valid>(_t: T) { }
+
+fn main() {
+    // works
+    must_be_valid( MaybeValid(True) );
+
+    // compiler error - trait bound not satisfied
+    // must_be_valid( MaybeValid(False) );
+}
+```
+
+## Automatic trait implementations
+
+When a type is declared as an `auto trait`, we will automatically
+create impls for every struct/enum/union, unless an explicit impl is
+provided. These automatic impls contain a where clause for each field
+of the form `T: AutoTrait`, where `T` is the type of the field and
+`AutoTrait` is the auto trait in question. As an example, consider the
+struct `List` and the auto trait `Send`:
+
+```rust
+struct List<T> {
+  data: T,
+  next: Option<Box<List<T>>>,
+}
+```
+
+Presuming that there is no explicit impl of `Send` for `List`, the
+compiler will supply an automatic impl of the form:
+
+```rust
+struct List<T> {
+  data: T,
+  next: Option<Box<List<T>>>,
+}
+
+unsafe impl<T> Send for List<T>
+where
+  T: Send, // from the field `data`
+  Option<Box<List<T>>>: Send, // from the field `next`
+{ }
+```
+
+Explicit impls may be either positive or negative. They take the form:
+
+```rust,ignore (partial-example)
+impl<...> AutoTrait for StructName<..> { }
+impl<...> !AutoTrait for StructName<..> { }
+```
+
+## Coinduction: Auto traits permit cyclic matching
+
+Unlike ordinary trait matching, auto traits are **coinductive**. This
+means, in short, that cycles which occur in trait matching are
+considered ok. As an example, consider the recursive struct `List`
+introduced in the previous section. In attempting to determine whether
+`List: Send`, we would wind up in a cycle: to apply the impl, we must
+show that `Option<Box<List>>: Send`, which will in turn require
+`Box<List>: Send` and then finally `List: Send` again. Under ordinary
+trait matching, this cycle would be an error, but for an auto trait it
+is considered a successful match.
+
+## Items
+
+Auto traits cannot have any trait items, such as methods or associated types. This ensures that we can generate default implementations.
+
+## Supertraits
+
+Auto traits cannot have supertraits. This is for soundness reasons, as the interaction of coinduction with implied bounds is difficult to reconcile.
+"##,
+    },
+    Lint {
+        label: "box_patterns",
+        description: r##"# `box_patterns`
+
+The tracking issue for this feature is: [#29641]
+
+[#29641]: https://github.com/rust-lang/rust/issues/29641
+
+See also [`box_syntax`](box-syntax.md)
+
+------------------------
+
+Box patterns let you match on `Box<T>`s:
+
+
+```rust
+#![feature(box_patterns)]
+
+fn main() {
+    let b = Some(Box::new(5));
+    match b {
+        Some(box n) if n < 0 => {
+            println!("Box contains negative number {}", n);
+        },
+        Some(box n) if n >= 0 => {
+            println!("Box contains non-negative number {}", n);
+        },
+        None => {
+            println!("No box");
+        },
+        _ => unreachable!()
+    }
+}
+```
+"##,
+    },
+    Lint {
+        label: "box_syntax",
+        description: r##"# `box_syntax`
+
+The tracking issue for this feature is: [#49733]
+
+[#49733]: https://github.com/rust-lang/rust/issues/49733
+
+See also [`box_patterns`](box-patterns.md)
+
+------------------------
+
+Currently the only stable way to create a `Box` is via the `Box::new` method.
+Also it is not possible in stable Rust to destructure a `Box` in a match
+pattern. The unstable `box` keyword can be used to create a `Box`. An example
+usage would be:
+
+```rust
+#![feature(box_syntax)]
+
+fn main() {
+    let b = box 5;
+}
+```
+"##,
+    },
+    Lint {
+        label: "c_unwind",
+        description: r##"# `c_unwind`
+
+The tracking issue for this feature is: [#74990]
+
+[#74990]: https://github.com/rust-lang/rust/issues/74990
+
+------------------------
+
+Introduces four new ABI strings: "C-unwind", "stdcall-unwind",
+"thiscall-unwind", and "system-unwind". These enable unwinding from other
+languages (such as C++) into Rust frames and from Rust into other languages.
+
+See [RFC 2945] for more information.
+
+[RFC 2945]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
+"##,
+    },
+    Lint {
+        label: "c_variadic",
+        description: r##"# `c_variadic`
+
+The tracking issue for this feature is: [#44930]
+
+[#44930]: https://github.com/rust-lang/rust/issues/44930
+
+------------------------
+
+The `c_variadic` language feature enables C-variadic functions to be
+defined in Rust. The may be called both from within Rust and via FFI.
+
+## Examples
+
+```rust
+#![feature(c_variadic)]
+
+pub unsafe extern "C" fn add(n: usize, mut args: ...) -> usize {
+    let mut sum = 0;
+    for _ in 0..n {
+        sum += args.arg::<usize>();
+    }
+    sum
+}
+```
+"##,
+    },
+    Lint {
+        label: "c_variadic",
+        description: r##"# `c_variadic`
+
+The tracking issue for this feature is: [#44930]
+
+[#44930]: https://github.com/rust-lang/rust/issues/44930
+
+------------------------
+
+The `c_variadic` library feature exposes the `VaList` structure,
+Rust's analogue of C's `va_list` type.
+
+## Examples
+
+```rust
+#![feature(c_variadic)]
+
+use std::ffi::VaList;
+
+pub unsafe extern "C" fn vadd(n: usize, mut args: VaList) -> usize {
+    let mut sum = 0;
+    for _ in 0..n {
+        sum += args.arg::<usize>();
+    }
+    sum
+}
+```
+"##,
+    },
+    Lint {
+        label: "c_void_variant",
+        description: r##"# `c_void_variant`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "cfg_panic",
+        description: r##"# `cfg_panic`
+
+The tracking issue for this feature is: [#77443]
+
+[#77443]: https://github.com/rust-lang/rust/issues/77443
+
+------------------------
+
+The `cfg_panic` feature makes it possible to execute different code
+depending on the panic strategy.
+
+Possible values at the moment are `"unwind"` or `"abort"`, although
+it is possible that new panic strategies may be added to Rust in the
+future.
+
+## Examples
+
+```rust
+#![feature(cfg_panic)]
+
+#[cfg(panic = "unwind")]
+fn a() {
+    // ...
+}
+
+#[cfg(not(panic = "unwind"))]
+fn a() {
+    // ...
+}
+
+fn b() {
+    if cfg!(panic = "abort") {
+        // ...
+    } else {
+        // ...
+    }
+}
+```
+"##,
+    },
+    Lint {
+        label: "cfg_sanitize",
+        description: r##"# `cfg_sanitize`
+
+The tracking issue for this feature is: [#39699]
+
+[#39699]: https://github.com/rust-lang/rust/issues/39699
+
+------------------------
+
+The `cfg_sanitize` feature makes it possible to execute different code
+depending on whether a particular sanitizer is enabled or not.
+
+## Examples
+
+```rust
+#![feature(cfg_sanitize)]
+
+#[cfg(sanitize = "thread")]
+fn a() {
+    // ...
+}
+
+#[cfg(not(sanitize = "thread"))]
+fn a() {
+    // ...
+}
+
+fn b() {
+    if cfg!(sanitize = "leak") {
+        // ...
+    } else {
+        // ...
+    }
+}
+```
+"##,
+    },
+    Lint {
+        label: "cfg_version",
+        description: r##"# `cfg_version`
+
+The tracking issue for this feature is: [#64796]
+
+[#64796]: https://github.com/rust-lang/rust/issues/64796
+
+------------------------
+
+The `cfg_version` feature makes it possible to execute different code
+depending on the compiler version. It will return true if the compiler
+version is greater than or equal to the specified version.
+
+## Examples
+
+```rust
+#![feature(cfg_version)]
+
+#[cfg(version("1.42"))] // 1.42 and above
+fn a() {
+    // ...
+}
+
+#[cfg(not(version("1.42")))] // 1.41 and below
+fn a() {
+    // ...
+}
+
+fn b() {
+    if cfg!(version("1.42")) {
+        // ...
+    } else {
+        // ...
+    }
+}
+```
+"##,
+    },
+    Lint {
+        label: "char_error_internals",
+        description: r##"# `char_error_internals`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "cmse_nonsecure_entry",
+        description: r##"# `cmse_nonsecure_entry`
+
+The tracking issue for this feature is: [#75835]
+
+[#75835]: https://github.com/rust-lang/rust/issues/75835
+
+------------------------
+
+The [TrustZone-M
+feature](https://developer.arm.com/documentation/100690/latest/) is available
+for targets with the Armv8-M architecture profile (`thumbv8m` in their target
+name).
+LLVM, the Rust compiler and the linker are providing
+[support](https://developer.arm.com/documentation/ecm0359818/latest/) for the
+TrustZone-M feature.
+
+One of the things provided, with this unstable feature, is the
+`cmse_nonsecure_entry` attribute.  This attribute marks a Secure function as an
+entry function (see [section
+5.4](https://developer.arm.com/documentation/ecm0359818/latest/) for details).
+With this attribute, the compiler will do the following:
+* add a special symbol on the function which is the `__acle_se_` prefix and the
+  standard function name
+* constrain the number of parameters to avoid using the Non-Secure stack
+* before returning from the function, clear registers that might contain Secure
+  information
+* use the `BXNS` instruction to return
+
+Because the stack can not be used to pass parameters, there will be compilation
+errors if:
+* the total size of all parameters is too big (for example more than four 32
+  bits integers)
+* the entry function is not using a C ABI
+
+The special symbol `__acle_se_` will be used by the linker to generate a secure
+gateway veneer.
+
+<!-- NOTE(ignore) this example is specific to thumbv8m targets -->
+
+``` rust,ignore
+#![feature(cmse_nonsecure_entry)]
+
+#[no_mangle]
+#[cmse_nonsecure_entry]
+pub extern "C" fn entry_function(input: u32) -> u32 {
+    input + 6
+}
+```
+
+``` text
+$ rustc --emit obj --crate-type lib --target thumbv8m.main-none-eabi function.rs
+$ arm-none-eabi-objdump -D function.o
+
+00000000 <entry_function>:
+   0:   b580            push    {r7, lr}
+   2:   466f            mov     r7, sp
+   4:   b082            sub     sp, #8
+   6:   9001            str     r0, [sp, #4]
+   8:   1d81            adds    r1, r0, #6
+   a:   460a            mov     r2, r1
+   c:   4281            cmp     r1, r0
+   e:   9200            str     r2, [sp, #0]
+  10:   d30b            bcc.n   2a <entry_function+0x2a>
+  12:   e7ff            b.n     14 <entry_function+0x14>
+  14:   9800            ldr     r0, [sp, #0]
+  16:   b002            add     sp, #8
+  18:   e8bd 4080       ldmia.w sp!, {r7, lr}
+  1c:   4671            mov     r1, lr
+  1e:   4672            mov     r2, lr
+  20:   4673            mov     r3, lr
+  22:   46f4            mov     ip, lr
+  24:   f38e 8800       msr     CPSR_f, lr
+  28:   4774            bxns    lr
+  2a:   f240 0000       movw    r0, #0
+  2e:   f2c0 0000       movt    r0, #0
+  32:   f240 0200       movw    r2, #0
+  36:   f2c0 0200       movt    r2, #0
+  3a:   211c            movs    r1, #28
+  3c:   f7ff fffe       bl      0 <_ZN4core9panicking5panic17h5c028258ca2fb3f5E>
+  40:   defe            udf     #254    ; 0xfe
+```
+"##,
+    },
+    Lint {
+        label: "compiler_builtins",
+        description: r##"# `compiler_builtins`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "concat_idents",
+        description: r##"# `concat_idents`
+
+The tracking issue for this feature is: [#29599]
+
+[#29599]: https://github.com/rust-lang/rust/issues/29599
+
+------------------------
+
+The `concat_idents` feature adds a macro for concatenating multiple identifiers
+into one identifier.
+
+## Examples
+
+```rust
+#![feature(concat_idents)]
+
+fn main() {
+    fn foobar() -> u32 { 23 }
+    let f = concat_idents!(foo, bar);
+    assert_eq!(f(), 23);
+}
+```
+"##,
+    },
+    Lint {
+        label: "const_eval_limit",
+        description: r##"# `const_eval_limit`
+
+The tracking issue for this feature is: [#67217]
+
+[#67217]: https://github.com/rust-lang/rust/issues/67217
+
+The `const_eval_limit` allows someone to limit the evaluation steps the CTFE undertakes to evaluate a `const fn`.
+"##,
+    },
+    Lint {
+        label: "core_intrinsics",
+        description: r##"# `core_intrinsics`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "core_panic",
+        description: r##"# `core_panic`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "core_private_bignum",
+        description: r##"# `core_private_bignum`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "core_private_diy_float",
+        description: r##"# `core_private_diy_float`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "crate_visibility_modifier",
+        description: r##"# `crate_visibility_modifier`
+
+The tracking issue for this feature is: [#53120]
+
+[#53120]: https://github.com/rust-lang/rust/issues/53120
+
+-----
+
+The `crate_visibility_modifier` feature allows the `crate` keyword to be used
+as a visibility modifier synonymous to `pub(crate)`, indicating that a type
+(function, _&c._) is to be visible to the entire enclosing crate, but not to
+other crates.
+
+```rust
+#![feature(crate_visibility_modifier)]
+
+crate struct Foo {
+    bar: usize,
+}
+```
+"##,
+    },
+    Lint {
+        label: "custom_test_frameworks",
+        description: r##"# `custom_test_frameworks`
+
+The tracking issue for this feature is: [#50297]
+
+[#50297]: https://github.com/rust-lang/rust/issues/50297
+
+------------------------
+
+The `custom_test_frameworks` feature allows the use of `#[test_case]` and `#![test_runner]`.
+Any function, const, or static can be annotated with `#[test_case]` causing it to be aggregated (like `#[test]`)
+and be passed to the test runner determined by the `#![test_runner]` crate attribute.
+
+```rust
+#![feature(custom_test_frameworks)]
+#![test_runner(my_runner)]
+
+fn my_runner(tests: &[&i32]) {
+    for t in tests {
+        if **t == 0 {
+            println!("PASSED");
+        } else {
+            println!("FAILED");
+        }
+    }
+}
+
+#[test_case]
+const WILL_PASS: i32 = 0;
+
+#[test_case]
+const WILL_FAIL: i32 = 4;
+```
+"##,
+    },
+    Lint {
+        label: "dec2flt",
+        description: r##"# `dec2flt`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "default_free_fn",
+        description: r##"# `default_free_fn`
+
+The tracking issue for this feature is: [#73014]
+
+[#73014]: https://github.com/rust-lang/rust/issues/73014
+
+------------------------
+
+Adds a free `default()` function to the `std::default` module.  This function
+just forwards to [`Default::default()`], but may remove repetition of the word
+"default" from the call site.
+
+[`Default::default()`]: https://doc.rust-lang.org/nightly/std/default/trait.Default.html#tymethod.default
+
+Here is an example:
+
+```rust
+#![feature(default_free_fn)]
+use std::default::default;
+
+#[derive(Default)]
+struct AppConfig {
+    foo: FooConfig,
+    bar: BarConfig,
+}
+
+#[derive(Default)]
+struct FooConfig {
+    foo: i32,
+}
+
+#[derive(Default)]
+struct BarConfig {
+    bar: f32,
+    baz: u8,
+}
+
+fn main() {
+    let options = AppConfig {
+        foo: default(),
+        bar: BarConfig {
+            bar: 10.1,
+            ..default()
+        },
+    };
+}
+```
+"##,
+    },
+    Lint {
+        label: "derive_clone_copy",
+        description: r##"# `derive_clone_copy`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "derive_eq",
+        description: r##"# `derive_eq`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "doc_cfg",
+        description: r##"# `doc_cfg`
+
+The tracking issue for this feature is: [#43781]
+
+------
+
+The `doc_cfg` feature allows an API be documented as only available in some specific platforms.
+This attribute has two effects:
+
+1. In the annotated item's documentation, there will be a message saying "This is supported on
+    (platform) only".
+
+2. The item's doc-tests will only run on the specific platform.
+
+In addition to allowing the use of the `#[doc(cfg)]` attribute, this feature enables the use of a
+special conditional compilation flag, `#[cfg(doc)]`, set whenever building documentation on your
+crate.
+
+This feature was introduced as part of PR [#43348] to allow the platform-specific parts of the
+standard library be documented.
+
+```rust
+#![feature(doc_cfg)]
+
+#[cfg(any(windows, doc))]
+#[doc(cfg(windows))]
+/// The application's icon in the notification area (a.k.a. system tray).
+///
+/// # Examples
+///
+/// ```no_run
+/// extern crate my_awesome_ui_library;
+/// use my_awesome_ui_library::current_app;
+/// use my_awesome_ui_library::windows::notification;
+///
+/// let icon = current_app().get::<notification::Icon>();
+/// icon.show();
+/// icon.show_message("Hello");
+/// ```
+pub struct Icon {
+    // ...
+}
+```
+
+[#43781]: https://github.com/rust-lang/rust/issues/43781
+[#43348]: https://github.com/rust-lang/rust/issues/43348
+"##,
+    },
+    Lint {
+        label: "doc_masked",
+        description: r##"# `doc_masked`
+
+The tracking issue for this feature is: [#44027]
+
+-----
+
+The `doc_masked` feature allows a crate to exclude types from a given crate from appearing in lists
+of trait implementations. The specifics of the feature are as follows:
+
+1. When rustdoc encounters an `extern crate` statement annotated with a `#[doc(masked)]` attribute,
+   it marks the crate as being masked.
+
+2. When listing traits a given type implements, rustdoc ensures that traits from masked crates are
+   not emitted into the documentation.
+
+3. When listing types that implement a given trait, rustdoc ensures that types from masked crates
+   are not emitted into the documentation.
+
+This feature was introduced in PR [#44026] to ensure that compiler-internal and
+implementation-specific types and traits were not included in the standard library's documentation.
+Such types would introduce broken links into the documentation.
+
+[#44026]: https://github.com/rust-lang/rust/pull/44026
+[#44027]: https://github.com/rust-lang/rust/pull/44027
+"##,
+    },
+    Lint {
+        label: "doc_notable_trait",
+        description: r##"# `doc_notable_trait`
+
+The tracking issue for this feature is: [#45040]
+
+The `doc_notable_trait` feature allows the use of the `#[doc(notable_trait)]`
+attribute, which will display the trait in a "Notable traits" dialog for
+functions returning types that implement the trait. For example, this attribute
+is applied to the `Iterator`, `Future`, `io::Read`, and `io::Write` traits in
+the standard library.
+
+You can do this on your own traits like so:
+
+```
+#![feature(doc_notable_trait)]
+
+#[doc(notable_trait)]
+pub trait MyTrait {}
+
+pub struct MyStruct;
+impl MyTrait for MyStruct {}
+
+/// The docs for this function will have a button that displays a dialog about
+/// `MyStruct` implementing `MyTrait`.
+pub fn my_fn() -> MyStruct { MyStruct }
+```
+
+This feature was originally implemented in PR [#45039].
+
+See also its documentation in [the rustdoc book][rustdoc-book-notable_trait].
+
+[#45040]: https://github.com/rust-lang/rust/issues/45040
+[#45039]: https://github.com/rust-lang/rust/pull/45039
+[rustdoc-book-notable_trait]: ../../rustdoc/unstable-features.html#adding-your-trait-to-the-notable-traits-dialog
+"##,
+    },
+    Lint {
+        label: "external_doc",
+        description: r##"# `external_doc`
+
+The tracking issue for this feature is: [#44732]
+
+The `external_doc` feature allows the use of the `include` parameter to the `#[doc]` attribute, to
+include external files in documentation. Use the attribute in place of, or in addition to, regular
+doc comments and `#[doc]` attributes, and `rustdoc` will load the given file when it renders
+documentation for your crate.
+
+With the following files in the same directory:
+
+`external-doc.md`:
+
+```markdown
+# My Awesome Type
+
+This is the documentation for this spectacular type.
+```
+
+`lib.rs`:
+
+```no_run (needs-external-files)
+#![feature(external_doc)]
+
+#[doc(include = "external-doc.md")]
+pub struct MyAwesomeType;
+```
+
+`rustdoc` will load the file `external-doc.md` and use it as the documentation for the `MyAwesomeType`
+struct.
+
+When locating files, `rustdoc` will base paths in the `src/` directory, as if they were alongside the
+`lib.rs` for your crate. So if you want a `docs/` folder to live alongside the `src/` directory,
+start your paths with `../docs/` for `rustdoc` to properly find the file.
+
+This feature was proposed in [RFC #1990] and initially implemented in PR [#44781].
+
+[#44732]: https://github.com/rust-lang/rust/issues/44732
+[RFC #1990]: https://github.com/rust-lang/rfcs/pull/1990
+[#44781]: https://github.com/rust-lang/rust/pull/44781
+"##,
+    },
+    Lint {
+        label: "fd",
+        description: r##"# `fd`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "fd_read",
+        description: r##"# `fd_read`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "ffi_const",
+        description: r##"# `ffi_const`
+
+The tracking issue for this feature is: [#58328]
+
+------
+
+The `#[ffi_const]` attribute applies clang's `const` attribute to foreign
+functions declarations.
+
+That is, `#[ffi_const]` functions shall have no effects except for its return
+value, which can only depend on the values of the function parameters, and is
+not affected by changes to the observable state of the program.
+
+Applying the `#[ffi_const]` attribute to a function that violates these
+requirements is undefined behaviour.
+
+This attribute enables Rust to perform common optimizations, like sub-expression
+elimination, and it can avoid emitting some calls in repeated invocations of the
+function with the same argument values regardless of other operations being
+performed in between these functions calls (as opposed to `#[ffi_pure]`
+functions).
+
+## Pitfalls
+
+A `#[ffi_const]` function can only read global memory that would not affect
+its return value for the whole execution of the program (e.g. immutable global
+memory). `#[ffi_const]` functions are referentially-transparent and therefore
+more strict than `#[ffi_pure]` functions.
+
+A common pitfall involves applying the `#[ffi_const]` attribute to a
+function that reads memory through pointer arguments which do not necessarily
+point to immutable global memory.
+
+A `#[ffi_const]` function that returns unit has no effect on the abstract
+machine's state, and a `#[ffi_const]` function cannot be `#[ffi_pure]`.
+
+A `#[ffi_const]` function must not diverge, neither via a side effect (e.g. a
+call to `abort`) nor by infinite loops.
+
+When translating C headers to Rust FFI, it is worth verifying for which targets
+the `const` attribute is enabled in those headers, and using the appropriate
+`cfg` macros in the Rust side to match those definitions. While the semantics of
+`const` are implemented identically by many C and C++ compilers, e.g., clang,
+[GCC], [ARM C/C++ compiler], [IBM ILE C/C++], etc. they are not necessarily
+implemented in this way on all of them. It is therefore also worth verifying
+that the semantics of the C toolchain used to compile the binary being linked
+against are compatible with those of the `#[ffi_const]`.
+
+[#58328]: https://github.com/rust-lang/rust/issues/58328
+[ARM C/C++ compiler]: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/Cacgigch.html
+[GCC]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-const-function-attribute
+[IBM ILE C/C++]: https://www.ibm.com/support/knowledgecenter/fr/ssw_ibm_i_71/rzarg/fn_attrib_const.htm
+"##,
+    },
+    Lint {
+        label: "ffi_pure",
+        description: r##"# `ffi_pure`
+
+The tracking issue for this feature is: [#58329]
+
+------
+
+The `#[ffi_pure]` attribute applies clang's `pure` attribute to foreign
+functions declarations.
+
+That is, `#[ffi_pure]` functions shall have no effects except for its return
+value, which shall not change across two consecutive function calls with
+the same parameters.
+
+Applying the `#[ffi_pure]` attribute to a function that violates these
+requirements is undefined behavior.
+
+This attribute enables Rust to perform common optimizations, like sub-expression
+elimination and loop optimizations. Some common examples of pure functions are
+`strlen` or `memcmp`.
+
+These optimizations are only applicable when the compiler can prove that no
+program state observable by the `#[ffi_pure]` function has changed between calls
+of the function, which could alter the result. See also the `#[ffi_const]`
+attribute, which provides stronger guarantees regarding the allowable behavior
+of a function, enabling further optimization.
+
+## Pitfalls
+
+A `#[ffi_pure]` function can read global memory through the function
+parameters (e.g. pointers), globals, etc. `#[ffi_pure]` functions are not
+referentially-transparent, and are therefore more relaxed than `#[ffi_const]`
+functions.
+
+However, accessing global memory through volatile or atomic reads can violate the
+requirement that two consecutive function calls shall return the same value.
+
+A `pure` function that returns unit has no effect on the abstract machine's
+state.
+
+A `#[ffi_pure]` function must not diverge, neither via a side effect (e.g. a
+call to `abort`) nor by infinite loops.
+
+When translating C headers to Rust FFI, it is worth verifying for which targets
+the `pure` attribute is enabled in those headers, and using the appropriate
+`cfg` macros in the Rust side to match those definitions. While the semantics of
+`pure` are implemented identically by many C and C++ compilers, e.g., clang,
+[GCC], [ARM C/C++ compiler], [IBM ILE C/C++], etc. they are not necessarily
+implemented in this way on all of them. It is therefore also worth verifying
+that the semantics of the C toolchain used to compile the binary being linked
+against are compatible with those of the `#[ffi_pure]`.
+
+
+[#58329]: https://github.com/rust-lang/rust/issues/58329
+[ARM C/C++ compiler]: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0491c/Cacigdac.html
+[GCC]: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-pure-function-attribute
+[IBM ILE C/C++]: https://www.ibm.com/support/knowledgecenter/fr/ssw_ibm_i_71/rzarg/fn_attrib_pure.htm
+"##,
+    },
+    Lint {
+        label: "flt2dec",
+        description: r##"# `flt2dec`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "fmt_internals",
+        description: r##"# `fmt_internals`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "fn_traits",
+        description: r##"# `fn_traits`
+
+The tracking issue for this feature is [#29625]
+
+See Also: [`unboxed_closures`](../language-features/unboxed-closures.md)
+
+[#29625]: https://github.com/rust-lang/rust/issues/29625
+
+----
+
+The `fn_traits` feature allows for implementation of the [`Fn*`] traits
+for creating custom closure-like types.
+
+[`Fn*`]: https://doc.rust-lang.org/std/ops/trait.Fn.html
+
+```rust
+#![feature(unboxed_closures)]
+#![feature(fn_traits)]
+
+struct Adder {
+    a: u32
+}
+
+impl FnOnce<(u32, )> for Adder {
+    type Output = u32;
+    extern "rust-call" fn call_once(self, b: (u32, )) -> Self::Output {
+        self.a + b.0
+    }
+}
+
+fn main() {
+    let adder = Adder { a: 3 };
+    assert_eq!(adder(2), 5);
+}
+```
+"##,
+    },
+    Lint {
+        label: "format_args_capture",
+        description: r##"# `format_args_capture`
+
+The tracking issue for this feature is: [#67984]
+
+[#67984]: https://github.com/rust-lang/rust/issues/67984
+
+------------------------
+
+Enables `format_args!` (and macros which use `format_args!` in their implementation, such
+as `format!`, `print!` and `panic!`) to capture variables from the surrounding scope.
+This avoids the need to pass named parameters when the binding in question
+already exists in scope.
+
+```rust
+#![feature(format_args_capture)]
+
+let (person, species, name) = ("Charlie Brown", "dog", "Snoopy");
+
+// captures named argument `person`
+print!("Hello {person}");
+
+// captures named arguments `species` and `name`
+format!("The {species}'s name is {name}.");
+```
+
+This also works for formatting parameters such as width and precision:
+
+```rust
+#![feature(format_args_capture)]
+
+let precision = 2;
+let s = format!("{:.precision$}", 1.324223);
+
+assert_eq!(&s, "1.32");
+```
+
+A non-exhaustive list of macros which benefit from this functionality include:
+- `format!`
+- `print!` and `println!`
+- `eprint!` and `eprintln!`
+- `write!` and `writeln!`
+- `panic!`
+- `unreachable!`
+- `unimplemented!`
+- `todo!`
+- `assert!` and similar
+- macros in many thirdparty crates, such as `log`
+"##,
+    },
+    Lint {
+        label: "generators",
+        description: r##"# `generators`
+
+The tracking issue for this feature is: [#43122]
+
+[#43122]: https://github.com/rust-lang/rust/issues/43122
+
+------------------------
+
+The `generators` feature gate in Rust allows you to define generator or
+coroutine literals. A generator is a "resumable function" that syntactically
+resembles a closure but compiles to much different semantics in the compiler
+itself. The primary feature of a generator is that it can be suspended during
+execution to be resumed at a later date. Generators use the `yield` keyword to
+"return", and then the caller can `resume` a generator to resume execution just
+after the `yield` keyword.
+
+Generators are an extra-unstable feature in the compiler right now. Added in
+[RFC 2033] they're mostly intended right now as a information/constraint
+gathering phase. The intent is that experimentation can happen on the nightly
+compiler before actual stabilization. A further RFC will be required to
+stabilize generators/coroutines and will likely contain at least a few small
+tweaks to the overall design.
+
+[RFC 2033]: https://github.com/rust-lang/rfcs/pull/2033
+
+A syntactical example of a generator is:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::{Generator, GeneratorState};
+use std::pin::Pin;
+
+fn main() {
+    let mut generator = || {
+        yield 1;
+        return "foo"
+    };
+
+    match Pin::new(&mut generator).resume(()) {
+        GeneratorState::Yielded(1) => {}
+        _ => panic!("unexpected value from resume"),
+    }
+    match Pin::new(&mut generator).resume(()) {
+        GeneratorState::Complete("foo") => {}
+        _ => panic!("unexpected value from resume"),
+    }
+}
+```
+
+Generators are closure-like literals which can contain a `yield` statement. The
+`yield` statement takes an optional expression of a value to yield out of the
+generator. All generator literals implement the `Generator` trait in the
+`std::ops` module. The `Generator` trait has one main method, `resume`, which
+resumes execution of the generator at the previous suspension point.
+
+An example of the control flow of generators is that the following example
+prints all numbers in order:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::pin::Pin;
+
+fn main() {
+    let mut generator = || {
+        println!("2");
+        yield;
+        println!("4");
+    };
+
+    println!("1");
+    Pin::new(&mut generator).resume(());
+    println!("3");
+    Pin::new(&mut generator).resume(());
+    println!("5");
+}
+```
+
+At this time the main intended use case of generators is an implementation
+primitive for async/await syntax, but generators will likely be extended to
+ergonomic implementations of iterators and other primitives in the future.
+Feedback on the design and usage is always appreciated!
+
+### The `Generator` trait
+
+The `Generator` trait in `std::ops` currently looks like:
+
+```rust
+# #![feature(arbitrary_self_types, generator_trait)]
+# use std::ops::GeneratorState;
+# use std::pin::Pin;
+
+pub trait Generator<R = ()> {
+    type Yield;
+    type Return;
+    fn resume(self: Pin<&mut Self>, resume: R) -> GeneratorState<Self::Yield, Self::Return>;
+}
+```
+
+The `Generator::Yield` type is the type of values that can be yielded with the
+`yield` statement. The `Generator::Return` type is the returned type of the
+generator. This is typically the last expression in a generator's definition or
+any value passed to `return` in a generator. The `resume` function is the entry
+point for executing the `Generator` itself.
+
+The return value of `resume`, `GeneratorState`, looks like:
+
+```rust
+pub enum GeneratorState<Y, R> {
+    Yielded(Y),
+    Complete(R),
+}
+```
+
+The `Yielded` variant indicates that the generator can later be resumed. This
+corresponds to a `yield` point in a generator. The `Complete` variant indicates
+that the generator is complete and cannot be resumed again. Calling `resume`
+after a generator has returned `Complete` will likely result in a panic of the
+program.
+
+### Closure-like semantics
+
+The closure-like syntax for generators alludes to the fact that they also have
+closure-like semantics. Namely:
+
+* When created, a generator executes no code. A closure literal does not
+  actually execute any of the closure's code on construction, and similarly a
+  generator literal does not execute any code inside the generator when
+  constructed.
+
+* Generators can capture outer variables by reference or by move, and this can
+  be tweaked with the `move` keyword at the beginning of the closure. Like
+  closures all generators will have an implicit environment which is inferred by
+  the compiler. Outer variables can be moved into a generator for use as the
+  generator progresses.
+
+* Generator literals produce a value with a unique type which implements the
+  `std::ops::Generator` trait. This allows actual execution of the generator
+  through the `Generator::resume` method as well as also naming it in return
+  types and such.
+
+* Traits like `Send` and `Sync` are automatically implemented for a `Generator`
+  depending on the captured variables of the environment. Unlike closures,
+  generators also depend on variables live across suspension points. This means
+  that although the ambient environment may be `Send` or `Sync`, the generator
+  itself may not be due to internal variables live across `yield` points being
+  not-`Send` or not-`Sync`. Note that generators do
+  not implement traits like `Copy` or `Clone` automatically.
+
+* Whenever a generator is dropped it will drop all captured environment
+  variables.
+
+### Generators as state machines
+
+In the compiler, generators are currently compiled as state machines. Each
+`yield` expression will correspond to a different state that stores all live
+variables over that suspension point. Resumption of a generator will dispatch on
+the current state and then execute internally until a `yield` is reached, at
+which point all state is saved off in the generator and a value is returned.
+
+Let's take a look at an example to see what's going on here:
+
+```rust
+#![feature(generators, generator_trait)]
+
+use std::ops::Generator;
+use std::pin::Pin;
+
+fn main() {
+    let ret = "foo";
+    let mut generator = move || {
+        yield 1;
+        return ret
+    };
+
+    Pin::new(&mut generator).resume(());
+    Pin::new(&mut generator).resume(());
+}
+```
+
+This generator literal will compile down to something similar to:
+
+```rust
+#![feature(arbitrary_self_types, generators, generator_trait)]
+
+use std::ops::{Generator, GeneratorState};
+use std::pin::Pin;
+
+fn main() {
+    let ret = "foo";
+    let mut generator = {
+        enum __Generator {
+            Start(&'static str),
+            Yield1(&'static str),
+            Done,
+        }
+
+        impl Generator for __Generator {
+            type Yield = i32;
+            type Return = &'static str;
+
+            fn resume(mut self: Pin<&mut Self>, resume: ()) -> GeneratorState<i32, &'static str> {
+                use std::mem;
+                match mem::replace(&mut *self, __Generator::Done) {
+                    __Generator::Start(s) => {
+                        *self = __Generator::Yield1(s);
+                        GeneratorState::Yielded(1)
+                    }
+
+                    __Generator::Yield1(s) => {
+                        *self = __Generator::Done;
+                        GeneratorState::Complete(s)
+                    }
+
+                    __Generator::Done => {
+                        panic!("generator resumed after completion")
+                    }
+                }
+            }
+        }
+
+        __Generator::Start(ret)
+    };
+
+    Pin::new(&mut generator).resume(());
+    Pin::new(&mut generator).resume(());
+}
+```
+
+Notably here we can see that the compiler is generating a fresh type,
+`__Generator` in this case. This type has a number of states (represented here
+as an `enum`) corresponding to each of the conceptual states of the generator.
+At the beginning we're closing over our outer variable `foo` and then that
+variable is also live over the `yield` point, so it's stored in both states.
+
+When the generator starts it'll immediately yield 1, but it saves off its state
+just before it does so indicating that it has reached the yield point. Upon
+resuming again we'll execute the `return ret` which returns the `Complete`
+state.
+
+Here we can also note that the `Done` state, if resumed, panics immediately as
+it's invalid to resume a completed generator. It's also worth noting that this
+is just a rough desugaring, not a normative specification for what the compiler
+does.
+"##,
+    },
+    Lint {
+        label: "global_asm",
+        description: r##"# `global_asm`
+
+The tracking issue for this feature is: [#35119]
+
+[#35119]: https://github.com/rust-lang/rust/issues/35119
+
+------------------------
+
+The `global_asm!` macro allows the programmer to write arbitrary
+assembly outside the scope of a function body, passing it through
+`rustc` and `llvm` to the assembler. That is to say, `global_asm!` is
+equivalent to assembling the asm with an external assembler and then
+linking the resulting object file with the current crate.
+
+`global_asm!` fills a role not currently satisfied by either `asm!`
+or `#[naked]` functions. The programmer has _all_ features of the
+assembler at their disposal. The linker will expect to resolve any
+symbols defined in the inline assembly, modulo any symbols marked as
+external. It also means syntax for directives and assembly follow the
+conventions of the assembler in your toolchain.
+
+A simple usage looks like this:
+
+```rust,ignore (requires-external-file)
+#![feature(global_asm)]
+# // you also need relevant target_arch cfgs
+global_asm!(include_str!("something_neato.s"));
+```
+
+And a more complicated usage looks like this:
+
+```rust,no_run
+#![feature(global_asm)]
+# #[cfg(any(target_arch="x86", target_arch="x86_64"))]
+# mod x86 {
+
+pub mod sally {
+    global_asm!(
+        ".global foo",
+        "foo:",
+        "jmp baz",
+    );
+
+    #[no_mangle]
+    pub unsafe extern "C" fn baz() {}
+}
+
+// the symbols `foo` and `bar` are global, no matter where
+// `global_asm!` was used.
+extern "C" {
+    fn foo();
+    fn bar();
+}
+
+pub mod harry {
+    global_asm!(
+        ".global bar",
+        "bar:",
+        "jmp quux",
+    );
+
+    #[no_mangle]
+    pub unsafe extern "C" fn quux() {}
+}
+# }
+```
+
+You may use `global_asm!` multiple times, anywhere in your crate, in
+whatever way suits you. However, you should not rely on assembler state
+(e.g. assembler macros) defined in one `global_asm!` to be available in
+another one. It is implementation-defined whether the multiple usages
+are concatenated into one or assembled separately.
+
+`global_asm!` also supports `const` operands like `asm!`, which allows
+constants defined in Rust to be used in assembly code:
+
+```rust,no_run
+#![feature(global_asm)]
+# #[cfg(any(target_arch="x86", target_arch="x86_64"))]
+# mod x86 {
+const C: i32 = 1234;
+global_asm!(
+    ".global bar",
+    "bar: .word {c}",
+    c = const C,
+);
+# }
+```
+
+The syntax for passing operands is the same as `asm!` except that only
+`const` operands are allowed. Refer to the [asm](asm.md) documentation
+for more details.
+
+On x86, the assembly code will use intel syntax by default. You can
+override this by adding `options(att_syntax)` at the end of the macro
+arguments list:
+
+```rust,no_run
+#![feature(global_asm)]
+# #[cfg(any(target_arch="x86", target_arch="x86_64"))]
+# mod x86 {
+global_asm!("movl ${}, %ecx", const 5, options(att_syntax));
+// is equivalent to
+global_asm!("mov ecx, {}", const 5);
+# }
+```
+
+------------------------
+
+If you don't need quite as much power and flexibility as
+`global_asm!` provides, and you don't mind restricting your inline
+assembly to `fn` bodies only, you might try the
+[asm](asm.md) feature instead.
+"##,
+    },
+    Lint {
+        label: "impl_trait_in_bindings",
+        description: r##"# `impl_trait_in_bindings`
+
+The tracking issue for this feature is: [#63065]
+
+[#63065]: https://github.com/rust-lang/rust/issues/63065
+
+------------------------
+
+The `impl_trait_in_bindings` feature gate lets you use `impl Trait` syntax in
+`let`, `static`, and `const` bindings.
+
+A simple example is:
+
+```rust
+#![feature(impl_trait_in_bindings)]
+
+use std::fmt::Debug;
+
+fn main() {
+    let a: impl Debug + Clone = 42;
+    let b = a.clone();
+    println!("{:?}", b); // prints `42`
+}
+```
+
+Note however that because the types of `a` and `b` are opaque in the above
+example, calling inherent methods or methods outside of the specified traits
+(e.g., `a.abs()` or `b.abs()`) is not allowed, and yields an error.
+"##,
+    },
+    Lint {
+        label: "infer_static_outlives_requirements",
+        description: r##"# `infer_static_outlives_requirements`
+
+The tracking issue for this feature is: [#54185]
+
+[#54185]: https://github.com/rust-lang/rust/issues/54185
+
+------------------------
+The `infer_static_outlives_requirements` feature indicates that certain
+`'static` outlives requirements can be inferred by the compiler rather than
+stating them explicitly.
+
+Note: It is an accompanying feature to `infer_outlives_requirements`,
+which must be enabled to infer outlives requirements.
+
+For example, currently generic struct definitions that contain
+references, require where-clauses of the form T: 'static. By using
+this feature the outlives predicates will be inferred, although
+they may still be written explicitly.
+
+```rust,ignore (pseudo-Rust)
+struct Foo<U> where U: 'static { // <-- currently required
+    bar: Bar<U>
+}
+struct Bar<T: 'static> {
+    x: T,
+}
+```
+
+
+## Examples:
+
+```rust,ignore (pseudo-Rust)
+#![feature(infer_outlives_requirements)]
+#![feature(infer_static_outlives_requirements)]
+
+#[rustc_outlives]
+// Implicitly infer U: 'static
+struct Foo<U> {
+    bar: Bar<U>
+}
+struct Bar<T: 'static> {
+    x: T,
+}
+```
+"##,
+    },
+    Lint {
+        label: "inline_const",
+        description: r##"# `inline_const`
+
+The tracking issue for this feature is: [#76001]
+
+------
+
+This feature allows you to use inline constant expressions. For example, you can
+turn this code:
+
+```rust
+# fn add_one(x: i32) -> i32 { x + 1 }
+const MY_COMPUTATION: i32 = 1 + 2 * 3 / 4;
+
+fn main() {
+    let x = add_one(MY_COMPUTATION);
+}
+```
+
+into this code:
+
+```rust
+#![feature(inline_const)]
+
+# fn add_one(x: i32) -> i32 { x + 1 }
+fn main() {
+    let x = add_one(const { 1 + 2 * 3 / 4 });
+}
+```
+
+You can also use inline constant expressions in patterns:
+
+```rust
+#![feature(inline_const)]
+
+const fn one() -> i32 { 1 }
+
+let some_int = 3;
+match some_int {
+    const { 1 + 2 } => println!("Matched 1 + 2"),
+    const { one() } => println!("Matched const fn returning 1"),
+    _ => println!("Didn't match anything :("),
+}
+```
+
+[#76001]: https://github.com/rust-lang/rust/issues/76001
+"##,
+    },
+    Lint {
+        label: "int_error_internals",
+        description: r##"# `int_error_internals`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "internal_output_capture",
+        description: r##"# `internal_output_capture`
+
+This feature is internal to the Rust compiler and is not intended for general use.
+
+------------------------
+"##,
+    },
+    Lint {
+        label: "intra_doc_pointers",
+        description: r##"# `intra-doc-pointers`
+
+The tracking issue for this feature is: [#80896]
+
+[#80896]: https://github.com/rust-lang/rust/issues/80896
+
+------------------------
+
+Rustdoc does not currently allow disambiguating between `*const` and `*mut`, and
+raw pointers in intra-doc links are unstable until it does.
+
+```rust
+#![feature(intra_doc_pointers)]
+//! [pointer::add]
+```
+"##,
+    },
+    Lint {
+        label: "intrinsics",
+        description: r##"# `intrinsics`
+
+The tracking issue for this feature is: None.
+
+Intrinsics are never intended to be stable directly, but intrinsics are often
+exported in some sort of stable manner. Prefer using the stable interfaces to
+the intrinsic directly when you can.
+
+------------------------
+
+
+These are imported as if they were FFI functions, with the special
+`rust-intrinsic` ABI. For example, if one was in a freestanding
+context, but wished to be able to `transmute` between types, and
+perform efficient pointer arithmetic, one would import those functions
+via a declaration like
+
+```rust
+#![feature(intrinsics)]
+# fn main() {}
+
+extern "rust-intrinsic" {
+    fn transmute<T, U>(x: T) -> U;
+
+    fn offset<T>(dst: *const T, offset: isize) -> *const T;
+}
+```
+
+As with any other FFI functions, these are always `unsafe` to call.
+"##,
+    },
+    Lint {
+        label: "is_sorted",
+        description: r##"# `is_sorted`
+
+The tracking issue for this feature is: [#53485]
+
+[#53485]: https://github.com/rust-lang/rust/issues/53485
+
+------------------------
+
+Add the methods `is_sorted`, `is_sorted_by` and `is_sorted_by_key` to `[T]`;
+add the methods `is_sorted`, `is_sorted_by` and `is_sorted_by_key` to
+`Iterator`.
+"##,
+    },
+    Lint {
+        label: "lang_items",
+        description: r##"# `lang_items`
+
+The tracking issue for this feature is: None.
+
+------------------------
+
+The `rustc` compiler has certain pluggable operations, that is,
+functionality that isn't hard-coded into the language, but is
+implemented in libraries, with a special marker to tell the compiler
+it exists. The marker is the attribute `#[lang = "..."]` and there are
+various different values of `...`, i.e. various different 'lang