1. The Unstable Book
  2. 1. Compiler flags
    1. 1.1. codegen_backend
    2. 1.2. control_flow_guard
    3. 1.3. emit_stack_sizes
    4. 1.4. extern_location
    5. 1.5. profile
    6. 1.6. report_time
    7. 1.7. sanitizer
    8. 1.8. self_profile
    9. 1.9. self_profile_events
    10. 1.10. source_based_code_coverage
    11. 1.11. src_hash_algorithm
    12. 1.12. strip
    13. 1.13. tls_model
    14. 1.14. unsound_mir_opts
  3. 2. Language features
    1. 2.1. aarch64_target_feature
    2. 2.2. abi_amdgpu_kernel
    3. 2.3. abi_avr_interrupt
    4. 2.4. abi_c_cmse_nonsecure_call
    5. 2.5. abi_efiapi
    6. 2.6. abi_msp430_interrupt
    7. 2.7. abi_ptx
    8. 2.8. abi_thiscall
    9. 2.9. abi_unadjusted
    10. 2.10. abi_vectorcall
    11. 2.11. abi_x86_interrupt
    12. 2.12. adx_target_feature
    13. 2.13. alloc_error_handler
    14. 2.14. allocator_internals
    15. 2.15. allow_fail
    16. 2.16. allow_internal_unsafe
    17. 2.17. allow_internal_unstable
    18. 2.18. arbitrary_enum_discriminant
    19. 2.19. arbitrary_self_types
    20. 2.20. arm_target_feature
    21. 2.21. associated_type_bounds
    22. 2.22. associated_type_defaults
    23. 2.23. async_closure
    24. 2.24. auto_traits
    25. 2.25. avx512_target_feature
    26. 2.26. bindings_after_at
    27. 2.27. box_patterns
    28. 2.28. box_syntax
    29. 2.29. c_unwind
    30. 2.30. c_variadic
    31. 2.31. capture_disjoint_fields
    32. 2.32. cfg_panic
    33. 2.33. cfg_sanitize
    34. 2.34. cfg_target_has_atomic
    35. 2.35. cfg_target_thread_local
    36. 2.36. cfg_version
    37. 2.37. cmpxchg16b_target_feature
    38. 2.38. cmse_nonsecure_entry
    39. 2.39. compiler_builtins
    40. 2.40. const_eval_limit
    41. 2.41. const_evaluatable_checked
    42. 2.42. const_extern_fn
    43. 2.43. const_fn
    44. 2.44. const_fn_floating_point_arithmetic
    45. 2.45. const_fn_fn_ptr_basics
    46. 2.46. const_fn_transmute
    47. 2.47. const_fn_union
    48. 2.48. const_generics
    49. 2.49. const_generics_defaults
    50. 2.50. const_impl_trait
    51. 2.51. const_mut_refs
    52. 2.52. const_panic
    53. 2.53. const_precise_live_drops
    54. 2.54. const_raw_ptr_deref
    55. 2.55. const_raw_ptr_to_usize_cast
    56. 2.56. const_refs_to_cell
    57. 2.57. const_trait_bound_opt_out
    58. 2.58. const_trait_impl
    59. 2.59. crate_visibility_modifier
    60. 2.60. custom_inner_attributes
    61. 2.61. custom_test_frameworks
    62. 2.62. decl_macro
    63. 2.63. default_alloc_error_handler
    64. 2.64. default_type_parameter_fallback
    65. 2.65. destructuring_assignment
    66. 2.66. doc_cfg
    67. 2.67. doc_keyword
    68. 2.68. doc_masked
    69. 2.69. doc_spotlight
    70. 2.70. dropck_eyepatch
    71. 2.71. edition_macro_pats
    72. 2.72. ermsb_target_feature
    73. 2.73. exclusive_range_pattern
    74. 2.74. exhaustive_patterns
    75. 2.75. extended_key_value_attributes
    76. 2.76. extern_types
    77. 2.77. external_doc
    78. 2.78. f16c_target_feature
    79. 2.79. ffi_const
    80. 2.80. ffi_pure
    81. 2.81. ffi_returns_twice
    82. 2.82. format_args_capture
    83. 2.83. fundamental
    84. 2.84. generators
    85. 2.85. generic_associated_types
    86. 2.86. half_open_range_patterns
    87. 2.87. hexagon_target_feature
    88. 2.88. if_let_guard
    89. 2.89. impl_trait_in_bindings
    90. 2.90. in_band_lifetimes
    91. 2.91. infer_static_outlives_requirements
    92. 2.92. inherent_associated_types
    93. 2.93. inline_const
    94. 2.94. intra_doc_pointers
    95. 2.95. intrinsics
    96. 2.96. isa_attribute
    97. 2.97. label_break_value
    98. 2.98. lang_items
    99. 2.99. lazy_normalization_consts
    100. 2.100. let_chains
    101. 2.101. link_args
    102. 2.102. link_cfg
    103. 2.103. link_llvm_intrinsics
    104. 2.104. linkage
    105. 2.105. lint_reasons
    106. 2.106. macro_attributes_in_derive_output
    107. 2.107. main
    108. 2.108. marker_trait_attr
    109. 2.109. member_constraints
    110. 2.110. min_specialization
    111. 2.111. min_type_alias_impl_trait
    112. 2.112. mips_target_feature
    113. 2.113. movbe_target_feature
    114. 2.114. naked_functions
    115. 2.115. needs_panic_runtime
    116. 2.116. negative_impls
    117. 2.117. never_type
    118. 2.118. never_type_fallback
    119. 2.119. nll
    120. 2.120. no_core
    121. 2.121. no_niche
    122. 2.122. no_sanitize
    123. 2.123. non_ascii_idents
    124. 2.124. object_safe_for_dispatch
    125. 2.125. omit_gdb_pretty_printer_section
    126. 2.126. optimize_attribute
    127. 2.127. or_patterns
    128. 2.128. panic_runtime
    129. 2.129. platform_intrinsics
    130. 2.130. plugin
    131. 2.131. plugin_registrar
    132. 2.132. powerpc_target_feature
    133. 2.133. precise_pointer_size_matching
    134. 2.134. prelude_import
    135. 2.135. proc_macro_hygiene
    136. 2.136. profiler_runtime
    137. 2.137. pub_macro_rules
    138. 2.138. raw_dylib
    139. 2.139. raw_ref_op
    140. 2.140. register_attr
    141. 2.141. register_tool
    142. 2.142. relaxed_struct_unsize
    143. 2.143. repr_simd
    144. 2.144. repr128
    145. 2.145. riscv_target_feature
    146. 2.146. rtm_target_feature
    147. 2.147. rustc_allow_const_fn_unstable
    148. 2.148. rustc_attrs
    149. 2.149. rustc_private
    150. 2.150. simd_ffi
    151. 2.151. specialization
    152. 2.152. sse4a_target_feature
    153. 2.153. staged_api
    154. 2.154. start
    155. 2.155. static_nobundle
    156. 2.156. stmt_expr_attributes
    157. 2.157. structural_match
    158. 2.158. target_feature_11
    159. 2.159. tbm_target_feature
    160. 2.160. test_2018_feature
    161. 2.161. thread_local
    162. 2.162. trait_alias
    163. 2.163. transparent_unions
    164. 2.164. trivial_bounds
    165. 2.165. try_blocks
    166. 2.166. type_alias_impl_trait
    167. 2.167. type_ascription
    168. 2.168. unboxed_closures
    169. 2.169. unsized_fn_params
    170. 2.170. unsized_locals
    171. 2.171. unsized_tuple_coercion
    172. 2.172. untagged_unions
    173. 2.173. unwind_attributes
    174. 2.174. wasm_target_feature
  4. 3. Library Features
    1. 3.1. alloc_error_hook
    2. 3.2. alloc_internals
    3. 3.3. alloc_layout_extra
    4. 3.4. alloc_prelude
    5. 3.5. allocator_api
    6. 3.6. arc_new_cyclic
    7. 3.7. array_chunks
    8. 3.8. array_error_internals
    9. 3.9. array_from_ref
    10. 3.10. array_map
    11. 3.11. array_methods
    12. 3.12. array_windows
    13. 3.13. array_zip
    14. 3.14. asm
    15. 3.15. async_stream
    16. 3.16. atomic_fetch_update
    17. 3.17. atomic_from_mut
    18. 3.18. atomic_mut_ptr
    19. 3.19. available_concurrency
    20. 3.20. backtrace
    21. 3.21. backtrace_frames
    22. 3.22. binary_heap_drain_sorted
    23. 3.23. binary_heap_into_iter_sorted
    24. 3.24. binary_heap_retain
    25. 3.25. bool_to_option
    26. 3.26. bound_as_ref
    27. 3.27. bound_cloned
    28. 3.28. box_into_boxed_slice
    29. 3.29. box_into_inner
    30. 3.30. box_into_pin
    31. 3.31. btree_drain_filter
    32. 3.32. btree_retain
    33. 3.33. bufreader_seek_relative
    34. 3.34. bufwriter_into_raw_parts
    35. 3.35. c_void_variant
    36. 3.36. can_vector
    37. 3.37. cell_filter_map
    38. 3.38. cell_leak
    39. 3.39. cell_update
    40. 3.40. cfg_accessible
    41. 3.41. cfg_eval
    42. 3.42. char_error_internals
    43. 3.43. char_internals
    44. 3.44. cmp_min_max_by
    45. 3.45. coerce_unsized
    46. 3.46. command_access
    47. 3.47. concat_idents
    48. 3.48. const_align_of_val
    49. 3.49. const_align_of_val_raw
    50. 3.50. const_alloc_layout
    51. 3.51. const_assert_type
    52. 3.52. const_assume
    53. 3.53. const_btree_new
    54. 3.54. const_caller_location
    55. 3.55. const_cell_into_inner
    56. 3.56. const_cow_is_borrowed
    57. 3.57. const_cstr_unchecked
    58. 3.58. const_cttz
    59. 3.59. const_discriminant
    60. 3.60. const_float_bits_conv
    61. 3.61. const_float_classify
    62. 3.62. const_heap
    63. 3.63. const_int_unchecked_arith
    64. 3.64. const_intrinsic_copy
    65. 3.65. const_intrinsic_forget
    66. 3.66. const_io_structs
    67. 3.67. const_ip
    68. 3.68. const_ipv4
    69. 3.69. const_ipv6
    70. 3.70. const_likely
    71. 3.71. const_maybe_uninit_as_ptr
    72. 3.72. const_maybe_uninit_assume_init
    73. 3.73. const_nonnull_slice_from_raw_parts
    74. 3.74. const_option
    75. 3.75. const_pin
    76. 3.76. const_pref_align_of
    77. 3.77. const_ptr_is_null
    78. 3.78. const_ptr_offset
    79. 3.79. const_ptr_offset_from
    80. 3.80. const_ptr_read
    81. 3.81. const_ptr_write
    82. 3.82. const_raw_ptr_comparison
    83. 3.83. const_result
    84. 3.84. const_size_of_val
    85. 3.85. const_size_of_val_raw
    86. 3.86. const_slice_from_raw_parts
    87. 3.87. const_slice_ptr_len
    88. 3.88. const_str_from_utf8_unchecked
    89. 3.89. const_swap
    90. 3.90. const_transmute_copy
    91. 3.91. const_type_id
    92. 3.92. const_type_name
    93. 3.93. const_unreachable_unchecked
    94. 3.94. container_error_extra
    95. 3.95. control_flow_enum
    96. 3.96. convert_float_to_int
    97. 3.97. core_intrinsics
    98. 3.98. core_panic
    99. 3.99. core_private_bignum
    100. 3.100. core_private_diy_float
    101. 3.101. cow_is_borrowed
    102. 3.102. cstring_from_vec_with_nul
    103. 3.103. deadline_api
    104. 3.104. debug_non_exhaustive
    105. 3.105. dec2flt
    106. 3.106. default_free_fn
    107. 3.107. derive_clone_copy
    108. 3.108. derive_eq
    109. 3.109. discriminant_kind
    110. 3.110. dispatch_from_dyn
    111. 3.111. div_duration
    112. 3.112. drain_filter
    113. 3.113. duration_constants
    114. 3.114. duration_consts_2
    115. 3.115. duration_saturating_ops
    116. 3.116. duration_zero
    117. 3.117. edition_panic
    118. 3.118. entry_insert
    119. 3.119. error_iter
    120. 3.120. error_type_id
    121. 3.121. exact_size_is_empty
    122. 3.122. extend_one
    123. 3.123. fd
    124. 3.124. fd_read
    125. 3.125. fixed_size_array
    126. 3.126. flt2dec
    127. 3.127. fmt_internals
    128. 3.128. fn_traits
    129. 3.129. foo
    130. 3.130. forget_unsized
    131. 3.131. format_args_nl
    132. 3.132. future_poll_fn
    133. 3.133. gen_future
    134. 3.134. generator_trait
    135. 3.135. get_mut_unchecked
    136. 3.136. global_asm
    137. 3.137. hash_drain_filter
    138. 3.138. hash_raw_entry
    139. 3.139. hash_set_entry
    140. 3.140. hashmap_internals
    141. 3.141. inplace_iteration
    142. 3.142. int_bits_const
    143. 3.143. int_error_internals
    144. 3.144. int_error_matching
    145. 3.145. integer_atomics
    146. 3.146. internal_output_capture
    147. 3.147. into_future
    148. 3.148. io_into_inner_error_parts
    149. 3.149. io_read_to_string
    150. 3.150. io_slice_advance
    151. 3.151. ip
    152. 3.152. is_sorted
    153. 3.153. is_subnormal
    154. 3.154. iter_advance_by
    155. 3.155. iter_intersperse
    156. 3.156. iter_is_partitioned
    157. 3.157. iter_map_while
    158. 3.158. iter_order_by
    159. 3.159. iter_partition_in_place
    160. 3.160. layout_for_ptr
    161. 3.161. liballoc_internals
    162. 3.162. libstd_sys_internals
    163. 3.163. libstd_thread_internals
    164. 3.164. linked_list_cursors
    165. 3.165. linked_list_prepend
    166. 3.166. linked_list_remove
    167. 3.167. llvm_asm
    168. 3.168. log_syntax
    169. 3.169. map_entry_replace
    170. 3.170. map_first_last
    171. 3.171. map_into_keys_values
    172. 3.172. map_try_insert
    173. 3.173. maybe_uninit_array_assume_init
    174. 3.174. maybe_uninit_extra
    175. 3.175. maybe_uninit_ref
    176. 3.176. maybe_uninit_slice
    177. 3.177. maybe_uninit_uninit_array
    178. 3.178. maybe_uninit_write_slice
    179. 3.179. mutex_unlock
    180. 3.180. new_uninit
    181. 3.181. nonnull_slice_from_raw_parts
    182. 3.182. nonzero_is_power_of_two
    183. 3.183. nonzero_leading_trailing_zeros
    184. 3.184. num_as_ne_bytes
    185. 3.185. once_cell
    186. 3.186. option_expect_none
    187. 3.187. option_get_or_insert_default
    188. 3.188. option_insert
    189. 3.189. option_result_contains
    190. 3.190. option_result_unwrap_unchecked
    191. 3.191. option_unwrap_none
    192. 3.192. option_zip
    193. 3.193. ordering_helpers
    194. 3.194. osstring_ascii
    195. 3.195. panic_abort
    196. 3.196. panic_info_message
    197. 3.197. panic_internals
    198. 3.198. panic_unwind
    199. 3.199. path_try_exists
    200. 3.200. pattern
    201. 3.201. peekable_peek_mut
    202. 3.202. peer_credentials_unix_socket
    203. 3.203. pin_static_ref
    204. 3.204. prelude_2015
    205. 3.205. prelude_2018
    206. 3.206. prelude_2021
    207. 3.207. print_internals
    208. 3.208. proc_macro_def_site
    209. 3.209. proc_macro_diagnostic
    210. 3.210. proc_macro_internals
    211. 3.211. proc_macro_is_available
    212. 3.212. proc_macro_quote
    213. 3.213. proc_macro_span
    214. 3.214. proc_macro_tracked_env
    215. 3.215. process_exitcode_placeholder
    216. 3.216. process_internals
    217. 3.217. profiler_runtime_lib
    218. 3.218. ptr_as_uninit
    219. 3.219. ptr_internals
    220. 3.220. ptr_metadata
    221. 3.221. raw
    222. 3.222. raw_os_nonzero
    223. 3.223. raw_vec_internals
    224. 3.224. read_initializer
    225. 3.225. ready_macro
    226. 3.226. receiver_trait
    227. 3.227. restricted_std
    228. 3.228. result_cloned
    229. 3.229. result_contains_err
    230. 3.230. result_copied
    231. 3.231. result_flattening
    232. 3.232. result_into_ok_or_err
    233. 3.233. rt
    234. 3.234. sealed
    235. 3.235. seek_stream_len
    236. 3.236. set_ptr_value
    237. 3.237. setgroups
    238. 3.238. sgx_platform
    239. 3.239. shrink_to
    240. 3.240. slice_as_chunks
    241. 3.241. slice_concat_ext
    242. 3.242. slice_concat_trait
    243. 3.243. slice_group_by
    244. 3.244. slice_index_methods
    245. 3.245. slice_internals
    246. 3.246. slice_iter_mut_as_slice
    247. 3.247. slice_partition_at_index
    248. 3.248. slice_partition_dedup
    249. 3.249. slice_pattern
    250. 3.250. slice_ptr_get
    251. 3.251. slice_ptr_len
    252. 3.252. slice_range
    253. 3.253. slice_split_at_unchecked
    254. 3.254. sort_internals
    255. 3.255. std_internals
    256. 3.256. stdsimd
    257. 3.257. step_trait
    258. 3.258. step_trait_ext
    259. 3.259. str_internals
    260. 3.260. str_split_as_str
    261. 3.261. str_split_inclusive_as_str
    262. 3.262. str_split_whitespace_as_str
    263. 3.263. string_drain_as_str
    264. 3.264. string_remove_matches
    265. 3.265. termination_trait_lib
    266. 3.266. test
    267. 3.267. thread_id_value
    268. 3.268. thread_local_internals
    269. 3.269. thread_spawn_unchecked
    270. 3.270. toowned_clone_into
    271. 3.271. total_cmp
    272. 3.272. trace_macros
    273. 3.273. trusted_len
    274. 3.274. trusted_random_access
    275. 3.275. try_find
    276. 3.276. try_reserve
    277. 3.277. try_trait
    278. 3.278. type_name_of_val
    279. 3.279. unchecked_math
    280. 3.280. unicode_internals
    281. 3.281. unix_process_wait_more
    282. 3.282. unix_socket_ancillary_data
    283. 3.283. unix_socket_peek
    284. 3.284. unsafe_cell_raw_get
    285. 3.285. unsize
    286. 3.286. unwrap_infallible
    287. 3.287. update_panic_count
    288. 3.288. variant_count
    289. 3.289. vec_extend_from_within
    290. 3.290. vec_into_raw_parts
    291. 3.291. vec_spare_capacity
    292. 3.292. vec_split_at_spare
    293. 3.293. vecdeque_binary_search
    294. 3.294. wasi_ext
    295. 3.295. windows_by_handle
    296. 3.296. windows_c
    297. 3.297. windows_file_type_ext
    298. 3.298. windows_handle
    299. 3.299. windows_net
    300. 3.300. windows_process_extensions_force_quotes
    301. 3.301. windows_stdio
    302. 3.302. with_options
    303. 3.303. wrapping_int_impl
    304. 3.304. wrapping_next_power_of_two
    305. 3.305. write_all_vectored

The Rust Unstable Book

Language features