All unstable features used on crates.io

~/C/c/results> cut -d : -f 2 <unstable_features.txt | tr -d '[:blank:]' | cut -d '(' -f 2 | cut -d ')' -f 1 | tr ',' '\n' | sort | uniq -c | sort -nr
   2174 test
    605 plugin
    574 proc_macro_hygiene
    321 const_fn
    316 rustc_private
    281 decl_macro
    238 proc_macro
    234 box_syntax
    222 specialization
    201 async_await
    192 custom_attribute
    184 core_intrinsics
    169 try_from
    162 plugin_registrar
    158 asm
    144 generators
    140 io
    136 alloc
    121 core
    118 never_type
    106 unboxed_closures
     98 custom_derive
     96 collections
     96 box_patterns
     95 allocator_api
     91 try_trait
     90 phase
     90 bufreader_buffer
     86 nll
     77 libc
     72 conservative_impl_trait
     71 lang_items
     70 quote
     70 futures_api
     67 stdsimd
     65 await_macro
     63 slice_patterns
     61 untagged_unions
     58
     56 optin_builtin_traits
     55 std_misc
     54 generator_trait
     53 type_ascription
     53 stmt_expr_attributes
     53 fn_traits
     52 trace_macros
     50 crate_visibility_modifier
     48 prelude_import
     48 macro_rules
     45 proc_macro_diagnostic
     43 cfg_target_feature
     40 take_set_limit
     39 use_extern_macros
     39 attr_literals
     38 inclusive_range_syntax
     38 drain_filter
     38 associated_type_defaults
     37 seek_convenience
     37 integer_atomics
     35 non_ascii_idents
     35 external_doc
     35 const_generics
     35 associated_consts
     34 type_alias_impl_trait
     34 rust_2018_preview
     34 custom_test_frameworks
     33 uniform_paths
     32 proc_macro_span
     32 concat_idents
     31 alloc_system
     30 unique
     30 more_io_inner_methods
     30 globs
     30 arbitrary_self_types
     28 vec_remove_item
     28 unsize
     28 pointer_methods
     28 pin
     28 i128_type
     27 raw
     26 heap_api
     26 extern_types
     25 unsafe_destructor
     25 thread_local
     25 convert
     24 trait_alias
     24 slicing_syntax
     24 fnbox
     24 alloc_layout_extra
     22 old_io
     22 const_transmute
     22 bufreader_is_empty
     21 vec_push_all
     21 start
     21 dropck_eyepatch
     20 try_blocks
     20 target_feature
     20 step_by
     20 slice_bytes
     19 range_contains
     19 proc_macro_non_items
     19 pattern
     18 unicode
     18 retain_hash_collection
     18 question_mark
     18 in_band_lifetimes
     18 const_slice_len
     18 coerce_unsized
     18 async_closure
     18 alloc_error_handler
     17 static_nobundle
     16 staged_api
     16 scheme
     16 ptr_internals
     16 path
     16 no_core
     16 extern_prelude
     16 exhaustive_patterns
     16 collections_range
     16 backtrace
     16 associated_type_bounds
     16 allow_internal_unstable
     15 try_reserve
     15 "subsumedby`#![feature
     15 naked_functions
     15 io_take_into_inner
     15 generic_associated_types
     15 const_int_conversion
     15 const_if_match
     14 step_trait
     14 proc_macro_path_invoc
     14 platform_intrinsics
     14 ip
     14 forktable
     14 exclusive_range_pattern
     14 collections_bound
     13 used
     13 repr_simd
     13 rand
     13 path_ext
     13 non_exhaustive
     13 loop_break_value
     13 link_llvm_intrinsics
     13 linkage
     13 label_break_value
     13 iterator_step_by
     13 inclusive_range
     13 global_asm
     13 global_allocator
     13 doc_cfg
     13 bool_to_option
     12 tool_lints
     12 pub_restricted
     12 panic_info_message
     12 maybe_uninit_extra
     12 ...
     11 raw_vec_internals
     11 oom
     11 no_std
     11 fs
     11 fixed_size_array
     11 allocator
     10 int_to_from_bytes
     10 intrinsics
     10 env
     10 const_panic
      9 track_caller
      9 shrink_to
      9 ptr_offset_from
      9 proc_macro_gen
      9 maybe_uninit_ref
      9 map_values_mut
      9 link_args
      9 if_let
      9 hash
      9 filling_drop
      9 extern_crate_item_prelude
      9 duration_as_u128
      9 arbitrary_enum_discriminant
      8 type_macros
      8 trusted_len
      8 slice_concat_ext
      8 shared
      8 reflect_marker
      8 os
      8 marker_trait_attr
      8 map_entry_replace
      8 get_type_id
      8 bind_by_move_pattern_guards
      8 abi_x86_interrupt
      7 zero_one
      7 unwind_attributes
      7 trivial_bounds
      7 termination_trait_lib
      7 struct_field_attributes
      7 simd_ffi
      7 rustc_attrs
      7 proc_macro_lib
      7 new_uninit
      7 match_default_bindings
      7 macro_reexport
      7 error_iter
      7 drop_types_in_const
      7 const_type_id
      7 const_raw_ptr_deref
      7 const_fn_union
      7 box_into_raw_non_null
      7 advanced_slice_patterns
      7 abi_msp430_interrupt
      6 unsafe_no_drop_flag
      6 unicode_internals
      6 type_alias_enum_variants
      6 set_stdio
      6 ptr_wrapping_offset_from
      6 option_expect_none
      6 on_unimplemented
      6 offset_to
      6 map_entry_recover_keys
      6 main
      6 macro_at_most_once_rep
      6 library
      6 inner_deref
      6 hash_raw_entry
      6 &format!
      6 field_init_shorthand
      6 const_loop
      6 atomic_min_max
      6 align_offset
      6 //#23973
      5 unrestricted_attribute_tokens
      5 str_escape
      5 std_internals
      5 slice_from_raw_parts
      5 scoped
      5 "removedinfavorof`#![feature
      5 refcell_replace_swap
      5 proc_macro_quote
      5 proc_macro_def_site
      5 old_path
      5 maybe_uninit
      5 map_get_key_value
      5 macro_vis_matcher
      5 iter_rfind
      5 iter_arith
      5 impl_trait_in_bindings
      5 hashmap_hasher
      5 "#![feature
      5 exact_size_is_empty
      5 duration
      5 const_size_of
      5 const_let
      5 clamp
      5 btree_range
      5 associated_types
      5 alloc_prelude
      4 underscore_imports
      4 tuple_indexing
      4 toowned_clone_into
      4 thread_local_state
      4 thread_id_value
      4 rt
      4 result_expect
      4 repr_align_enum
      4 read_initializer
      4 placement_new_protocol
      4 placement_in_syntax
      4 panic_unwind
      4 nonzero
      4 non_modrs_mods
      4 log_syntax
      4 linked_list_extras
      4 libstd_sys_internals
      4 iterator_for_each
      4 int_uint
      4 if_while_or_patterns
      4 i.e.
      4 hash_set_entry
      4 fmt_internals
      4 //`#![feature]`attributesshouldbeadded.
      4 `#![feature
      4 euclidean_division
      4 dyn_trait
      4 crate_in_paths
      4 core_float
      4 const_str_len
      4 checked_duration_since
      4 cell_update
      4 braced_empty_structs
      4 append
      4 allocator_internals
      4
      3 vec_resize_default
      3 vec_drain_as_slice
      3 universal_impl_trait
      3 underscore_lifetimes
      3 |uf|format!
      3 transparent_unions
      3 transparent_enums
      3 tcp
      3 str_strip
      3 str_internals
      3 static_in_const
      3 slice_splits
      3 sip_hash_13
      3 rust_2018_idioms
      3 result_map_or_else
      3 repr128
      3 register_attr
      3 proc_macro_mod
      3 process
      3 panic_implementation
      3 panic_handler
      3 old_orphan_check
      3 mpsc_select
      3 mmx_target_feature
      3 "mergedinto`#![feature
      3 maybe_uninit_slice
      3 map_first_last
      3 manually_drop
      3 iter_rfold
      3 int_error_matching
      3 hashmap_internals
      3 get_mut_unchecked
      3 gen_future
      3 generic_param_attrs
      3 fused
      3 fs_walk
      3 fs_time
      3 format_args_nl
      3 forerrorreporting.
      3 forerrorreporting
      3 feature="unstable"
      3 feature_name
      3 ///`#![feature]`attrsforlanguagefeatures
      3 "`#![feature
      3 duration_from_micros
      3 duration_float
      3 dropck_parametricity
      3 drain
      3 doc="#![feature
      3 default_type_params
      3 deadline_api
      3 c_variadic
      3 custom_inner_attributes
      3 const_vec_new
      3 const_str_as_bytes
      3 const_raw_ptr_to_usize_cast
      3 const_in_array_repeat_expressions
      3 cfg_target_has_atomic
      3 catch_panic
      3 catch_expr
      3 bufreader_seek_relative
      3 box_raw
      3 bindings_after_at
      3 arc_counts
      3 "Adda#![feature]declarationtothecrate."
      3 abi_ptx
      3 aarch64_target_feature
      2 wrapping_int_impl
      2 weak_into_raw
      2 weak_counts
      2 wasm_import_module
      2 vec_leak
      2 unsized_locals
      2 thread_spawn_unchecked
      2 tempdir
      2 str_char
      2 std_panic
      2 slice_rotate
      2 slice_index_methods
      2 slice_get_slice
      2 slice_concat_trait
      2 simd
      2 rustc_macro
      2 reverse_bits
      2 refcell_map_split
      2 recover
      2 read_exact
      2 raw_identifiers
      2 pubstaticTEXT
      2 ptr_as_ref
      2 proc_macro_raw_ident
      2 proc_macro_internals
      2 print_internals
      2 pm_span
      2 pattern_parentheses
      2 path_relative_from
      2 param_attrs
      2 option_result_contains
      2 option_entry
      2 op_assign_traits
      2 no_panic_pow
      2 needs_panic_runtime
      2 min_const_fn
      2 manually_drop_take
      2 managed_boxes
      2 list
      2 let_chains
      2 is_sorted
      2 ip_constructors
      2 ip_addr
      2 into_cow
      2 getpid
      2 fundamental
      2 fs_read_write
      2 flt2dec
      2 float_extras
      2 feature="nightly"
      2 "`#![feature]`maynotbeusedonthe{}releasechannel"
      2 ///#![feature]attrsforstablelanguagefeatures
      2 existential_type
      2 entry_or_default
      2 entry_insert
      2 doc="##![feature
      2 dispatch_from_dyn
      2 core_slice_ext
      2 core_panic
      2 const_raw_ptr
      2 const_ptr_null
      2 const_mut_refs
      2 compiler_builtins
      2 compile
      2 clone_from_slice
      2 cfg_target_vendor
      2 ca_span
      2 "Cannotuse`#![feature
      2 binary_heap_extras
      2 augmented_assignments
      2 allow_internal_unsafe
      1 with_options
      1 while_let
      1 wake_trait
      1 wait_timeout_until
      1 wait_timeout
      1 vecmap
      1 UP_TOP
      1 unstable_features
      1 //unstable_features
      1 unsized_tuple_coercion
      1 unmarked_api
      1 underscore_const_names
      1 unboxed_closure_sugar
      1 u128_type
      1 u128
      1 //typeRequest=st
      1 //typeRequest=Box<dynst
      1 typeInterface
      1 try_find
      1 transpose_result
      1 tool_attributes
      1 //TODO
      1 time2
      1 thread_sleep
      1 thread_id
      1 test_2018_feature
      1 tbm_target_feature
      1 swap_with_slice
      1 swap_nonoverlapping
      1 structural_match
      1 str_checked_slicing
      1 str_as_mut_ptr
      1 sse4a_target_feature
      1 split_off
      1 ///spansof#![feature]attrsforstablelanguagefeatures.forerrorreporting
      1 span
      1 sort_internals
      1 slice_rsplit
      1 slice_partition_dedup
      1 slice_partition_at_index
      1 slice_internals
      1 //silly;explicituseof#![feature]alreadyindicatesopt-in
      1 ////silly;explicituseof#![feature]alreadyindicatesopt-in
      1 set_recovery
      1 scoped_tls
      1 rustdoc
      1 rustc_macro_lib
      1 rustc_const_unstable
      1 r#"#![feature
      1 reverse_cmp_key
      1 repr_align
      1 read_and_zero
      1 rc_weak
      1 rc_raw
      1 rc_into_raw_non_null
      1 rc_downcast
      1 range_inclusive
      1 put
      1 ptr_eq
      1 prox_macro_non_items
      1 proc_macro_mixed_site
      1 process_exitcode_placeholder
      1 process_exec
      1 process_abort
      1 path_buf_capacity
      1 panic_runtime
      1 panic_propagate
      1 panic_internals
      1 panic_col
      1 page_size
      1 overlapping_marker_traits
      1 or_patterns
      1 ord_max_min
      1 option_replace
      1 option_ref_mut_cloned
      1 option_flattening
      1 num_bits_bytes
      1 nothreads
      1 nonnull_cast
      1 net
      1 negative_impls
      1 negate_unsigned
      1 more_struct_aliases
      1 mem_take
      1 may_dangle
      1 maybe_uninit_uninit_array
      1 maybe_uninit_slice_assume_init
      1 map_in_place
      1 lookup_host
      1 link_cfg
      1 iter_order_by
      1 iter_is_partitioned
      1 iter_idx
      1 iter_cmp
      1 iterator_flatten
      1 iterator_find_map
      1 items
      1 item
      1 //inyourcrateroot
      1 int_error_internals
      1 internal_uninit_const
      1 inclusive_range_fields
      1 import_shadowing
      1 ifc_old==commitment{//TODO
      1 i128
      1 //=help
      1 hash_map_remove_entry
      1 hasher_write
      1 half_open_range_patterns
      1 fs_ext
      1 fs_canonicalize
      1 foo
      1 fn_must_use
      1 fn_box
      1 float_from_str_radix
      1 float_bits_conv
      1 //`#![feature]`attrsforlanguagefeatures
      1 extra_log_consts
      1 extern_in_paths
      1 extern_absolute_paths
      1 exit_status
      1 "examples/ex.rs"
      1 exact_chunks
      1 Evrey
      1 enumset
      1 entry_and_modify
      1 duration_extras
      1 duration_constants
      1 discriminant_value
      1 //Disabled
      1 dir_entry_ext
      1 dir_builder
      1 deprecated
      1 decode_utf8
      1 dec2flt
      1 cstr_to_str
      1 cstr_memory
      1 crypto
      1 cow_is_borrowed
      1 core_private_diy_float
      1 core_private_bignum
      1 core_prelude
      1 copysign
      1 copy_from_slice
      1 const_unique_new
      1 const_type_name
      1 const_slice_from_raw_parts
      1 const_saturating_int_methods
      1 const_refcell_new
      1 const_needs_drop
      1 const_max_value
      1 const_int_wrapping
      1 const_int_pow
      1 const_extern_fn
      1 const_cstr_unchecked
      1 const_atomic_usize_new
      1 const_atomic_isize_new
      1 const_atomic_bool_new
      1 compiler_builtins_lib
      1 command_envs
      1 collections_drain
      1 char_error_internals
      1 cfg_target_thread_local
      1 cfg_doctest
      1 btree_append
      1 box_leak
      1 box_heap
      1 bound_cloned
      1 ///Basicusage
      1 avx512_target_feature
      1 as_unsafe_cell
      1 assoc_unix_epoch
      1 ascii_ctype
      1 array_value_iter
      1 array_error_internals
      1 A`#![feature]`attributewasdeclaredforafeaturethatisstablein
      1 abi_unadjusted
      1 abi_efiapi