Crate rustc_feature

Feature gates

This crate declares the set of past and present unstable features in the compiler. Feature gate checking itself is done in rustc_ast_passes/src/feature_gate.rs at the moment.

Features are enabled in programs via the crate-level attributes of #![feature(...)] with a comma-separated list of features.

For the purpose of future feature-tracking, once a feature gate is added, even if it is stabilized or removed, do not remove it. Instead, move the symbol to the accepted or removed modules respectively.

Modules

accepted 🔒

List of the accepted feature gates.

builtin_attrs 🔒

Built-in attributes and cfg flag gating.

removed 🔒

List of the removed feature gates.

unstable 🔒

List of the unstable feature gates.

Macros

template

A convenience macro for constructing attribute templates. E.g., template!(Word, List: "description") means that the attribute supports forms #[attr] and #[attr(description)].

Structs

AttributeTemplate

A template that the attribute input must match. Only top-level shape (#[attr] vs #[attr(...)] vs #[attr = ...]) is considered now.

BuiltinAttribute

EnabledLangFeature

Information about an enabled language feature.

EnabledLibFeature

Information about an enabled library feature.

Feature

Features

A set of features to be used by later passes.

Enums

AttributeDuplicates

How to handle multiple duplicate attributes on the same item.

AttributeGate

AttributeSafety

AttributeType

GateIssue

UnstableFeatures

Constants

INCOMPATIBLE_FEATURES

Some features are not allowed to be used together at the same time, if the two are present, produce an error.

Statics

ACCEPTED_LANG_FEATURES

Formerly unstable features that have now been accepted (stabilized).

BUILTIN_ATTRIBUTES

Attributes that have a special meaning to rustc or rustdoc.

BUILTIN_ATTRIBUTE_MAP

REMOVED_LANG_FEATURES

Formerly unstable features that have now been removed.

UNSTABLE_LANG_FEATURES

Unstable language features that are being implemented or being considered for acceptance (stabilization) or removal.

Functions

encode_cross_crate

Whether this builtin attribute is encoded cross crate. This means it can be used cross crate.

find_feature_issue

find_gated_cfg

Find a gated cfg determined by the predicate which is given the cfg’s name.

find_lang_feature_issue 🔒

is_builtin_attr_name

is_stable_diagnostic_attribute

is_valid_for_get_attr

to_nonzero 🔒

Type Aliases

GatedCfg