rust/compiler/rustc_expand/src/config.rs
Joshua Nelson 3c9765cff1 Rename debugging_opts to unstable_opts
This is no longer used only for debugging options (e.g. `-Zoutput-width`, `-Zallow-features`).
Rename it to be more clear.
2022-07-13 17:47:06 -05:00

536 lines
20 KiB
Rust

//! Conditional compilation stripping.
use rustc_ast::ptr::P;
use rustc_ast::token::{Delimiter, Token, TokenKind};
use rustc_ast::tokenstream::{AttrAnnotatedTokenStream, AttrAnnotatedTokenTree};
use rustc_ast::tokenstream::{DelimSpan, Spacing};
use rustc_ast::tokenstream::{LazyTokenStream, TokenTree};
use rustc_ast::NodeId;
use rustc_ast::{self as ast, AttrStyle, Attribute, HasAttrs, HasTokens, MetaItem};
use rustc_attr as attr;
use rustc_data_structures::fx::FxHashMap;
use rustc_data_structures::map_in_place::MapInPlace;
use rustc_errors::{error_code, struct_span_err, Applicability, Handler};
use rustc_feature::{Feature, Features, State as FeatureState};
use rustc_feature::{
ACCEPTED_FEATURES, ACTIVE_FEATURES, REMOVED_FEATURES, STABLE_REMOVED_FEATURES,
};
use rustc_parse::validate_attr;
use rustc_session::parse::feature_err;
use rustc_session::Session;
use rustc_span::edition::{Edition, ALL_EDITIONS};
use rustc_span::symbol::{sym, Symbol};
use rustc_span::{Span, DUMMY_SP};
/// A folder that strips out items that do not belong in the current configuration.
pub struct StripUnconfigured<'a> {
pub sess: &'a Session,
pub features: Option<&'a Features>,
/// If `true`, perform cfg-stripping on attached tokens.
/// This is only used for the input to derive macros,
/// which needs eager expansion of `cfg` and `cfg_attr`
pub config_tokens: bool,
pub lint_node_id: NodeId,
}
fn get_features(
sess: &Session,
span_handler: &Handler,
krate_attrs: &[ast::Attribute],
) -> Features {
fn feature_removed(span_handler: &Handler, span: Span, reason: Option<&str>) {
let mut err = struct_span_err!(span_handler, span, E0557, "feature has been removed");
err.span_label(span, "feature has been removed");
if let Some(reason) = reason {
err.note(reason);
}
err.emit();
}
fn active_features_up_to(edition: Edition) -> impl Iterator<Item = &'static Feature> {
ACTIVE_FEATURES.iter().filter(move |feature| {
if let Some(feature_edition) = feature.edition {
feature_edition <= edition
} else {
false
}
})
}
let mut features = Features::default();
let mut edition_enabled_features = FxHashMap::default();
let crate_edition = sess.edition();
for &edition in ALL_EDITIONS {
if edition <= crate_edition {
// The `crate_edition` implies its respective umbrella feature-gate
// (i.e., `#![feature(rust_20XX_preview)]` isn't needed on edition 20XX).
edition_enabled_features.insert(edition.feature_name(), edition);
}
}
for feature in active_features_up_to(crate_edition) {
feature.set(&mut features, DUMMY_SP);
edition_enabled_features.insert(feature.name, crate_edition);
}
// Process the edition umbrella feature-gates first, to ensure
// `edition_enabled_features` is completed before it's queried.
for attr in krate_attrs {
if !attr.has_name(sym::feature) {
continue;
}
let Some(list) = attr.meta_item_list() else {
continue;
};
for mi in list {
if !mi.is_word() {
continue;
}
let name = mi.name_or_empty();
let edition = ALL_EDITIONS.iter().find(|e| name == e.feature_name()).copied();
if let Some(edition) = edition {
if edition <= crate_edition {
continue;
}
for feature in active_features_up_to(edition) {
// FIXME(Manishearth) there is currently no way to set
// lib features by edition
feature.set(&mut features, DUMMY_SP);
edition_enabled_features.insert(feature.name, edition);
}
}
}
}
for attr in krate_attrs {
if !attr.has_name(sym::feature) {
continue;
}
let Some(list) = attr.meta_item_list() else {
continue;
};
let bad_input = |span| {
struct_span_err!(span_handler, span, E0556, "malformed `feature` attribute input")
};
for mi in list {
let name = match mi.ident() {
Some(ident) if mi.is_word() => ident.name,
Some(ident) => {
bad_input(mi.span())
.span_suggestion(
mi.span(),
"expected just one word",
format!("{}", ident.name),
Applicability::MaybeIncorrect,
)
.emit();
continue;
}
None => {
bad_input(mi.span()).span_label(mi.span(), "expected just one word").emit();
continue;
}
};
if let Some(edition) = edition_enabled_features.get(&name) {
let msg =
&format!("the feature `{}` is included in the Rust {} edition", name, edition);
span_handler.struct_span_warn_with_code(mi.span(), msg, error_code!(E0705)).emit();
continue;
}
if ALL_EDITIONS.iter().any(|e| name == e.feature_name()) {
// Handled in the separate loop above.
continue;
}
let removed = REMOVED_FEATURES.iter().find(|f| name == f.name);
let stable_removed = STABLE_REMOVED_FEATURES.iter().find(|f| name == f.name);
if let Some(Feature { state, .. }) = removed.or(stable_removed) {
if let FeatureState::Removed { reason } | FeatureState::Stabilized { reason } =
state
{
feature_removed(span_handler, mi.span(), *reason);
continue;
}
}
if let Some(Feature { since, .. }) = ACCEPTED_FEATURES.iter().find(|f| name == f.name) {
let since = Some(Symbol::intern(since));
features.declared_lang_features.push((name, mi.span(), since));
features.active_features.insert(name);
continue;
}
if let Some(allowed) = sess.opts.unstable_opts.allow_features.as_ref() {
if allowed.iter().all(|f| name.as_str() != f) {
struct_span_err!(
span_handler,
mi.span(),
E0725,
"the feature `{}` is not in the list of allowed features",
name
)
.emit();
continue;
}
}
if let Some(f) = ACTIVE_FEATURES.iter().find(|f| name == f.name) {
f.set(&mut features, mi.span());
features.declared_lang_features.push((name, mi.span(), None));
features.active_features.insert(name);
continue;
}
features.declared_lib_features.push((name, mi.span()));
features.active_features.insert(name);
}
}
features
}
// `cfg_attr`-process the crate's attributes and compute the crate's features.
pub fn features(
sess: &Session,
mut krate: ast::Crate,
lint_node_id: NodeId,
) -> (ast::Crate, Features) {
let mut strip_unconfigured =
StripUnconfigured { sess, features: None, config_tokens: false, lint_node_id };
let unconfigured_attrs = krate.attrs.clone();
let diag = &sess.parse_sess.span_diagnostic;
let err_count = diag.err_count();
let features = match strip_unconfigured.configure_krate_attrs(krate.attrs) {
None => {
// The entire crate is unconfigured.
krate.attrs = Vec::new();
krate.items = Vec::new();
Features::default()
}
Some(attrs) => {
krate.attrs = attrs;
let features = get_features(sess, diag, &krate.attrs);
if err_count == diag.err_count() {
// Avoid reconfiguring malformed `cfg_attr`s.
strip_unconfigured.features = Some(&features);
// Run configuration again, this time with features available
// so that we can perform feature-gating.
strip_unconfigured.configure_krate_attrs(unconfigured_attrs);
}
features
}
};
(krate, features)
}
#[macro_export]
macro_rules! configure {
($this:ident, $node:ident) => {
match $this.configure($node) {
Some(node) => node,
None => return Default::default(),
}
};
}
impl<'a> StripUnconfigured<'a> {
pub fn configure<T: HasAttrs + HasTokens>(&self, mut node: T) -> Option<T> {
self.process_cfg_attrs(&mut node);
if self.in_cfg(node.attrs()) {
self.try_configure_tokens(&mut node);
Some(node)
} else {
None
}
}
fn try_configure_tokens<T: HasTokens>(&self, node: &mut T) {
if self.config_tokens {
if let Some(Some(tokens)) = node.tokens_mut() {
let attr_annotated_tokens = tokens.create_token_stream();
*tokens = LazyTokenStream::new(self.configure_tokens(&attr_annotated_tokens));
}
}
}
fn configure_krate_attrs(&self, mut attrs: Vec<ast::Attribute>) -> Option<Vec<ast::Attribute>> {
attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
if self.in_cfg(&attrs) { Some(attrs) } else { None }
}
/// Performs cfg-expansion on `stream`, producing a new `AttrAnnotatedTokenStream`.
/// This is only used during the invocation of `derive` proc-macros,
/// which require that we cfg-expand their entire input.
/// Normal cfg-expansion operates on parsed AST nodes via the `configure` method
fn configure_tokens(&self, stream: &AttrAnnotatedTokenStream) -> AttrAnnotatedTokenStream {
fn can_skip(stream: &AttrAnnotatedTokenStream) -> bool {
stream.0.iter().all(|(tree, _spacing)| match tree {
AttrAnnotatedTokenTree::Attributes(_) => false,
AttrAnnotatedTokenTree::Token(_) => true,
AttrAnnotatedTokenTree::Delimited(_, _, inner) => can_skip(inner),
})
}
if can_skip(stream) {
return stream.clone();
}
let trees: Vec<_> = stream
.0
.iter()
.flat_map(|(tree, spacing)| match tree.clone() {
AttrAnnotatedTokenTree::Attributes(mut data) => {
let mut attrs: Vec<_> = std::mem::take(&mut data.attrs).into();
attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
data.attrs = attrs.into();
if self.in_cfg(&data.attrs) {
data.tokens = LazyTokenStream::new(
self.configure_tokens(&data.tokens.create_token_stream()),
);
Some((AttrAnnotatedTokenTree::Attributes(data), *spacing)).into_iter()
} else {
None.into_iter()
}
}
AttrAnnotatedTokenTree::Delimited(sp, delim, mut inner) => {
inner = self.configure_tokens(&inner);
Some((AttrAnnotatedTokenTree::Delimited(sp, delim, inner), *spacing))
.into_iter()
}
AttrAnnotatedTokenTree::Token(ref token) if let TokenKind::Interpolated(ref nt) = token.kind => {
panic!(
"Nonterminal should have been flattened at {:?}: {:?}",
token.span, nt
);
}
AttrAnnotatedTokenTree::Token(token) => {
Some((AttrAnnotatedTokenTree::Token(token), *spacing)).into_iter()
}
})
.collect();
AttrAnnotatedTokenStream::new(trees)
}
/// Parse and expand all `cfg_attr` attributes into a list of attributes
/// that are within each `cfg_attr` that has a true configuration predicate.
///
/// Gives compiler warnings if any `cfg_attr` does not contain any
/// attributes and is in the original source code. Gives compiler errors if
/// the syntax of any `cfg_attr` is incorrect.
fn process_cfg_attrs<T: HasAttrs>(&self, node: &mut T) {
node.visit_attrs(|attrs| {
attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
});
}
fn process_cfg_attr(&self, attr: Attribute) -> Vec<Attribute> {
if attr.has_name(sym::cfg_attr) { self.expand_cfg_attr(attr, true) } else { vec![attr] }
}
/// Parse and expand a single `cfg_attr` attribute into a list of attributes
/// when the configuration predicate is true, or otherwise expand into an
/// empty list of attributes.
///
/// Gives a compiler warning when the `cfg_attr` contains no attributes and
/// is in the original source file. Gives a compiler error if the syntax of
/// the attribute is incorrect.
pub(crate) fn expand_cfg_attr(&self, attr: Attribute, recursive: bool) -> Vec<Attribute> {
let Some((cfg_predicate, expanded_attrs)) =
rustc_parse::parse_cfg_attr(&attr, &self.sess.parse_sess) else {
return vec![];
};
// Lint on zero attributes in source.
if expanded_attrs.is_empty() {
self.sess.parse_sess.buffer_lint(
rustc_lint_defs::builtin::UNUSED_ATTRIBUTES,
attr.span,
ast::CRATE_NODE_ID,
"`#[cfg_attr]` does not expand to any attributes",
);
}
if !attr::cfg_matches(
&cfg_predicate,
&self.sess.parse_sess,
self.lint_node_id,
self.features,
) {
return vec![];
}
if recursive {
// We call `process_cfg_attr` recursively in case there's a
// `cfg_attr` inside of another `cfg_attr`. E.g.
// `#[cfg_attr(false, cfg_attr(true, some_attr))]`.
expanded_attrs
.into_iter()
.flat_map(|item| self.process_cfg_attr(self.expand_cfg_attr_item(&attr, item)))
.collect()
} else {
expanded_attrs.into_iter().map(|item| self.expand_cfg_attr_item(&attr, item)).collect()
}
}
fn expand_cfg_attr_item(
&self,
attr: &Attribute,
(item, item_span): (ast::AttrItem, Span),
) -> Attribute {
let orig_tokens = attr.tokens().to_tokenstream();
// We are taking an attribute of the form `#[cfg_attr(pred, attr)]`
// and producing an attribute of the form `#[attr]`. We
// have captured tokens for `attr` itself, but we need to
// synthesize tokens for the wrapper `#` and `[]`, which
// we do below.
// Use the `#` in `#[cfg_attr(pred, attr)]` as the `#` token
// for `attr` when we expand it to `#[attr]`
let mut orig_trees = orig_tokens.into_trees();
let TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }) = orig_trees.next().unwrap() else {
panic!("Bad tokens for attribute {:?}", attr);
};
let pound_span = pound_token.span;
let mut trees = vec![(AttrAnnotatedTokenTree::Token(pound_token), Spacing::Alone)];
if attr.style == AttrStyle::Inner {
// For inner attributes, we do the same thing for the `!` in `#![some_attr]`
let TokenTree::Token(bang_token @ Token { kind: TokenKind::Not, .. }) = orig_trees.next().unwrap() else {
panic!("Bad tokens for attribute {:?}", attr);
};
trees.push((AttrAnnotatedTokenTree::Token(bang_token), Spacing::Alone));
}
// We don't really have a good span to use for the synthesized `[]`
// in `#[attr]`, so just use the span of the `#` token.
let bracket_group = AttrAnnotatedTokenTree::Delimited(
DelimSpan::from_single(pound_span),
Delimiter::Bracket,
item.tokens
.as_ref()
.unwrap_or_else(|| panic!("Missing tokens for {:?}", item))
.create_token_stream(),
);
trees.push((bracket_group, Spacing::Alone));
let tokens = Some(LazyTokenStream::new(AttrAnnotatedTokenStream::new(trees)));
let attr = attr::mk_attr_from_item(item, tokens, attr.style, item_span);
if attr.has_name(sym::crate_type) {
self.sess.parse_sess.buffer_lint(
rustc_lint_defs::builtin::DEPRECATED_CFG_ATTR_CRATE_TYPE_NAME,
attr.span,
ast::CRATE_NODE_ID,
"`crate_type` within an `#![cfg_attr] attribute is deprecated`",
);
}
if attr.has_name(sym::crate_name) {
self.sess.parse_sess.buffer_lint(
rustc_lint_defs::builtin::DEPRECATED_CFG_ATTR_CRATE_TYPE_NAME,
attr.span,
ast::CRATE_NODE_ID,
"`crate_name` within an `#![cfg_attr] attribute is deprecated`",
);
}
attr
}
/// Determines if a node with the given attributes should be included in this configuration.
fn in_cfg(&self, attrs: &[Attribute]) -> bool {
attrs.iter().all(|attr| !is_cfg(attr) || self.cfg_true(attr))
}
pub(crate) fn cfg_true(&self, attr: &Attribute) -> bool {
let meta_item = match validate_attr::parse_meta(&self.sess.parse_sess, attr) {
Ok(meta_item) => meta_item,
Err(mut err) => {
err.emit();
return true;
}
};
parse_cfg(&meta_item, &self.sess).map_or(true, |meta_item| {
attr::cfg_matches(&meta_item, &self.sess.parse_sess, self.lint_node_id, self.features)
})
}
/// If attributes are not allowed on expressions, emit an error for `attr`
pub(crate) fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
if !self.features.map_or(true, |features| features.stmt_expr_attributes) {
let mut err = feature_err(
&self.sess.parse_sess,
sym::stmt_expr_attributes,
attr.span,
"attributes on expressions are experimental",
);
if attr.is_doc_comment() {
err.help("`///` is for documentation comments. For a plain comment, use `//`.");
}
err.emit();
}
}
pub fn configure_expr(&self, expr: &mut P<ast::Expr>) {
for attr in expr.attrs.iter() {
self.maybe_emit_expr_attr_err(attr);
}
// If an expr is valid to cfg away it will have been removed by the
// outer stmt or expression folder before descending in here.
// Anything else is always required, and thus has to error out
// in case of a cfg attr.
//
// N.B., this is intentionally not part of the visit_expr() function
// in order for filter_map_expr() to be able to avoid this check
if let Some(attr) = expr.attrs().iter().find(|a| is_cfg(*a)) {
let msg = "removing an expression is not supported in this position";
self.sess.parse_sess.span_diagnostic.span_err(attr.span, msg);
}
self.process_cfg_attrs(expr);
self.try_configure_tokens(&mut *expr);
}
}
pub fn parse_cfg<'a>(meta_item: &'a MetaItem, sess: &Session) -> Option<&'a MetaItem> {
let error = |span, msg, suggestion: &str| {
let mut err = sess.parse_sess.span_diagnostic.struct_span_err(span, msg);
if !suggestion.is_empty() {
err.span_suggestion(
span,
"expected syntax is",
suggestion,
Applicability::HasPlaceholders,
);
}
err.emit();
None
};
let span = meta_item.span;
match meta_item.meta_item_list() {
None => error(span, "`cfg` is not followed by parentheses", "cfg(/* predicate */)"),
Some([]) => error(span, "`cfg` predicate is not specified", ""),
Some([_, .., l]) => error(l.span(), "multiple `cfg` predicates are specified", ""),
Some([single]) => match single.meta_item() {
Some(meta_item) => Some(meta_item),
None => error(single.span(), "`cfg` predicate key cannot be a literal", ""),
},
}
}
fn is_cfg(attr: &Attribute) -> bool {
attr.has_name(sym::cfg)
}