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-rw-r--r--compiler/rustc_expand/src/config.rs535
1 files changed, 535 insertions, 0 deletions
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
new file mode 100644
index 000000000..3e1acf438
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+++ b/compiler/rustc_expand/src/config.rs
@@ -0,0 +1,535 @@
+//! 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",
+ 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)
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-10 12:21:53 +0000