Rollup merge of #82682 - petrochenkov:cfgeval, r=Aaron1011
Implement built-in attribute macro `#[cfg_eval]` + some refactoring This PR implements a built-in attribute macro `#[cfg_eval]` as it was suggested in https://github.com/rust-lang/rust/pull/79078 to avoid `#[derive()]` without arguments being abused as a way to configure input for other attributes. The macro is used for eagerly expanding all `#[cfg]` and `#[cfg_attr]` attributes in its input ("fully configuring" the input). The effect is identical to effect of `#[derive(Foo, Bar)]` which also fully configures its input before passing it to macros `Foo` and `Bar`, but unlike `#[derive]` `#[cfg_eval]` can be applied to any syntax nodes supporting macro attributes, not only certain items. `cfg_eval` was the first name suggested in https://github.com/rust-lang/rust/pull/79078, but other alternatives are also possible, e.g. `cfg_expand`. ```rust #[cfg_eval] #[my_attr] // Receives `struct S {}` as input, the field is configured away by `#[cfg_eval]` struct S { #[cfg(FALSE)] field: u8, } ``` Tracking issue: https://github.com/rust-lang/rust/issues/82679
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Dylan DPC
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9c310571a8
17 changed files with 453 additions and 259 deletions
157
compiler/rustc_builtin_macros/src/cfg_eval.rs
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157
compiler/rustc_builtin_macros/src/cfg_eval.rs
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@ -0,0 +1,157 @@
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use crate::util::check_builtin_macro_attribute;
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use rustc_ast::mut_visit::{self, MutVisitor};
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use rustc_ast::ptr::P;
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use rustc_ast::{self as ast, AstLike};
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use rustc_expand::base::{Annotatable, ExtCtxt};
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use rustc_expand::config::StripUnconfigured;
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use rustc_expand::configure;
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use rustc_span::symbol::sym;
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use rustc_span::Span;
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use smallvec::SmallVec;
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crate fn expand(
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ecx: &mut ExtCtxt<'_>,
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_span: Span,
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meta_item: &ast::MetaItem,
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annotatable: Annotatable,
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) -> Vec<Annotatable> {
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check_builtin_macro_attribute(ecx, meta_item, sym::cfg_eval);
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cfg_eval(ecx, annotatable)
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}
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crate fn cfg_eval(ecx: &ExtCtxt<'_>, annotatable: Annotatable) -> Vec<Annotatable> {
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let mut visitor = CfgEval {
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cfg: StripUnconfigured { sess: ecx.sess, features: ecx.ecfg.features, modified: false },
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};
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let mut annotatable = visitor.configure_annotatable(annotatable);
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if visitor.cfg.modified {
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// Erase the tokens if cfg-stripping modified the item
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// This will cause us to synthesize fake tokens
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// when `nt_to_tokenstream` is called on this item.
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if let Some(tokens) = annotatable.tokens_mut() {
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*tokens = None;
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}
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}
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vec![annotatable]
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}
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struct CfgEval<'a> {
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cfg: StripUnconfigured<'a>,
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}
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impl CfgEval<'_> {
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fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
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self.cfg.configure(node)
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}
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fn configure_annotatable(&mut self, annotatable: Annotatable) -> Annotatable {
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// Since the item itself has already been configured by the InvocationCollector,
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// we know that fold result vector will contain exactly one element
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match annotatable {
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Annotatable::Item(item) => Annotatable::Item(self.flat_map_item(item).pop().unwrap()),
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Annotatable::TraitItem(item) => {
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Annotatable::TraitItem(self.flat_map_trait_item(item).pop().unwrap())
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}
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Annotatable::ImplItem(item) => {
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Annotatable::ImplItem(self.flat_map_impl_item(item).pop().unwrap())
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}
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Annotatable::ForeignItem(item) => {
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Annotatable::ForeignItem(self.flat_map_foreign_item(item).pop().unwrap())
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}
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Annotatable::Stmt(stmt) => {
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Annotatable::Stmt(stmt.map(|stmt| self.flat_map_stmt(stmt).pop().unwrap()))
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}
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Annotatable::Expr(mut expr) => Annotatable::Expr({
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self.visit_expr(&mut expr);
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expr
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}),
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Annotatable::Arm(arm) => Annotatable::Arm(self.flat_map_arm(arm).pop().unwrap()),
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Annotatable::Field(field) => {
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Annotatable::Field(self.flat_map_field(field).pop().unwrap())
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}
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Annotatable::FieldPat(fp) => {
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Annotatable::FieldPat(self.flat_map_field_pattern(fp).pop().unwrap())
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}
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Annotatable::GenericParam(param) => {
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Annotatable::GenericParam(self.flat_map_generic_param(param).pop().unwrap())
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}
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Annotatable::Param(param) => {
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Annotatable::Param(self.flat_map_param(param).pop().unwrap())
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}
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Annotatable::StructField(sf) => {
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Annotatable::StructField(self.flat_map_struct_field(sf).pop().unwrap())
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}
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Annotatable::Variant(v) => {
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Annotatable::Variant(self.flat_map_variant(v).pop().unwrap())
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}
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}
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}
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}
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impl MutVisitor for CfgEval<'_> {
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fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
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self.cfg.configure_expr(expr);
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mut_visit::noop_visit_expr(expr, self);
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}
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fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
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let mut expr = configure!(self, expr);
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mut_visit::noop_visit_expr(&mut expr, self);
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Some(expr)
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}
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fn flat_map_generic_param(
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&mut self,
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param: ast::GenericParam,
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) -> SmallVec<[ast::GenericParam; 1]> {
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mut_visit::noop_flat_map_generic_param(configure!(self, param), self)
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}
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fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
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mut_visit::noop_flat_map_stmt(configure!(self, stmt), self)
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}
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fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
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mut_visit::noop_flat_map_item(configure!(self, item), self)
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}
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fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
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mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
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}
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fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
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mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
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}
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fn flat_map_foreign_item(
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&mut self,
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foreign_item: P<ast::ForeignItem>,
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) -> SmallVec<[P<ast::ForeignItem>; 1]> {
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mut_visit::noop_flat_map_foreign_item(configure!(self, foreign_item), self)
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}
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fn flat_map_arm(&mut self, arm: ast::Arm) -> SmallVec<[ast::Arm; 1]> {
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mut_visit::noop_flat_map_arm(configure!(self, arm), self)
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}
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fn flat_map_field(&mut self, field: ast::Field) -> SmallVec<[ast::Field; 1]> {
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mut_visit::noop_flat_map_field(configure!(self, field), self)
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}
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fn flat_map_field_pattern(&mut self, fp: ast::FieldPat) -> SmallVec<[ast::FieldPat; 1]> {
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mut_visit::noop_flat_map_field_pattern(configure!(self, fp), self)
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}
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fn flat_map_param(&mut self, p: ast::Param) -> SmallVec<[ast::Param; 1]> {
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mut_visit::noop_flat_map_param(configure!(self, p), self)
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}
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fn flat_map_struct_field(&mut self, sf: ast::StructField) -> SmallVec<[ast::StructField; 1]> {
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mut_visit::noop_flat_map_struct_field(configure!(self, sf), self)
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}
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fn flat_map_variant(&mut self, variant: ast::Variant) -> SmallVec<[ast::Variant; 1]> {
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mut_visit::noop_flat_map_variant(configure!(self, variant), self)
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}
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}
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@ -1,7 +1,8 @@
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use crate::cfg_eval::cfg_eval;
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use rustc_ast::{self as ast, token, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
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use rustc_errors::{struct_span_err, Applicability};
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use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
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use rustc_expand::config::StripUnconfigured;
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use rustc_feature::AttributeTemplate;
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use rustc_parse::validate_attr;
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use rustc_session::Session;
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@ -51,26 +52,7 @@ impl MultiItemModifier for Expander {
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// FIXME: Try to cache intermediate results to avoid collecting same paths multiple times.
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match ecx.resolver.resolve_derives(ecx.current_expansion.id, derives, ecx.force_mode) {
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Ok(()) => {
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let mut visitor =
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StripUnconfigured { sess, features: ecx.ecfg.features, modified: false };
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let mut item = visitor.fully_configure(item);
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if visitor.modified {
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// Erase the tokens if cfg-stripping modified the item
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// This will cause us to synthesize fake tokens
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// when `nt_to_tokenstream` is called on this item.
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match &mut item {
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Annotatable::Item(item) => item,
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Annotatable::Stmt(stmt) => match &mut stmt.kind {
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StmtKind::Item(item) => item,
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_ => unreachable!(),
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},
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_ => unreachable!(),
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}
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.tokens = None;
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}
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ExpandResult::Ready(vec![item])
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}
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Ok(()) => ExpandResult::Ready(cfg_eval(ecx, item)),
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Err(Indeterminate) => ExpandResult::Retry(item),
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}
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}
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@ -24,6 +24,7 @@ mod asm;
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mod assert;
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mod cfg;
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mod cfg_accessible;
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mod cfg_eval;
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mod compile_error;
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mod concat;
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mod concat_idents;
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@ -89,6 +90,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
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register_attr! {
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bench: test::expand_bench,
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cfg_accessible: cfg_accessible::Expander,
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cfg_eval: cfg_eval::expand,
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derive: derive::Expander,
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global_allocator: global_allocator::expand,
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test: test::expand_test,
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