Move full configuration logic from rustc_expand to `rustc_builtin_m…

…acros`

This logic is applicable to two specific macros and not to the expansion infrastructure in general.

compiler/rustc_builtin_macros/src/cfg_eval.rs

@@ -1,23 +1,29 @@
 use crate::util::check_builtin_macro_attribute;
 
+use rustc_ast::mut_visit::{self, MutVisitor};
+use rustc_ast::ptr::P;
 use rustc_ast::{self as ast, AstLike};
+use rustc_data_structures::map_in_place::MapInPlace;
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_expand::config::StripUnconfigured;
+use rustc_expand::configure;
 use rustc_span::symbol::sym;
 use rustc_span::Span;
+use smallvec::SmallVec;
 
-pub fn expand(
+crate fn expand(
     ecx: &mut ExtCtxt<'_>,
     _span: Span,
     meta_item: &ast::MetaItem,
     item: Annotatable,
 ) -> Vec<Annotatable> {
     check_builtin_macro_attribute(ecx, meta_item, sym::cfg_eval);
 
-    let mut visitor =
-        StripUnconfigured { sess: ecx.sess, features: ecx.ecfg.features, modified: false };
+    let mut visitor = CfgEval {
+        cfg: StripUnconfigured { sess: ecx.sess, features: ecx.ecfg.features, modified: false },
+    };
     let mut item = visitor.fully_configure(item);
-    if visitor.modified {
+    if visitor.cfg.modified {
         // Erase the tokens if cfg-stripping modified the item
         // This will cause us to synthesize fake tokens
         // when `nt_to_tokenstream` is called on this item.
@@ -27,3 +33,165 @@ pub fn expand(
     }
     vec![item]
 }
+
+crate struct CfgEval<'a> {
+    pub cfg: StripUnconfigured<'a>,
+}
+
+impl CfgEval<'_> {
+    fn configure<T: AstLike>(&mut self, node: T) -> Option<T> {
+        self.cfg.configure(node)
+    }
+
+    fn configure_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
+        let ast::ForeignMod { unsafety: _, abi: _, items } = foreign_mod;
+        items.flat_map_in_place(|item| self.configure(item));
+    }
+
+    fn configure_variant_data(&mut self, vdata: &mut ast::VariantData) {
+        match vdata {
+            ast::VariantData::Struct(fields, ..) | ast::VariantData::Tuple(fields, _) => {
+                fields.flat_map_in_place(|field| self.configure(field))
+            }
+            ast::VariantData::Unit(_) => {}
+        }
+    }
+
+    fn configure_item_kind(&mut self, item: &mut ast::ItemKind) {
+        match item {
+            ast::ItemKind::Struct(def, _generics) | ast::ItemKind::Union(def, _generics) => {
+                self.configure_variant_data(def)
+            }
+            ast::ItemKind::Enum(ast::EnumDef { variants }, _generics) => {
+                variants.flat_map_in_place(|variant| self.configure(variant));
+                for variant in variants {
+                    self.configure_variant_data(&mut variant.data);
+                }
+            }
+            _ => {}
+        }
+    }
+
+    fn configure_expr_kind(&mut self, expr_kind: &mut ast::ExprKind) {
+        match expr_kind {
+            ast::ExprKind::Match(_m, arms) => {
+                arms.flat_map_in_place(|arm| self.configure(arm));
+            }
+            ast::ExprKind::Struct(_path, fields, _base) => {
+                fields.flat_map_in_place(|field| self.configure(field));
+            }
+            _ => {}
+        }
+    }
+
+    fn configure_pat(&mut self, pat: &mut P<ast::Pat>) {
+        if let ast::PatKind::Struct(_path, fields, _etc) = &mut pat.kind {
+            fields.flat_map_in_place(|field| self.configure(field));
+        }
+    }
+
+    fn configure_fn_decl(&mut self, fn_decl: &mut ast::FnDecl) {
+        fn_decl.inputs.flat_map_in_place(|arg| self.configure(arg));
+    }
+
+    crate fn fully_configure(&mut self, item: Annotatable) -> Annotatable {
+        // Since the item itself has already been configured by the InvocationCollector,
+        // we know that fold result vector will contain exactly one element
+        match item {
+            Annotatable::Item(item) => Annotatable::Item(self.flat_map_item(item).pop().unwrap()),
+            Annotatable::TraitItem(item) => {
+                Annotatable::TraitItem(self.flat_map_trait_item(item).pop().unwrap())
+            }
+            Annotatable::ImplItem(item) => {
+                Annotatable::ImplItem(self.flat_map_impl_item(item).pop().unwrap())
+            }
+            Annotatable::ForeignItem(item) => {
+                Annotatable::ForeignItem(self.flat_map_foreign_item(item).pop().unwrap())
+            }
+            Annotatable::Stmt(stmt) => {
+                Annotatable::Stmt(stmt.map(|stmt| self.flat_map_stmt(stmt).pop().unwrap()))
+            }
+            Annotatable::Expr(mut expr) => Annotatable::Expr({
+                self.visit_expr(&mut expr);
+                expr
+            }),
+            Annotatable::Arm(arm) => Annotatable::Arm(self.flat_map_arm(arm).pop().unwrap()),
+            Annotatable::Field(field) => {
+                Annotatable::Field(self.flat_map_field(field).pop().unwrap())
+            }
+            Annotatable::FieldPat(fp) => {
+                Annotatable::FieldPat(self.flat_map_field_pattern(fp).pop().unwrap())
+            }
+            Annotatable::GenericParam(param) => {
+                Annotatable::GenericParam(self.flat_map_generic_param(param).pop().unwrap())
+            }
+            Annotatable::Param(param) => {
+                Annotatable::Param(self.flat_map_param(param).pop().unwrap())
+            }
+            Annotatable::StructField(sf) => {
+                Annotatable::StructField(self.flat_map_struct_field(sf).pop().unwrap())
+            }
+            Annotatable::Variant(v) => {
+                Annotatable::Variant(self.flat_map_variant(v).pop().unwrap())
+            }
+        }
+    }
+}
+
+impl MutVisitor for CfgEval<'_> {
+    fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
+        self.configure_foreign_mod(foreign_mod);
+        mut_visit::noop_visit_foreign_mod(foreign_mod, self);
+    }
+
+    fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
+        self.configure_item_kind(item);
+        mut_visit::noop_visit_item_kind(item, self);
+    }
+
+    fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
+        self.cfg.configure_expr(expr);
+        self.configure_expr_kind(&mut expr.kind);
+        mut_visit::noop_visit_expr(expr, self);
+    }
+
+    fn filter_map_expr(&mut self, expr: P<ast::Expr>) -> Option<P<ast::Expr>> {
+        let mut expr = configure!(self, expr);
+        self.configure_expr_kind(&mut expr.kind);
+        mut_visit::noop_visit_expr(&mut expr, self);
+        Some(expr)
+    }
+
+    fn flat_map_generic_param(
+        &mut self,
+        param: ast::GenericParam,
+    ) -> SmallVec<[ast::GenericParam; 1]> {
+        mut_visit::noop_flat_map_generic_param(configure!(self, param), self)
+    }
+
+    fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
+        mut_visit::noop_flat_map_stmt(configure!(self, stmt), self)
+    }
+
+    fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
+        mut_visit::noop_flat_map_item(configure!(self, item), self)
+    }
+
+    fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
+        mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
+    }
+
+    fn flat_map_trait_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
+        mut_visit::noop_flat_map_assoc_item(configure!(self, item), self)
+    }
+
+    fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
+        self.configure_pat(pat);
+        mut_visit::noop_visit_pat(pat, self)
+    }
+
+    fn visit_fn_decl(&mut self, mut fn_decl: &mut P<ast::FnDecl>) {
+        self.configure_fn_decl(&mut fn_decl);
+        mut_visit::noop_visit_fn_decl(fn_decl, self);
+    }
+}

compiler/rustc_builtin_macros/src/derive.rs

@@ -1,3 +1,5 @@
+use crate::cfg_eval::CfgEval;
+
 use rustc_ast::{self as ast, token, AstLike, ItemKind, MetaItemKind, NestedMetaItem, StmtKind};
 use rustc_errors::{struct_span_err, Applicability};
 use rustc_expand::base::{Annotatable, ExpandResult, ExtCtxt, Indeterminate, MultiItemModifier};
@@ -52,10 +54,11 @@ impl MultiItemModifier for Expander {
         // FIXME: Try to cache intermediate results to avoid collecting same paths multiple times.
         match ecx.resolver.resolve_derives(ecx.current_expansion.id, derives, ecx.force_mode) {
             Ok(()) => {
-                let mut visitor =
-                    StripUnconfigured { sess, features: ecx.ecfg.features, modified: false };
+                let mut visitor = CfgEval {
+                    cfg: StripUnconfigured { sess, features: ecx.ecfg.features, modified: false },
+                };
                 let mut item = visitor.fully_configure(item);
-                if visitor.modified {
+                if visitor.cfg.modified {
                     // Erase the tokens if cfg-stripping modified the item
                     // This will cause us to synthesize fake tokens
                     // when `nt_to_tokenstream` is called on this item.