Move full configuration logic from `rustc_expand` to `rustc_builtin_macros`

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

3 files changed, 184 insertions, 176 deletions

diff --git a/compiler/rustc_builtin_macros/src/cfg_eval.rs b/compiler/rustc_builtin_macros/src/cfg_eval.rs
index 805f9d0634c..8cf3be33e20 100644
--- a/compiler/rustc_builtin_macros/src/cfg_eval.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_eval.rs
@@ -1,12 +1,17 @@
 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,
@@ -14,10 +19,11 @@ pub fn expand(
 ) -> 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);
+    }
+}
diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index c307d8b2f53..48b1dddfdd1 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/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.
diff --git a/compiler/rustc_expand/src/config.rs b/compiler/rustc_expand/src/config.rs
index 7d0becf1f5d..a23731cf309 100644
--- a/compiler/rustc_expand/src/config.rs
+++ b/compiler/rustc_expand/src/config.rs
@@ -1,8 +1,5 @@
 //! Conditional compilation stripping.
 
-use crate::base::Annotatable;
-
-use rustc_ast::mut_visit::*;
 use rustc_ast::ptr::P;
 use rustc_ast::token::{DelimToken, Token, TokenKind};
 use rustc_ast::tokenstream::{DelimSpan, LazyTokenStream, Spacing, TokenStream, TokenTree};
@@ -22,8 +19,6 @@ use rustc_span::edition::{Edition, ALL_EDITIONS};
 use rustc_span::symbol::{sym, Symbol};
 use rustc_span::{Span, DUMMY_SP};
 
-use smallvec::SmallVec;
-
 /// A folder that strips out items that do not belong in the current configuration.
 pub struct StripUnconfigured<'a> {
     pub sess: &'a Session,
@@ -272,7 +267,7 @@ impl<'a> StripUnconfigured<'a> {
     /// 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.
-    pub fn process_cfg_attrs<T: AstLike>(&mut self, node: &mut T) {
+    fn process_cfg_attrs<T: AstLike>(&mut self, node: &mut T) {
         node.visit_attrs(|attrs| {
             attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
         });
@@ -387,7 +382,7 @@ impl<'a> StripUnconfigured<'a> {
     }
 
     /// Determines if a node with the given attributes should be included in this configuration.
-    pub fn in_cfg(&self, attrs: &[Attribute]) -> bool {
+    fn in_cfg(&self, attrs: &[Attribute]) -> bool {
         attrs.iter().all(|attr| {
             if !is_cfg(self.sess, attr) {
                 return true;
@@ -427,16 +422,8 @@ impl<'a> StripUnconfigured<'a> {
         })
     }
 
-    /// Visit attributes on expression and statements (but not attributes on items in blocks).
-    fn visit_expr_attrs(&mut self, attrs: &[Attribute]) {
-        // flag the offending attributes
-        for attr in attrs.iter() {
-            self.maybe_emit_expr_attr_err(attr);
-        }
-    }
-
     /// If attributes are not allowed on expressions, emit an error for `attr`
-    pub fn maybe_emit_expr_attr_err(&self, attr: &Attribute) {
+    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,
@@ -453,49 +440,10 @@ impl<'a> StripUnconfigured<'a> {
         }
     }
 
-    pub 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(_) => {}
-        }
-    }
-
-    pub 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);
-                }
-            }
-            _ => {}
-        }
-    }
-
-    pub 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));
-            }
-            _ => {}
-        }
-    }
-
     pub fn configure_expr(&mut self, expr: &mut P<ast::Expr>) {
-        self.visit_expr_attrs(expr.attrs());
+        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.
@@ -511,117 +459,6 @@ impl<'a> StripUnconfigured<'a> {
 
         self.process_cfg_attrs(expr)
     }
-
-    pub 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));
-        }
-    }
-
-    pub fn configure_fn_decl(&mut self, fn_decl: &mut ast::FnDecl) {
-        fn_decl.inputs.flat_map_in_place(|arg| self.configure(arg));
-    }
-
-    pub 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<'a> MutVisitor for StripUnconfigured<'a> {
-    fn visit_foreign_mod(&mut self, foreign_mod: &mut ast::ForeignMod) {
-        self.configure_foreign_mod(foreign_mod);
-        noop_visit_foreign_mod(foreign_mod, self);
-    }
-
-    fn visit_item_kind(&mut self, item: &mut ast::ItemKind) {
-        self.configure_item_kind(item);
-        noop_visit_item_kind(item, self);
-    }
-
-    fn visit_expr(&mut self, expr: &mut P<ast::Expr>) {
-        self.configure_expr(expr);
-        self.configure_expr_kind(&mut expr.kind);
-        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);
-        noop_visit_expr(&mut expr, self);
-        Some(expr)
-    }
-
-    fn flat_map_generic_param(
-        &mut self,
-        param: ast::GenericParam,
-    ) -> SmallVec<[ast::GenericParam; 1]> {
-        noop_flat_map_generic_param(configure!(self, param), self)
-    }
-
-    fn flat_map_stmt(&mut self, stmt: ast::Stmt) -> SmallVec<[ast::Stmt; 1]> {
-        noop_flat_map_stmt(configure!(self, stmt), self)
-    }
-
-    fn flat_map_item(&mut self, item: P<ast::Item>) -> SmallVec<[P<ast::Item>; 1]> {
-        noop_flat_map_item(configure!(self, item), self)
-    }
-
-    fn flat_map_impl_item(&mut self, item: P<ast::AssocItem>) -> SmallVec<[P<ast::AssocItem>; 1]> {
-        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]> {
-        noop_flat_map_assoc_item(configure!(self, item), self)
-    }
-
-    fn visit_pat(&mut self, pat: &mut P<ast::Pat>) {
-        self.configure_pat(pat);
-        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);
-        noop_visit_fn_decl(fn_decl, self);
-    }
 }
 
 fn is_cfg(sess: &Session, attr: &Attribute) -> bool {