Rollup merge of #92573 - petrochenkov:ltrattr3, r=Aaron1011

expand: Refactor InvocationCollector visitor for better code reuse

The refactoring part of https://github.com/rust-lang/rust/pull/92473.

Invocation collector visitor logic now lives in two main functions:
- `fn flat_map_node`, corresponding to "one to many" expansions
- `fn visit_node`, corresponding to "one to one" expansions

All specific mut visitor methods now use one of these functions.

The new `InvocationCollectorNode` trait implemented for all `AstFragment` nodes provides the necessary small pieces of functionality required to implement the `(flat_map,visit)_node` functions.
r? `@Aaron1011`

compiler/rustc_ast/src/ast_like.rs

@@ -6,12 +6,13 @@ use super::{AssocItem, Expr, ForeignItem, Item, Local, MacCallStmt};
 use super::{AttrItem, AttrKind, Block, Pat, Path, Ty, Visibility};
 use super::{AttrVec, Attribute, Stmt, StmtKind};
 
-use std::fmt::Debug;
+use std::fmt;
+use std::marker::PhantomData;
 
 /// An `AstLike` represents an AST node (or some wrapper around
 /// and AST node) which stores some combination of attributes
 /// and tokens.
-pub trait AstLike: Sized + Debug {
+pub trait AstLike: Sized + fmt::Debug {
     /// This is `true` if this `AstLike` might support 'custom' (proc-macro) inner
     /// attributes. Attributes like `#![cfg]` and `#![cfg_attr]` are not
     /// considered 'custom' attributes
@@ -285,3 +286,37 @@ derive_has_attrs_no_tokens! {
 derive_has_tokens_no_attrs! {
     Ty, Block, AttrItem, Pat, Path, Visibility
 }
+
+/// A newtype around an `AstLike` node that implements `AstLike` itself.
+pub struct AstLikeWrapper<Wrapped, Tag> {
+    pub wrapped: Wrapped,
+    pub tag: PhantomData<Tag>,
+}
+
+impl<Wrapped, Tag> AstLikeWrapper<Wrapped, Tag> {
+    pub fn new(wrapped: Wrapped, _tag: Tag) -> AstLikeWrapper<Wrapped, Tag> {
+        AstLikeWrapper { wrapped, tag: Default::default() }
+    }
+}
+
+impl<Wrapped: fmt::Debug, Tag> fmt::Debug for AstLikeWrapper<Wrapped, Tag> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("AstLikeWrapper")
+            .field("wrapped", &self.wrapped)
+            .field("tag", &self.tag)
+            .finish()
+    }
+}
+
+impl<Wrapped: AstLike, Tag> AstLike for AstLikeWrapper<Wrapped, Tag> {
+    const SUPPORTS_CUSTOM_INNER_ATTRS: bool = Wrapped::SUPPORTS_CUSTOM_INNER_ATTRS;
+    fn attrs(&self) -> &[Attribute] {
+        self.wrapped.attrs()
+    }
+    fn visit_attrs(&mut self, f: impl FnOnce(&mut Vec<Attribute>)) {
+        self.wrapped.visit_attrs(f)
+    }
+    fn tokens_mut(&mut self) -> Option<&mut Option<LazyTokenStream>> {
+        self.wrapped.tokens_mut()
+    }
+}

compiler/rustc_ast/src/lib.rs

@@ -41,7 +41,7 @@ pub mod tokenstream;
 pub mod visit;
 
 pub use self::ast::*;
-pub use self::ast_like::AstLike;
+pub use self::ast_like::{AstLike, AstLikeWrapper};
 
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 

compiler/rustc_expand/src/config.rs

@@ -238,7 +238,7 @@ macro_rules! configure {
 }
 
 impl<'a> StripUnconfigured<'a> {
-    pub fn configure<T: AstLike>(&mut self, mut node: T) -> Option<T> {
+    pub fn configure<T: AstLike>(&self, mut node: T) -> Option<T> {
         self.process_cfg_attrs(&mut node);
         if self.in_cfg(node.attrs()) {
             self.try_configure_tokens(&mut node);
@@ -248,7 +248,7 @@ impl<'a> StripUnconfigured<'a> {
         }
     }
 
-    fn try_configure_tokens<T: AstLike>(&mut self, node: &mut T) {
+    fn try_configure_tokens<T: AstLike>(&self, node: &mut T) {
         if self.config_tokens {
             if let Some(Some(tokens)) = node.tokens_mut() {
                 let attr_annotated_tokens = tokens.create_token_stream();
@@ -257,10 +257,7 @@ impl<'a> StripUnconfigured<'a> {
         }
     }
 
-    fn configure_krate_attrs(
-        &mut self,
-        mut attrs: Vec<ast::Attribute>,
-    ) -> Option<Vec<ast::Attribute>> {
+    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 }
     }
@@ -269,7 +266,7 @@ impl<'a> StripUnconfigured<'a> {
     /// 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(&mut self, stream: &AttrAnnotatedTokenStream) -> AttrAnnotatedTokenStream {
+    fn configure_tokens(&self, stream: &AttrAnnotatedTokenStream) -> AttrAnnotatedTokenStream {
         fn can_skip(stream: &AttrAnnotatedTokenStream) -> bool {
             stream.0.iter().all(|(tree, _spacing)| match tree {
                 AttrAnnotatedTokenTree::Attributes(_) => false,
@@ -325,7 +322,7 @@ 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.
-    fn process_cfg_attrs<T: AstLike>(&mut self, node: &mut T) {
+    fn process_cfg_attrs<T: AstLike>(&self, node: &mut T) {
         node.visit_attrs(|attrs| {
             attrs.flat_map_in_place(|attr| self.process_cfg_attr(attr));
         });
@@ -338,7 +335,7 @@ impl<'a> StripUnconfigured<'a> {
     /// 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.
-    fn process_cfg_attr(&mut self, attr: Attribute) -> Vec<Attribute> {
+    fn process_cfg_attr(&self, attr: Attribute) -> Vec<Attribute> {
         if !attr.has_name(sym::cfg_attr) {
             return vec![attr];
         }
@@ -461,7 +458,7 @@ impl<'a> StripUnconfigured<'a> {
         }
     }
 
-    pub fn configure_expr(&mut self, expr: &mut P<ast::Expr>) {
+    pub fn configure_expr(&self, expr: &mut P<ast::Expr>) {
         for attr in expr.attrs.iter() {
             self.maybe_emit_expr_attr_err(attr);
         }

compiler/rustc_expand/src/lib.rs

@@ -1,3 +1,5 @@
+#![feature(associated_type_bounds)]
+#![feature(associated_type_defaults)]
 #![feature(crate_visibility_modifier)]
 #![feature(decl_macro)]
 #![cfg_attr(bootstrap, feature(destructuring_assignment))]

compiler/rustc_expand/src/placeholders.rs

@@ -123,7 +123,7 @@ pub fn placeholder(
             span,
             is_placeholder: true,
         }]),
-        AstFragmentKind::Fields => AstFragment::Fields(smallvec![ast::ExprField {
+        AstFragmentKind::ExprFields => AstFragment::ExprFields(smallvec![ast::ExprField {
             attrs: Default::default(),
             expr: expr_placeholder(),
             id,
@@ -132,7 +132,7 @@ pub fn placeholder(
             span,
             is_placeholder: true,
         }]),
-        AstFragmentKind::FieldPats => AstFragment::FieldPats(smallvec![ast::PatField {
+        AstFragmentKind::PatFields => AstFragment::PatFields(smallvec![ast::PatField {
             attrs: Default::default(),
             id,
             ident,
@@ -159,7 +159,7 @@ pub fn placeholder(
             ty: ty(),
             is_placeholder: true,
         }]),
-        AstFragmentKind::StructFields => AstFragment::StructFields(smallvec![ast::FieldDef {
+        AstFragmentKind::FieldDefs => AstFragment::FieldDefs(smallvec![ast::FieldDef {
             attrs: Default::default(),
             id,
             ident: None,