Rollup merge of #82415 - petrochenkov:modin3, r=davidtwco

expand: Refactor module loading

This is an accompanying PR to https://github.com/rust-lang/rust/pull/82399, but they can be landed independently.
See individual commits for more details.

Anyone should be able to review this equally well because all people actually familiar with this code left the project.

compiler/rustc_expand/src/base.rs

@@ -1,11 +1,11 @@
 use crate::expand::{self, AstFragment, Invocation};
-use crate::module::DirectoryOwnership;
+use crate::module::DirOwnership;
 
 use rustc_ast::ptr::P;
 use rustc_ast::token::{self, Nonterminal};
 use rustc_ast::tokenstream::{CanSynthesizeMissingTokens, LazyTokenStream, TokenStream};
 use rustc_ast::visit::{AssocCtxt, Visitor};
-use rustc_ast::{self as ast, AstLike, Attribute, NodeId, PatKind};
+use rustc_ast::{self as ast, AstLike, Attribute, Item, NodeId, PatKind};
 use rustc_attr::{self as attr, Deprecation, Stability};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sync::{self, Lrc};
@@ -900,10 +900,26 @@ pub trait ResolverExpand {
     fn cfg_accessible(&mut self, expn_id: ExpnId, path: &ast::Path) -> Result<bool, Indeterminate>;
 }
 
-#[derive(Clone)]
+#[derive(Clone, Default)]
 pub struct ModuleData {
+    /// Path to the module starting from the crate name, like `my_crate::foo::bar`.
     pub mod_path: Vec<Ident>,
-    pub directory: PathBuf,
+    /// Stack of paths to files loaded by out-of-line module items,
+    /// used to detect and report recursive module inclusions.
+    pub file_path_stack: Vec<PathBuf>,
+    /// Directory to search child module files in,
+    /// often (but not necessarily) the parent of the top file path on the `file_path_stack`.
+    pub dir_path: PathBuf,
+}
+
+impl ModuleData {
+    pub fn with_dir_path(&self, dir_path: PathBuf) -> ModuleData {
+        ModuleData {
+            mod_path: self.mod_path.clone(),
+            file_path_stack: self.file_path_stack.clone(),
+            dir_path,
+        }
+    }
 }
 
 #[derive(Clone)]
@@ -911,10 +927,13 @@ pub struct ExpansionData {
     pub id: ExpnId,
     pub depth: usize,
     pub module: Rc<ModuleData>,
-    pub directory_ownership: DirectoryOwnership,
+    pub dir_ownership: DirOwnership,
     pub prior_type_ascription: Option<(Span, bool)>,
 }
 
+type OnExternModLoaded<'a> =
+    Option<&'a dyn Fn(Ident, Vec<Attribute>, Vec<P<Item>>, Span) -> (Vec<Attribute>, Vec<P<Item>>)>;
+
 /// One of these is made during expansion and incrementally updated as we go;
 /// when a macro expansion occurs, the resulting nodes have the `backtrace()
 /// -> expn_data` of their expansion context stored into their span.
@@ -932,7 +951,7 @@ pub struct ExtCtxt<'a> {
     /// Called directly after having parsed an external `mod foo;` in expansion.
     ///
     /// `Ident` is the module name.
-    pub(super) extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+    pub(super) extern_mod_loaded: OnExternModLoaded<'a>,
 }
 
 impl<'a> ExtCtxt<'a> {
@@ -940,7 +959,7 @@ impl<'a> ExtCtxt<'a> {
         sess: &'a Session,
         ecfg: expand::ExpansionConfig<'a>,
         resolver: &'a mut dyn ResolverExpand,
-        extern_mod_loaded: Option<&'a dyn Fn(&ast::Crate, Ident)>,
+        extern_mod_loaded: OnExternModLoaded<'a>,
     ) -> ExtCtxt<'a> {
         ExtCtxt {
             sess,
@@ -952,8 +971,8 @@ impl<'a> ExtCtxt<'a> {
             current_expansion: ExpansionData {
                 id: ExpnId::root(),
                 depth: 0,
-                module: Rc::new(ModuleData { mod_path: Vec::new(), directory: PathBuf::new() }),
-                directory_ownership: DirectoryOwnership::Owned { relative: None },
+                module: Default::default(),
+                dir_ownership: DirOwnership::Owned { relative: None },
                 prior_type_ascription: None,
             },
             force_mode: false,