Remove macro_defs map

We store store the `DefId` directly in `ExpnData`. This will allow us to
serialize `ExpnData` in PR #72121 without needing to manage a side
table.

src/librustc_ast_lowering/lib.rs

@@ -688,7 +688,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ) -> Span {
         span.fresh_expansion(ExpnData {
             allow_internal_unstable,
-            ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition())
+            ..ExpnData::default(ExpnKind::Desugaring(reason), span, self.sess.edition(), None)
         })
     }
 

src/librustc_expand/base.rs

@@ -13,6 +13,7 @@ use rustc_data_structures::sync::{self, Lrc};
 use rustc_errors::{DiagnosticBuilder, ErrorReported};
 use rustc_parse::{self, parser, MACRO_ARGUMENTS};
 use rustc_session::parse::ParseSess;
+use rustc_span::def_id::DefId;
 use rustc_span::edition::Edition;
 use rustc_span::hygiene::{AstPass, ExpnData, ExpnId, ExpnKind};
 use rustc_span::source_map::SourceMap;
@@ -857,7 +858,13 @@ impl SyntaxExtension {
         SyntaxExtension::default(SyntaxExtensionKind::NonMacroAttr { mark_used }, edition)
     }
 
-    pub fn expn_data(&self, parent: ExpnId, call_site: Span, descr: Symbol) -> ExpnData {
+    pub fn expn_data(
+        &self,
+        parent: ExpnId,
+        call_site: Span,
+        descr: Symbol,
+        macro_def_id: Option<DefId>,
+    ) -> ExpnData {
         ExpnData {
             kind: ExpnKind::Macro(self.macro_kind(), descr),
             parent,
@@ -867,6 +874,7 @@ impl SyntaxExtension {
             allow_internal_unsafe: self.allow_internal_unsafe,
             local_inner_macros: self.local_inner_macros,
             edition: self.edition,
+            macro_def_id,
         }
     }
 }

src/librustc_expand/expand.rs

@@ -988,6 +988,7 @@ impl<'a, 'b> InvocationCollector<'a, 'b> {
                     ExpnKind::Macro(MacroKind::Attr, sym::derive),
                     item.span(),
                     self.cx.parse_sess.edition,
+                    None,
                 )
             }),
             _ => None,

src/librustc_resolve/build_reduced_graph.rs

@@ -126,8 +126,8 @@ impl<'a> Resolver<'a> {
     }
 
     crate fn macro_def_scope(&mut self, expn_id: ExpnId) -> Module<'a> {
-        let def_id = match self.macro_defs.get(&expn_id) {
-            Some(def_id) => *def_id,
+        let def_id = match expn_id.expn_data().macro_def_id {
+            Some(def_id) => def_id,
             None => return self.ast_transform_scopes.get(&expn_id).unwrap_or(&self.graph_root),
         };
         if let Some(id) = self.definitions.as_local_node_id(def_id) {

src/librustc_resolve/lib.rs

@@ -922,7 +922,6 @@ pub struct Resolver<'a> {
     dummy_ext_bang: Lrc<SyntaxExtension>,
     dummy_ext_derive: Lrc<SyntaxExtension>,
     non_macro_attrs: [Lrc<SyntaxExtension>; 2],
-    macro_defs: FxHashMap<ExpnId, DefId>,
     local_macro_def_scopes: FxHashMap<NodeId, Module<'a>>,
     ast_transform_scopes: FxHashMap<ExpnId, Module<'a>>,
     unused_macros: NodeMap<Span>,
@@ -1152,9 +1151,6 @@ impl<'a> Resolver<'a> {
         let mut invocation_parent_scopes = FxHashMap::default();
         invocation_parent_scopes.insert(ExpnId::root(), ParentScope::module(graph_root));
 
-        let mut macro_defs = FxHashMap::default();
-        macro_defs.insert(ExpnId::root(), root_def_id);
-
         let features = session.features_untracked();
         let non_macro_attr =
             |mark_used| Lrc::new(SyntaxExtension::non_macro_attr(mark_used, session.edition()));
@@ -1229,7 +1225,6 @@ impl<'a> Resolver<'a> {
             invocation_parent_scopes,
             output_macro_rules_scopes: Default::default(),
             helper_attrs: Default::default(),
-            macro_defs,
             local_macro_def_scopes: FxHashMap::default(),
             name_already_seen: FxHashMap::default(),
             potentially_unused_imports: Vec::new(),
@@ -1335,8 +1330,8 @@ impl<'a> Resolver<'a> {
 
     fn macro_def(&self, mut ctxt: SyntaxContext) -> DefId {
         loop {
-            match self.macro_defs.get(&ctxt.outer_expn()) {
-                Some(&def_id) => return def_id,
+            match ctxt.outer_expn().expn_data().macro_def_id {
+                Some(def_id) => return def_id,
                 None => ctxt.remove_mark(),
             };
         }
@@ -1820,7 +1815,7 @@ impl<'a> Resolver<'a> {
                 && module.expansion.is_descendant_of(parent.expansion)
             {
                 // The macro is a proc macro derive
-                if let Some(&def_id) = self.macro_defs.get(&module.expansion) {
+                if let Some(def_id) = module.expansion.expn_data().macro_def_id {
                     if let Some(ext) = self.get_macro_by_def_id(def_id) {
                         if !ext.is_builtin && ext.macro_kind() == MacroKind::Derive {
                             if parent.expansion.outer_expn_is_descendant_of(span.ctxt()) {

src/librustc_resolve/macros.rs

@@ -186,6 +186,7 @@ impl<'a> base::Resolver for Resolver<'a> {
             call_site,
             self.session.edition(),
             features.into(),
+            None,
         )));
 
         let parent_scope = if let Some(module_id) = parent_module_id {
@@ -290,13 +291,17 @@ impl<'a> base::Resolver for Resolver<'a> {
         let (ext, res) = self.smart_resolve_macro_path(path, kind, parent_scope, force)?;
 
         let span = invoc.span();
-        invoc_id.set_expn_data(ext.expn_data(parent_scope.expansion, span, fast_print_path(path)));
-
-        if let Res::Def(_, def_id) = res {
+        invoc_id.set_expn_data(ext.expn_data(
+            parent_scope.expansion,
+            span,
+            fast_print_path(path),
+            res.opt_def_id(),
+        ));
+
+        if let Res::Def(_, _) = res {
             if after_derive {
                 self.session.span_err(span, "macro attributes must be placed before `#[derive]`");
             }
-            self.macro_defs.insert(invoc_id, def_id);
             let normal_module_def_id = self.macro_def_scope(invoc_id).normal_ancestor_id;
             self.definitions.add_parent_module_of_macro_def(invoc_id, normal_module_def_id);
         }

src/librustc_span/hygiene.rs

@@ -25,6 +25,7 @@
 // because getting it wrong can lead to nested `HygieneData::with` calls that
 // trigger runtime aborts. (Fortunately these are obvious and easy to fix.)
 
+use crate::def_id::{DefId, CRATE_DEF_INDEX};
 use crate::edition::Edition;
 use crate::symbol::{kw, sym, Symbol};
 use crate::GLOBALS;
@@ -155,7 +156,12 @@ crate struct HygieneData {
 impl HygieneData {
     crate fn new(edition: Edition) -> Self {
         HygieneData {
-            expn_data: vec![Some(ExpnData::default(ExpnKind::Root, DUMMY_SP, edition))],
+            expn_data: vec![Some(ExpnData::default(
+                ExpnKind::Root,
+                DUMMY_SP,
+                edition,
+                Some(DefId::local(CRATE_DEF_INDEX)),
+            ))],
             syntax_context_data: vec![SyntaxContextData {
                 outer_expn: ExpnId::root(),
                 outer_transparency: Transparency::Opaque,
@@ -673,11 +679,19 @@ pub struct ExpnData {
     pub local_inner_macros: bool,
     /// Edition of the crate in which the macro is defined.
     pub edition: Edition,
+    /// The `DefId` of the macro being invoked,
+    /// if this `ExpnData` corresponds to a macro invocation
+    pub macro_def_id: Option<DefId>,
 }
 
 impl ExpnData {
     /// Constructs expansion data with default properties.
-    pub fn default(kind: ExpnKind, call_site: Span, edition: Edition) -> ExpnData {
+    pub fn default(
+        kind: ExpnKind,
+        call_site: Span,
+        edition: Edition,
+        macro_def_id: Option<DefId>,
+    ) -> ExpnData {
         ExpnData {
             kind,
             parent: ExpnId::root(),
@@ -687,6 +701,7 @@ impl ExpnData {
             allow_internal_unsafe: false,
             local_inner_macros: false,
             edition,
+            macro_def_id,
         }
     }
 
@@ -695,10 +710,11 @@ impl ExpnData {
         call_site: Span,
         edition: Edition,
         allow_internal_unstable: Lrc<[Symbol]>,
+        macro_def_id: Option<DefId>,
     ) -> ExpnData {
         ExpnData {
             allow_internal_unstable: Some(allow_internal_unstable),
-            ..ExpnData::default(kind, call_site, edition)
+            ..ExpnData::default(kind, call_site, edition, macro_def_id)
         }
     }