Merge #3591

3591: Support local macro_rules r=matklad a=edwin0cheng

This PR implement local `macro_rules` in function body, by adding following things:

1. While lowering, add a `MacroDefId` in body's `ItemScope` as a textual legacy macro. 
2. Make `Expander::enter_expand` search with given `ItemScope`.
3. Make `Resolver::resolve_path_as_macro` search with `LocalItemScope`.

Fix #2181

Co-authored-by: Edwin Cheng <[email protected]>

4 files changed, 61 insertions, 16 deletions

diff --git a/crates/ra_hir_def/src/body.rs b/crates/ra_hir_def/src/body.rs
index 57ba45b45..2bc405a59 100644
--- a/crates/ra_hir_def/src/body.rs
+++ b/crates/ra_hir_def/src/body.rs
@@ -47,13 +47,19 @@ impl Expander {
     pub(crate) fn enter_expand<T: ast::AstNode, DB: DefDatabase>(
         &mut self,
         db: &DB,
+        local_scope: Option<&ItemScope>,
         macro_call: ast::MacroCall,
     ) -> Option<(Mark, T)> {
         let macro_call = InFile::new(self.current_file_id, &macro_call);
 
-        if let Some(call_id) =
-            macro_call.as_call_id(db, |path| self.resolve_path_as_macro(db, &path))
-        {
+        if let Some(call_id) = macro_call.as_call_id(db, |path| {
+            if let Some(local_scope) = local_scope {
+                if let Some(def) = path.as_ident().and_then(|n| local_scope.get_legacy_macro(n)) {
+                    return Some(def);
+                }
+            }
+            self.resolve_path_as_macro(db, &path)
+        }) {
             let file_id = call_id.as_file();
             if let Some(node) = db.parse_or_expand(file_id) {
                 if let Some(expr) = T::cast(node) {
diff --git a/crates/ra_hir_def/src/body/lower.rs b/crates/ra_hir_def/src/body/lower.rs
index ec1b0c2e7..54b5591d3 100644
--- a/crates/ra_hir_def/src/body/lower.rs
+++ b/crates/ra_hir_def/src/body/lower.rs
@@ -3,7 +3,10 @@
 
 use either::Either;
 
-use hir_expand::name::{name, AsName, Name};
+use hir_expand::{
+    name::{name, AsName, Name},
+    MacroDefId, MacroDefKind,
+};
 use ra_arena::Arena;
 use ra_syntax::{
     ast::{
@@ -452,19 +455,30 @@ where
                     None => self.alloc_expr(Expr::Missing, syntax_ptr),
                 }
             }
-            // FIXME expand to statements in statement position
             ast::Expr::MacroCall(e) => {
-                let macro_call = self.expander.to_source(AstPtr::new(&e));
-                match self.expander.enter_expand(self.db, e) {
-                    Some((mark, expansion)) => {
-                        self.source_map
-                            .expansions
-                            .insert(macro_call, self.expander.current_file_id);
-                        let id = self.collect_expr(expansion);
-                        self.expander.exit(self.db, mark);
-                        id
+                if let Some(name) = is_macro_rules(&e) {
+                    let mac = MacroDefId {
+                        krate: Some(self.expander.module.krate),
+                        ast_id: Some(self.expander.ast_id(&e)),
+                        kind: MacroDefKind::Declarative,
+                    };
+                    self.body.item_scope.define_legacy_macro(name, mac);
+
+                    // FIXME: do we still need to allocate this as missing ?
+                    self.alloc_expr(Expr::Missing, syntax_ptr)
+                } else {
+                    let macro_call = self.expander.to_source(AstPtr::new(&e));
+                    match self.expander.enter_expand(self.db, Some(&self.body.item_scope), e) {
+                        Some((mark, expansion)) => {
+                            self.source_map
+                                .expansions
+                                .insert(macro_call, self.expander.current_file_id);
+                            let id = self.collect_expr(expansion);
+                            self.expander.exit(self.db, mark);
+                            id
+                        }
+                        None => self.alloc_expr(Expr::Missing, syntax_ptr),
                     }
-                    None => self.alloc_expr(Expr::Missing, syntax_ptr),
                 }
             }
 
@@ -686,6 +700,16 @@ where
     }
 }
 
+fn is_macro_rules(m: &ast::MacroCall) -> Option<Name> {
+    let name = m.path()?.segment()?.name_ref()?.as_name();
+
+    if name == name![macro_rules] {
+        Some(m.name()?.as_name())
+    } else {
+        None
+    }
+}
+
 impl From<ast::BinOp> for BinaryOp {
     fn from(ast_op: ast::BinOp) -> Self {
         match ast_op {
diff --git a/crates/ra_hir_def/src/data.rs b/crates/ra_hir_def/src/data.rs
index 85df07e60..c0b16b7fa 100644
--- a/crates/ra_hir_def/src/data.rs
+++ b/crates/ra_hir_def/src/data.rs
@@ -290,7 +290,7 @@ fn collect_impl_items_in_macro(
         return Vec::new();
     }
 
-    if let Some((mark, items)) = expander.enter_expand(db, m) {
+    if let Some((mark, items)) = expander.enter_expand(db, None, m) {
         let items: InFile<ast::MacroItems> = expander.to_source(items);
         let mut res = collect_impl_items(
             db,
diff --git a/crates/ra_hir_def/src/resolver.rs b/crates/ra_hir_def/src/resolver.rs
index 2734d51a0..123fae72a 100644
--- a/crates/ra_hir_def/src/resolver.rs
+++ b/crates/ra_hir_def/src/resolver.rs
@@ -381,6 +381,11 @@ impl Resolver {
         db: &impl DefDatabase,
         path: &ModPath,
     ) -> Option<MacroDefId> {
+        // Search item scope legacy macro first
+        if let Some(def) = self.resolve_local_macro_def(path) {
+            return Some(def);
+        }
+
         let (item_map, module) = self.module_scope()?;
         item_map.resolve_path(db, module, &path, BuiltinShadowMode::Other).0.take_macros()
     }
@@ -413,6 +418,16 @@ impl Resolver {
         })
     }
 
+    fn resolve_local_macro_def(&self, path: &ModPath) -> Option<MacroDefId> {
+        let name = path.as_ident()?;
+        self.scopes.iter().rev().find_map(|scope| {
+            if let Scope::LocalItemsScope(body) = scope {
+                return body.item_scope.get_legacy_macro(name);
+            }
+            None
+        })
+    }
+
     pub fn module(&self) -> Option<ModuleId> {
         let (def_map, local_id) = self.module_scope()?;
         Some(ModuleId { krate: def_map.krate, local_id })