Merge #8201

8201: Fix recursive macro statements expansion r=edwin0cheng a=edwin0cheng

This PR attempts to properly handle macro statement expansion by implementing the following:

1.  Merge macro expanded statements to parent scope statements.
2.  Add a new hir `Expr::MacroStmts` for handle tail expression infer.

PS : The scope of macro expanded statements are so strange that it took more time than I thought to understand and implement it :(

Fixes  #8171



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

1 files changed, 33 insertions, 35 deletions

diff --git a/crates/hir_def/src/body/lower.rs b/crates/hir_def/src/body/lower.rs
index 19f5065d1..229e81dd4 100644
--- a/crates/hir_def/src/body/lower.rs
+++ b/crates/hir_def/src/body/lower.rs
@@ -74,6 +74,7 @@ pub(super) fn lower(
             _c: Count::new(),
         },
         expander,
+        statements_in_scope: Vec::new(),
     }
     .collect(params, body)
 }
@@ -83,6 +84,7 @@ struct ExprCollector<'a> {
     expander: Expander,
     body: Body,
     source_map: BodySourceMap,
+    statements_in_scope: Vec<Statement>,
 }
 
 impl ExprCollector<'_> {
@@ -533,15 +535,13 @@ impl ExprCollector<'_> {
                 ids[0]
             }
             ast::Expr::MacroStmts(e) => {
-                // FIXME:  these statements should be held by some hir containter
-                for stmt in e.statements() {
-                    self.collect_stmt(stmt);
-                }
-                if let Some(expr) = e.expr() {
-                    self.collect_expr(expr)
-                } else {
-                    self.alloc_expr(Expr::Missing, syntax_ptr)
-                }
+                e.statements().for_each(|s| self.collect_stmt(s));
+                let tail = e
+                    .expr()
+                    .map(|e| self.collect_expr(e))
+                    .unwrap_or_else(|| self.alloc_expr(Expr::Missing, syntax_ptr.clone()));
+
+                self.alloc_expr(Expr::MacroStmts { tail }, syntax_ptr)
             }
         })
     }
@@ -618,58 +618,54 @@ impl ExprCollector<'_> {
         }
     }
 
-    fn collect_stmt(&mut self, s: ast::Stmt) -> Option<Vec<Statement>> {
-        let stmt = match s {
+    fn collect_stmt(&mut self, s: ast::Stmt) {
+        match s {
             ast::Stmt::LetStmt(stmt) => {
-                self.check_cfg(&stmt)?;
-
+                if self.check_cfg(&stmt).is_none() {
+                    return;
+                }
                 let pat = self.collect_pat_opt(stmt.pat());
                 let type_ref = stmt.ty().map(|it| TypeRef::from_ast(&self.ctx(), it));
                 let initializer = stmt.initializer().map(|e| self.collect_expr(e));
-                vec![Statement::Let { pat, type_ref, initializer }]
+                self.statements_in_scope.push(Statement::Let { pat, type_ref, initializer });
             }
             ast::Stmt::ExprStmt(stmt) => {
-                self.check_cfg(&stmt)?;
+                if self.check_cfg(&stmt).is_none() {
+                    return;
+                }
 
                 // Note that macro could be expended to multiple statements
                 if let Some(ast::Expr::MacroCall(m)) = stmt.expr() {
                     let syntax_ptr = AstPtr::new(&stmt.expr().unwrap());
-                    let mut stmts = vec![];
 
                     self.collect_macro_call(m, syntax_ptr.clone(), false, |this, expansion| {
                         match expansion {
                             Some(expansion) => {
                                 let statements: ast::MacroStmts = expansion;
 
-                                statements.statements().for_each(|stmt| {
-                                    if let Some(mut r) = this.collect_stmt(stmt) {
-                                        stmts.append(&mut r);
-                                    }
-                                });
+                                statements.statements().for_each(|stmt| this.collect_stmt(stmt));
                                 if let Some(expr) = statements.expr() {
-                                    stmts.push(Statement::Expr(this.collect_expr(expr)));
+                                    let expr = this.collect_expr(expr);
+                                    this.statements_in_scope.push(Statement::Expr(expr));
                                 }
                             }
                             None => {
-                                stmts.push(Statement::Expr(
-                                    this.alloc_expr(Expr::Missing, syntax_ptr.clone()),
-                                ));
+                                let expr = this.alloc_expr(Expr::Missing, syntax_ptr.clone());
+                                this.statements_in_scope.push(Statement::Expr(expr));
                             }
                         }
                     });
-                    stmts
                 } else {
-                    vec![Statement::Expr(self.collect_expr_opt(stmt.expr()))]
+                    let expr = self.collect_expr_opt(stmt.expr());
+                    self.statements_in_scope.push(Statement::Expr(expr));
                 }
             }
             ast::Stmt::Item(item) => {
-                self.check_cfg(&item)?;
-
-                return None;
+                if self.check_cfg(&item).is_none() {
+                    return;
+                }
             }
-        };
-
-        Some(stmt)
+        }
     }
 
     fn collect_block(&mut self, block: ast::BlockExpr) -> ExprId {
@@ -685,10 +681,12 @@ impl ExprCollector<'_> {
         let module = if has_def_map { def_map.root() } else { self.expander.module };
         let prev_def_map = mem::replace(&mut self.expander.def_map, def_map);
         let prev_local_module = mem::replace(&mut self.expander.module, module);
+        let prev_statements = std::mem::take(&mut self.statements_in_scope);
+
+        block.statements().for_each(|s| self.collect_stmt(s));
 
-        let statements =
-            block.statements().filter_map(|s| self.collect_stmt(s)).flatten().collect();
         let tail = block.tail_expr().map(|e| self.collect_expr(e));
+        let statements = std::mem::replace(&mut self.statements_in_scope, prev_statements);
         let syntax_node_ptr = AstPtr::new(&block.into());
         let expr_id = self.alloc_expr(
             Expr::Block { id: block_id, statements, tail, label: None },