normalising BlockTrailingExpr where it returns into Block with a Ret expr

src/ast2/mod.rs

@@ -2591,6 +2591,35 @@ pub mod ast_gen {
             }
         }
 
+        /// folds more AST-patterns into structures that are easier to build the IR with
+        pub fn fold_more_patterns(&mut self) {
+            use visitor::AstExt;
+            self.ast.visitor_mut().visit_post(|ast, _, i, tag, data| {
+                match tag {
+                    // normalise functions with block-with-trailing-expr into block
+                    Tag::FunctionDecl => {
+                        let (_, block) = data.as_two_indices();
+
+                        let (block_tag, block_data) =
+                            ast.get_node_tag_and_data(block);
+                        if block_tag == Tag::BlockTrailingExpr {
+                            let (_, end) = block_data.as_extra_range();
+                            let end = end - 1;
+                            let expr = Index::new(ast.extra[end]);
+                            let loc = ast.get_loc(expr);
+                            let ret = ast.push_ret(Some(expr), loc);
+                            // modify last element in place to be a return instruction
+                            ast.extra[end] = *ret.as_u32();
+                            ast.tags[block.index()] = Tag::Block;
+                            eprintln!("folding ({block}): {block_tag:?} into Tag::Block");
+                            eprintln!("expr: {expr:?}");
+                        }
+                    }
+                    _ => {}
+                }
+            });
+        }
+
         pub fn intern_types(&mut self) {
             self.ast.visitor_mut().visit_post(|ast, _, i, tag, data| {
                         match tag {
@@ -4397,6 +4426,7 @@ pub mod ast_gen {
             self.create_comptime_folding_graph(intern::AMD64_POINTER_BITS);
             eprintln!("interning types:");
             self.intern_types();
+            self.fold_more_patterns();
         }
 
         fn push_scope(&mut self, ast: Index, name: intern::Index) {