Merge #1267

1267: Macro expand to r=edwin0cheng a=matklad

closes #1264 

The core problem this PR is trying to wrangle is that macros can expand to different stuffs, depending on context. 

That is, `foo!()` on the top-level expands to a list of items, but the same `foo!()` in expression position expands to expression.

Our current `hir_parse(HirFileId) -> TreeArc<SourceFile>` does not really support this. 

So, the plan is to change `hir_parse` to untyped inreface (`TreeArc<Syntaxnode>`), and add `expands_to` field to `MacroCallLoc`, such that the *target* of macro expansion is selected by the calling code and is part of macro id. 

This unfortunately looses some type-safety :( 


Moreover, this doesn't really fix #1264 by itself, because we die due to some other error inside macro expansion: expander fails to produce a tree with a single root, which trips assert inside rowan.

Co-authored-by: Aleksey Kladov <[email protected]>

1 files changed, 6 insertions, 6 deletions

diff --git a/crates/ra_hir/src/expr.rs b/crates/ra_hir/src/expr.rs
index a2b5db1a1..9618236e5 100644
--- a/crates/ra_hir/src/expr.rs
+++ b/crates/ra_hir/src/expr.rs
@@ -6,11 +6,11 @@ use rustc_hash::FxHashMap;
 use ra_arena::{Arena, RawId, impl_arena_id, map::ArenaMap};
 use ra_syntax::{
     SyntaxNodePtr, AstPtr, AstNode,
-    ast::{self, LoopBodyOwner, ArgListOwner, NameOwner, LiteralKind,ArrayExprKind, TypeAscriptionOwner}
+    ast::{self, LoopBodyOwner, ArgListOwner, NameOwner, LiteralKind,ArrayExprKind, TypeAscriptionOwner},
 };
 
 use crate::{
-    Path, Name, HirDatabase, Resolver,DefWithBody, Either, HirFileId, MacroCallLoc,
+    Path, Name, HirDatabase, Resolver,DefWithBody, Either, HirFileId, MacroCallLoc, MacroFileKind,
     name::AsName,
     type_ref::{Mutability, TypeRef},
 };
@@ -830,11 +830,11 @@ where
 
                 if let Some(def) = self.resolver.resolve_macro_call(path) {
                     let call_id = MacroCallLoc { def, ast_id }.id(self.db);
-                    if let Some(tt) = self.db.macro_expand(call_id).ok() {
-                        if let Some(expr) = mbe::token_tree_to_expr(&tt).ok() {
+                    let file_id = call_id.as_file(MacroFileKind::Expr);
+                    if let Some(node) = self.db.parse_or_expand(file_id) {
+                        if let Some(expr) = ast::Expr::cast(&*node) {
                             log::debug!("macro expansion {}", expr.syntax().debug_dump());
-                            let old_file_id =
-                                std::mem::replace(&mut self.current_file_id, call_id.into());
+                            let old_file_id = std::mem::replace(&mut self.current_file_id, file_id);
                             let id = self.collect_expr(&expr);
                             self.current_file_id = old_file_id;
                             return id;