Merge #1238

1238: Macro queries r=edwin0cheng a=matklad

In https://github.com/rust-analyzer/rust-analyzer/pull/1231, I've added aggressive clean up of `ast_id_to_node` query. 

The result of this query is a `SyntaxTree`, and we don't want to retain syntax trees in memory unless absolutely necessary.

Moreover, `SyntaxTree` has identity equality semantics, meaning that we'll get a diffferent syntax tree for a file after every reparse. That means that `ast_id_to_node` query should not genereally be used in HIR, unless it is behind some kind of salsa firewall, like the `raw` module of name resoulution.

However, that PR resulted in the abysmal performance: turns out we were using  ast_id_to_node quite heavily in hir when expanding macros! 

So this PR  installs the more incremental-friendly query structure:

* converting source to token tree is now a query; changing source without affecting token-trees will now preserve macro expansions
* expand macro (tt -> tt) is now a query as well, so we cache macro expansions *before* parsing them into item lists or expressions, which is nice: we can cache expansion without knowing the calling context!

r? @edwin0cheng 

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

1 files changed, 1 insertions, 1 deletions

diff --git a/crates/ra_hir/src/source_id.rs b/crates/ra_hir/src/source_id.rs
index a2bc9a799..0a8fb6d32 100644
--- a/crates/ra_hir/src/source_id.rs
+++ b/crates/ra_hir/src/source_id.rs
@@ -92,7 +92,7 @@ impl AstIdMap {
         Arc::new(AstIdMap::from_source_file(&source_file))
     }
 
-    pub(crate) fn ast_id_to_node_query(
+    pub(crate) fn file_item_query(
         db: &impl DefDatabase,
         file_id: HirFileId,
         ast_id: ErasedFileAstId,