Merge #1105

1105: [WIP] Implement ra_mbe meta variables support  r=matklad a=edwin0cheng

This PR implements the following meta variable support in `ra_mba` crate (issue  #720):

- [x] `path`
- [ ] `expr`
- [ ] `ty`
- [ ]  `pat`
- [ ] `stmt`
- [ ]  `block`
- [ ]  `meta`
- [ ] `item`

*Implementation Details*

In the macro expanding lhs phase, if we see a meta variable type, we try to create a `tt:TokenTree` from the remaining input. And then we use a special set of `ra_parser` to parse it to `SyntaxNode`. 


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

1 files changed, 4 insertions, 0 deletions

diff --git a/crates/ra_parser/src/grammar.rs b/crates/ra_parser/src/grammar.rs
index b2ffeff8c..c5f510e6b 100644
--- a/crates/ra_parser/src/grammar.rs
+++ b/crates/ra_parser/src/grammar.rs
@@ -49,6 +49,10 @@ pub(crate) fn root(p: &mut Parser) {
     m.complete(p, SOURCE_FILE);
 }
 
+pub(crate) fn path(p: &mut Parser) {
+    paths::type_path(p);
+}
+
 pub(crate) fn reparser(
     node: SyntaxKind,
     first_child: Option<SyntaxKind>,