Merge #1157

1157: Add mbe stmt matcher r=matklad a=edwin0cheng

Add `stmt` matcher in `ra_mbe` , and added corresponding `stmt()` parser in `ra_syntax`. 
This PR also help PR #1148 for `MarcoKind::Items` parsing.

Note: 
* According [the book](https://doc.rust-lang.org/reference/macros-by-example.html), mbe `stmt` matcher will only match statement without the trailing semicolon 
* `item` is a valid statement.





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

4 files changed, 28 insertions, 0 deletions

diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index a530f3b03..a1f438906 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -582,4 +582,19 @@ SOURCE_FILE@[0; 40)
         );
         assert_expansion(&rules, "foo! { (a, b) }", "fn foo () {let (a , b) ;}");
     }
+
+    #[test]
+    fn test_stmt() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {
+            ($ i:stmt) => (
+                fn bar() { $ i; }
+            )
+        }
+"#,
+        );
+        assert_expansion(&rules, "foo! { 2 }", "fn bar () {2 ;}");
+        assert_expansion(&rules, "foo! { let a = 0 }", "fn bar () {let a = 0 ;}");
+    }
 }
diff --git a/crates/ra_mbe/src/mbe_expander.rs b/crates/ra_mbe/src/mbe_expander.rs
index 7a259f338..7587b575d 100644
--- a/crates/ra_mbe/src/mbe_expander.rs
+++ b/crates/ra_mbe/src/mbe_expander.rs
@@ -157,6 +157,10 @@ fn match_lhs(pattern: &crate::Subtree, input: &mut TtCursor) -> Result<Bindings,
                             let pat = input.eat_pat().ok_or(ExpandError::UnexpectedToken)?.clone();
                             res.inner.insert(text.clone(), Binding::Simple(pat.into()));
                         }
+                        "stmt" => {
+                            let pat = input.eat_stmt().ok_or(ExpandError::UnexpectedToken)?.clone();
+                            res.inner.insert(text.clone(), Binding::Simple(pat.into()));
+                        }
                         _ => return Err(ExpandError::UnexpectedToken),
                     }
                 }
diff --git a/crates/ra_mbe/src/subtree_parser.rs b/crates/ra_mbe/src/subtree_parser.rs
index 13d5d2169..f075ce245 100644
--- a/crates/ra_mbe/src/subtree_parser.rs
+++ b/crates/ra_mbe/src/subtree_parser.rs
@@ -42,6 +42,10 @@ impl<'a> Parser<'a> {
         self.parse(ra_parser::parse_pat)
     }
 
+    pub fn parse_stmt(self) -> Option<tt::TokenTree> {
+        self.parse(|src, sink| ra_parser::parse_stmt(src, sink, false))
+    }
+
     fn parse<F>(self, f: F) -> Option<tt::TokenTree>
     where
         F: FnOnce(&dyn TokenSource, &mut dyn TreeSink),
diff --git a/crates/ra_mbe/src/tt_cursor.rs b/crates/ra_mbe/src/tt_cursor.rs
index f6cefe087..adfe5520d 100644
--- a/crates/ra_mbe/src/tt_cursor.rs
+++ b/crates/ra_mbe/src/tt_cursor.rs
@@ -99,6 +99,11 @@ impl<'a> TtCursor<'a> {
         parser.parse_pat()
     }
 
+    pub(crate) fn eat_stmt(&mut self) -> Option<tt::TokenTree> {
+        let parser = Parser::new(&mut self.pos, self.subtree);
+        parser.parse_stmt()
+    }
+
     pub(crate) fn expect_char(&mut self, char: char) -> Result<(), ParseError> {
         if self.at_char(char) {
             self.bump();