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, 54 insertions, 1 deletions

diff --git a/crates/ra_mbe/src/lib.rs b/crates/ra_mbe/src/lib.rs
index 4203929d4..a21ea4dbc 100644
--- a/crates/ra_mbe/src/lib.rs
+++ b/crates/ra_mbe/src/lib.rs
@@ -15,10 +15,13 @@ macro_rules! impl_froms {
     }
 }
 
-mod tt_cursor;
+// mod tt_cursor;
 mod mbe_parser;
 mod mbe_expander;
 mod syntax_bridge;
+mod tt_cursor;
+mod subtree_source;
+mod subtree_parser;
 
 use ra_syntax::SmolStr;
 
@@ -379,4 +382,54 @@ SOURCE_FILE@[0; 40)
         // [let] [s] [=] ["rust1"] [;]
         assert_eq!(to_literal(&stm_tokens[15 + 3]).text, "\"rust1\"");
     }
+
+    #[test]
+    fn test_two_idents() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {
+            ($ i:ident, $ j:ident) => {
+                fn foo() { let a = $ i; let b = $j; }
+            }
+        }
+"#,
+        );
+        assert_expansion(&rules, "foo! { foo, bar }", "fn foo () {let a = foo ; let b = bar ;}");
+    }
+
+    // The following tests are port from intellij-rust directly
+    // https://github.com/intellij-rust/intellij-rust/blob/c4e9feee4ad46e7953b1948c112533360b6087bb/src/test/kotlin/org/rust/lang/core/macros/RsMacroExpansionTest.kt
+
+    #[test]
+    fn test_path() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {
+            ($ i:path) => {
+                fn foo() { let a = $ i; }
+            }
+        }
+"#,
+        );
+        assert_expansion(&rules, "foo! { foo }", "fn foo () {let a = foo ;}");
+        assert_expansion(
+            &rules,
+            "foo! { bar::<u8>::baz::<u8> }",
+            "fn foo () {let a = bar ::< u8 > ::baz ::< u8 > ;}",
+        );
+    }
+
+    #[test]
+    fn test_two_paths() {
+        let rules = create_rules(
+            r#"
+        macro_rules! foo {
+            ($ i:path, $ j:path) => {
+                fn foo() { let a = $ i; let b = $j; }
+            }
+        }
+"#,
+        );
+        assert_expansion(&rules, "foo! { foo, bar }", "fn foo () {let a = foo ; let b = bar ;}");
+    }
 }