2 files changed, 58 insertions, 0 deletions

diff --git a/crates/ra_hir/src/lib.rs b/crates/ra_hir/src/lib.rs
index 5bbb09c01..e89410a76 100644
--- a/crates/ra_hir/src/lib.rs
+++ b/crates/ra_hir/src/lib.rs
@@ -22,6 +22,7 @@ mod path;
 mod arena;
 pub mod source_binder;
 
+mod macros;
 mod name;
 mod krate;
 mod module;
diff --git a/crates/ra_hir/src/macros.rs b/crates/ra_hir/src/macros.rs
new file mode 100644
index 000000000..050b97081
--- /dev/null
+++ b/crates/ra_hir/src/macros.rs
@@ -0,0 +1,57 @@
+use std::sync::Arc;
+
+use ra_db::SyntaxDatabase;
+use ra_syntax::{TextRange, TextUnit, SourceFileNode, AstNode, ast};
+
+// Hard-coded defs for now :-(
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub enum MacroDef {
+    CTry,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct MacroInput {
+    // Should be token trees
+    text: String,
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct MacroExpansion {
+    text: String,
+    ranges_map: Vec<(TextRange, TextRange)>,
+}
+
+salsa::query_group! {
+
+pub trait MacrosDatabase: SyntaxDatabase {
+    fn expand_macro(def: MacroDef, input: MacroInput) -> Option<Arc<MacroExpansion>> {
+        type ExpandMacroQuery;
+    }
+}
+
+}
+
+fn expand_macro(
+    _db: &impl MacrosDatabase,
+    def: MacroDef,
+    input: MacroInput,
+) -> Option<Arc<MacroExpansion>> {
+    let MacroDef::CTry = def;
+    let text = format!(
+        r"
+        fn dummy() {{
+            match {} {{
+                None => return Ok(None),
+                Some(it) => it,
+            }}
+        }}",
+        input.text
+    );
+    let file = SourceFileNode::parse(&text);
+    let match_expr = file.syntax().descendants().find_map(ast::MatchExpr::cast)?;
+    let match_arg = match_expr.expr()?;
+    let src_range = TextRange::offset_len(0.into(), TextUnit::of_str(&input.text));
+    let ranges_map = vec![(src_range, match_arg.syntax().range())];
+    let res = MacroExpansion { text, ranges_map };
+    Some(Arc::new(res))
+}