fix AST for if expressions

then is not always a block...

crates/ra_syntax/src/ast.rs

@@ -285,13 +285,27 @@ impl LetStmt {
     }
 }
 
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ElseBranchFlavor<'a> {
+    Block(&'a Block),
+    IfExpr(&'a IfExpr),
+}
+
 impl IfExpr {
     pub fn then_branch(&self) -> Option<&Block> {
         self.blocks().nth(0)
     }
-    pub fn else_branch(&self) -> Option<&Block> {
-        self.blocks().nth(1)
+    pub fn else_branch(&self) -> Option<ElseBranchFlavor> {
+        let res = match self.blocks().nth(1) {
+            Some(block) => ElseBranchFlavor::Block(block),
+            None => {
+                let elif: &IfExpr = child_opt(self)?;
+                ElseBranchFlavor::IfExpr(elif)
+            }
+        };
+        Some(res)
     }
+
     fn blocks(&self) -> AstChildren<Block> {
         children(self)
     }