Fix build for Diagnostic type change

Author: theotherphil

crates/ra_hir/src/diagnostics.rs

@@ -154,11 +154,8 @@ impl Diagnostic for MissingOkInTailExpr {
     fn message(&self) -> String {
         "wrap return expression in Ok".to_string()
     }
-    fn file(&self) -> HirFileId {
-        self.file
-    }
-    fn syntax_node_ptr(&self) -> SyntaxNodePtr {
-        self.expr.into()
+    fn source(&self) -> Source<SyntaxNodePtr> {
+        Source { file_id: self.file, ast: self.expr.into() }
     }
     fn as_any(&self) -> &(dyn Any + Send + 'static) {
         self
@@ -169,8 +166,8 @@ impl AstDiagnostic for MissingOkInTailExpr {
     type AST = ast::Expr;
 
     fn ast(&self, db: &impl HirDatabase) -> Self::AST {
-        let root = db.parse_or_expand(self.file()).unwrap();
-        let node = self.syntax_node_ptr().to_node(&root);
+        let root = db.parse_or_expand(self.file).unwrap();
+        let node = self.source().ast.to_node(&root);
         ast::Expr::cast(node).unwrap()
     }
 }