diff --git a/crates/els/diagnostics.rs b/crates/els/diagnostics.rs
index 32265704..dee39748 100644
--- a/crates/els/diagnostics.rs
+++ b/crates/els/diagnostics.rs
@@ -87,14 +87,14 @@ impl<Checker: BuildRunnable> Server<Checker> {
             return Ok(());
         };
         let ast_diff = ASTDiff::diff(old, &new);
-        crate::_log!("diff: {ast_diff:?}");
+        crate::_log!("diff: {ast_diff}");
         if let Some(mut lowerer) = self.get_lowerer(&uri) {
             let hir = self
                 .artifacts
                 .get_mut(&uri)
                 .and_then(|r| r.artifact.object.as_mut());
             if let Some((hir_diff, hir)) = HIRDiff::new(ast_diff, &mut lowerer).zip(hir) {
-                crate::_log!("hir_diff: {hir_diff:?}");
+                crate::_log!("hir_diff: {hir_diff}");
                 hir_diff.update(hir);
             }
             self.restore_mod_ctx(&uri, lowerer.pop_mod_ctx().unwrap());
diff --git a/crates/els/diff.rs b/crates/els/diff.rs
index ce24b5de..01363681 100644
--- a/crates/els/diff.rs
+++ b/crates/els/diff.rs
@@ -1,4 +1,5 @@
 use std::cmp::Ordering::*;
+use std::fmt;
 
 use erg_common::traits::Stream;
 use erg_compiler::erg_parser::ast;
@@ -15,6 +16,17 @@ pub enum ASTDiff {
     Nop,
 }
 
+impl fmt::Display for ASTDiff {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Deletion(idx) => write!(f, "Deletion({idx})"),
+            Self::Addition(idx, expr) => write!(f, "Addition({idx}, {expr})"),
+            Self::Modification(idx, expr) => write!(f, "Modification({idx}, {expr})"),
+            Self::Nop => write!(f, "Nop"),
+        }
+    }
+}
+
 /// diff(old: {x, y, z}, new: {x, a, y, z}) => ASTDiff::Addition(1)
 /// diff(old: {x, y}, new: {x, y, a}) => ASTDiff::Addition(2)
 /// diff(old: {x, y}, new: {x}) => ASTDiff::Deletion(1)
@@ -57,6 +69,17 @@ pub enum HIRDiff {
     Nop,
 }
 
+impl fmt::Display for HIRDiff {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Deletion(idx) => write!(f, "Deletion({idx})"),
+            Self::Addition(idx, expr) => write!(f, "Addition({idx}, {expr})"),
+            Self::Modification(idx, expr) => write!(f, "Modification({idx}, {expr})"),
+            Self::Nop => write!(f, "Nop"),
+        }
+    }
+}
+
 impl HIRDiff {
     pub fn new(diff: ASTDiff, lowerer: &mut ASTLowerer) -> Option<Self> {
         match diff {