fix #115

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "shadow-rs"
-version = "0.16.3"
+version = "0.17.0"
 authors = ["baoyachi <[email protected]>"]
 edition = "2021"
 description = "A build-time information stored in your rust project"

src/env.rs

@@ -264,7 +264,7 @@ pub fn new_system_env(std_env: &BTreeMap<String, String>) -> BTreeMap<ShadowCons
     );
 
     if let Err(e) = env.init(std_env) {
-        println!("{}", e.to_string());
+        println!("{}", e);
     }
     env.map
 }

src/err.rs

@@ -1,5 +1,7 @@
 use std::convert::From;
 use std::error::Error;
+use std::error::Error as StdError;
+use std::fmt::{Display, Formatter};
 use std::string::FromUtf8Error;
 
 pub type SdResult<T> = Result<T, ShadowError>;
@@ -15,14 +17,6 @@ impl ShadowError {
     }
 }
 
-impl ToString for ShadowError {
-    fn to_string(&self) -> String {
-        match self {
-            ShadowError::String(e) => e.to_string(),
-        }
-    }
-}
-
 impl From<std::string::FromUtf8Error> for ShadowError {
     fn from(e: FromUtf8Error) -> Self {
         ShadowError::String(e.to_string())
@@ -58,3 +52,13 @@ impl From<std::num::ParseIntError> for ShadowError {
         ShadowError::String(e.to_string())
     }
 }
+
+impl Display for ShadowError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            ShadowError::String(err) => f.write_str(err),
+        }
+    }
+}
+
+impl StdError for ShadowError {}

src/git.rs

@@ -256,7 +256,7 @@ pub fn new_git(
     );
 
     if let Err(e) = git.init(path, std_env) {
-        println!("{}", e.to_string());
+        println!("{}", e);
     }
 
     git.map