Use usual debug generation features, drop std dependency

Display has been moved into an own file.

src/debug.rs

@@ -19,22 +19,11 @@
 // SOFTWARE.
 
 use crate::Map;
-use core::fmt;
-use core::fmt::{Debug, Display, Formatter};
+use core::fmt::{self, Debug, Formatter};
 
-impl<K: PartialEq + Display, V: Display, const N: usize> Display for Map<K, V, N> {
+impl<K: PartialEq + Debug, V: Debug, const N: usize> Debug for Map<K, V, N> {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        <&Self as Debug>::fmt(&self, f)
-    }
-}
-
-impl<K: PartialEq + Display, V: Display, const N: usize> Debug for Map<K, V, N> {
-    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
-        let mut parts = vec![];
-        for (k, v) in self.iter() {
-            parts.push(std::format!("{k}: {v}"));
-        }
-        f.write_str(std::format!("{{{}}}", parts.join(", ").as_str()).as_str())
+        f.debug_map().entries(self.iter()).finish()
     }
 }
 
@@ -48,14 +37,20 @@ mod test {
         let mut m: Map<String, i32, 10> = Map::new();
         m.insert("one".to_string(), 42);
         m.insert("two".to_string(), 16);
-        assert_eq!("{one: 42, two: 16}", format!("{:?}", m));
+        assert_eq!(r#"{"one": 42, "two": 16}"#, format!("{:?}", m));
     }
 
     #[test]
-    fn displays_map() {
+    fn debug_alternate_map() {
         let mut m: Map<String, i32, 10> = Map::new();
         m.insert("one".to_string(), 42);
         m.insert("two".to_string(), 16);
-        assert_eq!("{one: 42, two: 16}", format!("{}", m));
+        assert_eq!(
+            r#"{
+    "one": 42,
+    "two": 16,
+}"#,
+            format!("{:#?}", m)
+        );
     }
 }

src/display.rs

@@ -0,0 +1,55 @@
+// Copyright (c) 2023 Yegor Bugayenko
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+use crate::Map;
+use core::fmt::{self, Display, Formatter, Write};
+
+impl<K: PartialEq + Display, V: Display, const N: usize> Display for Map<K, V, N> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let mut first = true;
+        f.write_char('{')?;
+        for (k, v) in self {
+            if first {
+                first = false;
+            } else {
+                f.write_str(", ")?;
+            }
+            k.fmt(f)?;
+            f.write_str(": ")?;
+            v.fmt(f)?;
+        }
+        f.write_char('}')?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod test {
+
+    use super::*;
+
+    #[test]
+    fn displays_map() {
+        let mut m: Map<String, i32, 10> = Map::new();
+        m.insert("one".to_string(), 42);
+        m.insert("two".to_string(), 16);
+        assert_eq!(r#"{one: 42, two: 16}"#, format!("{}", m));
+    }
+}

src/lib.rs

@@ -50,11 +50,10 @@
 #![allow(clippy::multiple_inherent_impl)]
 #![allow(clippy::multiple_crate_versions)]
 
-#[cfg(feature = "std")]
-mod debug;
-
 mod clone;
 mod ctors;
+mod debug;
+mod display;
 mod eq;
 mod from;
 mod index;