Primitive Char should be encoded with a single quote

ktoml-core/src/commonMain/kotlin/com/akuleshov7/ktoml/encoders/TomlAbstractEncoder.kt

@@ -152,7 +152,14 @@ public abstract class TomlAbstractEncoder protected constructor(
     override fun encodeShort(value: Short): Unit = encodeLong(value.toLong())
     override fun encodeInt(value: Int): Unit = encodeLong(value.toLong())
     override fun encodeFloat(value: Float): Unit = encodeDouble(value.toDouble())
-    override fun encodeChar(value: Char): Unit = encodeString(value.toString())
+
+    /**
+     * https://github.com/akuleshov7/ktoml/issues/260
+     * As per the TOML specification, there is no predefined Char type.
+     * However, we've introduced the concept in our TOML implementation to align more closely with Kotlin's syntax.
+     * So we are expecting Chars to have single quote on the decoding. So encoding should be done in a similar way.
+     */
+    override fun encodeChar(value: Char): Unit = appendValue(TomlLiteralString(value.toString()))
 
     // Structure
 

ktoml-core/src/commonTest/kotlin/com/akuleshov7/ktoml/encoders/PrimitiveEncoderTest.kt

@@ -126,4 +126,17 @@ class PrimitiveEncoderTest {
             expectedToml = "wholeNumberDouble = 3.0"
         )
     }
+
+    @Test
+    fun charRegression() {
+        @Serializable
+        data class File(
+            val charVal: Char = 'W'
+        )
+
+        assertEncodedEquals(
+            value = File(),
+            expectedToml = "charVal = \'W\'"
+        )
+    }
 }