refactor(CommandParseError): remove the display implementation

we want to be able to give additional arguments to the display function later,
so this is needed

src/command.rs

@@ -54,16 +54,12 @@ pub enum CommandParseError {
     Scan(ScanError),
 }
 
-impl std::fmt::Display for CommandParseError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+impl CommandParseError {
+    pub(crate) fn message(&self) -> String {
         match self {
-            CommandParseError::MetaCommand(meta_command_parse_error) => {
-                write!(f, "{meta_command_parse_error}")
-            }
-            CommandParseError::Statement(statement_parse_error) => {
-                write!(f, "{statement_parse_error}")
-            }
-            CommandParseError::Scan(scan_error) => write!(f, "{scan_error:?}"),
+            CommandParseError::MetaCommand(x) => format!("{x}"),
+            CommandParseError::Statement(x) => format!("{x}"),
+            CommandParseError::Scan(x) => format!("{x}"),
         }
     }
 }

src/error_display.rs

@@ -8,7 +8,7 @@ pub trait OSDBError {
 impl OSDBError for CommandParseError {
     fn display(&self, file: &str, input: &str) {
         Report::build(ReportKind::Error, (file, 0..input.len() - 1))
-            .with_message(format!("{self}"))
+            .with_message(self.message())
             .with_label(Label::new((file, 0..input.len() - 1)).with_color(Color::Red))
             .finish()
             .print((file, Source::from(input)))

src/tokens.rs

@@ -67,12 +67,30 @@ pub enum ScanErrorKind {
     UnknownMetaCommand(String),
 }
 
+impl std::fmt::Display for ScanErrorKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            ScanErrorKind::UnexpectedChar(c) => write!(f, "unexpected char: {c:?}"),
+            ScanErrorKind::UnexpectedEndOfInput => write!(f, "unexpected end of input"),
+            ScanErrorKind::UnknownKeyword(x) => write!(f, "unknown keyword: {x:?}"),
+            ScanErrorKind::UnknownMetaCommand(x) => write!(f, "unknown meta-command: {x:?}"),
+        }
+    }
+}
+
 #[derive(Debug, Eq, PartialEq)]
 pub struct ScanError {
     pub location: Location,
     pub kind: ScanErrorKind,
 }
 
+impl std::fmt::Display for ScanError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        let kind = &self.kind;
+        write!(f, "{kind}")
+    }
+}
+
 impl Tokenizer {
     fn new(input: String, file: String) -> Self {
         Self {