1 files changed, 107 insertions, 3 deletions

diff --git a/src/lisp/error.rs b/src/lisp/error.rs
index 99dec3b..4f90d14 100644
--- a/src/lisp/error.rs
+++ b/src/lisp/error.rs
@@ -1,5 +1,109 @@
-#[derive(Debug, PartialEq, Copy, Clone)]
+use crate::lisp::lex::{Span, SpanDisplay};
+
+use std::fmt;
+
+#[derive(Debug, PartialEq, Clone)]
 pub enum LispError {
-    ParseError,
-    EvalError,
+    Parse(ParseError),
+    Eval(EvalError),
+}
+
+impl fmt::Display for LispError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Parse(p) => write!(f, "parse error: {}", p.kind),
+            Self::Eval(e) => write!(f, "eval error: {}", e),
+        }
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub struct ParseError {
+    pub span: Span,
+    pub kind: ParseErrorKind,
+}
+
+impl ParseError {
+    pub fn new(span: Span, kind: ParseErrorKind) -> Self {
+        Self { span, kind }
+    }
+    pub fn fmt(&self, f: &mut fmt::Formatter<'_>, text: &str) -> fmt::Result {
+        let SpanDisplay { line, col, .. } = SpanDisplay::highlight_span(self.span, text);
+        write!(f, "line {}, col {}: {}", line, col, self.kind)
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum ParseErrorKind {
+    InvalidLiteral,
+    InvalidToken,
+    InvalidChar(char),
+    LiteralParseError,
+    MissingCloseParen,
+    UnbalancedComma,
+    UnexpectedEof,
+    UnexpectedToken {
+        expected: &'static str,
+        found: &'static str,
+    },
+    UnmatchedParen,
+    UnterminatedString,
+}
+
+impl fmt::Display for ParseErrorKind {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            ParseErrorKind::InvalidChar(ch) => write!(f, "invalid character {}", ch),
+            ParseErrorKind::InvalidToken => write!(f, "invalid token"),
+            ParseErrorKind::UnexpectedEof => write!(f, "unexpected end of file"),
+            ParseErrorKind::InvalidLiteral => write!(f, "invalid literal"),
+            ParseErrorKind::UnmatchedParen => write!(f, "unmatched `)`"),
+            ParseErrorKind::UnbalancedComma => write!(f, "unbalanced comma"),
+            ParseErrorKind::UnexpectedToken { expected, found } => {
+                write!(
+                    f,
+                    "unexpected token, got `{}`, expected `{}`",
+                    found, expected
+                )
+            }
+            ParseErrorKind::LiteralParseError => write!(f, "error parsing literal"),
+            ParseErrorKind::MissingCloseParen => write!(f, "missing `)`"),
+            ParseErrorKind::UnterminatedString => write!(f, "unterminated string literal"),
+        }
+    }
+}
+
+impl From<ParseError> for LispError {
+    fn from(p: ParseError) -> Self {
+        LispError::Parse(p)
+    }
+}
+
+#[derive(Debug, PartialEq, Clone)]
+pub enum EvalError {
+    ArgumentCount(Option<u32>), // expected
+    BadForm,
+    UnboundVariable(String),
+    DivByZero,
+    TypeMismatch,
+}
+
+impl fmt::Display for EvalError {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::ArgumentCount(i) => {
+                write!(f, "invalid number of arguments, expected atleast {:?}", i)
+            }
+            Self::BadForm => write!(f, "bad expression form"),
+            Self::UnboundVariable(s) => write!(f, "unbound variable {}", s),
+            Self::TypeMismatch => write!(f, "mismatched types"),
+            Self::DivByZero => write!(f, "attempt to divide by zero"),
+        }
+    }
+}
+
+impl From<EvalError> for LispError {
+    fn from(e: EvalError) -> Self {
+        LispError::Eval(e)
+    }
 }