More parser implementation

vasm/src/parse_error.rs

@@ -1,10 +1,26 @@
-use vcore::opcodes::InvalidOpcode;
+use vcore::opcodes::{InvalidMnemonic};
+use pest::iterators::Pair;
+use std::fmt::{Display, Formatter};
+use crate::vasm_parser::Rule;
 
 #[derive(Debug, PartialEq)]
-pub struct ParseError<'a>(pub &'a str);
+pub enum ParseError<'a> {
+    LineParseFailure,
+    InvalidInstruction(&'a str)
+}
 
-impl<'a> From<InvalidOpcode> for ParseError<'a> {
-    fn from(_: InvalidOpcode) -> Self {
-        Self("Invalid opcode")
+impl<'a> From<InvalidMnemonic<'a>> for ParseError<'a> {
+    fn from(err: InvalidMnemonic<'a>) -> Self {
+        Self::InvalidInstruction(err.0)
     }
 }
+
+impl<'a> Display for ParseError<'a> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        use ParseError::*;
+        match self {
+            LineParseFailure => write!(f, "Failed to parse line"),
+            InvalidInstruction(p) => write!(f, "Cannot parse {} as instruction", p)
+        }
+    }
+}