Refactor errors and clean up read_line

dust-lang/src/built_in_function.rs

@@ -92,7 +92,7 @@ impl BuiltInFunction {
 
                     stdin().read_line(&mut input)?;
 
-                    Ok(Some(Value::string(input)))
+                    Ok(Some(Value::string(input.trim_end_matches('\n'))))
                 } else {
                     Err(BuiltInFunctionError::WrongNumberOfValueArguments)
                 }

dust-lang/src/dust_error.rs

@@ -35,7 +35,7 @@ impl<'src> DustError<'src> {
                 AnalyzerError::ExpectedIntegerFloatOrString { position, .. } => position,
                 AnalyzerError::UnexpectedIdentifier { position, .. } => position,
             },
-            VmError::ParseError(_) => todo!(),
+            VmError::ParseError(parse_error) => &parse_error.position(),
             VmError::ValueError { position, .. } => position,
             VmError::BuiltInFunctionCallError(_) => todo!(),
             VmError::ExpectedIdentifier { position } => position,
@@ -44,6 +44,7 @@ impl<'src> DustError<'src> {
             VmError::ExpectedFunction { position, .. } => position,
             VmError::ExpectedList { position } => position,
             VmError::ExpectedValue { position } => position,
+            VmError::UndefinedIdentifier { position, .. } => position,
         };
         let label = self.vm_error.to_string();
         let message = Level::Error.title(title).snippet(

dust-lang/src/parse.rs

@@ -128,7 +128,13 @@ impl<'src> Parser<'src> {
     }
 
     fn next_token(&mut self) -> Result<(), ParseError> {
-        self.current = self.lexer.next_token(self.source)?;
+        self.current =
+            self.lexer
+                .next_token(self.source)
+                .map_err(|lex_error| ParseError::LexError {
+                    error: lex_error,
+                    position: self.current.1,
+                })?;
 
         Ok(())
     }
@@ -341,7 +347,10 @@ impl<'src> Parser<'src> {
                     left_span,
                 ))
             }
-            _ => Err(ParseError::UnexpectedToken(self.current.0.to_owned())),
+            _ => Err(ParseError::UnexpectedToken {
+                actual: self.current.0.to_owned(),
+                position: self.current.1,
+            }),
         }
     }
 
@@ -359,18 +368,30 @@ impl<'src> Parser<'src> {
 
 #[derive(Debug, PartialEq, Clone)]
 pub enum ParseError {
-    LexError(LexError),
+    LexError { error: LexError, position: Span },
 
     ExpectedClosingParenthesis { actual: TokenOwned, position: Span },
     ExpectedClosingSquareBrace { actual: TokenOwned, position: Span },
     ExpectedOpeningParenthesis { actual: TokenOwned, position: Span },
-    UnexpectedToken(TokenOwned),
+    UnexpectedToken { actual: TokenOwned, position: Span },
+}
+
+impl ParseError {
+    pub fn position(&self) -> Span {
+        match self {
+            Self::LexError { position, .. } => *position,
+            Self::ExpectedClosingParenthesis { position, .. } => *position,
+            Self::ExpectedClosingSquareBrace { position, .. } => *position,
+            Self::ExpectedOpeningParenthesis { position, .. } => *position,
+            Self::UnexpectedToken { position, .. } => *position,
+        }
+    }
 }
 
 impl Error for ParseError {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         match self {
-            Self::LexError(error) => Some(error),
+            Self::LexError { error, .. } => Some(error),
             _ => None,
         }
     }
@@ -379,7 +400,7 @@ impl Error for ParseError {
 impl Display for ParseError {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         match self {
-            Self::LexError(error) => write!(f, "{}", error),
+            Self::LexError { error, .. } => write!(f, "{}", error),
             Self::ExpectedClosingParenthesis { actual, .. } => {
                 write!(f, "Expected closing parenthesis, found {actual}",)
             }
@@ -389,17 +410,11 @@ impl Display for ParseError {
             Self::ExpectedOpeningParenthesis { actual, .. } => {
                 write!(f, "Expected opening parenthesis, found {actual}",)
             }
-            Self::UnexpectedToken(actual) => write!(f, "Unexpected token {actual}"),
+            Self::UnexpectedToken { actual, .. } => write!(f, "Unexpected token {actual}"),
         }
     }
 }
 
-impl From<LexError> for ParseError {
-    fn from(v: LexError) -> Self {
-        Self::LexError(v)
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use crate::Identifier;

dust-lang/src/value.rs

@@ -131,6 +131,9 @@ impl Value {
             (ValueInner::Integer(left), ValueInner::Integer(right)) => {
                 Ok(Value::integer(left.saturating_add(*right)))
             }
+            (ValueInner::String(left), ValueInner::String(right)) => {
+                Ok(Value::string(left.to_string() + right))
+            }
             _ => Err(ValueError::CannotAdd(self.clone(), other.clone())),
         }
     }

dust-lang/src/vm.rs

@@ -171,7 +171,16 @@ impl Vm {
 
                 Ok(function.clone().call(None, value_parameters, variables)?)
             }
-            Statement::Identifier(_) => Ok(None),
+            Statement::Identifier(identifier) => {
+                if let Some(value) = variables.get(&identifier) {
+                    Ok(Some(value.clone()))
+                } else {
+                    Err(VmError::UndefinedIdentifier {
+                        identifier,
+                        position: node.position,
+                    })
+                }
+            }
             Statement::List(nodes) => {
                 let values = nodes
                     .into_iter()
@@ -303,17 +312,37 @@ impl Vm {
 pub enum VmError {
     AnaylyzerError(AnalyzerError),
     ParseError(ParseError),
-    ValueError { error: ValueError, position: Span },
+    ValueError {
+        error: ValueError,
+        position: Span,
+    },
 
     // Anaylsis Failures
     // These should be prevented by running the analyzer before the VM
     BuiltInFunctionCallError(BuiltInFunctionError),
-    ExpectedIdentifier { position: Span },
-    ExpectedIdentifierOrInteger { position: Span },
-    ExpectedInteger { position: Span },
-    ExpectedFunction { actual: Value, position: Span },
-    ExpectedList { position: Span },
-    ExpectedValue { position: Span },
+    ExpectedIdentifier {
+        position: Span,
+    },
+    ExpectedIdentifierOrInteger {
+        position: Span,
+    },
+    ExpectedInteger {
+        position: Span,
+    },
+    ExpectedFunction {
+        actual: Value,
+        position: Span,
+    },
+    ExpectedList {
+        position: Span,
+    },
+    ExpectedValue {
+        position: Span,
+    },
+    UndefinedIdentifier {
+        identifier: Identifier,
+        position: Span,
+    },
 }
 
 impl From<BuiltInFunctionError> for VmError {
@@ -383,6 +412,16 @@ impl Display for VmError {
             Self::ExpectedValue { position } => {
                 write!(f, "Expected a value at position: {:?}", position)
             }
+            Self::UndefinedIdentifier {
+                identifier,
+                position,
+            } => {
+                write!(
+                    f,
+                    "Undefined identifier: {} at position: {:?}",
+                    identifier, position
+                )
+            }
         }
     }
 }