magc 0.8.0

The Mag Language Compiler
Documentation 
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//! Parse a variable identifier with an optional type annotation.

use crate::parser::{Parser, ParserResult, PrefixParselet};

use crate::types::{Expression, ExpressionKind, Pattern, Token, TokenKind, VariablePattern};

#[derive(Debug, Clone)]
/// Parse a variable identifier with an optional type annotation.
pub struct VariablePatternParselet;

impl PrefixParselet for VariablePatternParselet {
    fn parse(&self, parser: &mut Parser, token: Token) -> ParserResult {
        let name;

        let lexeme = parser.get_lexeme(token.start_pos, token.end_pos)?;

        if lexeme == "_".to_string() {
            name = None;
        } else {
            name = Some(lexeme.clone());
        }

        if !parser.eof() {
            let next_token = parser.peek()?;

            let pattern = match next_token.kind {
                TokenKind::Type => {
                    let type_token = parser.consume();
                    let type_name = parser.get_lexeme(type_token.start_pos, type_token.end_pos)?;

                    Pattern::Variable(VariablePattern {
                        name,
                        type_id: Some(type_name),
                    })
                }

                _ => Pattern::Variable(VariablePattern {
                    name,
                    type_id: None,
                }),
            };

            Ok(Expression {
                kind: ExpressionKind::Pattern(pattern),

                start_pos: token.start_pos,
                end_pos: token.end_pos,
            })
        } else {
            Ok(Expression {
                kind: ExpressionKind::Pattern(Pattern::Variable(VariablePattern {
                    name,
                    type_id: None,
                })),

                start_pos: token.start_pos,
                end_pos: token.end_pos,
            })
        }
    }
}

/*#[cfg(test)]
mod tests {
    use super::;
    use crate::lexer::*;

    #[test]
    fn type_and_name() {
        let mut lexer = Lexer::new("name String");
        let tokens = lexer.parse();
        let mut parser = Parser::new(tokens);

        assert_eq!(
            Ok(Expression {
                kind:      ExpressionKind::Pattern(Pattern::Variable {
                    name: Some("name".to_string()),
                    type_id: Some("String".to_string()),
                }),

                start_pos: 0,
                end_pos:   4,
            }),
            parser.parse_expression(0)
        );
    }

    #[test]
    fn no_type_and_no_name() {
        let mut lexer = Lexer::new("_");
        let tokens = lexer.parse();
        let mut parser = Parser::new(tokens);

        assert_eq!(
            Ok(Expression {
                kind:      ExpressionKind::Pattern(Pattern::Variable {
                    name: None,
                    type_id: None,
                }),

                start_pos: 0,
                end_pos:   1,
            }),
            parser.parse_expression(0)
        );
    }

    #[test]
    fn type_but_no_name() {
        let mut lexer = Lexer::new("_ Int");
        let tokens = lexer.parse();
        let mut parser = Parser::new(tokens);

        assert_eq!(
            Ok(Expression {
                kind:      ExpressionKind::Pattern(Pattern::Variable {
                    name: None,
                    type_id: Some("Int".to_string()),
                }),

                start_pos: 0,
                end_pos:   1,
            }),
            parser.parse_expression(0)
        );
    }

    #[test]
    fn name_but_no_type() {
        let mut lexer = Lexer::new("lexer");
        let tokens = lexer.parse();
        let mut parser = Parser::new(tokens);

        assert_eq!(
            Ok(Expression {
                kind:      ExpressionKind::Pattern(Pattern::Variable {
                    name: Some("lexer".to_string()),
                    type_id: None,
                }),

                start_pos: 0,
                end_pos:   5,
            }),
            parser.parse_expression(0)
        );
    }
}*/