magc 0.8.0

The Mag Language Compiler
Documentation 
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use crate::parser::{InfixParselet, Parser, ParserError, ParserResult, PREC_CALL};
use crate::types::{
    Call, Expression, ExpressionKind, Pattern, Token, TokenKind, ValuePattern, VariablePattern,
};

#[derive(Debug, Clone)]
/// Parse a call expression like `fib(32)`.
pub struct CallParselet;

impl CallParselet {
    fn pattern_or_value_pattern(
        &self,
        expression: Box<Expression>,
    ) -> Result<Pattern, ParserError> {
        match expression.kind {
            ExpressionKind::Pattern(pattern) => Ok(pattern),

            _ => Ok(Pattern::Value(ValuePattern { expression })),
        }
    }

    fn expect_typeless_variable_pattern(
        &self,
        expression: Box<Expression>,
    ) -> Result<String, ParserError> {
        match expression.kind {
            ExpressionKind::Pattern(Pattern::Variable(pattern)) => {
                if let VariablePattern {
                    name: Some(name),
                    type_id: None,
                } = pattern
                {
                    Ok(name)
                } else {
                    Err(ParserError::ExpectedPattern)
                }
            }

            _ => Err(ParserError::ExpectedPattern),
        }
    }
}

impl InfixParselet for CallParselet {
    fn parse(&self, parser: &mut Parser, left: Box<Expression>, token: Token) -> ParserResult {
        let name = self.expect_typeless_variable_pattern(left)?;
        parser.consume_expect(TokenKind::LeftParen)?;

        let t = parser.peek()?;

        match t.kind {
            TokenKind::RightParen => parser.consume_expect(TokenKind::RightParen)?,
            _ => {
                let expr = parser.parse_expression(0)?;

                parser.consume_expect(TokenKind::RightParen)?;

                return Ok(Expression {
                    kind: ExpressionKind::Call(Call {
                        name,
                        signature: Some(self.pattern_or_value_pattern(Box::new(expr))?),
                    }),

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

        Ok(Expression {
            kind: ExpressionKind::Call(Call {
                name,
                signature: None,
            }),

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

    fn get_precedence(&self) -> usize {
        PREC_CALL
    }
}