NexaCore/crates/nxc-frontend/tests/parser_tests.rs

use nxc_frontend::{
    BinaryOp, ExprKind, Item, Lexer, Literal, Parser, StmtKind, UnaryOp,
};

fn parse(source: &str) -> nxc_frontend::ParseResult {
    let lexed = Lexer::new(source).lex();
    assert!(
        lexed.diagnostics.is_empty(),
        "unexpected lexer diagnostics: {:?}",
        lexed.diagnostics
    );
    Parser::new(lexed.tokens).parse_module()
}

#[test]
fn parses_function_with_if_else_and_returns() {
    let source = "\
fn classify(value: Int) -> Int:
    if value > 10:
        return 1
    else:
        return 0
";

    let parsed = parse(source);
    assert!(parsed.diagnostics.is_empty(), "{:?}", parsed.diagnostics);
    assert_eq!(parsed.module.items.len(), 1);

    let Item::Function(function) = &parsed.module.items[0] else {
        panic!("expected function item");
    };

    assert_eq!(function.name, "classify");
    assert_eq!(function.params.len(), 1);
    assert_eq!(function.body.statements.len(), 1);

    let StmtKind::If(if_stmt) = &function.body.statements[0].kind else {
        panic!("expected if statement");
    };

    match &if_stmt.condition.kind {
        ExprKind::Binary { op, .. } => assert_eq!(*op, BinaryOp::Greater),
        other => panic!("unexpected condition: {other:?}"),
    }
    assert!(if_stmt.else_block.is_some());
}

#[test]
fn respects_binary_operator_precedence() {
    let source = "\
fn main() -> Int:
    return 1 + 2 * 3 == 7 || false
";

    let parsed = parse(source);
    assert!(parsed.diagnostics.is_empty(), "{:?}", parsed.diagnostics);

    let Item::Function(function) = &parsed.module.items[0] else {
        panic!("expected function item");
    };

    let StmtKind::Return(Some(expr)) = &function.body.statements[0].kind else {
        panic!("expected return statement");
    };

    let ExprKind::Binary { left, op, right } = &expr.kind else {
        panic!("expected binary expression");
    };
    assert_eq!(*op, BinaryOp::LogicalOr);

    let ExprKind::Binary {
        left: equality_left,
        op: equality_op,
        right: equality_right,
    } = &left.kind
    else {
        panic!("expected equality expression");
    };
    assert_eq!(*equality_op, BinaryOp::Equal);

    let ExprKind::Binary {
        left: add_left,
        op: add_op,
        right: add_right,
    } = &equality_left.kind
    else {
        panic!("expected additive expression");
    };
    assert_eq!(*add_op, BinaryOp::Add);

    match &add_left.kind {
        ExprKind::Literal(Literal::Integer(1)) => {}
        other => panic!("unexpected left additive operand: {other:?}"),
    }

    let ExprKind::Binary {
        left: mul_left,
        op: mul_op,
        right: mul_right,
    } = &add_right.kind
    else {
        panic!("expected multiplicative expression");
    };
    assert_eq!(*mul_op, BinaryOp::Multiply);

    match &mul_left.kind {
        ExprKind::Literal(Literal::Integer(2)) => {}
        other => panic!("unexpected left multiplicative operand: {other:?}"),
    }
    match &mul_right.kind {
        ExprKind::Literal(Literal::Integer(3)) => {}
        other => panic!("unexpected right multiplicative operand: {other:?}"),
    }
    match &equality_right.kind {
        ExprKind::Literal(Literal::Integer(7)) => {}
        other => panic!("unexpected equality right operand: {other:?}"),
    }
    match &right.kind {
        ExprKind::Literal(Literal::Bool(false)) => {}
        other => panic!("unexpected logical-or right operand: {other:?}"),
    }
}

#[test]
fn parses_grouping_unary_and_calls() {
    let source = "\
fn main() -> Int:
    return -(compute(1, 2) + 3)
";

    let parsed = parse(source);
    assert!(parsed.diagnostics.is_empty(), "{:?}", parsed.diagnostics);

    let Item::Function(function) = &parsed.module.items[0] else {
        panic!("expected function item");
    };
    let StmtKind::Return(Some(expr)) = &function.body.statements[0].kind else {
        panic!("expected return statement");
    };

    let ExprKind::Unary { op, expr: inner } = &expr.kind else {
        panic!("expected unary expression");
    };
    assert_eq!(*op, UnaryOp::Negate);

    let ExprKind::Group(grouped) = &inner.kind else {
        panic!("expected grouped expression");
    };

    let ExprKind::Binary { left, op, .. } = &grouped.kind else {
        panic!("expected additive expression");
    };
    assert_eq!(*op, BinaryOp::Add);

    let ExprKind::Call { args, .. } = &left.kind else {
        panic!("expected call expression");
    };
    assert_eq!(args.len(), 2);
}

#[test]
fn recovers_and_reports_syntax_errors() {
    let source = "\
fn broken(value: Int) -> Int
    let x = 1

struct Config:
    port: Int
";

    let parsed = parse(source);
    assert!(!parsed.diagnostics.is_empty());
    assert_eq!(parsed.module.items.len(), 1);

    let Item::Struct(struct_decl) = &parsed.module.items[0] else {
        panic!("expected recovered struct declaration");
    };
    assert_eq!(struct_decl.name, "Config");
}