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use crate::ast;
use crate::{ParseError, Parser, Spanned, ToTokens};

/// A let expression `let <name> = <expr>;`
///
/// # Examples
///
/// ```rust
/// use rune::{testing, ast};
///
/// testing::roundtrip::<ast::ExprLet>("let x = 1");
/// testing::roundtrip::<ast::ExprLet>("#[attr] let a = f()");
/// ```
#[derive(Debug, Clone, PartialEq, Eq, ToTokens, Spanned)]
pub struct ExprLet {
    /// The attributes for the let expression
    #[rune(iter)]
    pub attributes: Vec<ast::Attribute>,
    /// The `let` keyword.
    pub let_token: T![let],
    /// The name of the binding.
    pub pat: ast::Pat,
    /// The equality keyword.
    pub eq: T![=],
    /// The expression the binding is assigned to.
    pub expr: ast::Expr,
}

impl ExprLet {
    /// Parse with the given meta.
    pub fn parse_with_meta(
        parser: &mut Parser<'_>,
        attributes: Vec<ast::Attribute>,
    ) -> Result<Self, ParseError> {
        Ok(Self {
            attributes,
            let_token: parser.parse()?,
            pat: parser.parse()?,
            eq: parser.parse()?,
            expr: ast::Expr::parse_without_eager_brace(parser)?,
        })
    }

    /// Parse a let expression without eager bracing.
    pub fn parse_without_eager_brace(parser: &mut Parser) -> Result<Self, ParseError> {
        Ok(Self {
            attributes: vec![],
            let_token: parser.parse()?,
            pat: parser.parse()?,
            eq: parser.parse()?,
            expr: ast::Expr::parse_without_eager_brace(parser)?,
        })
    }
}

expr_parse!(Let, ExprLet, "let expression");