nixfmt_rs 0.4.0

Rust implementation of nixfmt with exact Haskell compatibility
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93

//! Keyword expression parsing
//!
//! This module handles parsing of Nix's keyword-based control flow expressions:
//! - `let ... in ...` - Let bindings
//! - `if ... then ... else ...` - Conditional expressions
//! - `with ...; ...` - With expressions (scope introduction)
//! - `assert ...; ...` - Assert expressions

use crate::ast::{Expression, Leaf, Token};
use crate::error::Result;

use super::Parser;

impl Parser {
    /// Parse let expression: let bindings in expr
    pub(super) fn parse_let(&mut self) -> Result<Expression> {
        let let_tok = self.expect_token(Token::Let, "'let'")?;
        let bindings = self.parse_binders()?;
        let in_tok = self.expect_token(Token::In, "'in'")?;
        let body = self.parse_expression()?;

        Ok(Expression::Let {
            kw_let: let_tok,
            bindings,
            kw_in: in_tok,
            body: Box::new(body),
        })
    }

    /// Parse if expression: if cond then expr else expr
    pub(super) fn parse_if(&mut self) -> Result<Expression> {
        let if_tok = self.expect_token(Token::If, "'if'")?;
        let cond = self.parse_expression()?;
        let then_tok = self.expect_token(Token::Then, "'then'")?;
        let then_expr = self.parse_expression()?;
        let else_tok = self.expect_token(Token::Else, "'else'")?;
        let else_expr = self.parse_expression()?;

        Ok(Expression::If {
            kw_if: if_tok,
            cond: Box::new(cond),
            kw_then: then_tok,
            then_branch: Box::new(then_expr),
            kw_else: else_tok,
            else_branch: Box::new(else_expr),
        })
    }

    /// Parse with expression: with expr ; expr
    pub(super) fn parse_with(&mut self) -> Result<Expression> {
        self.parse_keyword_semi_expr(
            Token::With,
            "'with'",
            "'with' expression",
            |kw, head, semi, body| Expression::With {
                kw_with: kw,
                scope: head,
                semi,
                body,
            },
        )
    }

    /// Parse assert expression: assert cond ; expr
    pub(super) fn parse_assert(&mut self) -> Result<Expression> {
        self.parse_keyword_semi_expr(
            Token::Assert,
            "'assert'",
            "'assert' condition",
            |kw, head, semi, body| Expression::Assert {
                kw_assert: kw,
                cond: head,
                semi,
                body,
            },
        )
    }

    /// Shared shape for `with` / `assert`: `<kw> expr ; expr`.
    fn parse_keyword_semi_expr(
        &mut self,
        keyword: Token,
        kw_label: &'static str,
        semi_after: &'static str,
        build: fn(Leaf, Box<Expression>, Leaf, Box<Expression>) -> Expression,
    ) -> Result<Expression> {
        let kw = self.expect_token(keyword, kw_label)?;
        let head = self.parse_expression()?;
        let semi = self.expect_semicolon_after(semi_after)?;
        let body = self.parse_expression()?;
        Ok(build(kw, Box::new(head), semi, Box::new(body)))
    }
}