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
use anyhow::{anyhow, Result};
use itertools::{Itertools, Position};
use crate::ast::pl::Expr;
use crate::error::{Error, Reason};
pub trait IntoOnly {
type Item;
fn into_only(self) -> Result<Self::Item>;
}
impl<T, I> IntoOnly for I
where
I: IntoIterator<Item = T>,
{
type Item = T;
fn into_only(self) -> Result<T> {
match self.into_iter().with_position().next() {
Some(Position::Only(item)) => Ok(item),
Some(Position::First(_)) => Err(anyhow!("Expected only one element, but found more.",)),
None => Err(anyhow!("Expected one element, but found none.",)),
_ => unreachable!(),
}
}
}
pub trait IntoOnlyNode {
fn into_only_node(self, who: &str, occupation: &str) -> Result<Expr, Error>;
}
impl IntoOnlyNode for Vec<Expr> {
fn into_only_node(mut self, who: &str, occupation: &str) -> Result<Expr, Error> {
match self.len() {
1 => Ok(self.remove(0)),
0 => Err(Error {
reason: Reason::Expected {
who: Some(who.to_string()),
expected: format!("only one {occupation}"),
found: "none".to_string(),
},
span: None,
help: None,
}),
_ => Err(Error {
reason: Reason::Expected {
who: Some(who.to_string()),
expected: format!("only one {occupation}"),
found: "more".to_string(),
},
span: self[1].span,
help: None,
}),
}
}
}
pub trait Only<T> {
fn only(&self) -> Result<&T>;
}
impl<T> Only<T> for [T]
where
T: std::fmt::Debug,
{
fn only(&self) -> Result<&T> {
if self.len() == 1 {
Ok(self.first().unwrap())
} else {
Err(anyhow!("Expected 1 item, got {}; {:?}", self.len(), self))
}
}
}