ide_diagnostics/handlers/
mismatched_array_pat_len.rs

1use crate::{Diagnostic, DiagnosticCode, DiagnosticsContext};
2
3// Diagnostic: mismatched-array-pat-len
4//
5// This diagnostic is triggered when an array pattern's element count does not
6// match the array's declared length.
7pub(crate) fn mismatched_array_pat_len(
8    ctx: &DiagnosticsContext<'_, '_>,
9    d: &hir::MismatchedArrayPatLen,
10) -> Diagnostic {
11    let (code, message) = if d.has_rest {
12        (
13            "E0528",
14            format!(
15                "pattern requires at least {} element{} but array has {}",
16                d.found,
17                if d.found == 1 { "" } else { "s" },
18                d.expected,
19            ),
20        )
21    } else {
22        (
23            "E0527",
24            format!(
25                "pattern requires {} element{} but array has {}",
26                d.found,
27                if d.found == 1 { "" } else { "s" },
28                d.expected,
29            ),
30        )
31    };
32    Diagnostic::new_with_syntax_node_ptr(
33        ctx,
34        DiagnosticCode::RustcHardError(code),
35        message,
36        d.pat.map(Into::into),
37    )
38    .stable()
39}
40
41#[cfg(test)]
42mod tests {
43    use crate::tests::check_diagnostics;
44
45    #[test]
46    fn array_pattern_too_few_elements() {
47        check_diagnostics(
48            r#"
49fn f(arr: [i32; 3]) {
50    let [_a, _b] = arr;
51      //^^^^^^^^ error: pattern requires 2 elements but array has 3
52}
53"#,
54        );
55    }
56
57    #[test]
58    fn array_pattern_too_many_elements() {
59        check_diagnostics(
60            r#"
61fn f(arr: [i32; 2]) {
62    let [_a, _b, _c] = arr;
63      //^^^^^^^^^^^^ error: pattern requires 3 elements but array has 2
64}
65"#,
66        );
67    }
68
69    #[test]
70    fn array_pattern_with_rest_too_short() {
71        check_diagnostics(
72            r#"
73fn f(arr: [i32; 2]) {
74    let [_a, _b, _c, ..] = arr;
75      //^^^^^^^^^^^^^^^^ error: pattern requires at least 3 elements but array has 2
76}
77"#,
78        );
79    }
80
81    #[test]
82    fn array_pattern_with_rest_ok() {
83        check_diagnostics(
84            r#"
85fn f(arr: [i32; 5]) {
86    let [_a, _b, ..] = arr;
87}
88"#,
89        );
90    }
91
92    #[test]
93    fn array_pattern_exact_length_ok() {
94        check_diagnostics(
95            r#"
96fn f(arr: [i32; 3]) {
97    let [_a, _b, _c] = arr;
98}
99"#,
100        );
101    }
102
103    #[test]
104    fn array_pattern_singular_element_uses_singular() {
105        check_diagnostics(
106            r#"
107fn f(arr: [i32; 3]) {
108    let [_a] = arr;
109      //^^^^ error: pattern requires 1 element but array has 3
110}
111"#,
112        );
113    }
114}
ide_diagnostics/handlers/mismatched_array_pat_len.rs

ide_diagnostics/handlers/
mismatched_array_pat_len.rs
