clippy_lints/src/misc_early/unneeded_field_pattern.rs

use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::source::SpanRangeExt;
use itertools::Itertools;
use rustc_ast::ast::{Pat, PatKind};
use rustc_lint::EarlyContext;

use super::UNNEEDED_FIELD_PATTERN;

pub(super) fn check(cx: &EarlyContext<'_>, pat: &Pat) {
    if let PatKind::Struct(_, ref npat, ref pfields, _) = pat.kind {
        let mut wilds = 0;
        let type_name = npat
            .segments
            .last()
            .expect("A path must have at least one segment")
            .ident
            .name;

        for field in pfields {
            if let PatKind::Wild = field.pat.kind {
                wilds += 1;
            }
        }
        if !pfields.is_empty() && wilds == pfields.len() {
            #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
            span_lint_and_then(
                cx,
                UNNEEDED_FIELD_PATTERN,
                pat.span,
                "all the struct fields are matched to a wildcard pattern, consider using `..`",
                |diag| {
                    diag.help(format!("try with `{type_name} {{ .. }}` instead"));
                },
            );
            return;
        }
        if wilds > 0 {
            for field in pfields {
                if let PatKind::Wild = field.pat.kind {
                    wilds -= 1;
                    if wilds > 0 {
                        span_lint(
                            cx,
                            UNNEEDED_FIELD_PATTERN,
                            field.span,
                            "you matched a field with a wildcard pattern, consider using `..` instead",
                        );
                    } else {
                        #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
                        span_lint_and_then(
                            cx,
                            UNNEEDED_FIELD_PATTERN,
                            field.span,
                            "you matched a field with a wildcard pattern, consider using `..` instead",
                            |diag| {
                                diag.help(format!(
                                    "try with `{type_name} {{ {}, .. }}`",
                                    pfields
                                        .iter()
                                        .filter_map(|f| match f.pat.kind {
                                            PatKind::Wild => None,
                                            _ => f.span.get_source_text(cx),
                                        })
                                        .format(", "),
                                ));
                            },
                        );
                    }
                }
            }
        }
    }
}