src/tools/clippy/clippy_lints/src/misc_early/unneeded_field_pattern.rs

   1 use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
   2 use rustc_ast::ast::{Pat, PatKind};
   3 use rustc_lint::{EarlyContext, LintContext};
   4
   5 use super::UNNEEDED_FIELD_PATTERN;
   6
   7 pub(super) fn check(cx: &EarlyContext<'_>, pat: &Pat) {
   8     if let PatKind::Struct(_, ref npat, ref pfields, _) = pat.kind {
   9         let mut wilds = 0;
  10         let type_name = npat
  11             .segments
  12             .last()
  13             .expect("A path must have at least one segment")
  14             .ident
  15             .name;
  16
  17         for field in pfields {
  18             if let PatKind::Wild = field.pat.kind {
  19                 wilds += 1;
  20             }
  21         }
  22         if !pfields.is_empty() && wilds == pfields.len() {
  23             span_lint_and_help(
  24                 cx,
  25                 UNNEEDED_FIELD_PATTERN,
  26                 pat.span,
  27                 "all the struct fields are matched to a wildcard pattern, consider using `..`",
  28                 None,
  29                 &format!("try with `{} {{ .. }}` instead", type_name),
  30             );
  31             return;
  32         }
  33         if wilds > 0 {
  34             for field in pfields {
  35                 if let PatKind::Wild = field.pat.kind {
  36                     wilds -= 1;
  37                     if wilds > 0 {
  38                         span_lint(
  39                             cx,
  40                             UNNEEDED_FIELD_PATTERN,
  41                             field.span,
  42                             "you matched a field with a wildcard pattern, consider using `..` instead",
  43                         );
  44                     } else {
  45                         let mut normal = vec![];
  46
  47                         for field in pfields {
  48                             match field.pat.kind {
  49                                 PatKind::Wild => {},
  50                                 _ => {
  51                                     if let Ok(n) = cx.sess().source_map().span_to_snippet(field.span) {
  52                                         normal.push(n);
  53                                     }
  54                                 },
  55                             }
  56                         }
  57
  58                         span_lint_and_help(
  59                             cx,
  60                             UNNEEDED_FIELD_PATTERN,
  61                             field.span,
  62                             "you matched a field with a wildcard pattern, consider using `..` \
  63                              instead",
  64                             None,
  65                             &format!("try with `{} {{ {}, .. }}`", type_name, normal[..].join(", ")),
  66                         );
  67                     }
  68                 }
  69             }
  70         }
  71     }
  72 }