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 clippy_utils::source::snippet_opt;
   3 use rustc_ast::ast::{Pat, PatKind};
   4 use rustc_lint::EarlyContext;
   5
   6 use super::UNNEEDED_FIELD_PATTERN;
   7
   8 pub(super) fn check(cx: &EarlyContext<'_>, pat: &Pat) {
   9     if let PatKind::Struct(_, ref npat, ref pfields, _) = pat.kind {
  10         let mut wilds = 0;
  11         let type_name = npat
  12             .segments
  13             .last()
  14             .expect("A path must have at least one segment")
  15             .ident
  16             .name;
  17
  18         for field in pfields {
  19             if let PatKind::Wild = field.pat.kind {
  20                 wilds += 1;
  21             }
  22         }
  23         if !pfields.is_empty() && wilds == pfields.len() {
  24             span_lint_and_help(
  25                 cx,
  26                 UNNEEDED_FIELD_PATTERN,
  27                 pat.span,
  28                 "all the struct fields are matched to a wildcard pattern, consider using `..`",
  29                 None,
  30                 &format!("try with `{type_name} {{ .. }}` instead"),
  31             );
  32             return;
  33         }
  34         if wilds > 0 {
  35             for field in pfields {
  36                 if let PatKind::Wild = field.pat.kind {
  37                     wilds -= 1;
  38                     if wilds > 0 {
  39                         span_lint(
  40                             cx,
  41                             UNNEEDED_FIELD_PATTERN,
  42                             field.span,
  43                             "you matched a field with a wildcard pattern, consider using `..` instead",
  44                         );
  45                     } else {
  46                         let mut normal = vec![];
  47
  48                         for field in pfields {
  49                             match field.pat.kind {
  50                                 PatKind::Wild => {},
  51                                 _ => {
  52                                     if let Some(n) = snippet_opt(cx, field.span) {
  53                                         normal.push(n);
  54                                     }
  55                                 },
  56                             }
  57                         }
  58
  59                         span_lint_and_help(
  60                             cx,
  61                             UNNEEDED_FIELD_PATTERN,
  62                             field.span,
  63                             "you matched a field with a wildcard pattern, consider using `..` \
  64                              instead",
  65                             None,
  66                             &format!("try with `{type_name} {{ {}, .. }}`", normal[..].join(", ")),
  67                         );
  68                     }
  69                 }
  70             }
  71         }
  72     }
  73 }