src/tools/clippy/clippy_lints/src/methods/option_map_unwrap_or.rs

   1 use clippy_utils::diagnostics::span_lint_and_then;
   2 use clippy_utils::source::snippet_with_applicability;
   3 use clippy_utils::ty::is_copy;
   4 use clippy_utils::ty::is_type_diagnostic_item;
   5 use rustc_data_structures::fx::FxHashSet;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::intravisit::{walk_path, Visitor};
   8 use rustc_hir::{self, HirId, Path};
   9 use rustc_lint::LateContext;
  10 use rustc_middle::hir::nested_filter;
  11 use rustc_span::source_map::Span;
  12 use rustc_span::{sym, Symbol};
  13
  14 use super::MAP_UNWRAP_OR;
  15
  16 /// lint use of `map().unwrap_or()` for `Option`s
  17 pub(super) fn check<'tcx>(
  18     cx: &LateContext<'tcx>,
  19     expr: &rustc_hir::Expr<'_>,
  20     recv: &rustc_hir::Expr<'_>,
  21     map_arg: &'tcx rustc_hir::Expr<'_>,
  22     unwrap_recv: &rustc_hir::Expr<'_>,
  23     unwrap_arg: &'tcx rustc_hir::Expr<'_>,
  24     map_span: Span,
  25 ) {
  26     // lint if the caller of `map()` is an `Option`
  27     if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(recv), sym::Option) {
  28         if !is_copy(cx, cx.typeck_results().expr_ty(unwrap_arg)) {
  29             // Do not lint if the `map` argument uses identifiers in the `map`
  30             // argument that are also used in the `unwrap_or` argument
  31
  32             let mut unwrap_visitor = UnwrapVisitor {
  33                 cx,
  34                 identifiers: FxHashSet::default(),
  35             };
  36             unwrap_visitor.visit_expr(unwrap_arg);
  37
  38             let mut map_expr_visitor = MapExprVisitor {
  39                 cx,
  40                 identifiers: unwrap_visitor.identifiers,
  41                 found_identifier: false,
  42             };
  43             map_expr_visitor.visit_expr(map_arg);
  44
  45             if map_expr_visitor.found_identifier {
  46                 return;
  47             }
  48         }
  49
  50         if unwrap_arg.span.ctxt() != map_span.ctxt() {
  51             return;
  52         }
  53
  54         let mut applicability = Applicability::MachineApplicable;
  55         // get snippet for unwrap_or()
  56         let unwrap_snippet = snippet_with_applicability(cx, unwrap_arg.span, "..", &mut applicability);
  57         // lint message
  58         // comparing the snippet from source to raw text ("None") below is safe
  59         // because we already have checked the type.
  60         let arg = if unwrap_snippet == "None" { "None" } else { "<a>" };
  61         let unwrap_snippet_none = unwrap_snippet == "None";
  62         let suggest = if unwrap_snippet_none {
  63             "and_then(<f>)"
  64         } else {
  65             "map_or(<a>, <f>)"
  66         };
  67         let msg = &format!(
  68             "called `map(<f>).unwrap_or({})` on an `Option` value. \
  69             This can be done more directly by calling `{}` instead",
  70             arg, suggest
  71         );
  72
  73         span_lint_and_then(cx, MAP_UNWRAP_OR, expr.span, msg, |diag| {
  74             let map_arg_span = map_arg.span;
  75
  76             let mut suggestion = vec![
  77                 (
  78                     map_span,
  79                     String::from(if unwrap_snippet_none { "and_then" } else { "map_or" }),
  80                 ),
  81                 (expr.span.with_lo(unwrap_recv.span.hi()), String::new()),
  82             ];
  83
  84             if !unwrap_snippet_none {
  85                 suggestion.push((map_arg_span.with_hi(map_arg_span.lo()), format!("{}, ", unwrap_snippet)));
  86             }
  87
  88             diag.multipart_suggestion(&format!("use `{}` instead", suggest), suggestion, applicability);
  89         });
  90     }
  91 }
  92
  93 struct UnwrapVisitor<'a, 'tcx> {
  94     cx: &'a LateContext<'tcx>,
  95     identifiers: FxHashSet<Symbol>,
  96 }
  97
  98 impl<'a, 'tcx> Visitor<'tcx> for UnwrapVisitor<'a, 'tcx> {
  99     type NestedFilter = nested_filter::All;
 100
 101     fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
 102         self.identifiers.insert(ident(path));
 103         walk_path(self, path);
 104     }
 105
 106     fn nested_visit_map(&mut self) -> Self::Map {
 107         self.cx.tcx.hir()
 108     }
 109 }
 110
 111 struct MapExprVisitor<'a, 'tcx> {
 112     cx: &'a LateContext<'tcx>,
 113     identifiers: FxHashSet<Symbol>,
 114     found_identifier: bool,
 115 }
 116
 117 impl<'a, 'tcx> Visitor<'tcx> for MapExprVisitor<'a, 'tcx> {
 118     type NestedFilter = nested_filter::All;
 119
 120     fn visit_path(&mut self, path: &'tcx Path<'_>, _id: HirId) {
 121         if self.identifiers.contains(&ident(path)) {
 122             self.found_identifier = true;
 123             return;
 124         }
 125         walk_path(self, path);
 126     }
 127
 128     fn nested_visit_map(&mut self) -> Self::Map {
 129         self.cx.tcx.hir()
 130     }
 131 }
 132
 133 fn ident(path: &Path<'_>) -> Symbol {
 134     path.segments
 135         .last()
 136         .expect("segments should be composed of at least 1 element")
 137         .ident
 138         .name
 139 }