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

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::eager_or_lazy::switch_to_lazy_eval;
   3 use clippy_utils::source::{snippet, snippet_with_macro_callsite};
   4 use clippy_utils::ty::{implements_trait, match_type};
   5 use clippy_utils::{contains_return, is_trait_item, last_path_segment, paths};
   6 use if_chain::if_chain;
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_lint::LateContext;
  10 use rustc_span::source_map::Span;
  11 use rustc_span::symbol::{kw, sym};
  12 use std::borrow::Cow;
  13
  14 use super::OR_FUN_CALL;
  15
  16 /// Checks for the `OR_FUN_CALL` lint.
  17 #[allow(clippy::too_many_lines)]
  18 pub(super) fn check<'tcx>(
  19     cx: &LateContext<'tcx>,
  20     expr: &hir::Expr<'_>,
  21     method_span: Span,
  22     name: &str,
  23     receiver: &'tcx hir::Expr<'_>,
  24     args: &'tcx [hir::Expr<'_>],
  25 ) {
  26     /// Checks for `unwrap_or(T::new())`, `unwrap_or(T::default())`,
  27     /// `or_insert(T::new())` or `or_insert(T::default())`.
  28     #[allow(clippy::too_many_arguments)]
  29     fn check_unwrap_or_default(
  30         cx: &LateContext<'_>,
  31         name: &str,
  32         fun: &hir::Expr<'_>,
  33         arg: &hir::Expr<'_>,
  34         or_has_args: bool,
  35         span: Span,
  36         method_span: Span,
  37     ) -> bool {
  38         let is_default_default = || is_trait_item(cx, fun, sym::Default);
  39
  40         let implements_default = |arg, default_trait_id| {
  41             let arg_ty = cx.typeck_results().expr_ty(arg);
  42             implements_trait(cx, arg_ty, default_trait_id, &[])
  43         };
  44
  45         if_chain! {
  46             if !or_has_args;
  47             if let Some(sugg) = match name {
  48                 "unwrap_or" => Some("unwrap_or_default"),
  49                 "or_insert" => Some("or_default"),
  50                 _ => None,
  51             };
  52             if let hir::ExprKind::Path(ref qpath) = fun.kind;
  53             if let Some(default_trait_id) = cx.tcx.get_diagnostic_item(sym::Default);
  54             let path = last_path_segment(qpath).ident.name;
  55             // needs to target Default::default in particular or be *::new and have a Default impl
  56             // available
  57             if (matches!(path, kw::Default) && is_default_default())
  58                 || (matches!(path, sym::new) && implements_default(arg, default_trait_id));
  59
  60             then {
  61                 span_lint_and_sugg(
  62                     cx,
  63                     OR_FUN_CALL,
  64                     method_span.with_hi(span.hi()),
  65                     &format!("use of `{name}` followed by a call to `{path}`"),
  66                     "try this",
  67                     format!("{sugg}()"),
  68                     Applicability::MachineApplicable,
  69                 );
  70
  71                 true
  72             } else {
  73                 false
  74             }
  75         }
  76     }
  77
  78     /// Checks for `*or(foo())`.
  79     #[allow(clippy::too_many_arguments)]
  80     fn check_general_case<'tcx>(
  81         cx: &LateContext<'tcx>,
  82         name: &str,
  83         method_span: Span,
  84         self_expr: &hir::Expr<'_>,
  85         arg: &'tcx hir::Expr<'_>,
  86         span: Span,
  87         // None if lambda is required
  88         fun_span: Option<Span>,
  89     ) {
  90         // (path, fn_has_argument, methods, suffix)
  91         const KNOW_TYPES: [(&[&str], bool, &[&str], &str); 4] = [
  92             (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
  93             (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
  94             (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
  95             (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
  96         ];
  97
  98         if_chain! {
  99             if KNOW_TYPES.iter().any(|k| k.2.contains(&name));
 100
 101             if switch_to_lazy_eval(cx, arg);
 102             if !contains_return(arg);
 103
 104             let self_ty = cx.typeck_results().expr_ty(self_expr);
 105
 106             if let Some(&(_, fn_has_arguments, poss, suffix)) =
 107                 KNOW_TYPES.iter().find(|&&i| match_type(cx, self_ty, i.0));
 108
 109             if poss.contains(&name);
 110
 111             then {
 112                 let macro_expanded_snipped;
 113                 let sugg: Cow<'_, str> = {
 114                     let (snippet_span, use_lambda) = match (fn_has_arguments, fun_span) {
 115                         (false, Some(fun_span)) => (fun_span, false),
 116                         _ => (arg.span, true),
 117                     };
 118                     let snippet = {
 119                         let not_macro_argument_snippet = snippet_with_macro_callsite(cx, snippet_span, "..");
 120                         if not_macro_argument_snippet == "vec![]" {
 121                             macro_expanded_snipped = snippet(cx, snippet_span, "..");
 122                             match macro_expanded_snipped.strip_prefix("$crate::vec::") {
 123                                 Some(stripped) => Cow::from(stripped),
 124                                 None => macro_expanded_snipped
 125                             }
 126                         }
 127                         else {
 128                             not_macro_argument_snippet
 129                         }
 130                     };
 131
 132                     if use_lambda {
 133                         let l_arg = if fn_has_arguments { "_" } else { "" };
 134                         format!("|{l_arg}| {snippet}").into()
 135                     } else {
 136                         snippet
 137                     }
 138                 };
 139                 let span_replace_word = method_span.with_hi(span.hi());
 140                 span_lint_and_sugg(
 141                     cx,
 142                     OR_FUN_CALL,
 143                     span_replace_word,
 144                     &format!("use of `{name}` followed by a function call"),
 145                     "try this",
 146                     format!("{name}_{suffix}({sugg})"),
 147                     Applicability::HasPlaceholders,
 148                 );
 149             }
 150         }
 151     }
 152
 153     if let [arg] = args {
 154         let inner_arg = if let hir::ExprKind::Block(
 155             hir::Block {
 156                 stmts: [],
 157                 expr: Some(expr),
 158                 ..
 159             },
 160             _,
 161         ) = arg.kind
 162         {
 163             expr
 164         } else {
 165             arg
 166         };
 167         match inner_arg.kind {
 168             hir::ExprKind::Call(fun, or_args) => {
 169                 let or_has_args = !or_args.is_empty();
 170                 if !check_unwrap_or_default(cx, name, fun, arg, or_has_args, expr.span, method_span) {
 171                     let fun_span = if or_has_args { None } else { Some(fun.span) };
 172                     check_general_case(cx, name, method_span, receiver, arg, expr.span, fun_span);
 173                 }
 174             },
 175             hir::ExprKind::Index(..) | hir::ExprKind::MethodCall(..) => {
 176                 check_general_case(cx, name, method_span, receiver, arg, expr.span, None);
 177             },
 178             _ => (),
 179         }
 180     }
 181 }