clippy_lints/src/methods/or_fun_call.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::eager_or_lazy::is_lazyness_candidate;
   3 use clippy_utils::source::{snippet, snippet_with_applicability, snippet_with_macro_callsite};
   4 use clippy_utils::ty::{implements_trait, is_type_diagnostic_item, match_type};
   5 use clippy_utils::{contains_return, get_trait_def_id, last_path_segment, paths};
   6 use if_chain::if_chain;
   7 use rustc_errors::Applicability;
   8 use rustc_hir as hir;
   9 use rustc_hir::{BlockCheckMode, UnsafeSource};
  10 use rustc_lint::LateContext;
  11 use rustc_middle::ty;
  12 use rustc_span::source_map::Span;
  13 use rustc_span::symbol::sym;
  14 use std::borrow::Cow;
  15
  16 use super::OR_FUN_CALL;
  17
  18 /// Checks for the `OR_FUN_CALL` lint.
  19 #[allow(clippy::too_many_lines)]
  20 pub(super) fn check<'tcx>(
  21     cx: &LateContext<'tcx>,
  22     expr: &hir::Expr<'_>,
  23     method_span: Span,
  24     name: &str,
  25     args: &'tcx [hir::Expr<'_>],
  26 ) {
  27     /// Checks for `unwrap_or(T::new())` or `unwrap_or(T::default())`.
  28     fn check_unwrap_or_default(
  29         cx: &LateContext<'_>,
  30         name: &str,
  31         fun: &hir::Expr<'_>,
  32         self_expr: &hir::Expr<'_>,
  33         arg: &hir::Expr<'_>,
  34         or_has_args: bool,
  35         span: Span,
  36     ) -> bool {
  37         if_chain! {
  38             if !or_has_args;
  39             if name == "unwrap_or";
  40             if let hir::ExprKind::Path(ref qpath) = fun.kind;
  41             let path = &*last_path_segment(qpath).ident.as_str();
  42             if ["default", "new"].contains(&path);
  43             let arg_ty = cx.typeck_results().expr_ty(arg);
  44             if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
  45             if implements_trait(cx, arg_ty, default_trait_id, &[]);
  46
  47             then {
  48                 let mut applicability = Applicability::MachineApplicable;
  49                 span_lint_and_sugg(
  50                     cx,
  51                     OR_FUN_CALL,
  52                     span,
  53                     &format!("use of `{}` followed by a call to `{}`", name, path),
  54                     "try this",
  55                     format!(
  56                         "{}.unwrap_or_default()",
  57                         snippet_with_applicability(cx, self_expr.span, "..", &mut applicability)
  58                     ),
  59                     applicability,
  60                 );
  61
  62                 true
  63             } else {
  64                 false
  65             }
  66         }
  67     }
  68
  69     /// Checks for `*or(foo())`.
  70     #[allow(clippy::too_many_arguments)]
  71     fn check_general_case<'tcx>(
  72         cx: &LateContext<'tcx>,
  73         name: &str,
  74         method_span: Span,
  75         self_expr: &hir::Expr<'_>,
  76         arg: &'tcx hir::Expr<'_>,
  77         span: Span,
  78         // None if lambda is required
  79         fun_span: Option<Span>,
  80     ) {
  81         // (path, fn_has_argument, methods, suffix)
  82         static KNOW_TYPES: [(&[&str], bool, &[&str], &str); 4] = [
  83             (&paths::BTREEMAP_ENTRY, false, &["or_insert"], "with"),
  84             (&paths::HASHMAP_ENTRY, false, &["or_insert"], "with"),
  85             (&paths::OPTION, false, &["map_or", "ok_or", "or", "unwrap_or"], "else"),
  86             (&paths::RESULT, true, &["or", "unwrap_or"], "else"),
  87         ];
  88
  89         if let hir::ExprKind::MethodCall(ref path, _, ref args, _) = &arg.kind {
  90             if path.ident.as_str() == "len" {
  91                 let ty = cx.typeck_results().expr_ty(&args[0]).peel_refs();
  92
  93                 match ty.kind() {
  94                     ty::Slice(_) | ty::Array(_, _) | ty::Str => return,
  95                     _ => (),
  96                 }
  97
  98                 if is_type_diagnostic_item(cx, ty, sym::vec_type) {
  99                     return;
 100                 }
 101             }
 102         }
 103
 104         if_chain! {
 105             if KNOW_TYPES.iter().any(|k| k.2.contains(&name));
 106
 107             if is_lazyness_candidate(cx, arg);
 108             if !contains_return(&arg);
 109
 110             let self_ty = cx.typeck_results().expr_ty(self_expr);
 111
 112             if let Some(&(_, fn_has_arguments, poss, suffix)) =
 113                 KNOW_TYPES.iter().find(|&&i| match_type(cx, self_ty, i.0));
 114
 115             if poss.contains(&name);
 116
 117             then {
 118                 let macro_expanded_snipped;
 119                 let sugg: Cow<'_, str> = {
 120                     let (snippet_span, use_lambda) = match (fn_has_arguments, fun_span) {
 121                         (false, Some(fun_span)) => (fun_span, false),
 122                         _ => (arg.span, true),
 123                     };
 124                     let snippet = {
 125                         let not_macro_argument_snippet = snippet_with_macro_callsite(cx, snippet_span, "..");
 126                         if not_macro_argument_snippet == "vec![]" {
 127                             macro_expanded_snipped = snippet(cx, snippet_span, "..");
 128                             match macro_expanded_snipped.strip_prefix("$crate::vec::") {
 129                                 Some(stripped) => Cow::from(stripped),
 130                                 None => macro_expanded_snipped
 131                             }
 132                         }
 133                         else {
 134                             not_macro_argument_snippet
 135                         }
 136                     };
 137
 138                     if use_lambda {
 139                         let l_arg = if fn_has_arguments { "_" } else { "" };
 140                         format!("|{}| {}", l_arg, snippet).into()
 141                     } else {
 142                         snippet
 143                     }
 144                 };
 145                 let span_replace_word = method_span.with_hi(span.hi());
 146                 span_lint_and_sugg(
 147                     cx,
 148                     OR_FUN_CALL,
 149                     span_replace_word,
 150                     &format!("use of `{}` followed by a function call", name),
 151                     "try this",
 152                     format!("{}_{}({})", name, suffix, sugg),
 153                     Applicability::HasPlaceholders,
 154                 );
 155             }
 156         }
 157     }
 158     if args.len() == 2 {
 159         match args[1].kind {
 160             hir::ExprKind::Call(ref fun, ref or_args) => {
 161                 let or_has_args = !or_args.is_empty();
 162                 if !check_unwrap_or_default(cx, name, fun, &args[0], &args[1], or_has_args, expr.span) {
 163                     let fun_span = if or_has_args { None } else { Some(fun.span) };
 164                     check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, fun_span);
 165                 }
 166             },
 167             hir::ExprKind::Index(..) | hir::ExprKind::MethodCall(..) => {
 168                 check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, None);
 169             },
 170             hir::ExprKind::Block(block, _) => {
 171                 if let BlockCheckMode::UnsafeBlock(UnsafeSource::UserProvided) = block.rules {
 172                     if let Some(block_expr) = block.expr {
 173                         if let hir::ExprKind::MethodCall(..) = block_expr.kind {
 174                             check_general_case(cx, name, method_span, &args[0], &args[1], expr.span, None);
 175                         }
 176                     }
 177                 }
 178             },
 179             _ => (),
 180         }
 181     }
 182 }