src/tools/clippy/clippy_lints/src/assertions_on_result_states.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::macros::{find_assert_args, root_macro_call_first_node, PanicExpn};
   3 use clippy_utils::source::snippet_with_context;
   4 use clippy_utils::ty::{has_debug_impl, is_copy, is_type_diagnostic_item};
   5 use clippy_utils::usage::local_used_after_expr;
   6 use clippy_utils::{is_expr_final_block_expr, path_res};
   7 use rustc_errors::Applicability;
   8 use rustc_hir::def::Res;
   9 use rustc_hir::{Expr, ExprKind};
  10 use rustc_lint::{LateContext, LateLintPass};
  11 use rustc_middle::ty::{self, Ty};
  12 use rustc_session::{declare_lint_pass, declare_tool_lint};
  13 use rustc_span::sym;
  14
  15 declare_clippy_lint! {
  16     /// ### What it does
  17     /// Checks for `assert!(r.is_ok())` or `assert!(r.is_err())` calls.
  18     ///
  19     /// ### Why is this bad?
  20     /// An assertion failure cannot output an useful message of the error.
  21     ///
  22     /// ### Known problems
  23     /// The suggested replacement decreases the readability of code and log output.
  24     ///
  25     /// ### Example
  26     /// ```rust,ignore
  27     /// # let r = Ok::<_, ()>(());
  28     /// assert!(r.is_ok());
  29     /// # let r = Err::<_, ()>(());
  30     /// assert!(r.is_err());
  31     /// ```
  32     #[clippy::version = "1.64.0"]
  33     pub ASSERTIONS_ON_RESULT_STATES,
  34     restriction,
  35     "`assert!(r.is_ok())`/`assert!(r.is_err())` gives worse error message than directly calling `r.unwrap()`/`r.unwrap_err()`"
  36 }
  37
  38 declare_lint_pass!(AssertionsOnResultStates => [ASSERTIONS_ON_RESULT_STATES]);
  39
  40 impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
  41     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  42         if let Some(macro_call) = root_macro_call_first_node(cx, e)
  43             && matches!(cx.tcx.get_diagnostic_name(macro_call.def_id), Some(sym::assert_macro))
  44             && let Some((condition, panic_expn)) = find_assert_args(cx, e, macro_call.expn)
  45             && matches!(panic_expn, PanicExpn::Empty)
  46             && let ExprKind::MethodCall(method_segment, recv, [], _) = condition.kind
  47             && let result_type_with_refs = cx.typeck_results().expr_ty(recv)
  48             && let result_type = result_type_with_refs.peel_refs()
  49             && is_type_diagnostic_item(cx, result_type, sym::Result)
  50             && let ty::Adt(_, substs) = result_type.kind()
  51         {
  52             if !is_copy(cx, result_type) {
  53                 if result_type_with_refs != result_type {
  54                     return;
  55                 } else if let Res::Local(binding_id) = path_res(cx, recv)
  56                     && local_used_after_expr(cx, binding_id, recv)
  57                 {
  58                     return;
  59                 }
  60             }
  61             let semicolon = if is_expr_final_block_expr(cx.tcx, e) {";"} else {""};
  62             let mut app = Applicability::MachineApplicable;
  63             match method_segment.ident.as_str() {
  64                 "is_ok" if type_suitable_to_unwrap(cx, substs.type_at(1)) => {
  65                     span_lint_and_sugg(
  66                         cx,
  67                         ASSERTIONS_ON_RESULT_STATES,
  68                         macro_call.span,
  69                         "called `assert!` with `Result::is_ok`",
  70                         "replace with",
  71                         format!(
  72                             "{}.unwrap(){}",
  73                             snippet_with_context(cx, recv.span, condition.span.ctxt(), "..", &mut app).0,
  74                             semicolon
  75                         ),
  76                         app,
  77                     );
  78                 }
  79                 "is_err" if type_suitable_to_unwrap(cx, substs.type_at(0)) => {
  80                     span_lint_and_sugg(
  81                         cx,
  82                         ASSERTIONS_ON_RESULT_STATES,
  83                         macro_call.span,
  84                         "called `assert!` with `Result::is_err`",
  85                         "replace with",
  86                         format!(
  87                             "{}.unwrap_err(){}",
  88                             snippet_with_context(cx, recv.span, condition.span.ctxt(), "..", &mut app).0,
  89                             semicolon
  90                         ),
  91                         app,
  92                     );
  93                 }
  94                 _ => (),
  95             };
  96         }
  97     }
  98 }
  99
 100 fn type_suitable_to_unwrap<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
 101     has_debug_impl(cx, ty) && !ty.is_unit() && !ty.is_never()
 102 }