src/tools/clippy/clippy_lints/src/manual_assert.rs

   1 use clippy_utils::diagnostics::span_lint_and_sugg;
   2 use clippy_utils::macros::{root_macro_call, FormatArgsExpn};
   3 use clippy_utils::source::snippet_with_applicability;
   4 use clippy_utils::{peel_blocks_with_stmt, sugg};
   5 use rustc_errors::Applicability;
   6 use rustc_hir::{Expr, ExprKind, UnOp};
   7 use rustc_lint::{LateContext, LateLintPass};
   8 use rustc_session::{declare_lint_pass, declare_tool_lint};
   9 use rustc_span::sym;
  10
  11 declare_clippy_lint! {
  12     /// ### What it does
  13     /// Detects `if`-then-`panic!` that can be replaced with `assert!`.
  14     ///
  15     /// ### Why is this bad?
  16     /// `assert!` is simpler than `if`-then-`panic!`.
  17     ///
  18     /// ### Example
  19     /// ```rust
  20     /// let sad_people: Vec<&str> = vec![];
  21     /// if !sad_people.is_empty() {
  22     ///     panic!("there are sad people: {:?}", sad_people);
  23     /// }
  24     /// ```
  25     /// Use instead:
  26     /// ```rust
  27     /// let sad_people: Vec<&str> = vec![];
  28     /// assert!(sad_people.is_empty(), "there are sad people: {:?}", sad_people);
  29     /// ```
  30     #[clippy::version = "1.57.0"]
  31     pub MANUAL_ASSERT,
  32     pedantic,
  33     "`panic!` and only a `panic!` in `if`-then statement"
  34 }
  35
  36 declare_lint_pass!(ManualAssert => [MANUAL_ASSERT]);
  37
  38 impl<'tcx> LateLintPass<'tcx> for ManualAssert {
  39     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
  40         if_chain! {
  41             if let ExprKind::If(cond, then, None) = expr.kind;
  42             if !matches!(cond.kind, ExprKind::Let(_));
  43             if !expr.span.from_expansion();
  44             let then = peel_blocks_with_stmt(then);
  45             if let Some(macro_call) = root_macro_call(then.span);
  46             if cx.tcx.item_name(macro_call.def_id) == sym::panic;
  47             if !cx.tcx.sess.source_map().is_multiline(cond.span);
  48             if let Some(format_args) = FormatArgsExpn::find_nested(cx, then, macro_call.expn);
  49             then {
  50                 let mut applicability = Applicability::MachineApplicable;
  51                 let format_args_snip = snippet_with_applicability(cx, format_args.inputs_span(), "..", &mut applicability);
  52                 let cond = cond.peel_drop_temps();
  53                 let (cond, not) = match cond.kind {
  54                     ExprKind::Unary(UnOp::Not, e) => (e, ""),
  55                     _ => (cond, "!"),
  56                 };
  57                 let cond_sugg = sugg::Sugg::hir_with_applicability(cx, cond, "..", &mut applicability).maybe_par();
  58                 let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip});");
  59                 span_lint_and_sugg(
  60                     cx,
  61                     MANUAL_ASSERT,
  62                     expr.span,
  63                     "only a `panic!` in `if`-then statement",
  64                     "try",
  65                     sugg,
  66                     Applicability::MachineApplicable,
  67                 );
  68             }
  69         }
  70     }
  71 }