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

   1 use crate::rustc_lint::LintContext;
   2 use clippy_utils::diagnostics::span_lint_and_then;
   3 use clippy_utils::macros::root_macro_call;
   4 use clippy_utils::{is_else_clause, peel_blocks_with_stmt, span_extract_comment, 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 let ExprKind::If(cond, then, None) = expr.kind
  41             && !matches!(cond.kind, ExprKind::Let(_))
  42             && !expr.span.from_expansion()
  43             && let then = peel_blocks_with_stmt(then)
  44             && let Some(macro_call) = root_macro_call(then.span)
  45             && cx.tcx.item_name(macro_call.def_id) == sym::panic
  46             && !cx.tcx.sess.source_map().is_multiline(cond.span)
  47             && let Ok(panic_snippet) = cx.sess().source_map().span_to_snippet(macro_call.span)
  48             && let Some(panic_snippet) = panic_snippet.strip_suffix(')')
  49             && let Some((_, format_args_snip)) = panic_snippet.split_once('(')
  50             // Don't change `else if foo { panic!(..) }` to `else { assert!(foo, ..) }` as it just
  51             // shuffles the condition around.
  52             // Should this have a config value?
  53             && !is_else_clause(cx.tcx, expr)
  54         {
  55             let mut applicability = Applicability::MachineApplicable;
  56             let cond = cond.peel_drop_temps();
  57             let mut comments = span_extract_comment(cx.sess().source_map(), expr.span);
  58             if !comments.is_empty() {
  59                 comments += "\n";
  60             }
  61             let (cond, not) = match cond.kind {
  62                 ExprKind::Unary(UnOp::Not, e) => (e, ""),
  63                 _ => (cond, "!"),
  64             };
  65             let cond_sugg = sugg::Sugg::hir_with_applicability(cx, cond, "..", &mut applicability).maybe_par();
  66             let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip});");
  67             // we show to the user the suggestion without the comments, but when applying the fix, include the comments in the block
  68             span_lint_and_then(
  69                 cx,
  70                 MANUAL_ASSERT,
  71                 expr.span,
  72                 "only a `panic!` in `if`-then statement",
  73                 |diag| {
  74                     // comments can be noisy, do not show them to the user
  75                     if !comments.is_empty() {
  76                         diag.tool_only_span_suggestion(
  77                             expr.span.shrink_to_lo(),
  78                             "add comments back",
  79                             comments,
  80                             applicability
  81                         );
  82                     }
  83                     diag.span_suggestion(
  84                         expr.span,
  85                         "try instead",
  86                         sugg,
  87                         applicability
  88                     );
  89                 }
  90             );
  91         }
  92     }
  93 }