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use crate::rustc_lint::LintContext;
use clippy_utils::diagnostics::span_lint_and_then;
use clippy_utils::macros::{root_macro_call, FormatArgsExpn};
use clippy_utils::source::snippet_with_applicability;
use clippy_utils::{is_else_clause, peel_blocks_with_stmt, span_extract_comment, sugg};
use rustc_errors::Applicability;
use rustc_hir::{Expr, ExprKind, UnOp};
use rustc_lint::{LateContext, LateLintPass};
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Detects `if`-then-`panic!` that can be replaced with `assert!`.
///
/// ### Why is this bad?
/// `assert!` is simpler than `if`-then-`panic!`.
///
/// ### Example
/// ```rust
/// let sad_people: Vec<&str> = vec![];
/// if !sad_people.is_empty() {
/// panic!("there are sad people: {:?}", sad_people);
/// }
/// ```
/// Use instead:
/// ```rust
/// let sad_people: Vec<&str> = vec![];
/// assert!(sad_people.is_empty(), "there are sad people: {:?}", sad_people);
/// ```
#[clippy::version = "1.57.0"]
pub MANUAL_ASSERT,
pedantic,
"`panic!` and only a `panic!` in `if`-then statement"
}
declare_lint_pass!(ManualAssert => [MANUAL_ASSERT]);
impl<'tcx> LateLintPass<'tcx> for ManualAssert {
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'tcx>) {
if_chain! {
if let ExprKind::If(cond, then, None) = expr.kind;
if !matches!(cond.kind, ExprKind::Let(_));
if !expr.span.from_expansion();
let then = peel_blocks_with_stmt(then);
if let Some(macro_call) = root_macro_call(then.span);
if cx.tcx.item_name(macro_call.def_id) == sym::panic;
if !cx.tcx.sess.source_map().is_multiline(cond.span);
if let Some(format_args) = FormatArgsExpn::find_nested(cx, then, macro_call.expn);
// Don't change `else if foo { panic!(..) }` to `else { assert!(foo, ..) }` as it just
// shuffles the condition around.
// Should this have a config value?
if !is_else_clause(cx.tcx, expr);
then {
let mut applicability = Applicability::MachineApplicable;
let format_args_snip = snippet_with_applicability(cx, format_args.inputs_span(), "..", &mut applicability);
let cond = cond.peel_drop_temps();
let mut comments = span_extract_comment(cx.sess().source_map(), expr.span);
if !comments.is_empty() {
comments += "\n";
}
let (cond, not) = match cond.kind {
ExprKind::Unary(UnOp::Not, e) => (e, ""),
_ => (cond, "!"),
};
let cond_sugg = sugg::Sugg::hir_with_applicability(cx, cond, "..", &mut applicability).maybe_par();
let sugg = format!("assert!({not}{cond_sugg}, {format_args_snip});");
// we show to the user the suggestion without the comments, but when applicating the fix, include the comments in the block
span_lint_and_then(
cx,
MANUAL_ASSERT,
expr.span,
"only a `panic!` in `if`-then statement",
|diag| {
// comments can be noisy, do not show them to the user
if !comments.is_empty() {
diag.tool_only_span_suggestion(
expr.span.shrink_to_lo(),
"add comments back",
comments,
applicability);
}
diag.span_suggestion(
expr.span,
"try instead",
sugg,
applicability);
}
);
}
}
}
}
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