1 use clippy_utils::consts::{constant, Constant};
2 use clippy_utils::diagnostics::span_lint_and_help;
3 use clippy_utils::source::snippet_opt;
4 use clippy_utils::{is_direct_expn_of, is_expn_of, match_panic_call};
5 use if_chain::if_chain;
6 use rustc_hir::{Expr, ExprKind, UnOp};
7 use rustc_lint::{LateContext, LateLintPass};
8 use rustc_session::{declare_lint_pass, declare_tool_lint};
10 declare_clippy_lint! {
11 /// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
13 /// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
14 /// `panic!()` or `unreachable!()`
16 /// **Known problems:** None
22 /// const B: bool = false;
25 pub ASSERTIONS_ON_CONSTANTS,
27 "`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
30 declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
32 impl<'tcx> LateLintPass<'tcx> for AssertionsOnConstants {
33 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
34 let lint_true = |is_debug: bool| {
37 ASSERTIONS_ON_CONSTANTS,
40 "`debug_assert!(true)` will be optimized out by the compiler"
42 "`assert!(true)` will be optimized out by the compiler"
48 let lint_false_without_message = || {
51 ASSERTIONS_ON_CONSTANTS,
53 "`assert!(false)` should probably be replaced",
55 "use `panic!()` or `unreachable!()`",
58 let lint_false_with_message = |panic_message: String| {
61 ASSERTIONS_ON_CONSTANTS,
63 &format!("`assert!(false, {})` should probably be replaced", panic_message),
65 &format!("use `panic!({})` or `unreachable!({})`", panic_message, panic_message),
69 if let Some(debug_assert_span) = is_expn_of(e.span, "debug_assert") {
70 if debug_assert_span.from_expansion() {
74 if let ExprKind::Unary(_, lit) = e.kind;
75 if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), lit);
81 } else if let Some(assert_span) = is_direct_expn_of(e.span, "assert") {
82 if assert_span.from_expansion() {
85 if let Some(assert_match) = match_assert_with_message(cx, e) {
87 // matched assert but not message
88 AssertKind::WithoutMessage(false) => lint_false_without_message(),
89 AssertKind::WithoutMessage(true) | AssertKind::WithMessage(_, true) => lint_true(false),
90 AssertKind::WithMessage(panic_message, false) => lint_false_with_message(panic_message),
97 /// Result of calling `match_assert_with_message`.
99 WithMessage(String, bool),
100 WithoutMessage(bool),
103 /// Check if the expression matches
108 /// ::std::rt::begin_panic(message, _)
113 /// where `message` is any expression and `c` is a constant bool.
114 fn match_assert_with_message<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<AssertKind> {
116 if let ExprKind::If(cond, then, _) = expr.kind;
117 if let ExprKind::Unary(UnOp::Not, expr) = cond.kind;
118 // bind the first argument of the `assert!` macro
119 if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), expr);
121 if let ExprKind::Block(block, _) = then.kind;
122 if block.stmts.is_empty();
123 if let Some(block_expr) = &block.expr;
124 // inner block is optional. unwrap it if it exists, or use the expression as is otherwise.
125 if let Some(begin_panic_call) = match block_expr.kind {
126 ExprKind::Block(inner_block, _) => &inner_block.expr,
130 if let Some(arg) = match_panic_call(cx, begin_panic_call);
131 // bind the second argument of the `assert!` macro if it exists
132 if let panic_message = snippet_opt(cx, arg.span);
133 // second argument of begin_panic is irrelevant
134 // as is the second match arm
136 // an empty message occurs when it was generated by the macro
137 // (and not passed by the user)
139 .filter(|msg| !msg.is_empty())
140 .map(|msg| AssertKind::WithMessage(msg, is_true))
141 .or(Some(AssertKind::WithoutMessage(is_true)));