1 use crate::consts::{constant, Constant};
2 use crate::utils::{is_direct_expn_of, is_expn_of, match_panic_call, snippet_opt, span_lint_and_help};
3 use if_chain::if_chain;
4 use rustc_hir::{Expr, ExprKind, UnOp};
5 use rustc_lint::{LateContext, LateLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
9 /// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
11 /// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
12 /// `panic!()` or `unreachable!()`
14 /// **Known problems:** None
20 /// const B: bool = false;
23 pub ASSERTIONS_ON_CONSTANTS,
25 "`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
28 declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
30 impl<'tcx> LateLintPass<'tcx> for AssertionsOnConstants {
31 fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
32 let lint_true = |is_debug: bool| {
35 ASSERTIONS_ON_CONSTANTS,
38 "`debug_assert!(true)` will be optimized out by the compiler"
40 "`assert!(true)` will be optimized out by the compiler"
46 let lint_false_without_message = || {
49 ASSERTIONS_ON_CONSTANTS,
51 "`assert!(false)` should probably be replaced",
53 "use `panic!()` or `unreachable!()`",
56 let lint_false_with_message = |panic_message: String| {
59 ASSERTIONS_ON_CONSTANTS,
61 &format!("`assert!(false, {})` should probably be replaced", panic_message),
63 &format!("use `panic!({})` or `unreachable!({})`", panic_message, panic_message),
67 if let Some(debug_assert_span) = is_expn_of(e.span, "debug_assert") {
68 if debug_assert_span.from_expansion() {
72 if let ExprKind::Unary(_, ref lit) = e.kind;
73 if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), lit);
79 } else if let Some(assert_span) = is_direct_expn_of(e.span, "assert") {
80 if assert_span.from_expansion() {
83 if let Some(assert_match) = match_assert_with_message(&cx, e) {
85 // matched assert but not message
86 AssertKind::WithoutMessage(false) => lint_false_without_message(),
87 AssertKind::WithoutMessage(true) | AssertKind::WithMessage(_, true) => lint_true(false),
88 AssertKind::WithMessage(panic_message, false) => lint_false_with_message(panic_message),
95 /// Result of calling `match_assert_with_message`.
97 WithMessage(String, bool),
101 /// Check if the expression matches
106 /// ::std::rt::begin_panic(message, _)
111 /// where `message` is any expression and `c` is a constant bool.
112 fn match_assert_with_message<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<AssertKind> {
114 if let ExprKind::If(ref cond, ref then, _) = expr.kind;
115 if let ExprKind::Unary(UnOp::Not, ref expr) = cond.kind;
116 // bind the first argument of the `assert!` macro
117 if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), expr);
119 if let ExprKind::Block(ref block, _) = then.kind;
120 if block.stmts.is_empty();
121 if let Some(block_expr) = &block.expr;
122 // inner block is optional. unwrap it if it exists, or use the expression as is otherwise.
123 if let Some(begin_panic_call) = match block_expr.kind {
124 ExprKind::Block(ref inner_block, _) => &inner_block.expr,
128 if let Some(args) = match_panic_call(cx, begin_panic_call);
130 // bind the second argument of the `assert!` macro if it exists
131 if let panic_message = snippet_opt(cx, args[0].span);
132 // second argument of begin_panic is irrelevant
133 // as is the second match arm
135 // an empty message occurs when it was generated by the macro
136 // (and not passed by the user)
138 .filter(|msg| !msg.is_empty())
139 .map(|msg| AssertKind::WithMessage(msg, is_true))
140 .or(Some(AssertKind::WithoutMessage(is_true)));