mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-12-23 03:23:33 +00:00
145 lines
5.3 KiB
Rust
145 lines
5.3 KiB
Rust
use crate::consts::{constant, Constant};
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use clippy_utils::diagnostics::span_lint_and_help;
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use clippy_utils::source::snippet_opt;
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use clippy_utils::{is_direct_expn_of, is_expn_of, match_panic_call};
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use if_chain::if_chain;
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use rustc_hir::{Expr, ExprKind, UnOp};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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declare_clippy_lint! {
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/// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
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///
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/// **Why is this bad?** Will be optimized out by the compiler or should probably be replaced by a
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/// `panic!()` or `unreachable!()`
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///
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/// **Known problems:** None
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///
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/// **Example:**
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/// ```rust,ignore
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/// assert!(false)
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/// assert!(true)
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/// const B: bool = false;
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/// assert!(B)
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/// ```
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pub ASSERTIONS_ON_CONSTANTS,
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style,
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"`assert!(true)` / `assert!(false)` will be optimized out by the compiler, and should probably be replaced by a `panic!()` or `unreachable!()`"
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}
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declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
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impl<'tcx> LateLintPass<'tcx> for AssertionsOnConstants {
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fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
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let lint_true = |is_debug: bool| {
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span_lint_and_help(
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cx,
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ASSERTIONS_ON_CONSTANTS,
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e.span,
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if is_debug {
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"`debug_assert!(true)` will be optimized out by the compiler"
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} else {
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"`assert!(true)` will be optimized out by the compiler"
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},
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None,
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"remove it",
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);
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};
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let lint_false_without_message = || {
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span_lint_and_help(
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cx,
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ASSERTIONS_ON_CONSTANTS,
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e.span,
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"`assert!(false)` should probably be replaced",
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None,
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"use `panic!()` or `unreachable!()`",
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);
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};
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let lint_false_with_message = |panic_message: String| {
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span_lint_and_help(
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cx,
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ASSERTIONS_ON_CONSTANTS,
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e.span,
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&format!("`assert!(false, {})` should probably be replaced", panic_message),
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None,
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&format!("use `panic!({})` or `unreachable!({})`", panic_message, panic_message),
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)
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};
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if let Some(debug_assert_span) = is_expn_of(e.span, "debug_assert") {
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if debug_assert_span.from_expansion() {
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return;
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}
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if_chain! {
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if let ExprKind::Unary(_, lit) = e.kind;
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if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), lit);
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if is_true;
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then {
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lint_true(true);
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}
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};
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} else if let Some(assert_span) = is_direct_expn_of(e.span, "assert") {
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if assert_span.from_expansion() {
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return;
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}
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if let Some(assert_match) = match_assert_with_message(cx, e) {
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match assert_match {
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// matched assert but not message
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AssertKind::WithoutMessage(false) => lint_false_without_message(),
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AssertKind::WithoutMessage(true) | AssertKind::WithMessage(_, true) => lint_true(false),
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AssertKind::WithMessage(panic_message, false) => lint_false_with_message(panic_message),
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};
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}
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}
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}
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}
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/// Result of calling `match_assert_with_message`.
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enum AssertKind {
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WithMessage(String, bool),
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WithoutMessage(bool),
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}
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/// Check if the expression matches
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///
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/// ```rust,ignore
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/// if !c {
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/// {
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/// ::std::rt::begin_panic(message, _)
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/// }
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/// }
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/// ```
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///
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/// where `message` is any expression and `c` is a constant bool.
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fn match_assert_with_message<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<AssertKind> {
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if_chain! {
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if let ExprKind::If(cond, then, _) = expr.kind;
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if let ExprKind::Unary(UnOp::Not, expr) = cond.kind;
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// bind the first argument of the `assert!` macro
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if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.typeck_results(), expr);
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// block
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if let ExprKind::Block(block, _) = then.kind;
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if block.stmts.is_empty();
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if let Some(block_expr) = &block.expr;
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// inner block is optional. unwrap it if it exists, or use the expression as is otherwise.
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if let Some(begin_panic_call) = match block_expr.kind {
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ExprKind::Block(inner_block, _) => &inner_block.expr,
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_ => &block.expr,
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};
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// function call
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if let Some(arg) = match_panic_call(cx, begin_panic_call);
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// bind the second argument of the `assert!` macro if it exists
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if let panic_message = snippet_opt(cx, arg.span);
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// second argument of begin_panic is irrelevant
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// as is the second match arm
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then {
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// an empty message occurs when it was generated by the macro
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// (and not passed by the user)
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return panic_message
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.filter(|msg| !msg.is_empty())
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.map(|msg| AssertKind::WithMessage(msg, is_true))
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.or(Some(AssertKind::WithoutMessage(is_true)));
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}
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}
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None
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}
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