From 206b1a1ac9df38ca5278a6db9954f9c62bd34b17 Mon Sep 17 00:00:00 2001 From: Quinn Sinclair Date: Wed, 17 Apr 2024 13:25:39 +0300 Subject: [PATCH] Threadlocal_initializer_can_be_made_const will not trigger for unreachable initializers This commit introduces a check to ensure that the lint won't trigger when the initializer is unreachable, such as: ``` thread_local! { static STATE: Cell = panic!(); } ``` This is achieved by looking at the unpeeled initializer expression and ensuring that the parent macro is not `panic!()`, `todo!()`, `unreachable!()`, `unimplemented!()`. fixes #12637 changelog: [`threadlocal_initializer_can_be_made_const`] will no longer trigger on `unreachable` macros. --- ...ead_local_initializer_can_be_made_const.rs | 36 ++++++++++++++++--- ..._local_initializer_can_be_made_const.fixed | 33 ++++++++++++++++- ...ead_local_initializer_can_be_made_const.rs | 33 ++++++++++++++++- 3 files changed, 95 insertions(+), 7 deletions(-) diff --git a/clippy_lints/src/thread_local_initializer_can_be_made_const.rs b/clippy_lints/src/thread_local_initializer_can_be_made_const.rs index c1e24674e..4af3ee74d 100644 --- a/clippy_lints/src/thread_local_initializer_can_be_made_const.rs +++ b/clippy_lints/src/thread_local_initializer_can_be_made_const.rs @@ -1,13 +1,14 @@ use clippy_config::msrvs::{self, Msrv}; use clippy_utils::diagnostics::span_lint_and_sugg; +use clippy_utils::macros::macro_backtrace; use clippy_utils::qualify_min_const_fn::is_min_const_fn; use clippy_utils::source::snippet; use clippy_utils::{fn_has_unsatisfiable_preds, peel_blocks}; use rustc_errors::Applicability; -use rustc_hir::{intravisit, ExprKind}; +use rustc_hir::{intravisit, Expr, ExprKind}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::impl_lint_pass; -use rustc_span::sym::thread_local_macro; +use rustc_span::sym::{self, thread_local_macro}; declare_clippy_lint! { /// ### What it does @@ -69,6 +70,26 @@ fn is_thread_local_initializer( ) } +fn is_unreachable(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool { + if let Some(macro_call) = macro_backtrace(expr.span).next() + && let Some(diag_name) = cx.tcx.get_diagnostic_name(macro_call.def_id) + { + return (matches!( + diag_name, + sym::core_panic_macro + | sym::std_panic_macro + | sym::core_panic_2015_macro + | sym::std_panic_2015_macro + | sym::core_panic_2021_macro + ) && !cx.tcx.hir().is_inside_const_context(expr.hir_id)) + || matches!( + diag_name, + sym::unimplemented_macro | sym::todo_macro | sym::unreachable_macro | sym::unreachable_2015_macro + ); + } + false +} + #[inline] fn initializer_can_be_made_const(cx: &LateContext<'_>, defid: rustc_span::def_id::DefId, msrv: &Msrv) -> bool { // Building MIR for `fn`s with unsatisfiable preds results in ICE. @@ -102,12 +123,17 @@ impl<'tcx> LateLintPass<'tcx> for ThreadLocalInitializerCanBeMadeConst { // for details on this issue, see: // https://github.com/rust-lang/rust-clippy/pull/12276 && !cx.tcx.is_const_fn(defid) - && initializer_can_be_made_const(cx, defid, &self.msrv) - // we know that the function is const-qualifiable, so now - // we need only to get the initializer expression to span-lint it. && let ExprKind::Block(block, _) = body.value.kind && let Some(unpeeled) = block.expr && let ret_expr = peel_blocks(unpeeled) + // A common pattern around threadlocal! is to make the value unreachable + // to force an initialization before usage + // https://github.com/rust-lang/rust-clippy/issues/12637 + // we ensure that this is reachable before we check in mir + && !is_unreachable(cx, ret_expr) + && initializer_can_be_made_const(cx, defid, &self.msrv) + // we know that the function is const-qualifiable, so now + // we need only to get the initializer expression to span-lint it. && let initializer_snippet = snippet(cx, ret_expr.span, "thread_local! { ... }") && initializer_snippet != "thread_local! { ... }" { diff --git a/tests/ui/thread_local_initializer_can_be_made_const.fixed b/tests/ui/thread_local_initializer_can_be_made_const.fixed index a6ed59d49..4c9bd0bd8 100644 --- a/tests/ui/thread_local_initializer_can_be_made_const.fixed +++ b/tests/ui/thread_local_initializer_can_be_made_const.fixed @@ -1,6 +1,6 @@ #![warn(clippy::thread_local_initializer_can_be_made_const)] -use std::cell::RefCell; +use std::cell::{Cell, RefCell}; fn main() { // lint and suggest const @@ -36,6 +36,37 @@ fn main() { } } +fn issue_12637() { + /// The set methods on LocalKey> and LocalKey> are + /// guaranteed to bypass the thread_local's initialization expression. + /// See rust-lang/rust#92122. Thus, = panic!() is a useful idiom for + /// forcing the use of set on each thread before it accesses the thread local in any other + /// manner. + thread_local! { + static STATE_12637_PANIC: Cell = panic!(); + } + STATE_12637_PANIC.set(9); + println!("{}", STATE_12637_PANIC.get()); + + thread_local! { + static STATE_12637_TODO: Cell = todo!(); + } + STATE_12637_TODO.set(9); + println!("{}", STATE_12637_TODO.get()); + + thread_local! { + static STATE_12637_UNIMPLEMENTED: Cell = unimplemented!(); + } + STATE_12637_UNIMPLEMENTED.set(9); + println!("{}", STATE_12637_UNIMPLEMENTED.get()); + + thread_local! { + static STATE_12637_UNREACHABLE: Cell = unreachable!(); + } + STATE_12637_UNREACHABLE.set(9); + println!("{}", STATE_12637_UNREACHABLE.get()); +} + #[clippy::msrv = "1.58"] fn f() { thread_local! { diff --git a/tests/ui/thread_local_initializer_can_be_made_const.rs b/tests/ui/thread_local_initializer_can_be_made_const.rs index 3f0159c58..eb336f0dd 100644 --- a/tests/ui/thread_local_initializer_can_be_made_const.rs +++ b/tests/ui/thread_local_initializer_can_be_made_const.rs @@ -1,6 +1,6 @@ #![warn(clippy::thread_local_initializer_can_be_made_const)] -use std::cell::RefCell; +use std::cell::{Cell, RefCell}; fn main() { // lint and suggest const @@ -36,6 +36,37 @@ fn main() { } } +fn issue_12637() { + /// The set methods on LocalKey> and LocalKey> are + /// guaranteed to bypass the thread_local's initialization expression. + /// See rust-lang/rust#92122. Thus, = panic!() is a useful idiom for + /// forcing the use of set on each thread before it accesses the thread local in any other + /// manner. + thread_local! { + static STATE_12637_PANIC: Cell = panic!(); + } + STATE_12637_PANIC.set(9); + println!("{}", STATE_12637_PANIC.get()); + + thread_local! { + static STATE_12637_TODO: Cell = todo!(); + } + STATE_12637_TODO.set(9); + println!("{}", STATE_12637_TODO.get()); + + thread_local! { + static STATE_12637_UNIMPLEMENTED: Cell = unimplemented!(); + } + STATE_12637_UNIMPLEMENTED.set(9); + println!("{}", STATE_12637_UNIMPLEMENTED.get()); + + thread_local! { + static STATE_12637_UNREACHABLE: Cell = unreachable!(); + } + STATE_12637_UNREACHABLE.set(9); + println!("{}", STATE_12637_UNREACHABLE.get()); +} + #[clippy::msrv = "1.58"] fn f() { thread_local! {