Merge commit 'dc5423ad448877e33cca28db2f1445c9c4473c75' into clippyup

1 files changed, 56 insertions, 0 deletions

diff --git a/clippy_lints/src/loops/missing_spin_loop.rs b/clippy_lints/src/loops/missing_spin_loop.rs
new file mode 100644
index 00000000000..0696afa3922
--- /dev/null
+++ b/clippy_lints/src/loops/missing_spin_loop.rs
@@ -0,0 +1,56 @@
+use super::MISSING_SPIN_LOOP;
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_no_std_crate;
+use rustc_errors::Applicability;
+use rustc_hir::{Block, Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::ty;
+use rustc_span::sym;
+
+fn unpack_cond<'tcx>(cond: &'tcx Expr<'tcx>) -> &'tcx Expr<'tcx> {
+    match &cond.kind {
+        ExprKind::Block(
+            Block {
+                stmts: [],
+                expr: Some(e),
+                ..
+            },
+            _,
+        )
+        | ExprKind::Unary(_, e) => unpack_cond(e),
+        ExprKind::Binary(_, l, r) => {
+            let l = unpack_cond(l);
+            if let ExprKind::MethodCall(..) = l.kind {
+                l
+            } else {
+                unpack_cond(r)
+            }
+        },
+        _ => cond,
+    }
+}
+
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, cond: &'tcx Expr<'_>, body: &'tcx Expr<'_>) {
+    if_chain! {
+        if let ExprKind::Block(Block { stmts: [], expr: None, ..}, _) = body.kind;
+        if let ExprKind::MethodCall(method, [callee, ..], _) = unpack_cond(cond).kind;
+        if [sym::load, sym::compare_exchange, sym::compare_exchange_weak].contains(&method.ident.name);
+        if let ty::Adt(def, _substs) = cx.typeck_results().expr_ty(callee).kind();
+        if cx.tcx.is_diagnostic_item(sym::AtomicBool, def.did());
+        then {
+            span_lint_and_sugg(
+                cx,
+                MISSING_SPIN_LOOP,
+                body.span,
+                "busy-waiting loop should at least have a spin loop hint",
+                "try this",
+                (if is_no_std_crate(cx) {
+                    "{ core::hint::spin_loop() }"
+                } else {
+                    "{ std::hint::spin_loop() }"
+                }).into(),
+                Applicability::MachineApplicable
+            );
+        }
+    }
+}