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+### What it does
+Checks for empty `loop` expressions.
+
+### Why is this bad?
+These busy loops burn CPU cycles without doing
+anything. It is _almost always_ a better idea to `panic!` than to have
+a busy loop.
+
+If panicking isn't possible, think of the environment and either:
+  - block on something
+  - sleep the thread for some microseconds
+  - yield or pause the thread
+
+For `std` targets, this can be done with
+[`std::thread::sleep`](https://doc.rust-lang.org/std/thread/fn.sleep.html)
+or [`std::thread::yield_now`](https://doc.rust-lang.org/std/thread/fn.yield_now.html).
+
+For `no_std` targets, doing this is more complicated, especially because
+`#[panic_handler]`s can't panic. To stop/pause the thread, you will
+probably need to invoke some target-specific intrinsic. Examples include:
+  - [`x86_64::instructions::hlt`](https://docs.rs/x86_64/0.12.2/x86_64/instructions/fn.hlt.html)
+  - [`cortex_m::asm::wfi`](https://docs.rs/cortex-m/0.6.3/cortex_m/asm/fn.wfi.html)
+
+### Example
+```
+loop {}
+```
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