implement constant power-of-two check

Cargo.toml

@@ -17,6 +17,7 @@ const_panic = "0.2"
 
 [dev-dependencies]
 criterion = "0.1.2"
+compiletest_rs = "0.9.0"
 
 [features]
 default = ["alloc"]

src/with_const_generics.rs

@@ -72,10 +72,14 @@ impl<T: PartialEq, const CAP: usize> PartialEq for ConstGenericRingBuffer<T, CAP
 impl<T: PartialEq, const CAP: usize> Eq for ConstGenericRingBuffer<T, CAP> {}
 
 impl<T, const CAP: usize> ConstGenericRingBuffer<T, CAP> {
+    const ERROR_CAPACITY_IS_NOT_ALLOWED_TO_BE_ZERO: () =
+        assert!(CAP != 0, "Capacity is not allowed to be zero");
+
     /// Creates a const generic ringbuffer, size is passed as a const generic.
     #[inline]
     pub const fn new() -> Self {
-        assert!(CAP != 0, "Capacity is not allowed to be zero");
+        #[allow(clippy::let_unit_value)]
+        let _ = Self::ERROR_CAPACITY_IS_NOT_ALLOWED_TO_BE_ZERO;
 
         // allow here since we are constructing an array of MaybeUninit<T>
         // which explicitly *is* defined behavior
@@ -232,12 +236,6 @@ impl<T, const CAP: usize> IndexMut<isize> for ConstGenericRingBuffer<T, CAP> {
 mod tests {
     use super::*;
 
-    #[test]
-    #[should_panic]
-    fn test_no_empty() {
-        let _ = ConstGenericRingBuffer::<u32, 0>::new();
-    }
-
     #[test]
     fn test_not_power_of_two() {
         let mut rb = ConstGenericRingBuffer::<usize, 10>::new();

tests/compile-fail/test_const_generic_array_zero_length.rs

@@ -0,0 +1,9 @@
+extern crate ringbuffer;
+
+use ringbuffer::ConstGenericRingBuffer;
+
+fn main() {
+    let _ = ConstGenericRingBuffer::<i32, 0>::new();
+    //~^ note: the above error was encountered while instantiating `fn ringbuffer::ConstGenericRingBuffer::<i32, 0>::new`
+    // ringbuffer can't be zero length
+}

tests/compiletests.rs

@@ -0,0 +1,19 @@
+extern crate compiletest_rs as compiletest;
+
+use std::path::PathBuf;
+
+fn run_mode(mode: &'static str) {
+    let mut config = compiletest::Config::default();
+
+    config.mode = mode.parse().expect("Invalid mode");
+    config.src_base = PathBuf::from(format!("tests/{}", mode));
+    config.link_deps(); // Populate config.target_rustcflags with dependencies on the path
+    config.clean_rmeta(); // If your tests import the parent crate, this helps with E0464
+
+    compiletest::run_tests(&config);
+}
+
+#[test]
+fn compile_test() {
+    run_mode("compile-fail");
+}