From fff586c13d642da57fed8bb60e7ed88ac1a3cb9f Mon Sep 17 00:00:00 2001
From: Terts Diepraam <terts.diepraam@gmail.com>
Date: Thu, 8 Jun 2023 19:12:13 +0200
Subject: [PATCH] Add a size parameter for ConstGenericRingBuffer::new

---
 src/with_const_generics.rs                        |  5 ++++-
 .../test_const_generic_array_zero_length.rs       |  4 ++--
 .../test_const_generic_array_zero_length_new.rs   | 10 ++++++++++
 tests/conversions.rs                              | 15 +++++++++++++++
 4 files changed, 31 insertions(+), 3 deletions(-)
 create mode 100644 tests/compile-fail/test_const_generic_array_zero_length_new.rs

diff --git a/src/with_const_generics.rs b/src/with_const_generics.rs
index 56e6cf8..557a770 100644
--- a/src/with_const_generics.rs
+++ b/src/with_const_generics.rs
@@ -174,7 +174,10 @@ impl<T, const CAP: usize> ConstGenericRingBuffer<T, CAP> {
     /// of two might be significantly (up to 3 times) slower.
     #[inline]
     #[must_use]
-    pub const fn new() -> Self {
+    pub const fn new<const N: usize>() -> Self
+    where
+        ConstGenericRingBuffer<T, CAP>: From<ConstGenericRingBuffer<T, N>>,
+    {
         #[allow(clippy::let_unit_value)]
         let _ = Self::ERROR_CAPACITY_IS_NOT_ALLOWED_TO_BE_ZERO;
 
diff --git a/tests/compile-fail/test_const_generic_array_zero_length.rs b/tests/compile-fail/test_const_generic_array_zero_length.rs
index b9caa56..3b69f1a 100644
--- a/tests/compile-fail/test_const_generic_array_zero_length.rs
+++ b/tests/compile-fail/test_const_generic_array_zero_length.rs
@@ -4,6 +4,6 @@ use ringbuffer::ConstGenericRingBuffer;
 
 fn main() {
     let _ = ConstGenericRingBuffer::<i32, 0>::new();
-    //~^ note: the above error was encountered while instantiating `fn ringbuffer::ConstGenericRingBuffer::<i32, 0>::new`
+    //~^ note: the above error was encountered while instantiating `fn ringbuffer::ConstGenericRingBuffer::<i32, 0>::new::<0>`
     // ringbuffer can't be zero length
-}
\ No newline at end of file
+}
diff --git a/tests/compile-fail/test_const_generic_array_zero_length_new.rs b/tests/compile-fail/test_const_generic_array_zero_length_new.rs
new file mode 100644
index 0000000..24a3494
--- /dev/null
+++ b/tests/compile-fail/test_const_generic_array_zero_length_new.rs
@@ -0,0 +1,10 @@
+extern crate ringbuffer;
+
+use ringbuffer::{ConstGenericRingBuffer, RingBufferWrite};
+
+fn main() {
+    let mut buf = ConstGenericRingBuffer::new::<0>();
+    //~^ note: the above error was encountered while instantiating `fn ringbuffer::ConstGenericRingBuffer::<i32, 0>::new::<0>`
+    // ringbuffer can't be zero length
+    buf.push(5);
+}
diff --git a/tests/conversions.rs b/tests/conversions.rs
index 8140f40..969427e 100644
--- a/tests/conversions.rs
+++ b/tests/conversions.rs
@@ -118,3 +118,18 @@ fn test_extra_conversions_const() {
     let a = ConstGenericRingBuffer::<_, 2>::from(a);
     assert_eq!(a.to_vec(), vec![1, 2]);
 }
+
+#[test]
+fn test_const_generic_new_parameter() {
+    // Can we specify size only on the method?
+    let mut a = ConstGenericRingBuffer::new::<2>();
+    a.push(5);
+
+    // Can we specify size in both positions?
+    let mut a = ConstGenericRingBuffer::<i32, 50>::new::<50>();
+    a.push(5);
+
+    // Can we specify size only on the struct?
+    let mut a = ConstGenericRingBuffer::<i32, 50>::new();
+    a.push(5);
+}