Replace debug assertions with assertion macrothe and express constraint in the documentation properly

Author: jon-zu

src/array_string.rs

@@ -91,7 +91,7 @@ impl<const CAP: usize> ArrayString<CAP>
     /// i.e. that `len <= CAP` and that the first `len` bytes of `xs` form a valid UTF-8 string.
     pub const unsafe fn from_raw_parts(xs: [MaybeUninit<u8>; CAP], len: usize) -> Self {
         assert_capacity_limit_const!(CAP);
-        debug_assert!(len <= CAP);
+        assert_capacity_len_const!(CAP, len);
         ArrayString { xs, len: len as _ }
     }
 

src/arrayvec.rs

@@ -105,10 +105,10 @@ impl<T, const CAP: usize> ArrayVec<T, CAP> {
     ///
     /// # Safety
     /// The caller must ensure that the first `len` elements of `xs` are
-    /// properly initialized.
+    /// properly initialized and that len is less than or equal to `CAP`.
     pub const unsafe fn from_raw_parts(xs: [MaybeUninit<T>; CAP], len: usize) -> Self {
         assert_capacity_limit_const!(CAP);
-        debug_assert!(len <= CAP);
+        assert_capacity_len_const!(CAP, len);
         ArrayVec { xs, len: len as LenUint }
     }
 

src/const_helper.rs

@@ -2,8 +2,6 @@ use core::mem::MaybeUninit;
 
 use crate::ArrayString;
 
-
-
 /// Creates a const ArrayString from a str slice.
 pub const fn str<const CAP: usize>(s: &str) -> ArrayString<CAP> {
     assert_capacity_limit_const!(CAP);

src/lib.rs

@@ -57,6 +57,14 @@ macro_rules! assert_capacity_limit_const {
     }
 }
 
+macro_rules! assert_capacity_len_const {
+    ($cap:expr, $len:expr) => {
+        if $len > $cap {
+            [/*ArrayVec/ArrayString: len over capacity*/][$len]
+        }
+    };
+}
+
 mod arrayvec_impl;
 mod arrayvec;
 mod array_string;