vec![v; n] and clippy warnings

src/impls.rs

@@ -1,9 +1,17 @@
 //! Implements `Debug`, and `PartialEq` for various list-like types.
 
+#[allow(clippy::wildcard_imports)]
 use super::*;
 
 use std::fmt::Debug;
 
+impl<T: ?Sized> Default for Vec<T> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+
 impl<T: ?Sized + Debug> Debug for Vec<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_list().entries(self.iter()).finish()

src/iter.rs

@@ -1,5 +1,6 @@
 //! Iteration.
 
+#[allow(clippy::wildcard_imports)]
 use super::*;
 
 struct BaseIter<T: ?Sized> {
@@ -93,6 +94,7 @@ impl<'a, T: ?Sized> IntoIterator for &'a mut Vec<T> {
 }
 
 /// A by-mut iterator over the elements of a [`Vec`].
+#[allow(clippy::module_name_repetitions)]
 pub struct IterMut<'a, T: ?Sized> {
     base: BaseIter<T>,
     _phantom: PhantomData<&'a mut T>
@@ -132,6 +134,7 @@ impl<T: ?Sized> IntoIterator for Vec<T> {
 }
 
 /// A by-value iterator over the elements of a [`Vec`].
+#[allow(clippy::module_name_repetitions)]
 pub struct IntoIter<T: ?Sized> {
     ptr: NonNull<u8>,
     capacity: usize,
@@ -205,7 +208,7 @@ impl<T> FromIterator<T> for Vec<T> {
     fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
         let mut vec = Vec::new();
 
-        for item in iter.into_iter() {
+        for item in iter {
             vec.push(item);
         }
 

src/lib.rs

@@ -95,6 +95,8 @@
 #![feature(coerce_unsized)]
 
 #![warn(missing_docs)]
+#![warn(clippy::pedantic)]
+#![allow(clippy::must_use_candidate)]
 
 #[cfg(test)]
 mod test;
@@ -171,16 +173,31 @@ impl<T: ?Sized> Vec<T> {
         }
     }
 
-    /// Creates a new vector with the given capacity, measured in bytes.
-    pub fn with_capacity_bytes(cap: usize) -> Self {
-        let ptr = NonNull::new(unsafe { alloc(Layout::from_size_align(cap, 8).unwrap().pad_to_align()) }).unwrap();
-        Self {
-            ptr,
-            len: 0,
-            capacity: cap,
-            end_ptr: ptr,
-            _phantom: PhantomData
+    /// Creates a new vector that holds `len` copies of `v`.
+    /// 
+    /// Only avaliable when `T: Sized`.
+    pub fn from_elem(v: T, len: usize) -> Self where T: Sized + Clone {
+        let mut vec = Self::with_capacity(len);
+
+        for _ in 0..len {
+            vec.push(v.clone());
         }
+
+        vec
+    }
+
+    /// Creates a new vector that can hold the given amount of `T`s.
+    /// 
+    /// Only avaliable when `T: Sized`.
+    pub fn with_capacity(cap: usize) -> Self where T: Sized {
+        Self::with_capacity_for::<T>(cap)
+    }
+
+    /// Creates a new vector with the given capacity, measured in bytes.\
+    pub fn with_capacity_bytes(cap: usize) -> Self {
+        let mut vec = Self::new();
+        unsafe { vec.realloc(cap); }
+        vec
     }
 
     /// Creates a new vector with enough capacity to hold the given amount of `U`s.
@@ -287,7 +304,7 @@ impl<T: ?Sized> Vec<T> {
 
                 let size = size_of_val(v);
                 ptr = align_up_mut(ptr, align_of_val(v));
-                memcpy(v as *const _ as _, ptr, size);
+                memcpy((v as *const T).cast(), ptr, size);
                 let meta = self.get_ptr(i).to_raw_parts().1;
                 self.set_extra_from_ptr(i, ptr::from_raw_parts(ptr.cast(), meta));
                 ptr = ptr.wrapping_add(size);
@@ -344,6 +361,8 @@ impl<T: ?Sized> Vec<T> {
 
     /// Gets a reference to the element at the specified index.
     /// 
+    /// # Safety
+    /// 
     /// Immediate UB if the index is out-of-bounds.
     pub unsafe fn get_unchecked(&self, index: usize) -> &T {
         &*self.get_ptr(index)
@@ -362,6 +381,8 @@ impl<T: ?Sized> Vec<T> {
 
     /// Gets a mutable reference to the element at the specified index.
     /// 
+    /// # Safety
+    /// 
     /// Immediate UB if the index is out-of-bounds.
     pub unsafe fn get_unchecked_mut(&mut self, index: usize) -> &mut T {
         &mut *(self.get_ptr(index) as *mut _)
@@ -372,6 +393,11 @@ impl<T: ?Sized> Vec<T> {
         self.len
     }
 
+    /// Returns `true` if the vector holds no elements.
+    pub fn is_empty(&self) -> bool {
+        self.len == 0
+    }
+
     /// Returns the capacity, which is the size of the allocation in bytes.
     pub fn capacity(&self) -> usize {
         self.capacity
@@ -448,13 +474,16 @@ impl<T> Vec<[T]> {
     /// 
     /// Only avaliable for `Vec<[T]>`.
     pub fn as_slice_flatten(&self) -> &[T] {
-        assert!(self.len > 0);
+        if self.len == 0 {
+            return unsafe { slice::from_raw_parts(NonNull::dangling().as_ptr(), 0) }
+        }
 
         // SAFETY: the slices should be contiguous by the logic of `push_raw_unchecked`
         unsafe {
-            slice::from_raw_parts(self.get_ptr(0).to_raw_parts().0 as _, {
+            slice::from_raw_parts(self.get_ptr(0).to_raw_parts().0.cast(), {
                 let start = self.get_ptr(0).to_raw_parts().0 as usize;
                 let end = self.end_ptr.as_ptr() as usize;
+                debug_assert_eq!((end - start) % size_of::<T>(), 0);
                 (end - start) / size_of::<T>() // integer division!
             })
         }
@@ -464,13 +493,16 @@ impl<T> Vec<[T]> {
     /// 
     /// Only avaliable for `Vec<[T]>`.
     pub fn as_mut_slice_flatten(&mut self) -> &mut [T] {
-        assert!(self.len > 0);
+        if self.len == 0 {
+            return unsafe { slice::from_raw_parts_mut(NonNull::dangling().as_ptr(), 0) }
+        }
 
         // SAFETY: the slices should be contiguous by the logic of `push_raw_unchecked`
         unsafe {
             slice::from_raw_parts_mut(self.get_ptr(0).to_raw_parts().0 as _, {
                 let start = self.get_ptr(0).to_raw_parts().0 as usize;
                 let end = self.end_ptr.as_ptr() as usize;
+                debug_assert_eq!((end - start) % size_of::<T>(), 0);
                 (end - start) / size_of::<T>() // integer division!
             })
         }
@@ -507,15 +539,6 @@ impl Vec<dyn Any> {
     }
 }
 
-impl<T> Vec<T> {
-    /// Creates a new vector that can hold the given amount of `T`s.
-    /// 
-    /// Only avaliable when `T: Sized`.
-    pub fn with_capacity(cap: usize) -> Self {
-        Self::with_capacity_for::<T>(cap)
-    }
-}
-
 impl<T: ?Sized> Drop for Vec<T> {
     fn drop(&mut self) {
         unsafe {
@@ -582,7 +605,7 @@ macro_rules! vec {
         vec
     }};
     ($elem:expr; $n:expr) => {
-        compile_error!("dyn_vec::vec![T; N] is currently not supported");
+        $crate::Vec::from_elem($elem, $n)
     };
     ($($elem:expr),+ $(,)?) => {{
         let mut vec = $crate::Vec::new();

src/test.rs

@@ -50,6 +50,9 @@ fn all_macro() {
     ];
     let vec3: Vec<dyn Debug> = vec![unsized: 1, String::from("foo"), true];
     assert_eq!(vec2.debug(), vec3.debug());
+
+    let vec4: Vec<i32> = vec![3; 5];
+    assert_eq!(vec4, [3; 5]);
 }
 
 #[test]
@@ -177,4 +180,11 @@ fn with_capacity() {
     vec.push(4);
 
     assert_eq!(prev_ptr, vec.as_ptr());
+
+    vec.push(5);
+    vec.push(6);
+    vec.push(7);
+    // should have realloc'ed by now
+
+    assert_ne!(prev_ptr, vec.as_ptr());
 }