+.. note::
+
+ Prefer to use ``SmallVectorImpl<T>`` as a parameter type.
+
+ In APIs that don't care about the "small size" (most?), prefer to use
+ the ``SmallVectorImpl<T>`` class, which is basically just the "vector
+ header" (and methods) without the elements allocated after it. Note that
+ ``SmallVector<T, N>`` inherits from ``SmallVectorImpl<T>`` so the
+ conversion is implicit and costs nothing. E.g.
+
+ .. code-block:: c++
+
+ // BAD: Clients cannot pass e.g. SmallVector<Foo, 4>.
+ hardcodedSmallSize(SmallVector<Foo, 2> &Out);
+ // GOOD: Clients can pass any SmallVector<Foo, N>.
+ allowsAnySmallSize(SmallVectorImpl<Foo> &Out);
+
+ void someFunc() {
+ SmallVector<Foo, 8> Vec;
+ hardcodedSmallSize(Vec); // Error.
+ allowsAnySmallSize(Vec); // Works.
+ }
+
+ Even though it has "``Impl``" in the name, this is so widely used that
+ it really isn't "private to the implementation" anymore. A name like
+ ``SmallVectorHeader`` would be more appropriate.
+