Add a not to the turbofish section about impl Trait
@@ -81,6 +81,9 @@ arguments, then const arguments, then equality constraints.
Const arguments must be surrounded by braces unless they are a
[literal] or a single segment path.
+The synthetic type parameters corresponding to `impl Trait` types are implicit,
+and these cannot be explicitly specified.
+
## Qualified paths
> **<sup>Syntax</sup>**\
