add description

Author: tamaroning

clippy_lints/src/read_zero_byte_vec.rs

@@ -4,21 +4,33 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
     /// ### What it does
+    /// This lint catches reads into a zero-length `Vec`.
+    /// Especially in the case of a call to `with_capacity`, this lint warns that read
+    /// gets the number of bytes from the `Vec`'s length, not its capacity.
     ///
     /// ### Why is this bad?
+    /// Reading zero bytes is almost certainly not the intended behavior.
+    ///
+    /// ### Known problems
+    /// In theory, a very unusual read implementation could assign some semantic meaning
+    /// to zero-byte reads. But it seems exceptionally unlikely that code intending to do
+    /// a zero-byte read would allocate a `Vec` for it.
     ///
     /// ### Example
     /// ```rust
-    /// // example code where clippy issues a warning
+    /// let mut data = Vec::with_capacity(len);
+    /// r.read_exact(&mut data)?;
     /// ```
     /// Use instead:
     /// ```rust
-    /// // example code which does not raise clippy warning
+    /// let mut data = Vec::with_capacity(len);
+    /// data.resize(len, 0);
+    /// r.read_exact(&mut data)?;
     /// ```
     #[clippy::version = "1.63.0"]
     pub READ_ZERO_BYTE_VEC,
     correctness,
-    "default lint description"
+    "checks for reads into a zero-length `Vec`"
 }
 declare_lint_pass!(ReadZeroByteVec => [READ_ZERO_BYTE_VEC]);