Rust: Add a missing model for std::io.

Author: geoffw0

rust/ql/lib/codeql/rust/frameworks/stdlib/io.model.yml

@@ -36,3 +36,4 @@ extensions:
       - ["lang:std", "crate::io::Read::chain", "Argument[0]", "ReturnValue", "taint", "manual"]
       - ["lang:std", "crate::io::Read::take", "Argument[self]", "ReturnValue", "taint", "manual"]
       - ["lang:std", "<crate::io::stdio::Stdin>::lock", "Argument[self]", "ReturnValue", "taint", "manual"]
+      - ["lang:std", "<crate::io::Split as crate::iter::traits::iterator::Iterator>::next", "Argument[self]", "ReturnValue.Field[crate::option::Option::Some(0)].Field[crate::result::Result::Ok(0)]", "taint", "manual"]

rust/ql/test/library-tests/dataflow/sources/test.rs

@@ -270,7 +270,7 @@ fn test_io_stdin() -> std::io::Result<()> {
 
     {
         let mut reader_split = std::io::BufReader::new(std::io::stdin()).split(b','); // $ Alert[rust/summary/taint-sources]
-        sink(reader_split.next().unwrap().unwrap()); // $ MISSING: hasTaintFlow
+        sink(reader_split.next().unwrap().unwrap()); // $ hasTaintFlow
         while let Some(chunk) = reader_split.next() {
             sink(chunk.unwrap()); // $ MISSING: hasTaintFlow
         }