Rust: Add trait mode for char::from_u32 and a couple of similar methods.

Author: geoffw0

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

@@ -29,6 +29,9 @@ extensions:
       - ["<_ as core::convert::TryInto>::try_into", "Argument[self].Reference.Element", "ReturnValue.Field[core::result::Result::Ok(0)].Element", "taint", "manual"]
       - ["<_ as core::convert::AsMut>::as_mut", "Argument[self]", "ReturnValue", "value", "manual"]
       - ["<_ as core::convert::AsRef>::as_ref", "Argument[self]", "ReturnValue", "value", "manual"]
+      - ["core::char::from_digit", "Argument[0]", "ReturnValue.Field[core::option::Option::Some(0)]", "taint", "manual"]
+      - ["core::char::from_u32", "Argument[0]", "ReturnValue.Field[core::option::Option::Some(0)]", "taint", "manual"]
+      - ["core::char::from_u32_unchecked", "Argument[0]", "ReturnValue", "taint", "manual"]
       # Iterator
       - ["<core::result::Result>::iter", "Argument[self].Element", "ReturnValue.Element", "value", "manual"]
       - ["<_ as value_trait::array::Array>::iter", "Argument[self].Element", "ReturnValue.Element", "value", "manual"]

rust/ql/test/library-tests/dataflow/local/main.rs

@@ -576,7 +576,7 @@ fn conversions() {
     sink(i64::from(b)); // $ hasTaintFlow=51
 
     let c: char = std::char::from_u32(source(52) as u32).unwrap();
-    sink(c as i64); // $ MISSING: hasTaintFlow=52
+    sink(c as i64); // $ hasTaintFlow=52
 }
 
 fn clone() {