Rust: Add extractor warnings query.

Author: geoffw0

rust/ql/lib/codeql/rust/Diagnostics.qll

@@ -52,3 +52,8 @@ class Diagnostic extends @diagnostic {
 class ExtractionError extends Diagnostic {
   ExtractionError() { this.getTag() = "parse_error" }
 }
+
+/** A diagnostic that is warning severity. */
+class ExtractionWarning extends Diagnostic {
+  ExtractionWarning() { this.getSeverity() = 30 }
+}

rust/ql/src/queries/diagnostics/ExtractionWarnings.ql

@@ -0,0 +1,19 @@
+/**
+ * @name Extraction warnings
+ * @description List all extraction warnings for files in the source code directory.
+ * @kind diagnostic
+ * @id rust/diagnostics/extraction-warnings
+ */
+
+import codeql.rust.Diagnostics
+import codeql.files.FileSystem
+
+/** Gets the SARIF severity to associate with a warning. */
+int getSeverity() { result = 1 }
+
+from ExtractionWarning warning, File f
+where
+  f = warning.getLocation().getFile() and
+  exists(f.getRelativePath())
+select warning, "Extraction warning in " + f + " with message " + warning.getMessage(),
+  getSeverity()