Swift: Move first, last into Collection, BidirectionalCollection.

Author: geoffw0

swift/ql/lib/codeql/swift/frameworks/StandardLibrary/Collection.qll

@@ -34,3 +34,21 @@ private class CollectionSummaries extends SummaryModelCsv {
       ]
   }
 }
+
+/**
+ * A content implying that, if a `Collection` is tainted, certain fields are also
+ * tainted.
+ */
+private class CollectionFieldsInheritTaint extends TaintInheritingContent,
+  DataFlow::Content::FieldContent {
+  CollectionFieldsInheritTaint() {
+    exists(FieldDecl f | this.getField() = f |
+      (
+        f.getEnclosingDecl().(NominalTypeDecl).getName() = ["Collection", "BidirectionalCollection"] or
+        f.getEnclosingDecl().(ExtensionDecl).getExtendedTypeDecl().getName() =
+          ["Collection", "BidirectionalCollection"]
+      ) and
+      f.getName() = ["first", "last"]
+    )
+  }
+}

swift/ql/lib/codeql/swift/frameworks/StandardLibrary/String.qll

@@ -135,7 +135,7 @@ private class StringFieldsInheritTaint extends TaintInheritingContent,
       ) and
       f.getName() =
         [
-          "first", "last", "unicodeScalars", "utf8", "utf16", "lazy", "utf8CString", "description",
+          "unicodeScalars", "utf8", "utf16", "lazy", "utf8CString", "description",
           "debugDescription", "dataValue", "identifierValue", "capitalized", "localizedCapitalized",
           "localizedLowercase", "localizedUppercase", "decomposedStringWithCanonicalMapping",
           "decomposedStringWithCompatibilityMapping", "precomposedStringWithCanonicalMapping",