Swift: Redesign as a FreeFunctionDecl class + add some qldoc.

Author: geoffw0

swift/ql/lib/codeql/swift/elements/decl/AbstractFunctionDecl.qll

@@ -1,19 +1,21 @@
 private import codeql.swift.generated.decl.AbstractFunctionDecl
 private import codeql.swift.elements.decl.MethodDecl
 
+/**
+ * A function.
+ */
 class AbstractFunctionDecl extends Generated::AbstractFunctionDecl {
   override string toString() { result = this.getName() }
 
   /**
    * Holds if this function is called `funcName`.
    */
   predicate hasName(string funcName) { this.getName() = funcName }
+}
 
-  /**
-   * Holds if this is a global (non-member) function called `funcName`.
-   */
-  predicate hasGlobalName(string funcName) {
-    this.hasName(funcName) and
-    not this instanceof MethodDecl
-  }
+/**
+ * A free (non-member) function.
+ */
+class FreeFunctionDecl extends AbstractFunctionDecl {
+  FreeFunctionDecl() { not this instanceof MethodDecl }
 }

swift/ql/lib/codeql/swift/elements/decl/MethodDecl.qll

@@ -9,6 +9,9 @@ private Decl getAMember(IterableDeclContext ctx) {
   )
 }
 
+/**
+ * A function that is a member of a class, struct, enum or protocol.
+ */
 class MethodDecl extends AbstractFunctionDecl {
   MethodDecl() {
     this = getAMember(any(ClassDecl c))

swift/ql/src/queries/Security/CWE-089/SqlInjection.ql

@@ -29,7 +29,8 @@ class CApiSqlSink extends SqlSink {
     // `sqlite3_exec` and variants of `sqlite3_prepare`.
     exists(CallExpr call |
       call.getStaticTarget()
-          .hasGlobalName([
+          .(FreeFunctionDecl)
+          .hasName([
               "sqlite3_exec(_:_:_:_:_:)", "sqlite3_prepare(_:_:_:_:_:)",
               "sqlite3_prepare_v2(_:_:_:_:_:)", "sqlite3_prepare_v3(_:_:_:_:_:_:)",
               "sqlite3_prepare16(_:_:_:_:_:)", "sqlite3_prepare16_v2(_:_:_:_:_:)",