Swift: Add AutoClosureExpr.getExpr.

Author: geoffw0

swift/ql/lib/codeql/swift/dataflow/internal/DataFlowPrivate.qll

@@ -162,7 +162,7 @@ private module Cached {
       nodeFrom.asExpr() = nco.getAnOperand()
       or
       // unpack closure (the second argument is typically an `AutoClosureExpr` argument)
-      nodeFrom.asExpr() = nco.getAnOperand().(AutoClosureExpr).getReturn().getResult()
+      nodeFrom.asExpr() = nco.getAnOperand().(AutoClosureExpr).getExpr()
     )
     or
     // flow through ternary operator `? :`

swift/ql/lib/codeql/swift/elements/expr/AutoClosureExpr.qll

@@ -1,9 +1,15 @@
 private import codeql.swift.generated.expr.AutoClosureExpr
 private import codeql.swift.elements.stmt.ReturnStmt
+private import codeql.swift.elements.expr.Expr
 
 class AutoClosureExpr extends Generated::AutoClosureExpr {
   /** Gets the implicit return statement generated by this autoclosure expression. */
   ReturnStmt getReturn() { result = unique( | | this.getBody().getAnElement()) }
 
+  /**
+   * Gets the expression returned by this autoclosure expression.
+   */
+  Expr getExpr() { result = this.getReturn().getResult() }
+
   override string toString() { result = this.getBody().toString() }
 }