C++: Improve solution for UsingDeclarationEntry.

Author: geoffw0

cpp/ql/src/semmle/code/cpp/Declaration.qll

@@ -98,7 +98,12 @@ class Declaration extends Locatable, @declaration {
     this.hasQualifiedName(namespaceQualifier, "", baseName)
   }
 
-  override string toString() { result = this.getName() }
+  /**
+   * Gets a description of this `Declaration` for display purposes.
+   */
+  string getDescription() { result = this.getName() }
+
+  final override string toString() { result = this.getDescription() }
 
   /**
    * Gets the name of this declaration.

cpp/ql/src/semmle/code/cpp/Namespace.qll

@@ -153,7 +153,7 @@ class UsingDeclarationEntry extends UsingEntry {
    */
   Declaration getDeclaration() { usings(underlyingElement(this), unresolveElement(result), _) }
 
-  override string toString() { result = "using declaration" }
+  override string toString() { result = "using " + this.getDeclaration().getDescription() }
 }
 
 /**

cpp/ql/src/semmle/code/cpp/exprs/Lambda.qll

@@ -86,7 +86,7 @@ class Closure extends Class {
     result.getName() = "operator()"
   }
 
-  override string toString() { result = "decltype([...](...){...})" }
+  override string getDescription() { result = "decltype([...](...){...})" }
 }
 
 /**

cpp/ql/test/library-tests/usings/Usings1.expected

@@ -1,7 +1,7 @@
-| templates.cpp:9:5:9:14 | using declaration | UsingDeclarationEntry, enclosingElement:std |
-| usings.cpp:8:1:8:11 | using declaration | UsingDeclarationEntry, enclosingElement:(global namespace) |
+| templates.cpp:9:5:9:14 | using c | UsingDeclarationEntry, enclosingElement:std |
+| usings.cpp:8:1:8:11 | using nf | UsingDeclarationEntry, enclosingElement:(global namespace) |
 | usings.cpp:9:1:9:17 | using namespace N | UsingDirectiveEntry, enclosingElement:(global namespace) |
-| usings.cpp:18:3:18:13 | using declaration | UsingDeclarationEntry, enclosingElement:D |
-| usings.cpp:21:5:21:14 | using declaration | UsingDeclarationEntry, enclosingElement:{ ... } |
-| usings.cpp:34:3:34:20 | using declaration | UsingDeclarationEntry, enclosingElement:TD |
-| usings.cpp:42:5:42:22 | using declaration | UsingDeclarationEntry, enclosingElement:nsbar |
+| usings.cpp:18:3:18:13 | using bf | UsingDeclarationEntry, enclosingElement:D |
+| usings.cpp:21:5:21:14 | using gf | UsingDeclarationEntry, enclosingElement:{ ... } |
+| usings.cpp:34:3:34:20 | using tbf | UsingDeclarationEntry, enclosingElement:TD |
+| usings.cpp:42:5:42:22 | using foo | UsingDeclarationEntry, enclosingElement:nsbar |