C++: Add a way to test the behavior of 'asExpr' and 'toString' on dataflow nodes.

cpp/ql/test/library-tests/dataflow/asExpr/test-indirect.expected

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+testFailures
+failures

cpp/ql/test/library-tests/dataflow/asExpr/test-indirect.ql

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+import cpp
+import TestUtilities.InlineExpectationsTest
+import semmle.code.cpp.dataflow.new.DataFlow::DataFlow
+
+bindingset[s]
+string quote(string s) { if s.matches("% %") then result = "\"" + s + "\"" else result = s }
+
+string formatNumberOfNodesForIndirectExpr(Expr e) {
+  exists(int n | n = strictcount(Node node | node.asIndirectExpr() = e) |
+    n > 1 and result = ": " + n
+  )
+}
+
+module AsIndirectExprTest implements TestSig {
+  string getARelevantTag() { result = ["asIndirectExpr", "numberOfIndirectNodes"] }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(Node n, Expr e, string exprString |
+      e = n.asIndirectExpr() and
+      location = e.getLocation() and
+      element = n.toString() and
+      exprString = e.toString()
+    |
+      tag = "asIndirectExpr" and
+      (
+        // The toString on an indirect is often formatted like `***myExpr`.
+        // If the node's `toString` is of that form then we don't show it in
+        // the expected output.
+        if element.matches("%" + exprString)
+        then value = quote(exprString)
+        else value = quote(exprString + "(" + element + ")")
+      )
+      or
+      tag = "numberOfIndirectNodes" and
+      value = quote(exprString + formatNumberOfNodesForIndirectExpr(e))
+    )
+  }
+}
+
+import MakeTest<AsIndirectExprTest>

cpp/ql/test/library-tests/dataflow/asExpr/test.cpp

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+void take_const_ref_int(const int &);
+
+void test_materialize_temp_int()
+{
+  take_const_ref_int(42); // $ asExpr=42 numberOfNodes="42: 2" asIndirectExpr=42 numberOfIndirectNodes="42: 2"
+}
+
+struct A {};
+
+A get();
+void take_const_ref(const A &);
+
+void test1(){
+  take_const_ref(get()); // $ asExpr="call to get" numberOfNodes="call to get: 2" asIndirectExpr="call to get" numberOfIndirectNodes="call to get: 2"
+}
+
+void take_ref(A &);
+
+A& get_ref();
+
+void test2() {
+  take_ref(get_ref()); // $ asExpr="call to get_ref" asIndirectExpr="call to get_ref"
+}

cpp/ql/test/library-tests/dataflow/asExpr/test.expected

@@ -0,0 +1,2 @@
+testFailures
+failures

cpp/ql/test/library-tests/dataflow/asExpr/test.ql

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+import cpp
+import TestUtilities.InlineExpectationsTest
+import semmle.code.cpp.dataflow.new.DataFlow::DataFlow
+
+bindingset[s]
+string quote(string s) { if s.matches("% %") then result = "\"" + s + "\"" else result = s }
+
+string formatNumberOfNodesForExpr(Expr e) {
+  exists(int n | n = strictcount(Node node | node.asExpr() = e) | n > 1 and result = ": " + n)
+}
+
+module AsExprTest implements TestSig {
+  string getARelevantTag() { result = ["asExpr", "numberOfNodes"] }
+
+  predicate hasActualResult(Location location, string element, string tag, string value) {
+    exists(Node n, Expr e, string exprString |
+      e = n.asExpr() and
+      location = e.getLocation() and
+      element = n.toString() and
+      exprString = e.toString()
+    |
+      tag = "asExpr" and
+      (
+        // If the `toString` on the node is identical to the `toString` of the
+        // expression then we don't show it in the expected output.
+        if exprString = element
+        then value = quote(exprString)
+        else value = quote(exprString + "(" + element + ")")
+      )
+      or
+      tag = "numberOfNodes" and
+      value = quote(exprString + formatNumberOfNodesForExpr(e))
+    )
+  }
+}
+
+import MakeTest<AsExprTest>