Work around GCC 5.4 bug in Wshadow (RobotLocomotion#8339)

The problem is that variables within a generic lambda are misinterpreted
as shadowing the varablies in the code that calls the lambda.  The GCC
bug report is https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67273.

We can revert this patch once GCC 6 is our minimum supported version.

bindings/pydrake/util/test/wrap_function_test.cc

@@ -39,7 +39,7 @@ GTEST_TEST(WrapFunction, FunctionPointer) {
 // Lambdas / basic functors.
 GTEST_TEST(WrapFunction, Lambda) {
   int value{0};
-  auto func_1_lambda = [](int value) {};
+  auto func_1_lambda = [](int) {};
   WrapIdentity(func_1_lambda)(value);
 
   std::function<void(int)> func_1_func = func_1_lambda;

math/test/jacobian_test.cc

@@ -32,7 +32,12 @@ TEST_F(AutodiffJacobianTest, QuadraticForm) {
   Matrix3d A;
   FillWithNumbersIncreasingFromZero(A);
 
+  // Work around GCC 5.4 Wshadow bug; the bug is fixed as of GCC 6.1.
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67273.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wshadow"
   auto quadratic_form = [&](const auto& x) {
+#pragma GCC diagnostic pop
     using Scalar = typename std::remove_reference<decltype(x)>::type::Scalar;
     return (x.transpose() * A.cast<Scalar>().eval() * x).eval();
   };
@@ -98,7 +103,12 @@ TEST_F(AutoDiffHessianTest, QuadraticFunction) {
   FillWithNumbersIncreasingFromZero(D);
   FillWithNumbersIncreasingFromZero(e);
 
+  // Work around GCC 5.4 Wshadow bug; the bug is fixed as of GCC 6.1.
+  // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67273.
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wshadow"
   auto quadratic_function = [&](const auto& x) {
+#pragma GCC diagnostic pop
     using Scalar = typename std::remove_reference<decltype(x)>::type::Scalar;
     return ((A.cast<Scalar>() * x + b.cast<Scalar>()).transpose() *
             C.cast<Scalar>() * (D.cast<Scalar>() * x + e.cast<Scalar>()))

systems/framework/test_utilities/scalar_conversion.h

@@ -31,16 +31,21 @@ static T copysign_int_to_non_symbolic_scalar(int magic, const T& value) {
 template <template <typename> class S, typename Callback>
 ::testing::AssertionResult is_autodiffxd_convertible(
      const S<double>& dut, Callback callback) {
+  // We must use salted local variable names ("_67273" suffix) to work around
+  // GCC 5.4 bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67273 because the
+  // `callback` is a generic lambda.  The bug is fixed as of GCC 6.1.
+
   // Check if a proper type came out; return early if not.
-  std::unique_ptr<System<AutoDiffXd>> converted = dut.ToAutoDiffXdMaybe();
-  ::testing::AssertionResult result =
-        is_dynamic_castable<S<AutoDiffXd>>(converted);
-  if (!result) { return result; }
+  std::unique_ptr<System<AutoDiffXd>> converted_67273 =
+      dut.ToAutoDiffXdMaybe();
+  ::testing::AssertionResult result_67273 =
+        is_dynamic_castable<S<AutoDiffXd>>(converted_67273);
+  if (!result_67273) { return result_67273; }
 
   // Allow calling code to specify additional tests on the converted System.
-  const S<AutoDiffXd>& downcast =
-      dynamic_cast<const S<AutoDiffXd>&>(*converted);
-  callback(downcast);
+  const S<AutoDiffXd>& downcast_67273 =
+      dynamic_cast<const S<AutoDiffXd>&>(*converted_67273);
+  callback(downcast_67273);
 
   return ::testing::AssertionSuccess();
 }
@@ -61,17 +66,21 @@ ::testing::AssertionResult is_autodiffxd_convertible(const S<double>& dut) {
 template <template <typename> class S, typename Callback>
 ::testing::AssertionResult is_symbolic_convertible(
      const S<double>& dut, Callback callback) {
+  // We must use salted local variable names ("_67273" suffix) to work around
+  // GCC 5.4 bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67273 because the
+  // `callback` is a generic lambda.  The bug is fixed as of GCC 6.1.
+
   // Check if a proper type came out; return early if not.
-  std::unique_ptr<System<symbolic::Expression>> converted =
+  std::unique_ptr<System<symbolic::Expression>> converted_67273 =
       dut.ToSymbolicMaybe();
-  ::testing::AssertionResult result =
-        is_dynamic_castable<S<symbolic::Expression>>(converted);
-  if (!result) { return result; }
+  ::testing::AssertionResult result_67273 =
+        is_dynamic_castable<S<symbolic::Expression>>(converted_67273);
+  if (!result_67273) { return result_67273; }
 
   // Allow calling code to specify additional tests on the converted System.
-  const S<symbolic::Expression>& downcast =
-      dynamic_cast<const S<symbolic::Expression>&>(*converted);
-  callback(downcast);
+  const S<symbolic::Expression>& downcast_67273 =
+      dynamic_cast<const S<symbolic::Expression>&>(*converted_67273);
+  callback(downcast_67273);
 
   return ::testing::AssertionSuccess();
 }