Create muzzle references from ldc instructions

dd-java-agent/agent-tooling/src/main/java/datadog/trace/agent/tooling/muzzle/ReferenceCreator.java

@@ -347,5 +347,20 @@ public class ReferenceCreator extends ClassVisitor {
               .build());
       super.visitMethodInsn(opcode, owner, name, descriptor, isInterface);
     }
+
+    @Override
+    public void visitLdcInsn(final Object value) {
+      if (value instanceof Type) {
+        final Type type = underlyingType((Type) value);
+        if (type.getSort() == Type.OBJECT) {
+          addReference(
+              new Reference.Builder(type.getInternalName())
+                  .withSource(refSourceClassName, currentLineNumber)
+                  .withFlag(computeMinimumClassAccess(refSourceType, type))
+                  .build());
+        }
+      }
+      super.visitLdcInsn(value);
+    }
   }
 }

dd-java-agent/testing/src/test/groovy/muzzle/ReferenceCreatorTest.groovy

@@ -57,6 +57,14 @@ class ReferenceCreatorTest extends AgentTestRunner {
     findMethod(bMethods, "protectedMethod", "()V").getFlags().contains(Reference.Flag.PROTECTED_OR_HIGHER)
   }
 
+  def "ldc creates references" () {
+    setup:
+    Map<String, Reference> references = ReferenceCreator.createReferencesFrom(LdcAdvice.getName(), this.getClass().getClassLoader())
+
+    expect:
+    references.get('muzzle.TestClasses$MethodBodyAdvice$A') != null
+  }
+
   private static Reference.Method findMethod(Set<Reference.Method> methods, String methodName, String methodDesc) {
     for (Reference.Method method : methods) {
       if (method == new Reference.Method(methodName, methodDesc)) {

dd-java-agent/testing/src/test/java/muzzle/TestClasses.java

@@ -68,4 +68,10 @@ public class TestClasses {
 
     public interface AnotherInterface extends SomeInterface {}
   }
+
+  public static class LdcAdvice {
+    public static void ldcMethod() {
+      MethodBodyAdvice.A.class.getName();
+    }
+  }
 }