Fix handling deeply nested java classes.

internal/zinc-classfile/src/main/scala/sbt/internal/inc/classfile/Analyze.scala

@@ -50,8 +50,16 @@ private[sbt] object Analyze {
          binaryClassName = classFile.className;
          loadedClass <- load(binaryClassName, Some("Error reading API from class file"))) {
       binaryClassNameToLoadedClass.update(binaryClassName, loadedClass)
-      val srcClassName = binaryToSourceName(loadedClass)
-        .orElse(Option(loadedClass.getEnclosingClass).flatMap(binaryToSourceName))
+
+      def loadEnclosingClass(clazz: Class[_]): Option[String] = {
+        binaryToSourceName(clazz) match {
+          case None if clazz.getEnclosingClass != null =>
+            loadEnclosingClass(clazz.getEnclosingClass)
+          case other => other
+        }
+      }
+
+      val srcClassName = loadEnclosingClass(loadedClass)
 
       srcClassName match {
         case Some(className) =>

zinc/src/test/resources/sources/NestedJavaClasses.java

@@ -0,0 +1,15 @@
+class NestedJavaClasses {
+    public NestedJavaClasses nest() {
+        return new NestedJavaClasses() {
+            @Override
+            public NestedJavaClasses nest() {
+                return new NestedJavaClasses() {
+                    @Override
+                    public NestedJavaClasses nest() {
+                        throw new RuntimeException("Way too deep!");
+                    }
+                };
+            }
+        };
+    }
+}

zinc/src/test/scala/sbt/inc/NestedJavaClassSpec.scala

@@ -0,0 +1,20 @@
+package sbt.inc
+
+import sbt.internal.inc.Analysis
+import sbt.io.IO
+
+class NestedJavaClassSpec extends BaseCompilerSpec {
+  it should "handle nested Java classes" in {
+    IO.withTemporaryDirectory { tempDir =>
+      val projectSetup =
+        ProjectSetup.simple(tempDir.toPath, Seq("NestedJavaClasses.java"))
+
+      val result = projectSetup.createCompiler().doCompile()
+      result.analysis() match {
+        case analysis: Analysis =>
+          analysis.relations.libraryDep._2s
+            .filter(_.toPath.startsWith(tempDir.toPath)) shouldBe 'empty
+      }
+    }
+  }
+}