Fix memory leak by disposing a classloader. The real issue though is located in TypeInfoParser, that has WeakHashMap with values referencing keys.

compiler/backend/src/org/jetbrains/jet/codegen/GeneratedClassLoader.java

@@ -6,7 +6,7 @@ import org.jetbrains.annotations.NotNull;
 * @author yole
 */
 public class GeneratedClassLoader extends ClassLoader {
-    private final ClassFileFactory state;
+    private ClassFileFactory state;
 
     public GeneratedClassLoader(@NotNull ClassFileFactory state) {
         this(state, GeneratedClassLoader.class.getClassLoader());
@@ -26,4 +26,8 @@ public class GeneratedClassLoader extends ClassLoader {
         }
         return super.findClass(name);
     }
+
+    public void dispose() {
+        state = null;
+    }
 }

compiler/cli/src/org/jetbrains/jet/compiler/CompileEnvironment.java

@@ -174,7 +174,7 @@ public class CompileEnvironment {
     }
 
     private List<Module> runDefineModules(String moduleFile, ClassFileFactory factory) {
-        ClassLoader loader = myStdlib != null ? new GeneratedClassLoader(factory, new URLClassLoader(new URL[] {myStdlib}, AllModules.class.getClassLoader())) : new GeneratedClassLoader(factory);
+        GeneratedClassLoader loader = myStdlib != null ? new GeneratedClassLoader(factory, new URLClassLoader(new URL[] {myStdlib}, AllModules.class.getClassLoader())) : new GeneratedClassLoader(factory);
         try {
             Class namespaceClass = loader.loadClass(JvmAbi.PACKAGE_CLASS);
             final Method method = namespaceClass.getDeclaredMethod("project");
@@ -188,9 +188,13 @@ public class CompileEnvironment {
             ArrayList<Module> answer = new ArrayList<Module>(AllModules.modules);
             AllModules.modules.clear();
             return answer;
-        } catch (Exception e) {
+        }
+        catch (Exception e) {
             throw new ModuleExecutionException(e);
         }
+        finally {
+            loader.dispose();
+        }
     }
 
     public ClassFileFactory compileModule(Module moduleBuilder, String directory) {

compiler/tests/org/jetbrains/jet/codegen/CodegenTestCase.java

@@ -91,10 +91,14 @@ public abstract class CodegenTestCase extends JetLiteFixture {
         ClassFileFactory codegens = generateClassesInFile();
         GeneratedClassLoader loader = new GeneratedClassLoader(codegens);
 
-        String fqName = NamespaceCodegen.getJVMClassName(JetPsiUtil.getFQName(myFile), true).replace("/", ".");
-        Class<?> namespaceClass = loader.loadClass(fqName);
-        Method method = namespaceClass.getMethod("box");
-        return (String) method.invoke(null);
+        try {
+            String fqName = NamespaceCodegen.getJVMClassName(JetPsiUtil.getFQName(myFile), true).replace("/", ".");
+            Class<?> namespaceClass = loader.loadClass(fqName);
+            Method method = namespaceClass.getMethod("box");
+            return (String) method.invoke(null);
+        } finally {
+           loader.dispose();
+        }
     }
 
     protected String generateToText() {

compiler/tests/org/jetbrains/jet/codegen/TestlibTest.java

@@ -4,6 +4,7 @@ import com.intellij.openapi.vfs.VirtualFile;
 import com.intellij.openapi.vfs.local.CoreLocalFileSystem;
 import gnu.trove.THashSet;
 import junit.framework.TestCase;
+import junit.framework.TestResult;
 import junit.framework.TestSuite;
 import org.jetbrains.jet.compiler.CompileSession;
 import org.jetbrains.jet.lang.descriptors.ClassDescriptor;
@@ -74,13 +75,19 @@ public class TestlibTest extends CodegenTestCase {
 
             ClassFileFactory classFileFactory = session.generate();
 
-            GeneratedClassLoader loader = new GeneratedClassLoader(
+            final GeneratedClassLoader loader = new GeneratedClassLoader(
                     classFileFactory,
                     new URLClassLoader(new URL[]{ForTestCompileStdlib.stdlibJarForTests().toURI().toURL(), junitJar.toURI().toURL()},
                                        TestCase.class.getClassLoader()));
 
             JetTypeMapper typeMapper = new JetTypeMapper(classFileFactory.state.getStandardLibrary(), session.getMyBindingContext());
-            TestSuite suite = new TestSuite("StandardLibrary");
+            TestSuite suite = new TestSuite("StandardLibrary") {
+                @Override
+                public void run(TestResult result) {
+                    super.run(result);
+                    loader.dispose();
+                }
+            };
             try {
                 for(JetFile jetFile : session.getSourceFileNamespaces()) {
                     for(JetDeclaration decl : jetFile.getDeclarations()) {