LHS of callable reference can't be a type parameter

compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/Errors.java

@@ -348,6 +348,7 @@ public interface Errors {
     // Callable references
 
     DiagnosticFactory1<JetExpression, CallableMemberDescriptor> EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED = DiagnosticFactory1.create(ERROR);
+    DiagnosticFactory0<JetExpression> CALLABLE_REFERENCE_LHS_NOT_A_CLASS = DiagnosticFactory0.create(ERROR);
 
     // Multi-declarations
 

compiler/frontend/src/org/jetbrains/jet/lang/diagnostics/rendering/DefaultErrorMessages.java

@@ -442,6 +442,7 @@ public class DefaultErrorMessages {
 
         MAP.put(EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED,
                 "''{0}'' is a member and an extension at the same time. References to such elements are not allowed", TO_STRING);
+        MAP.put(CALLABLE_REFERENCE_LHS_NOT_A_CLASS, "Callable reference left-hand side cannot be a type parameter");
 
         MAP.setImmutable();
 

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/BasicExpressionTypingVisitor.java

@@ -657,8 +657,10 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         }
 
         ClassifierDescriptor classifier = lhsType.getConstructor().getDeclarationDescriptor();
-        // TODO: report an error if the classifier is not a class
-        assert classifier instanceof ClassDescriptor : "TODO";
+        if (!(classifier instanceof ClassDescriptor)) {
+            context.trace.report(CALLABLE_REFERENCE_LHS_NOT_A_CLASS.on(expression));
+            return null;
+        }
 
         ReceiverValue receiver = new TransientReceiver(lhsType);
         TemporaryBindingTrace traceWithReceiver = TemporaryBindingTrace.create(context.trace,

compiler/testData/diagnostics/tests/callableReference/lhsNotAClass.kt

@@ -0,0 +1,9 @@
+class A<T, U : Any> {
+    fun foo() = <!CALLABLE_REFERENCE_LHS_NOT_A_CLASS!>T::<!UNRESOLVED_REFERENCE!>toString<!><!>
+
+    fun bar() = <!CALLABLE_REFERENCE_LHS_NOT_A_CLASS!>U::<!UNRESOLVED_REFERENCE!>toString<!><!>
+}
+
+fun <T> foo() = <!CALLABLE_REFERENCE_LHS_NOT_A_CLASS!>T::<!UNRESOLVED_REFERENCE!>toString<!><!>
+
+fun <U : Any> bar() = <!CALLABLE_REFERENCE_LHS_NOT_A_CLASS!>U::<!UNRESOLVED_REFERENCE!>toString<!><!>

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -811,6 +811,11 @@ public class JetDiagnosticsTestGenerated extends AbstractDiagnosticsTestWithEage
                 doTest("compiler/testData/diagnostics/tests/callableReference/innerConstructorFromTopLevel.kt");
             }
             
+            @TestMetadata("lhsNotAClass.kt")
+            public void testLhsNotAClass() throws Exception {
+                doTest("compiler/testData/diagnostics/tests/callableReference/lhsNotAClass.kt");
+            }
+            
             @TestMetadata("localConstructor.kt")
             public void testLocalConstructor() throws Exception {
                 doTest("compiler/testData/diagnostics/tests/callableReference/localConstructor.kt");