added 'getCurrentSubstitutor' to ConstraintSystem

which returns DON_CARE type projection for unknown type parameters

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/CallResolver.java

@@ -350,7 +350,7 @@ public class CallResolver {
             for (ValueArgument valueArgument : resolvedValueArgument.getArguments()) {
                 if (!JetPsiUtil.isFunctionLiteralWithoutDeclaredParameterTypes(valueArgument.getArgumentExpression())) continue;
 
-                addConstraintForValueArgument(valueArgument, valueParameterDescriptor, constraintsSystem.getResultingSubstitutor(),
+                addConstraintForValueArgument(valueArgument, valueParameterDescriptor, constraintsSystem.getCurrentSubstitutor(),
                                               constraintsSystem, context);
             }
         }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintsSystem.java

@@ -121,4 +121,11 @@ public interface ConstraintsSystem {
      */
     @NotNull
     TypeSubstitutor getResultingSubstitutor();
+
+    /**
+     * Returns a current result of solving the constraint system (mapping from the type variable to the resulting type projection).
+     * If there is no information for type parameter, returns type projection for DONT_CARE type.
+     */
+    @NotNull
+    TypeSubstitutor getCurrentSubstitutor();
 }

compiler/frontend/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintsSystemImpl.java

@@ -39,10 +39,16 @@ public class ConstraintsSystemImpl implements ConstraintsSystem {
     private final Map<TypeParameterDescriptor, TypeConstraintsImpl> typeParameterConstraints = Maps.newLinkedHashMap();
     private final Set<ConstraintPosition> errorConstraintPositions = Sets.newHashSet();
     private final TypeSubstitutor resultingSubstitutor;
+    private final TypeSubstitutor currentSubstitutor;
     private boolean hasErrorInConstrainingTypes;
 
     public ConstraintsSystemImpl() {
-        this.resultingSubstitutor = TypeSubstitutor.create(new TypeSubstitution() {
+        this.resultingSubstitutor = createTypeSubstitutorWithDefaultForUnknownTypeParameter(null);
+        this.currentSubstitutor = createTypeSubstitutorWithDefaultForUnknownTypeParameter(new TypeProjection(DONT_CARE));
+    }
+
+    private TypeSubstitutor createTypeSubstitutorWithDefaultForUnknownTypeParameter(@Nullable final TypeProjection defaultTypeProjection) {
+        return TypeSubstitutor.create(new TypeSubstitution() {
             @Override
             public TypeProjection get(TypeConstructor key) {
                 DeclarationDescriptor declarationDescriptor = key.getDeclarationDescriptor();
@@ -54,7 +60,9 @@ public class ConstraintsSystemImpl implements ConstraintsSystem {
                             DONT_CARE.getConstructor()))) {
                         return new TypeProjection(value);
                     }
-                    return new TypeProjection(DONT_CARE);
+                    if (typeParameterConstraints.containsKey(descriptor)) {
+                        return defaultTypeProjection;
+                    }
                 }
                 return null;
             }
@@ -231,4 +239,10 @@ public class ConstraintsSystemImpl implements ConstraintsSystem {
     public TypeSubstitutor getResultingSubstitutor() {
         return resultingSubstitutor;
     }
+
+    @NotNull
+    @Override
+    public TypeSubstitutor getCurrentSubstitutor() {
+        return currentSubstitutor;
+    }
 }