Support for a?b

idea/src/org/jetbrains/jet/lang/parsing/JetExpressionParsing.java

@@ -409,7 +409,7 @@ public class JetExpressionParsing extends AbstractJetParsing {
     private void parseCallExpression() {
         PsiBuilder.Marker mark = mark();
         parseAtomicExpression();
-        if (parseCallSuffix()) {
+        if (!myBuilder.newlineBeforeCurrentToken() && parseCallSuffix()) {
             mark.done(CALL_EXPRESSION);
         }
         else {

idea/src/org/jetbrains/jet/lang/psi/JetChangeUtil.java

@@ -45,7 +45,7 @@ public class JetChangeUtil {
         JetFile file = createFile(project, text);
         JetNamespace rootNamespace = file.getRootNamespace();
         List<JetDeclaration> dcls = rootNamespace.getDeclarations();
-        assert dcls.size() == 1;
+        assert dcls.size() == 1 : dcls.size();
         @SuppressWarnings("unchecked")
         T result = (T) dcls.get(0);
         return result;

idea/src/org/jetbrains/jet/lang/types/JetTypeInferrer.java

@@ -543,24 +543,6 @@ public class JetTypeInferrer {
             throw new UnsupportedOperationException(); // TODO
         }
 
-        @Override
-        public void visitPredicateExpression(JetPredicateExpression expression) {
-//            JetExpression receiverExpression = expression.getReceiverExpression();
-//            JetExpression selectorExpression = expression.getSelectorExpression();
-//            JetType receiverType = getType(scope, receiverExpression, false);
-//            if (receiverType != null) {
-//                if (selectorExpression instanceof JetSimpleNameExpression) {
-//                    JetScope compositeScope = new ScopeWithReceiver(scope, receiverType);
-//                    result = getType(compositeScope, selectorExpression, false);
-//                }
-//                else if (selectorExpression != null) {
-//                    // TODO : not a simple name -> resolve in scope, expect property type or a function type
-//                    throw new UnsupportedOperationException();
-//                }
-//            }
-            throw new UnsupportedOperationException(); // TODO
-        }
-
         @Override
         public void visitQualifiedExpression(JetQualifiedExpression expression) {
             // TODO : functions
@@ -569,30 +551,45 @@ public class JetTypeInferrer {
             JetType receiverType = getType(scope, receiverExpression, false);
             if (receiverType != null) {
                 checkNullSafety(receiverType, expression);
-                JetScope compositeScope = new ScopeWithReceiver(scope, receiverType);
-                if (selectorExpression instanceof JetCallExpression) {
-                    JetCallExpression callExpression = (JetCallExpression) selectorExpression;
-                    OverloadDomain overloadDomain = getOverloadDomain(compositeScope, callExpression.getCalleeExpression());
-                    resolveOverloads(scope, callExpression, overloadDomain);
-                }
-                else if (selectorExpression instanceof JetSimpleNameExpression) {
-                    result = getType(compositeScope, selectorExpression, false);
+                JetType selectorReturnType = getSelectorReturnType(receiverType, selectorExpression);
+                if (expression.getOperationSign() == JetTokens.QUEST) {
+                    if (selectorReturnType != null && !isBoolean(selectorReturnType)) {
+                        // TODO : more comprehensible error message
+                        semanticServices.getErrorHandler().typeMismatch(selectorExpression, semanticServices.getStandardLibrary().getBooleanType(), selectorReturnType);
+                    }
+                    result = TypeUtils.makeNullable(receiverType);
                 }
-                else if (selectorExpression != null) {
-                    // TODO : not a simple name -> resolve in scope, expect property type or a function type
-                    throw new UnsupportedOperationException();
+                else {
+                    result = selectorReturnType;
                 }
             }
         }
 
+        private JetType getSelectorReturnType(JetType receiverType, JetExpression selectorExpression) {
+            JetScope compositeScope = new ScopeWithReceiver(scope, receiverType);
+            if (selectorExpression instanceof JetCallExpression) {
+                JetCallExpression callExpression = (JetCallExpression) selectorExpression;
+                OverloadDomain overloadDomain = getOverloadDomain(compositeScope, callExpression.getCalleeExpression());
+                return resolveOverloads(scope, callExpression, overloadDomain);
+            }
+            else if (selectorExpression instanceof JetSimpleNameExpression) {
+                return getType(compositeScope, selectorExpression, false);
+            }
+            else if (selectorExpression != null) {
+                // TODO : not a simple name -> resolve in scope, expect property type or a function type
+                throw new UnsupportedOperationException();
+            }
+            return receiverType;
+        }
+
         @Override
         public void visitCallExpression(JetCallExpression expression) {
             JetExpression calleeExpression = expression.getCalleeExpression();
             OverloadDomain overloadDomain = getOverloadDomain(scope, calleeExpression);
-            resolveOverloads(scope, expression, overloadDomain);
+            result = resolveOverloads(scope, expression, overloadDomain);
         }
 
-        private void resolveOverloads(JetScope scope, JetCallExpression expression, OverloadDomain overloadDomain) {
+        private JetType resolveOverloads(JetScope scope, JetCallExpression expression, OverloadDomain overloadDomain) {
             // 1) ends with a name -> (scope, name) to look up
             // 2) ends with something else -> just check types
 
@@ -640,9 +637,10 @@ public class JetTypeInferrer {
 
                 FunctionDescriptor functionDescriptor = overloadDomain.getFunctionDescriptorForPositionedArguments(types, valueArgumentTypes);
                 if (functionDescriptor != null) {
-                    result = functionDescriptor.getUnsubstitutedReturnType();
+                    return functionDescriptor.getUnsubstitutedReturnType();
                 }
             }
+            return null;
         }
 
         @Override

idea/tests/org/jetbrains/jet/types/JetTypeCheckerTest.java

@@ -406,6 +406,9 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
         assertType("true && false", "Boolean");
         assertType("true || false", "Boolean");
         assertType("null ?: false", "Boolean");
+        assertType("new WithPredicate()?isValid()", "WithPredicate?");
+        assertType("new WithPredicate()?isValid(1)", "WithPredicate?");
+        assertType("new WithPredicate()?p", "WithPredicate?");
     }
 
     private void assertSubtype(String type1, String type2) {
@@ -500,7 +503,12 @@ public class JetTypeCheckerTest extends LightDaemonAnalyzerTestCase {
                     "fun f(a : T) : Any {} " +
                     "fun f(a : (Int, Int)) : T {} " +
                     "fun f<E>(a : E) : T {} " +
-                    "}"
+                    "}",
+            "class WithPredicate { " +
+                    "fun isValid() : Boolean " +
+                    "fun isValid(x : Int) : Boolean " +
+                    "val p : Boolean " +
+            "}"
         };
         private String[] FUNCTION_DECLARATIONS = {
             "fun f() : Unit {}",