properly handle empty lines in REPL

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

@@ -177,9 +177,6 @@ public class ExpressionTypingServices {
     @Nullable
     public JetType getBlockReturnedType(@NotNull JetScope outerScope, @NotNull JetBlockExpression expression, @NotNull CoercionStrategy coercionStrategyForLastExpression, ExpressionTypingContext context, BindingTrace trace) {
         List<JetElement> block = expression.getStatements();
-        if (block.isEmpty()) {
-            return DataFlowUtils.checkType(JetStandardClasses.getUnitType(), expression, context);
-        }
 
         DeclarationDescriptor containingDescriptor = outerScope.getContainingDeclaration();
         if (containingDescriptor instanceof ScriptDescriptor) {
@@ -192,7 +189,14 @@ public class ExpressionTypingServices {
         WritableScope scope = new WritableScopeImpl(
                 outerScope, containingDescriptor, new TraceBasedRedeclarationHandler(context.trace), "getBlockReturnedType");
         scope.changeLockLevel(WritableScope.LockLevel.BOTH);
-        JetType r = getBlockReturnedTypeWithWritableScope(scope, block, coercionStrategyForLastExpression, context, trace);
+
+        JetType r;
+        if (block.isEmpty()) {
+            r = DataFlowUtils.checkType(JetStandardClasses.getUnitType(), expression, context);
+        }
+        else {
+            r = getBlockReturnedTypeWithWritableScope(scope, block, coercionStrategyForLastExpression, context, trace);
+        }
         scope.changeLockLevel(WritableScope.LockLevel.READING);
 
         if (containingDescriptor instanceof ScriptDescriptor) {

compiler/testData/codegen/script/empty.ktscript

@@ -0,0 +1,2 @@
+
+// expected: rv: null

compiler/testData/repl/empty.repl

@@ -0,0 +1,8 @@
+>>>
+null
+>>> 101
+101
+>>>
+null
+>>> 102
+102

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

@@ -82,4 +82,8 @@ public class ScriptGenTest extends CodegenTestCase {
         blackBoxFile("script/parameterClosure.ktscript");
     }
 
+    public void testEmpty() {
+        blackBoxFile("script/empty.ktscript");
+    }
+
 }

compiler/tests/org/jetbrains/jet/repl/ReplInterpreterTest.java

@@ -92,5 +92,10 @@ public class ReplInterpreterTest {
         testFile("twoClosures.repl");
     }
 
+    @Test
+    public void empty() {
+        testFile("empty.repl");
+    }
+
 
 }

compiler/tests/org/jetbrains/jet/repl/ReplSessionTestFile.java

@@ -26,6 +26,8 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStreamReader;
 import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 /**
  * @author Stepan Koltsov
@@ -66,10 +68,12 @@ public class ReplSessionTestFile {
                 return new ReplSessionTestFile(list);
             }
 
-            if (!odd.startsWith(">>> ")) {
+            Pattern pattern = Pattern.compile(">>>( |$)(.*)");
+            Matcher matcher = pattern.matcher(odd);
+            if (!matcher.matches()) {
                 throw new IllegalStateException("odd lines must start with >>>");
             }
-            String code = odd.substring(4);
+            String code = matcher.group(2);
 
             String even = reader.readLine();
             if (even == null) {