repl: do not print null is last expression type is unit

compiler/cli/src/org/jetbrains/jet/cli/jvm/repl/ReplFromTerminal.java

@@ -116,8 +116,10 @@ public class ReplFromTerminal {
                 return oneCommand(line.substring(1));
             }
 
-            Object value = getReplInterpreter().eval(line);
-            System.out.println(value);
+            ReplInterpreter.LineResult lineResult = getReplInterpreter().eval(line);
+            if (!lineResult.isUnit()) {
+                System.out.println(lineResult.getValue());
+            }
             return true;
         }
         catch (Exception e) {

compiler/cli/src/org/jetbrains/jet/cli/jvm/repl/ReplInterpreter.java

@@ -118,7 +118,26 @@ public class ReplInterpreter {
         classLoader = new ReplClassLoader(new URLClassLoader(classpath.toArray(new URL[0])));
     }
 
-    public Object eval(@NotNull String line) {
+    public static class LineResult {
+        private final Object value;
+        private final boolean unit;
+
+        public LineResult(Object value, boolean unit) {
+            this.value = value;
+            this.unit = unit;
+        }
+
+        public Object getValue() {
+            return value;
+        }
+
+        public boolean isUnit() {
+            return unit;
+        }
+    }
+
+    @NotNull
+    public LineResult eval(@NotNull String line) {
         ++lineNumber;
 
         JvmClassName scriptClassName = JvmClassName.byInternalName("Line" + lineNumber);
@@ -173,7 +192,7 @@ public class ReplInterpreter {
 
             earlierLines.add(new EarlierLine(line, scriptDescriptor, scriptClass, scriptInstance, scriptClassName));
 
-            return rv;
+            return new LineResult(rv, scriptDescriptor.getReturnType().equals(JetStandardClasses.getUnitType()));
         } catch (Throwable e) {
             PrintWriter writer = new PrintWriter(System.err);
             classLoader.dumpClasses(writer);

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

@@ -60,7 +60,7 @@ public class ReplInterpreterTest {
             String code = t.first;
             String expected = t.second;
 
-            Object actual = repl.eval(code);
+            Object actual = repl.eval(code).getValue();
             String actualString = actual != null ? actual.toString() : "null";
 
             Assert.assertEquals("after evaluation of: " + code, actualString, expected);