REPL: do not report warnings when there are errors

#KT-18349 Fixed

compiler/cli/src/org/jetbrains/kotlin/cli/jvm/repl/messages/ReplTerminalDiagnosticMessageHolder.kt

@@ -16,15 +16,25 @@
 
 package org.jetbrains.kotlin.cli.jvm.repl.messages
 
-import org.jetbrains.kotlin.cli.common.messages.*
+import org.jetbrains.kotlin.cli.common.messages.GroupingMessageCollector
+import org.jetbrains.kotlin.cli.common.messages.MessageCollectorBasedReporter
+import org.jetbrains.kotlin.cli.common.messages.MessageRenderer
+import org.jetbrains.kotlin.cli.common.messages.PrintingMessageCollector
 import java.io.ByteArrayOutputStream
 import java.io.PrintStream
 import java.nio.ByteBuffer
 
-class ReplTerminalDiagnosticMessageHolder() : MessageCollectorBasedReporter, DiagnosticMessageHolder {
+class ReplTerminalDiagnosticMessageHolder : MessageCollectorBasedReporter, DiagnosticMessageHolder {
     private val outputStream = ByteArrayOutputStream()
-    override val messageCollector = PrintingMessageCollector(PrintStream(outputStream), MessageRenderer.WITHOUT_PATHS, false)
+
+    override val messageCollector: GroupingMessageCollector = GroupingMessageCollector(
+            PrintingMessageCollector(PrintStream(outputStream), MessageRenderer.WITHOUT_PATHS, false)
+    )
 
     override val renderedDiagnostics: String
-        get() = Charsets.UTF_8.decode(ByteBuffer.wrap(outputStream.toByteArray())).toString()
-}
+        get() {
+            messageCollector.flush()
+            val bytes = outputStream.toByteArray()
+            return Charsets.UTF_8.decode(ByteBuffer.wrap(bytes)).toString()
+        }
+}

compiler/testData/repl/controlFlow/incompleteWhen.repl

@@ -2,9 +2,6 @@
 error: 'when' expression must be exhaustive, add necessary 'else' branch
 val a = when(null) { }
         ^
-warning: the expression is unused
-val a = when(null) { }
-             ^
 >>> "" + when (true) { true -> 42 }
 error: 'when' expression must be exhaustive, add necessary 'false' branch or 'else' branch instead
 "" + when (true) { true -> 42 }

compiler/testData/repl/noWarningsWithErrors.repl

@@ -0,0 +1,11 @@
+>>> (listOf(1) as List<String>).unresolved()
+error: unresolved reference: unresolved
+(listOf(1) as List<String>).unresolved()
+                            ^
+>>> listOf<String>(1!!)
+error: the integer literal does not conform to the expected type String?
+listOf<String>(1!!)
+               ^
+error: type mismatch: inferred type is Int but String was expected
+listOf<String>(1!!)
+               ^

compiler/tests/org/jetbrains/kotlin/repl/ReplInterpreterTestGenerated.java

@@ -114,6 +114,12 @@ public class ReplInterpreterTestGenerated extends AbstractReplInterpreterTest {
         doTest(fileName);
     }
 
+    @TestMetadata("noWarningsWithErrors.repl")
+    public void testNoWarningsWithErrors() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/repl/noWarningsWithErrors.repl");
+        doTest(fileName);
+    }
+
     @TestMetadata("simple.repl")
     public void testSimple() throws Exception {
         String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/repl/simple.repl");