Generate substatements as statements too

Preventing pushing on stack redundant Unit instances

 #KT-5667 fixed

compiler/backend/src/org/jetbrains/jet/codegen/ExpressionCodegen.java

@@ -261,7 +261,7 @@ public class ExpressionCodegen extends JetVisitor<StackValue, StackValue> implem
     }
 
     public void gen(JetElement expr, Type type) {
-        StackValue value = gen(expr);
+        StackValue value = Type.VOID_TYPE.equals(type) ? genStatement(expr) : gen(expr);
         value.put(type, v);
     }
 

compiler/testData/codegen/bytecodeText/statements/statementsComposition.kt

@@ -0,0 +1,36 @@
+
+fun foo() {
+    val array = intArray(1,2,3)
+
+    var count = 0
+    for (element in array) if (element > 0) count++
+    while (count > 0) if (count > 0) count++
+
+    if (count == 1)
+        if (count != 1)
+            count++
+        else
+            print("1")
+        else
+            print("2")
+
+    when (count) {
+        1 -> if (count == 1) count++ else print("123")
+        else -> if (count == 1) count++ else print("123")
+    }
+
+    for (element in array)
+        when (element) {
+            1 -> if (count == 1) count++ else print("123")
+            else -> if (count == 1) count++ else print("123")
+        }
+
+    while (count > 0)
+        when (count) {
+            1 -> if (count == 1) count++ else print("123")
+            else -> if (count == 1) count++ else print("123")
+        }
+}
+
+// 0 valueOf
+// 0 GETSTATIC

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

@@ -341,6 +341,12 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             doTest(fileName);
         }
         
+        @TestMetadata("statementsComposition.kt")
+        public void testStatementsComposition() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/statements/statementsComposition.kt");
+            doTest(fileName);
+        }
+        
         @TestMetadata("tryCatchFinally.kt")
         public void testTryCatchFinally() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/statements/tryCatchFinally.kt");