translator: fix for null return from function

translator/src/main/kotlin/org/kotlinnative/translator/BlockCodegen.kt

@@ -816,6 +816,7 @@ abstract class BlockCodegen(val state: TranslationState, val variableManager: Va
                 firstOp.type!!.operatorNeq(firstPointedArgument, secondPointedArgument)
             }
             KtTokens.EQ -> {
+                codeBuilder.addComment("start variable assignment")
                 if (secondOp.type is LLVMNullType) {
                     val result = codeBuilder.getNewVariable(firstOp.type!!, firstOp.pointer)
                     codeBuilder.allocStaticVar(result)
@@ -828,6 +829,7 @@ abstract class BlockCodegen(val state: TranslationState, val variableManager: Va
                 val result = firstOp as LLVMVariable
                 val sourceArgument = if (result.pointer == secondOp.pointer + 1) secondOp else secondNativeOp
                 codeBuilder.storeVariable(result, sourceArgument)
+                codeBuilder.addComment("end variable assignment")
                 return result
             }
             else -> addPrimitiveReferenceOperation(referenceName!!, firstOp, secondNativeOp)
@@ -1059,13 +1061,20 @@ abstract class BlockCodegen(val state: TranslationState, val variableManager: Va
 
     private fun evaluateReturnInstruction(element: PsiElement, scopeDepth: Int): LLVMVariable? {
         val next = element.getNextSiblingIgnoringWhitespaceAndComments()
-        val retVar = evaluateExpression(next, scopeDepth)
+        var retVar = evaluateExpression(next, scopeDepth)
         val type = retVar?.type ?: LLVMVoidType()
 
         when (type) {
             is LLVMReferenceType -> genReferenceReturn(retVar!!)
-            is LLVMVoidType,
             is LLVMNullType -> {
+                retVar = when (retVar) {
+                    is LLVMConstant -> LLVMConstant(retVar.value, LLVMNullType(returnType!!.type), returnType!!.pointer - 1)
+                    is LLVMVariable -> LLVMVariable(retVar.label, LLVMNullType(returnType!!.type), retVar.kotlinName, retVar.scope, returnType!!.pointer - 1)
+                    else -> throw IllegalStateException()
+                }
+                genReferenceReturn(retVar)
+            }
+            is LLVMVoidType -> {
                 codeBuilder.addAnyReturn(LLVMVoidType())
             }
             else -> {

translator/src/main/kotlin/org/kotlinnative/translator/llvm/types/LLVMNullType.kt

@@ -16,7 +16,10 @@ class LLVMNullType(var basetype: LLVMType? = null) : LLVMReferred, LLVMType() {
         return other is LLVMNullType
     }
 
+    override fun parseArg(inputArg: String) = "null"
+
     override fun hashCode() =
             "null".hashCode()
 
+    override fun toString() = basetype?.toString() ?: ""
 }

translator/src/test/kotlin/tests/input/null_comparison_1.txt

@@ -0,0 +1 @@
+null_comparison_1() == 87

translator/src/test/kotlin/tests/kotlin/null_comparison_1.kt

@@ -0,0 +1,14 @@
+class null_comparison_1_class
+
+fun null_comparison_1_getClass(): null_comparison_1_class? {
+    return null
+}
+
+fun null_comparison_1(): Int {
+    val a: null_comparison_1_class? = null_comparison_1_getClass()
+    println(if (a == null) 555 else 9990)
+    if (a == null) {
+        return 87
+    }
+    return 945
+}