Fix default value generation after suspension point

Replace coercion from VOID with call 'pushDefaultValueOnStack'

It's necessary because coercion of VOID to java/lang/Object ends with Unit instance on stack
that makes variables spilling algorithm thinking that variable is Unit

 #KT-13409 Fixed

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

@@ -2875,7 +2875,7 @@ public class ExpressionCodegen extends KtVisitor<StackValue, StackValue> impleme
         callGenerator.genCall(callableMethod, resolvedCall, defaultMaskWasGenerated, this);
 
         if (isSuspensionPoint) {
-            StackValue.coerce(Type.VOID_TYPE, getSuspensionReturnTypeByResolvedCall(resolvedCall), v);
+            AsmUtil.pushDefaultValueOnStack(getSuspensionReturnTypeByResolvedCall(resolvedCall), v);
             v.invokestatic(
                     CoroutineCodegenUtilKt.COROUTINE_MARKER_OWNER,
                     CoroutineCodegenUtilKt.AFTER_SUSPENSION_POINT_MARKER_NAME, "()V", false);

compiler/testData/codegen/box/coroutines/falseUnitCoercion.kt

@@ -0,0 +1,24 @@
+class Controller {
+    suspend fun <T> suspendHere(v: T, x: Continuation<T>) {
+        x.resume(v)
+    }
+}
+
+fun builder(coroutine c: Controller.() -> Continuation<Unit>) {
+    c(Controller()).resume(Unit)
+}
+
+var result: Any = ""
+
+fun <T : Any> foo(v: T) {
+    builder {
+        val r = suspendHere(v)
+        suspendHere("")
+        result = r
+    }
+}
+
+fun box(): String {
+    foo("OK")
+    return result as String
+}

compiler/tests/org/jetbrains/kotlin/codegen/BlackBoxCodegenTestGenerated.java

@@ -4348,6 +4348,12 @@ public class BlackBoxCodegenTestGenerated extends AbstractBlackBoxCodegenTest {
             doTest(fileName);
         }
 
+        @TestMetadata("falseUnitCoercion.kt")
+        public void testFalseUnitCoercion() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/falseUnitCoercion.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("generate.kt")
         public void testGenerate() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/box/coroutines/generate.kt");