x?.y is now nullable even if y is Unit + three tests + codegen test fix + source code fix #KT-7936 Fixed #KT-8347 Fixed

compiler/testData/diagnostics/tests/nullableTypes/elvisOnUnit.kt

@@ -0,0 +1,11 @@
+class My {
+    fun other() {}
+}
+
+fun another() {}
+
+fun foo(x: My?) {
+    // Both elvis parts should be alive
+    // See also KT-7936, KT-8347
+    x?.other() ?: another()
+}

compiler/testData/diagnostics/tests/nullableTypes/elvisOnUnit.txt

@@ -0,0 +1,12 @@
+package
+
+internal fun another(): kotlin.Unit
+internal fun foo(/*0*/ x: My?): kotlin.Unit
+
+internal final class My {
+    public constructor My()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    internal final fun other(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/nullableTypes/safeAccessOnUnit.kt

@@ -0,0 +1,7 @@
+data class My(val x: Unit)
+
+fun foo(my: My?): Int? {
+    val x = my?.x
+    // ?. is required here
+    return x?.hashCode()
+}

compiler/testData/diagnostics/tests/nullableTypes/safeAccessOnUnit.txt

@@ -0,0 +1,13 @@
+package
+
+internal fun foo(/*0*/ my: My?): kotlin.Int?
+
+kotlin.data() internal final class My {
+    public constructor My(/*0*/ x: kotlin.Unit)
+    internal final val x: kotlin.Unit
+    internal final /*synthesized*/ fun component1(): kotlin.Unit
+    public final /*synthesized*/ fun copy(/*0*/ x: kotlin.Unit = ...): My
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/testsWithStdLib/elvisOnUnitInLet.kt

@@ -0,0 +1,9 @@
+fun foo(x: Int?) {
+    // Both parts of the Elvis should be alive, see KT-7936
+    x?.let {
+        smth()
+    }?: orElse()
+}
+
+fun smth() {}
+fun orElse() {}

compiler/testData/diagnostics/testsWithStdLib/elvisOnUnitInLet.txt

@@ -0,0 +1,5 @@
+package
+
+internal fun foo(/*0*/ x: kotlin.Int?): kotlin.Unit
+internal fun orElse(): kotlin.Unit
+internal fun smth(): kotlin.Unit