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/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