Elvis / if / when now infer error type in case of ErrorType + Nothing #KT-6665 Fixed

(cherry picked from commit 9a50a0b)

compiler/testData/diagnostics/tests/controlFlowAnalysis/elvisNotProcessed.kt

@@ -9,7 +9,7 @@ else {
     { true } <!USELESS_ELVIS_ON_LAMBDA_EXPRESSION!>?:<!> null!!
 }
 
-val <!IMPLICIT_NOTHING_PROPERTY_TYPE!>ww<!> = if (true) {
+val ww = if (true) {
     <!TYPE_MISMATCH!>{ true }<!> <!USELESS_ELVIS_ON_LAMBDA_EXPRESSION!>?:<!> null!!
 }
 else if (true) {

compiler/testData/diagnostics/tests/controlFlowAnalysis/elvisNotProcessed.txt

@@ -7,6 +7,6 @@ public val bbbb: (() -> kotlin.Boolean)?
 public val n: kotlin.Nothing
 public val v: () -> kotlin.Boolean
 public val w: () -> kotlin.Boolean
-public val ww: kotlin.Nothing
+public val ww: ???
 public fun f(/*0*/ x: kotlin.Long?): kotlin.Long
 public fun l(): (() -> kotlin.Boolean)?

compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.kt

@@ -0,0 +1,48 @@
+// See KT-6665: unresolved reference (v.bar) should not produce "unreachable code" after it
+fun foo(): Int {
+    val v = 1
+    val <!UNUSED_VARIABLE!>c<!> = v.<!UNRESOLVED_REFERENCE!>bar<!> ?: return 0
+    return 42
+}
+
+fun foo2(): Int {
+    val v = 1
+    val c = if (true) v.<!UNRESOLVED_REFERENCE!>bar<!> else return 3
+    val <!UNUSED_VARIABLE!>b<!> = <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>c<!>
+    return 42
+}
+
+fun foo3(): Int {
+    val v = 1
+    val c = when {
+        true -> v.<!UNRESOLVED_REFERENCE!>bar<!>
+        else -> return 3
+    }
+    val <!UNUSED_VARIABLE!>b<!> = <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>c<!>
+    return 42
+}
+
+// Type + ErrorType should give Type, unless Type is Nothing
+
+fun bar(): Int {
+    val v = 1
+    val c = v.<!UNRESOLVED_REFERENCE!>bar<!> ?: 42
+    return c
+}
+
+fun bar2(): Int {
+    val v = 1
+    val c = if (true) v.<!UNRESOLVED_REFERENCE!>bar<!> else 3
+    val b = c
+    return b
+}
+
+fun bar3(): Int {
+    val v = 1
+    val c = when {
+        true -> v.<!UNRESOLVED_REFERENCE!>bar<!>
+        else -> 3
+    }
+    val b = c
+    return b
+}

compiler/testData/diagnostics/tests/controlFlowAnalysis/unresolvedReference.txt

@@ -0,0 +1,8 @@
+package
+
+public fun bar(): kotlin.Int
+public fun bar2(): kotlin.Int
+public fun bar3(): kotlin.Int
+public fun foo(): kotlin.Int
+public fun foo2(): kotlin.Int
+public fun foo3(): kotlin.Int