More precise type handling for equality #KT-2311 Fixed

compiler/testData/diagnostics/tests/smartCasts/typeDegradation.kt

@@ -0,0 +1,17 @@
+open class VeryBase
+
+open class Base : VeryBase()
+
+class Derived : Base() {
+    fun original(): VeryBase = this
+}
+
+class Another : Base()
+
+fun foo(d: Derived, a: Another?): Base? {
+    // d is compared with d.original(): VeryBase but should retain its own type
+    if (d.original() != d) return null
+    // ad should be of type Base, not VeryBase
+    val ad = a ?: d
+    return ad
+}

compiler/testData/diagnostics/tests/smartCasts/typeDegradation.txt

@@ -0,0 +1,32 @@
+package
+
+public fun foo(/*0*/ d: Derived, /*1*/ a: Another?): Base?
+
+public final class Another : Base {
+    public constructor Another()
+    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
+}
+
+public open class Base : VeryBase {
+    public constructor Base()
+    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
+}
+
+public final class Derived : Base {
+    public constructor Derived()
+    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 final fun original(): VeryBase
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public open class VeryBase {
+    public constructor VeryBase()
+    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/tests/smartCasts/typeInComparison.kt

@@ -0,0 +1,8 @@
+fun foo(): Int {
+    val x: Any? = null
+    val y = 2
+    if (x == y) {
+        return <!DEBUG_INFO_SMARTCAST!>x<!> + y
+    }
+    return y
+}

compiler/testData/diagnostics/tests/smartCasts/typeInComparison.txt

@@ -0,0 +1,3 @@
+package
+
+public fun foo(): kotlin.Int