[FE 1.0] Make type of safe call always nullable

^KT-46860 In Progress

compiler/testData/diagnostics/tests/smartCasts/safecalls/safeCallIsAlwaysNullable.fir.kt

@@ -0,0 +1,20 @@
+// LANGUAGE: +SafeCallsAreAlwaysNullable
+// ISSUE: KT-46860
+
+interface A {
+    fun foo(): Int
+}
+
+fun takeInt(x: Int) {}
+
+fun test_1(a: A) {
+    val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int")!>a<!UNNECESSARY_SAFE_CALL!>?.<!>foo()<!>
+    takeInt(x) // should be an error
+}
+
+fun test_2(a: A?) {
+    if (a != null) {
+        val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int")!>a<!UNNECESSARY_SAFE_CALL!>?.<!>foo()<!>
+        takeInt(x) // should be an error
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/safecalls/safeCallIsAlwaysNullable.kt

@@ -0,0 +1,20 @@
+// LANGUAGE: +SafeCallsAreAlwaysNullable
+// ISSUE: KT-46860
+
+interface A {
+    fun foo(): Int
+}
+
+fun takeInt(x: Int) {}
+
+fun test_1(a: A) {
+    val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a<!UNNECESSARY_SAFE_CALL!>?.<!>foo()<!>
+    takeInt(<!TYPE_MISMATCH!>x<!>) // should be an error
+}
+
+fun test_2(a: A?) {
+    if (a != null) {
+        val x = <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Int?")!>a<!UNNECESSARY_SAFE_CALL!>?.<!>foo()<!>
+        takeInt(<!TYPE_MISMATCH!>x<!>) // should be an error
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/safecalls/safeCallIsAlwaysNullable.txt

@@ -0,0 +1,12 @@
+package
+
+public fun takeInt(/*0*/ x: kotlin.Int): kotlin.Unit
+public fun test_1(/*0*/ a: A): kotlin.Unit
+public fun test_2(/*0*/ a: A?): kotlin.Unit
+
+public interface A {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public abstract fun foo(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}