[FE 1.0] Properly handle intersection types in check if cast possible or not

^KT-47685 Fixed

compiler/testData/diagnostics/tests/cast/kt47685.fir.kt

@@ -0,0 +1,29 @@
+// KT-47685
+interface KtFunction {
+    fun foo() {}
+}
+
+abstract class ASTDelegatePsiElement {
+    fun bar() {}
+}
+
+class KtNamedFunction : ASTDelegatePsiElement(), KtFunction {
+    fun baz() {}
+}
+class KtFunctionLiteral : ASTDelegatePsiElement(), KtFunction
+
+fun test_1(namedFunction: KtNamedFunction, functionLiteral: KtFunctionLiteral, cond: Boolean) {
+    val function = when (cond) {
+        true -> namedFunction
+        false -> functionLiteral
+    }
+    // approve that foo has type (ASTDelegatePsiElement & KtFunction)
+    function.foo()
+    function.bar()
+
+    if (function is KtNamedFunction) {
+        function.baz()
+    }
+
+    val myNamedFunction = function as KtNamedFunction
+}

compiler/testData/diagnostics/tests/cast/kt47685.kt

@@ -0,0 +1,29 @@
+// KT-47685
+interface KtFunction {
+    fun foo() {}
+}
+
+abstract class ASTDelegatePsiElement {
+    fun bar() {}
+}
+
+class KtNamedFunction : ASTDelegatePsiElement(), KtFunction {
+    fun baz() {}
+}
+class KtFunctionLiteral : ASTDelegatePsiElement(), KtFunction
+
+fun test_1(namedFunction: KtNamedFunction, functionLiteral: KtFunctionLiteral, cond: Boolean) {
+    val function = when (cond) {
+        true -> namedFunction
+        false -> functionLiteral
+    }
+    // approve that foo has type (ASTDelegatePsiElement & KtFunction)
+    function.foo()
+    function.bar()
+
+    if (function is KtNamedFunction) {
+        <!DEBUG_INFO_SMARTCAST!>function<!>.baz()
+    }
+
+    val myNamedFunction = function as KtNamedFunction
+}

compiler/testData/diagnostics/tests/cast/kt47685.txt

@@ -0,0 +1,37 @@
+package
+
+public fun test_1(/*0*/ namedFunction: KtNamedFunction, /*1*/ functionLiteral: KtFunctionLiteral, /*2*/ cond: kotlin.Boolean): kotlin.Unit
+
+public abstract class ASTDelegatePsiElement {
+    public constructor ASTDelegatePsiElement()
+    public final fun bar(): kotlin.Unit
+    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 interface KtFunction {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun foo(): kotlin.Unit
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class KtFunctionLiteral : ASTDelegatePsiElement, KtFunction {
+    public constructor KtFunctionLiteral()
+    public final override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class KtNamedFunction : ASTDelegatePsiElement, KtFunction {
+    public constructor KtNamedFunction()
+    public final override /*1*/ /*fake_override*/ fun bar(): kotlin.Unit
+    public final fun baz(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun foo(): kotlin.Unit
+    public open override /*2*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*2*/ /*fake_override*/ fun toString(): kotlin.String
+}