diff --git a/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutableProperty.kt b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutableProperty.kt
new file mode 100644
index 00000000000..e0a7fe50732
--- /dev/null
+++ b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutableProperty.kt
@@ -0,0 +1,29 @@
+// IGNORE_BACKEND_K1: ANY
+// ISSUE: KT-63705
+
+fun box(): String {
+    KlassA({})
+    KlassB()
+    return "OK"
+}
+
+class KlassA(arg: (() -> Unit)?) {
+    val func: (() -> Unit)? = arg
+    init {
+        if (func != null) {
+            func()
+        }
+    }
+}
+
+class KlassB {
+    val func: (() -> Unit)?
+    init {
+        if (true) {
+            func = {}
+            func()
+        } else {
+            func = null
+        }
+    }
+}
diff --git a/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutablePropertyFromConstructor.kt b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutablePropertyFromConstructor.kt
new file mode 100644
index 00000000000..8a0dea73bcb
--- /dev/null
+++ b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsMemberImmutablePropertyFromConstructor.kt
@@ -0,0 +1,15 @@
+// IGNORE_BACKEND_K1: ANY
+// ISSUE: KT-63705
+
+fun box(): String {
+    Klass({})
+    return "OK"
+}
+
+class Klass(val func: (() -> Unit)?) {
+    init {
+        if (func != null) {
+            func()
+        }
+    }
+}
diff --git a/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsPrimaryConstructorParameter.kt b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsPrimaryConstructorParameter.kt
new file mode 100644
index 00000000000..366f5c078e4
--- /dev/null
+++ b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsPrimaryConstructorParameter.kt
@@ -0,0 +1,12 @@
+fun box(): String {
+    Klass({})
+    return "OK"
+}
+
+class Klass(func: (() -> Unit)?) {
+    init {
+        if (func != null) {
+            func()
+        }
+    }
+}
diff --git a/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsSecondaryConstructorParameter.kt b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsSecondaryConstructorParameter.kt
new file mode 100644
index 00000000000..2581b812d16
--- /dev/null
+++ b/compiler/testData/codegen/box/smartCasts/NullableFunctionTypeAsSecondaryConstructorParameter.kt
@@ -0,0 +1,12 @@
+fun box(): String {
+    Klass({})
+    return "OK"
+}
+
+class Klass {
+    constructor(func: (() -> Unit)?) {
+        if (func != null) {
+            func()
+        }
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.fir.kt b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.fir.kt
new file mode 100644
index 00000000000..9f7d886550e
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.fir.kt
@@ -0,0 +1,26 @@
+fun box(): String {
+    KlassA({})
+    KlassB()
+    return "OK"
+}
+
+class KlassA(arg: (() -> Unit)?) {
+    var func: (() -> Unit)? = arg
+    init {
+        if (func != null) {
+            <!SMARTCAST_IMPOSSIBLE!>func<!>()
+        }
+    }
+}
+
+class KlassB {
+    var func: (() -> Unit)?
+    init {
+        if (true) {
+            func = {}
+            <!UNSAFE_IMPLICIT_INVOKE_CALL!>func<!>()
+        } else {
+            func = null
+        }
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.kt b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.kt
new file mode 100644
index 00000000000..fcde810067a
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutableProperty.kt
@@ -0,0 +1,26 @@
+fun box(): String {
+    KlassA({})
+    KlassB()
+    return "OK"
+}
+
+class KlassA(arg: (() -> Unit)?) {
+    var func: (() -> Unit)? = arg
+    init {
+        if (func != null) {
+            <!UNSAFE_IMPLICIT_INVOKE_CALL!>func<!>()
+        }
+    }
+}
+
+class KlassB {
+    var func: (() -> Unit)?
+    init {
+        if (true) {
+            func = {}
+            <!UNSAFE_IMPLICIT_INVOKE_CALL!>func<!>()
+        } else {
+            func = null
+        }
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.fir.kt b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.fir.kt
new file mode 100644
index 00000000000..6410483128c
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.fir.kt
@@ -0,0 +1,12 @@
+fun box(): String {
+    Klass({})
+    return "OK"
+}
+
+class Klass(var func: (() -> Unit)?) {
+    init {
+        if (func != null) {
+            <!SMARTCAST_IMPOSSIBLE!>func<!>()
+        }
+    }
+}
diff --git a/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.kt b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.kt
new file mode 100644
index 00000000000..5fe2fcb4d65
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/smartCasts/NullableFunctionTypeAsMemberMutablePropertyFromConstructor.kt
@@ -0,0 +1,12 @@
+fun box(): String {
+    Klass({})
+    return "OK"
+}
+
+class Klass(var func: (() -> Unit)?) {
+    init {
+        if (func != null) {
+            <!UNSAFE_IMPLICIT_INVOKE_CALL!>func<!>()
+        }
+    }
+}