diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.1.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.1.fir.kt
new file mode 100644
index 00000000000..a7279a1bb28
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.1.fir.kt
@@ -0,0 +1,69 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (NEGATIVE)
+ *
+ * SPEC VERSION: 0.1-100
+ * PLACE: type-system, introduction-1 -> paragraph 6 -> sentence 2
+ * NUMBER: 1
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1() {
+    val x: Int = null
+}
+
+// TESTCASE NUMBER: 2
+fun case_2() {
+    val x: Any = null
+}
+
+// TESTCASE NUMBER: 3
+fun case_3() {
+    val x: Nothing = null
+}
+
+// TESTCASE NUMBER: 4
+fun case_4() {
+    var x: Int = null
+}
+
+// TESTCASE NUMBER: 5
+fun case_5() {
+    var x: Any = null
+}
+
+// TESTCASE NUMBER: 6
+fun case_6() {
+    var x: Nothing = null
+}
+
+// TESTCASE NUMBER: 7
+fun case_7() {
+    val x: Int
+    x = null
+}
+
+// TESTCASE NUMBER: 8
+fun case_8() {
+    var x: Int = 10
+    x = null
+}
+
+// TESTCASE NUMBER: 9
+fun case_9() {
+    val x = null
+    val y: Int = x
+}
+
+// TESTCASE NUMBER: 10
+fun case_10(x: Int?) {
+    var y = 10
+    y = x
+}
+
+// TESTCASE NUMBER: 11
+fun case_11(x: Int?, y: Int = x) = null
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.2.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.2.fir.kt
new file mode 100644
index 00000000000..acd3ec43365
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.2.fir.kt
@@ -0,0 +1,101 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (NEGATIVE)
+ *
+ * SPEC VERSION: 0.1-100
+ * PLACE: type-system, introduction-1 -> paragraph 6 -> sentence 2
+ * NUMBER: 2
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1(x: Int = null) {
+    println(x)
+}
+
+// TESTCASE NUMBER: 2
+fun case_2(x: Any = null) {
+    println(x)
+}
+
+// TESTCASE NUMBER: 3
+fun case_3(x: Nothing = null) {
+    <!AMBIGUITY!>println<!>(x)
+}
+
+// TESTCASE NUMBER: 4
+class Case4(x: Int = null)
+
+// TESTCASE NUMBER: 5
+class Case5 constructor(x: Any = null)
+
+// TESTCASE NUMBER: 6
+class Case6 {
+    fun foo(x: Nothing = null) {}
+}
+
+// TESTCASE NUMBER: 7
+class Case7 {
+    val x: Int get() = null
+}
+
+// TESTCASE NUMBER: 8
+class Case8 {
+    var x: Any = 0
+        get() = 0
+        set(value) {
+            field = null
+        }
+}
+
+// TESTCASE NUMBER: 9
+fun case_9(): Any = null
+
+// TESTCASE NUMBER: 10
+fun case_10(x: Int, y: Boolean): Any = if (y) x else null
+
+// TESTCASE NUMBER: 11
+fun case_11(x: Int, y: Boolean): Any = if (y) x else null
+
+// TESTCASE NUMBER: 12
+class Case12 {
+    val x: Any
+    var y: Any
+    var z: Any
+    init {
+        x = null
+        y = null
+        z = 10
+        z = null
+    }
+}
+
+// TESTCASE NUMBER: 13
+open class Case13_1 {
+    open val x: Int = 10
+}
+
+class Case13: Case13_1() {
+    override val x = null
+}
+
+// TESTCASE NUMBER: 14
+abstract class Case14_1 {
+    abstract val x: Int
+}
+
+class Case14: Case14_1() {
+    override val x = null
+}
+
+// TESTCASE NUMBER: 15
+interface Case15_1 {
+    fun foo(): Int = 10
+}
+
+class Case15(): Case15_1 {
+    override fun foo() = null
+}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.3.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.3.fir.kt
new file mode 100644
index 00000000000..7d1a3f695b5
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-6/neg/2.3.fir.kt
@@ -0,0 +1,39 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (NEGATIVE)
+ *
+ * SPEC VERSION: 0.1-100
+ * PLACE: type-system, introduction-1 -> paragraph 6 -> sentence 2
+ * NUMBER: 3
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ */
+
+// TESTCASE NUMBER: 1
+fun <T: Any> case_1(x: T = null) {
+    println(x)
+}
+
+// TESTCASE NUMBER: 2
+fun <T: K, K: Number> case_2(x: T = null) {
+    println(x)
+}
+
+// TESTCASE NUMBER: 3
+fun <K: Number> case_3() {
+    class Case4<T: K> (x: T = null)
+}
+
+// TESTCASE NUMBER: 4
+fun <T> case_4() {
+    class Case4(x: T = null)
+}
+
+// TESTCASE NUMBER: 5
+fun <T, K> case_5(x: T) where T: Number?, K: Number {
+    if (x == null) {
+        class Case5 constructor(y: K = x)
+    }
+}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/1.1.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/1.1.fir.kt
new file mode 100644
index 00000000000..eabdd76c4bb
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/1.1.fir.kt
@@ -0,0 +1,84 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
+ *
+ * SPEC VERSION: 0.1-296
+ * PLACE: type-system, introduction-1 -> paragraph 8 -> sentence 1
+ * RELEVANT PLACES: type-system, type-kinds, built-in-types, kotlin.any -> paragraph 1 -> sentence 1
+ * NUMBER: 1
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ * HELPERS: checkType
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1() {
+    checkSubtype<Any?>(10)
+}
+
+// TESTCASE NUMBER: 2
+fun case_2(x: String) {
+    checkSubtype<Any?>(x)
+}
+
+// TESTCASE NUMBER: 3
+class Case3(val x: String, val y: Any? = checkSubtype<Any?>(x))
+
+// TESTCASE NUMBER: 4
+class Case4(val x: String, val y: Any? = checkSubtype<Any?>(throw Exception()))
+
+// TESTCASE NUMBER: 5
+fun case_5() {
+    checkSubtype<Any?>(return)
+}
+
+// TESTCASE NUMBER: 6
+fun case_6() {
+    while (true) {
+        checkSubtype<Any?>(break)
+    }
+}
+
+// TESTCASE NUMBER: 7
+fun case_7(x: Boolean) {
+    while (x) {
+        checkSubtype<Any?>(continue)
+    }
+}
+
+// TESTCASE NUMBER: 8
+fun case_8(x: Boolean) {
+    checkSubtype<Any?>({}())
+}
+
+// TESTCASE NUMBER: 9
+fun case_9(x: Boolean) {
+    checkSubtype<Any?>(kotlin.Unit)
+}
+
+// TESTCASE NUMBER: 10
+fun case_10(x: Boolean) {
+    checkSubtype<Any?>({while (true) {}}())
+}
+
+// TESTCASE NUMBER: 11
+fun <T> case_11(x: T) {
+    checkSubtype<Any?>(x)
+}
+
+// TESTCASE NUMBER: 12
+class Case12<K> {
+    inline fun <reified T: K> case_12(x: T) {
+        checkSubtype<Any?>(x)
+    }
+}
+
+// TESTCASE NUMBER: 13
+class Case13<K> {
+    inline fun <reified T: K> case_12(x: T) {
+        x!!
+        checkSubtype<Any?>(x)
+    }
+}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/2.1.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/2.1.fir.kt
new file mode 100644
index 00000000000..ce185564a5f
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/introduction-1/p-8/pos/2.1.fir.kt
@@ -0,0 +1,87 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -UNREACHABLE_CODE
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
+ *
+ * SPEC VERSION: 0.1-100
+ * PLACE: type-system, introduction-1 -> paragraph 8 -> sentence 2
+ * NUMBER: 1
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ * HELPERS: checkType
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1() {
+    checkSubtype<Any?>(return)
+}
+
+// TESTCASE NUMBER: 2
+fun case_2(x: Nothing) {
+    checkSubtype<Nothing>(x)
+}
+
+// TESTCASE NUMBER: 3
+class Case3(val x: Any? = checkSubtype<Nothing?>(throw Exception()))
+
+// TESTCASE NUMBER: 4
+class Case4(val x: Nothing, val y: Any? = checkSubtype<Int>(x))
+
+// TESTCASE NUMBER: 5
+fun case_5() {
+    checkSubtype<Unit>(null!!)
+}
+
+// TESTCASE NUMBER: 6
+fun <T> case_6() {
+    while (true) {
+        checkSubtype<Comparable<T>>(break)
+    }
+}
+
+// TESTCASE NUMBER: 7
+fun <T> case_7(x: Boolean) {
+    while (x) {
+        checkSubtype<T>(continue)
+    }
+}
+
+// TESTCASE NUMBER: 8
+class Case8<K> {
+    inline fun <reified T: K, L: Nothing?> case_12(x: L) {
+        x!!
+        checkSubtype<K>(x)
+    }
+}
+
+// TESTCASE NUMBER: 9
+inline fun <reified L: Nothing?> case_9(x: L) = x!! as Int
+
+// TESTCASE NUMBER: 10
+fun <K> case_10(x: Nothing) = x as Iterable<K>
+
+// TESTCASE NUMBER: 11
+fun case_11() {
+    return as Nothing?
+}
+
+// TESTCASE NUMBER: 12
+fun case_12() = (throw Exception()) as String
+
+// TESTCASE NUMBER: 13
+fun case_13() = null as Float?
+
+// TESTCASE NUMBER: 14
+inline fun <reified T, K> case_14() {
+    while (true) {
+        break as Map<T, K>
+    }
+}
+
+// TESTCASE NUMBER: 15
+inline fun <reified T> case_15() {
+    while (true) {
+        continue as T
+    }
+}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.any/p-1/pos/1.2.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.any/p-1/pos/1.2.fir.kt
new file mode 100644
index 00000000000..32d69e115af
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.any/p-1/pos/1.2.fir.kt
@@ -0,0 +1,107 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER
+// !LANGUAGE: +NewInference
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
+ *
+ * SPEC VERSION: 0.1-296
+ * PLACE: type-system, type-kinds, built-in-types, kotlin.any -> paragraph 1 -> sentence 1
+ * RELEVANT PLACES: type-system, introduction-1 -> paragraph 7 -> sentence 1
+ * NUMBER: 2
+ * DESCRIPTION: The use of Boolean literals as the identifier (with backtick) in the class.
+ * HELPERS: checkType, functions
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1() {
+    checkSubtype<Any>("")
+    val x: Any = ""
+    funWithAnyArg("")
+    checkSubtype<Any>("""
+        ………
+    """)
+    val y: Any = """0"""
+    funWithAnyArg("""
+        =====
+    """.trimIndent())
+}
+
+// TESTCASE NUMBER: 2
+fun case_2() {
+    checkSubtype<Any>(0)
+    fun z(): Any = 0
+    funWithAnyArg(0)
+}
+
+// TESTCASE NUMBER: 3
+fun case_3() {
+    checkSubtype<Any>(-0f)
+    fun z(): Any = -.10000e1
+    funWithAnyArg(10.1)
+}
+
+// TESTCASE NUMBER: 4
+fun case_4() {
+    checkSubtype<Any>(throw Exception())
+    var z1: Any = return@case_4
+    while (true) {
+        funWithAnyArg(break)
+    }
+    checkSubtype<Any>(null!!)
+    fun z2(): Any = null!!
+    funWithAnyArg(null!!)
+}
+
+// TESTCASE NUMBER: 5
+fun case_5() {
+    checkSubtype<Any>('1')
+    var z: Any = 'a'
+    funWithAnyArg('…')
+}
+
+// TESTCASE NUMBER: 6
+fun case_6() {
+    checkSubtype<Any>({})
+    val z: Any = { x: Any -> println(x) }
+    funWithAnyArg {}
+}
+
+// TESTCASE NUMBER: 7
+fun case_7() {
+    checkSubtype<Any>(object {})
+    val z: Any = { x: Any -> object { val y = x } }(10)
+    funWithAnyArg(object : Comparable<Any> {
+        override fun compareTo(other: Any) = TODO()
+    })
+}
+
+// TESTCASE NUMBER: 8
+fun case_8() {
+    checkSubtype<Any>(object {}::class)
+    val z: Any = {}::class
+    funWithAnyArg(0E0::class)
+}
+
+// TESTCASE NUMBER: 9
+fun case_9() {
+    checkSubtype<Any>(object {}::class)
+    val z: Any = {}::class
+    funWithAnyArg(0E0::class)
+}
+
+// TESTCASE NUMBER: 10
+fun case_10() {
+    checkSubtype<Any>(0 + 0.0)
+    val z: Any = if (true) "" else '"'
+    label@ {
+        funWithAnyArg(return@label)
+    }
+}
+
+// TESTCASE NUMBER: 11
+fun case_11() {
+    checkSubtype<Any>(Any())
+    val z: Any = if (true) Any() else Any()
+    funWithAnyArg(Any())
+}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.nothing/p-1/neg/2.1.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.nothing/p-1/neg/2.1.fir.kt
new file mode 100644
index 00000000000..d616953c7f1
--- /dev/null
+++ b/compiler/tests-spec/testData/diagnostics/linked/type-system/type-kinds/built-in-types/kotlin.nothing/p-1/neg/2.1.fir.kt
@@ -0,0 +1,32 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION -UNREACHABLE_CODE
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS SPEC TEST (NEGATIVE)
+ *
+ * SPEC VERSION: 0.1-213
+ * PLACE: type-system, type-kinds, built-in-types, kotlin.nothing -> paragraph 1 -> sentence 2
+ * NUMBER: 1
+ * DESCRIPTION: Check of Nothing type
+ * HELPERS: checkType
+ */
+
+
+// TESTCASE NUMBER: 1
+class Case1(val nothing: Nothing)
+
+fun case1() {
+    val res = Case1(<!INAPPLICABLE_CANDIDATE!>Nothing<!>())
+}
+
+
+// TESTCASE NUMBER: 2
+class Case2 {
+    var data: String? = null
+}
+
+fun case2(c: Case2) {
+    val testValue = c.data ?: throw IllegalArgumentException("data required")
+    testValue checkType { <!INAPPLICABLE_CANDIDATE!>check<!><Nothing>() }
+}