[Test] KT-61360: add tests for the IrFakeOverrideBuilder

Add tests for fake overrides with focus on java interoperability

Co-authored-by: Aleksandra Arsenteva <aleksandra.arsenteva@jetbrains.com>

compiler/testData/ir/irText/fakeOverrides/charsequence/javaCharSequenceOverride.kt

@@ -0,0 +1,207 @@
+// TARGET_BACKEND: JVM
+// FULL_JDK
+// WITH_STDLIB
+// MUTE_SIGNATURE_COMPARISON_K2: JVM_IR
+
+// FILE: Java1.java
+import org.jetbrains.annotations.NotNull;
+
+public class Java1 implements CharSequence {
+
+    @Override
+    public int length() {
+        return 0;
+    }
+
+    @Override
+    public char charAt(int index) {
+        return 0;
+    }
+
+    @NotNull
+    @Override
+    public CharSequence subSequence(int start, int end) {
+        return null;
+    }
+}
+
+// FILE: Java2.java
+import java.util.stream.IntStream;
+
+public interface Java2  {
+    public IntStream codePoints();
+}
+
+// FILE: Java3.java
+import java.util.stream.IntStream;
+
+public interface Java3  {
+    public String toString();
+    public IntStream codePoints();
+}
+
+// FILE: Java4.java
+public abstract class Java4 implements A { }
+
+// FILE: 1.kt
+import java.util.stream.IntStream
+
+interface A : java.lang.CharSequence   //Kotlin ← Java
+
+class B : A {
+    override fun length(): Int {
+        return 1
+    }
+
+    override fun charAt(index: Int): Char {
+        return '1'
+    }
+
+    override fun subSequence(start: Int, end: Int): CharSequence {
+        return null!!
+    }
+}
+
+class C : Java1()   //Kotlin ← Java1 ← Java2
+
+class D : Java1() {
+    override val length: Int
+        get() = 10
+
+    override fun get(index: Int): Char {
+        return 'a'
+    }
+}
+
+class E : Java1(), Java2 {  //Kotlin ← Java1, Java2 ← Java3
+    override fun codePoints(): IntStream {
+        return null!!
+    }
+}
+
+class F : Java1(), KotlinInterface {  //Kotlin ← Java, Kotlin2
+    override operator fun get(index: Number): Char {
+        return 'a'
+    }
+}
+
+class G : Java1(), KotlinInterface {
+    override fun get(index: Int): Char {
+        return 'a'
+    }
+    override operator fun get(index: Number): Char {
+        return 'b'
+    }
+}
+
+class H : Java1(), Java2, KotlinInterface {  //Kotlin ← Java1, Java2, Kotlin2
+    override operator fun get(index: Number): Char {
+        return 'a'
+    }
+
+    override fun codePoints(): IntStream {
+        return null!!
+    }
+}
+
+class I : Java1(), Java2, Java3 {   //Kotlin ← Java1, Java2, Java3
+    override fun codePoints(): IntStream {
+        return null!!
+    }
+
+}
+
+abstract class J : Java4()   // Kotlin ← Java ← Kotlin ← Java
+
+class K : Java4() {
+    override fun length(): Int {
+        return 1
+    }
+
+    override fun charAt(index: Int): Char {
+        return 'a'
+    }
+
+    override fun subSequence(start: Int, end: Int): CharSequence {
+        return null!!
+    }
+}
+
+abstract class L : Java1(), A {         // Kotlin ← Java, Kotlin2 ← Java2, Java3
+    override fun chars(): IntStream {
+        return null!!
+    }
+    override fun codePoints(): IntStream {
+        return null!!
+    }
+}
+
+abstract class M : Java1(), java.lang.CharSequence {    //Kotlin ← Java1, Java2
+    override fun chars(): IntStream {
+        return null!!
+    }
+
+    override fun codePoints(): IntStream {
+        return null!!
+    }
+}
+
+interface KotlinInterface {
+    val length: Number
+    fun get(index: Number): Char
+}
+
+fun test(a: A, b: B, c: C, d: D, e: E, f: F, g: G, h: H, i: I, j: J, k: K, l: L, m: M) {
+    a.length()
+    a.charAt(1)
+    a.chars()
+    a.toString()
+
+    b.length()
+    b.charAt(1)
+    b.subSequence(1,2)
+
+    c.length
+    c[1]
+    c.chars()
+
+    d.length
+    d[1]
+    d.isEmpty()
+
+    e.length
+    e[1]
+    e.isEmpty()
+    e.codePoints()
+
+    f.length
+    f.isEmpty()
+    f[1]
+
+    g.length
+    g[1]
+
+    h.length
+    h[1]
+    h.codePoints()
+
+    i.length
+    i.isEmpty()
+    i[1]
+    i.codePoints()
+
+    j.length()
+    j.charAt(1)
+
+    k.charAt(1)
+    k.length()
+
+    l.length
+    l[1]
+    l.length()
+
+    m.length
+    m.length()
+    m[1]
+    m.get(1)
+}