Added tests on labels

#KT-1703 Fixed
 #KT-361 Fixed
 #KT-3920 Fixed
 #KT-3988 Fixed
 #KT-4247 Fixed
 #KT-4586 Fixed
 #KT-4603 Fixed
 #KT-591 Fixed

compiler/testData/diagnostics/tests/labels/kt1703.kt

@@ -0,0 +1,15 @@
+//KT-1703 Reference to label is unresolved
+
+fun test() {
+    val ints = Array<Int?>(2, { null })
+    ints.forEach @lit {
+        if (it == null) <!RETURN_NOT_ALLOWED_EXPLICIT_RETURN_TYPE_REQUIRED!>return @lit<!>
+        use(<!DEBUG_INFO_AUTOCAST!>it<!> + 5)
+    }
+}
+
+fun <T> Array<out T>.forEach(operation: (T) -> Unit) {
+    for (element in this) operation(element)
+}
+
+fun use(a: Any?) = a

compiler/testData/diagnostics/tests/labels/kt361.kt

@@ -0,0 +1,12 @@
+fun nonlocals(b : Boolean) {
+    @a{(): Int ->
+        fun foo() {
+            if (b) {
+                <!RETURN_NOT_ALLOWED!>return@a 1<!> // The label must be resolved, but an error should be reported for a non-local return
+            }
+        }
+
+        return@a 5
+    }
+}
+

compiler/testData/diagnostics/tests/labels/kt3920.kt

@@ -0,0 +1,11 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+//KT-3920 Labeling information is lost when passing through some expressions
+
+fun test() {
+    run @f{ (): Int ->
+        val x = if (1 > 2) return@f 1 else 2
+        2
+    }
+}
+
+fun <T> run(f: () -> T): T = f()

compiler/testData/diagnostics/tests/labels/kt3988.kt

@@ -0,0 +1,21 @@
+//KT-3988 This@label for outer function not resolved
+
+class Comment() {
+    var article = ""
+
+}
+class Comment2() {
+    var article2 = ""
+}
+
+fun new(body: Comment.() -> Unit) = body
+
+fun new2(body: Comment2.() -> Unit) = body
+
+fun main(args: Array<String>) {
+    new {
+        new2 {
+            this@new //UNRESOLVED REFERENCE
+        }
+    }
+}

compiler/testData/diagnostics/tests/labels/kt4247.kt

@@ -0,0 +1,11 @@
+//KT-4247 LABEL_NAME_CLASH
+
+fun foo(bar1: (String.() -> Int) -> Int) {
+    bar1 {
+        this.length
+    }
+
+    bar1 {
+        this@bar1.length
+    }
+}

compiler/testData/diagnostics/tests/labels/kt4586.kt

@@ -0,0 +1,17 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+//KT-4586 this@ does not work for builders
+
+fun string(init: StringBuilder.() -> Unit): String{
+    val answer = StringBuilder()
+    answer.init()
+    return answer.toString()
+}
+
+val str = string @l{
+    append("hello, ")
+
+    val sub = string {
+        append("world!")
+        this@l.append(this)
+    }
+}

compiler/testData/diagnostics/tests/labels/kt4603.kt

@@ -0,0 +1,12 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+//KT-4603 Labeling information is lost when passing through local classes or objects
+
+fun foo() {
+    val s = @l{ Int.() ->
+        class Local(val y: Int = this@l) {
+            fun bar() {
+                val x: Int = this@l //unresolved
+            }
+        }
+    }
+}

compiler/testData/diagnostics/tests/labels/kt591.kt

@@ -0,0 +1,11 @@
+//KT-591 Unresolved label in valid code
+
+fun test() {
+    val <!UNUSED_VARIABLE!>a<!> = @a{(Int?).() ->
+        if (this != null) {
+            val <!UNUSED_VARIABLE!>b<!> = {String.() ->
+                <!DEBUG_INFO_AUTOCAST!>this@a<!>.times(5) // @a Unresolved
+            }
+        }
+    }
+}

compiler/testData/diagnostics/tests/labels/labelReferencesInsideObjectExpressions.kt

@@ -0,0 +1,25 @@
+trait A {
+    fun foo()
+}
+
+trait B {
+    fun bar()
+}
+
+fun B.b() {
+    object : A {
+        override fun foo() {
+            this@b.bar()
+        }
+    }
+}
+
+fun test() {
+    @b { B.() ->
+        object : A {
+            override fun foo() {
+                this@b.bar()
+            }
+        }
+    }
+}