Added check for incompatible variance modifiers and repeated modifiers

compiler/testData/diagnostics/tests/modifiers/incompatibleVarianceModifiers.kt

@@ -0,0 +1,23 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+
+trait Foo<T>
+trait Foo1<<!INCOMPATIBLE_MODIFIERS!>in<!> <!INCOMPATIBLE_MODIFIERS!>out<!> T>
+trait Foo2<<!REPEATED_MODIFIER!>in<!> <!REPEATED_MODIFIER!>in<!> T>
+
+fun test1(foo: Foo<<!INCOMPATIBLE_MODIFIERS!>in<!> <!INCOMPATIBLE_MODIFIERS!>out<!> Int>) = foo
+fun test2(): Foo<<!REPEATED_MODIFIER!>in<!> <!REPEATED_MODIFIER!>in<!> Int> = throw Exception()
+
+fun test3() {
+    val f: Foo<<!REPEATED_MODIFIER!>out<!> <!REPEATED_MODIFIER!>out<!> <!REPEATED_MODIFIER!>out<!> <!REPEATED_MODIFIER!>out<!> Int>
+
+    class Bzz<<!REPEATED_MODIFIER!>in<!> <!REPEATED_MODIFIER!>in<!> T>
+}
+
+class A {
+    fun <<!VARIANCE_ON_TYPE_PARAMETER_OF_FUNCTION_OR_PROPERTY, REPEATED_MODIFIER!>out<!> <!REPEATED_MODIFIER!>out<!> T> bar() {
+    }
+}
+
+fun test4(a: A) {
+    a.bar<<!PROJECTION_ON_NON_CLASS_TYPE_ARGUMENT, REPEATED_MODIFIER!>out<!> <!REPEATED_MODIFIER!>out<!> Int>()
+}