UNUSED_TYPEALIAS_PARAMETER: special diagnostic for typealias parameters

explicitly telling that such type parameters are not used in type checking.
Move typealias-related utility functions on types to TypeUtils.kt.

compiler/testData/diagnostics/tests/typealias/genericTypeAliasObject.kt

@@ -3,7 +3,7 @@ object AnObject {
     fun foo() = "OK"
 }
 
-typealias GenericTestObject<T> = AnObject
+typealias GenericTestObject<<!UNUSED_TYPEALIAS_PARAMETER!>T<!>> = AnObject
 
 val test11: AnObject = GenericTestObject
 val test12: GenericTestObject<*> = GenericTestObject

compiler/testData/diagnostics/tests/typealias/parameterRestrictions.kt

@@ -1,3 +1,5 @@
+// !DIAGNOSTICS: -UNUSED_TYPEALIAS_PARAMETER
+
 typealias WithVariance<<!VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED!>in<!> X, <!VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED!>out<!> Y> = Int
 typealias WithBounds1<T : <!BOUND_ON_TYPE_ALIAS_PARAMETER_NOT_ALLOWED!>T<!>> = Int
 typealias WithBounds2<X : <!BOUND_ON_TYPE_ALIAS_PARAMETER_NOT_ALLOWED!>Y<!>, Y : <!BOUND_ON_TYPE_ALIAS_PARAMETER_NOT_ALLOWED!>X<!>> = Int

compiler/testData/diagnostics/tests/typealias/substitutionVariance.kt

@@ -5,16 +5,16 @@ class Inv<T>
 typealias In1<T> = In<T>
 typealias In2<T> = In<<!REDUNDANT_PROJECTION!>in<!> T>
 typealias In3<T> = In<<!CONFLICTING_PROJECTION!>out<!> T>
-typealias In4<T> = In<*>
+typealias In4<<!UNUSED_TYPEALIAS_PARAMETER!>T<!>> = In<*>
 
 typealias Out1<T> = Out<T>
 typealias Out2<T> = Out<<!CONFLICTING_PROJECTION!>in<!> T>
 typealias Out3<T> = Out<<!REDUNDANT_PROJECTION!>out<!> T>
-typealias Out4<T> = Out<*>
+typealias Out4<<!UNUSED_TYPEALIAS_PARAMETER!>T<!>> = Out<*>
 
 typealias Inv1<T> = Inv<T>
 typealias Inv2<T> = Inv<in T>
 typealias Inv3<T> = Inv<out T>
-typealias Inv4<T> = Inv<*>
+typealias Inv4<<!UNUSED_TYPEALIAS_PARAMETER!>T<!>> = Inv<*>
 
 val inv1: Inv1<Int> = Inv<Int>()

compiler/testData/diagnostics/tests/typealias/typeAliasShouldExpandToClass.kt

@@ -1,6 +1,6 @@
 typealias ToTypeParam1<T> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>T<!>
 typealias ToTypeParam2<T> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam1<T><!>
-typealias ToTypeParam3<T1, T2> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam2<T1><!>
+typealias ToTypeParam3<T1, <!UNUSED_TYPEALIAS_PARAMETER!>T2<!>> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam2<T1><!>
 typealias ToTypeParam4 = ToTypeParam1<Any>
 
 typealias ToFun1 = () -> Unit
@@ -9,6 +9,6 @@ typealias ToFun2<T> = (T) -> Unit
 class Outer {
     typealias ToTypeParam1<T> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>T<!>
     typealias ToTypeParam2<T> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam1<T><!>
-    typealias ToTypeParam3<T1, T2> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam2<T1><!>
+    typealias ToTypeParam3<T1, <!UNUSED_TYPEALIAS_PARAMETER!>T2<!>> = <!TYPEALIAS_SHOULD_EXPAND_TO_CLASS!>ToTypeParam2<T1><!>
     typealias ToTypeParam4 = ToTypeParam1<Any>
 }

compiler/testData/diagnostics/tests/typealias/unusedTypeAliasParameter.kt

@@ -0,0 +1,2 @@
+typealias Test<T, <!UNUSED_TYPEALIAS_PARAMETER!>X<!>> = List<T>
+typealias Test2<T, <!UNUSED_TYPEALIAS_PARAMETER!>X<!>> = Test<T, X>

compiler/testData/diagnostics/tests/typealias/unusedTypeAliasParameter.txt

@@ -0,0 +1,4 @@
+package
+
+public typealias Test</*0*/ T, /*1*/ X>  = kotlin.collections.List<T>
+public typealias Test2</*0*/ T, /*1*/ X>  = Test<T, X>