Better equals in FuzzyType + do not need to treat not used parameters as free

idea/ide-common/src/org/jetbrains/kotlin/idea/util/FuzzyType.kt

@@ -43,16 +43,29 @@ fun FuzzyType.makeNotNullable() = FuzzyType(type.makeNotNullable(), freeParamete
 fun FuzzyType.makeNullable() = FuzzyType(type.makeNullable(), freeParameters)
 fun FuzzyType.nullability() = type.nullability()
 
-data class FuzzyType(
+class FuzzyType(
         val type: JetType,
-        val freeParameters: Collection<TypeParameterDescriptor>
+        freeParameters: Collection<TypeParameterDescriptor>
 ) {
-    private val usedTypeParameters: HashSet<TypeParameterDescriptor>? = if (freeParameters.isNotEmpty()) HashSet() else null
+    private val usedTypeParameters: HashSet<TypeParameterDescriptor>?
+    public val freeParameters: Set<TypeParameterDescriptor>
 
     ;{
-        usedTypeParameters?.addUsedTypeParameters(type)
+        if (freeParameters.isNotEmpty()) {
+            usedTypeParameters = HashSet()
+            usedTypeParameters!!.addUsedTypeParameters(type)
+            this.freeParameters = freeParameters.filter { it in usedTypeParameters }.toSet()
+        }
+        else {
+            usedTypeParameters = null
+            this.freeParameters = setOf()
+        }
     }
 
+    override fun equals(other: Any?) = other is FuzzyType && other.type == type && other.freeParameters == freeParameters
+
+    override fun hashCode() = type.hashCode()
+
     private fun MutableSet<TypeParameterDescriptor>.addUsedTypeParameters(type: JetType) {
         addIfNotNull(type.getConstructor().getDeclarationDescriptor() as? TypeParameterDescriptor)
 
@@ -90,9 +103,7 @@ data class FuzzyType(
         val constraintSystem = ConstraintSystemImpl()
         val typeVariables = LinkedHashMap<TypeParameterDescriptor, Variance>()
         for (typeParameter in freeParameters) {
-            if (typeParameter in usedTypeParameters) {
+            typeVariables[typeParameter] = Variance.INVARIANT
-                typeVariables[typeParameter] = Variance.INVARIANT
-            }
         }
         constraintSystem.registerTypeVariables(typeVariables)