CommonSupertypes support for flexible types

core/descriptors/src/org/jetbrains/jet/lang/types/CommonSupertypes.java

@@ -47,6 +47,28 @@ public class CommonSupertypes {
 
     @NotNull
     public static JetType commonSupertype(@NotNull Collection<JetType> types) {
+        boolean hasFlexible = false;
+        List<JetType> upper = new ArrayList<JetType>(types.size());
+        List<JetType> lower = new ArrayList<JetType>(types.size());
+        for (JetType type : types) {
+            if (TypesPackage.isFlexible(type)) {
+                hasFlexible = true;
+                FlexibleType flexibleType = (FlexibleType) type;
+                upper.add(flexibleType.getUpperBound());
+                lower.add(flexibleType.getLowerBound());
+            }
+            else {
+                upper.add(type);
+                lower.add(type);
+            }
+        }
+
+        if (!hasFlexible) return commonSuperTypeForInflexible(types);
+        return new DelegatingFlexibleType(commonSuperTypeForInflexible(lower), commonSuperTypeForInflexible(upper));
+    }
+
+    @NotNull
+    private static JetType commonSuperTypeForInflexible(@NotNull Collection<JetType> types) {
         assert !types.isEmpty();
         Collection<JetType> typeSet = new HashSet<JetType>(types);
         if (typeSet.size() == 1) return typeSet.iterator().next();
@@ -57,6 +79,7 @@ public class CommonSupertypes {
         for (Iterator<JetType> iterator = typeSet.iterator(); iterator.hasNext();) {
             JetType type = iterator.next();
             assert type != null;
+            assert !TypesPackage.isFlexible(type) : "Flexible type " + type + " passed to commonSuperTypeForInflexible";
             if (KotlinBuiltIns.getInstance().isNothingOrNullableNothing(type)) {
                 iterator.remove();
             }

core/descriptors/src/org/jetbrains/jet/lang/types/CustomTypeVariable.kt

@@ -22,14 +22,14 @@ import org.jetbrains.jet.lang.descriptors.TypeParameterDescriptor
 // even if it turns out that the type an instance represents is not actually a type variable
 // (i.e. it is not derived from a type parameter), see isTypeVariable
 public trait CustomTypeVariable : JetType {
-    val isTypeVariable: Boolean
+    public val isTypeVariable: Boolean
 
     // If typeParameterDescriptor != null <=> isTypeVariable == true, this is not a type variable
-    val typeParameterDescriptor: TypeParameterDescriptor?
+    public val typeParameterDescriptor: TypeParameterDescriptor?
 
 
     // Throws an exception when isTypeVariable == false
-    fun substitutionResult(replacement: JetType): JetType
+    public fun substitutionResult(replacement: JetType): JetType
 }
 
 fun JetType.isCustomTypeVariable() = (this as? CustomTypeVariable)?.isTypeVariable ?: false

core/descriptors/src/org/jetbrains/jet/lang/types/flexibleTypes.kt

@@ -17,8 +17,8 @@
 package org.jetbrains.jet.lang.types
 
 public trait FlexibleType : JetType {
-    val lowerBound: JetType
-    val upperBound: JetType
+    public val lowerBound: JetType
+    public val upperBound: JetType
 }
 
 public fun JetType.isFlexible(): Boolean = this is FlexibleType