CommonSupertypes support for flexible types

compiler/testData/diagnostics/tests/platformTypes/methodCall/inferenceWithBound.kt

@@ -0,0 +1,41 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: p/Super.java
+
+package p;
+
+public interface Super {
+
+}
+
+// FILE: p/Sub.java
+
+package p;
+
+public interface Sub extends Super {}
+
+// FILE: p/Other.java
+
+package p;
+
+import java.util.*;
+
+public class Other {
+
+    public static Sub sub;
+
+    public static Collection<Sub> subs;
+    public static Collection<Super> supers;
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun test() {
+    val col = if (1 < 2) Other.subs else Other.supers
+    col.foo()
+}
+
+fun <T: Super> Collection<T>.foo(): T = null!!
+fun listOf<T>(t: T): List<T> = null!!

compiler/tests/org/jetbrains/jet/checkers/JetDiagnosticsTestGenerated.java

@@ -7742,6 +7742,11 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/platformTypes/methodCall"), Pattern.compile("^(.+)\\.kt$"), true);
                 }
                 
+                @TestMetadata("inferenceWithBound.kt")
+                public void testInferenceWithBound() throws Exception {
+                    doTest("compiler/testData/diagnostics/tests/platformTypes/methodCall/inferenceWithBound.kt");
+                }
+                
                 @TestMetadata("int.kt")
                 public void testInt() throws Exception {
                     String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/methodCall/int.kt");

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