Fix JetType.equals(): flexible types are not equal to non-flexible ones, when we store them in a HashSet

compiler/frontend/src/org/jetbrains/jet/lang/types/expressions/BasicExpressionTypingVisitor.java

@@ -1081,7 +1081,12 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         JetType type = resolvedCall.getResultingDescriptor().getReturnType();
         if (type == null || rightType == null) return JetTypeInfo.create(null, dataFlowInfo);
 
-        return JetTypeInfo.create(TypeUtils.makeNullableAsSpecified(type, rightType.isNullable()), dataFlowInfo);
+        // Sometimes return type for special call for elvis operator might be nullable,
+        // but result is not nullable if the right type is not nullable
+        if (!TypeUtils.isNullableType(rightType) && TypeUtils.isNullableType(type)) {
+            type = TypeUtils.makeNotNullable(type);
+        }
+        return JetTypeInfo.create(type, dataFlowInfo);
     }
 
     @NotNull

compiler/testData/diagnostics/tests/inference/immutableArrayList.kt

@@ -0,0 +1,17 @@
+// FILE: p/J.java
+package p;
+
+public interface J {
+    public interface Super<T> {}
+    public interface Sub<T> extends Super<T> {}
+}
+
+// FILE: k.kt
+
+import p.J.*
+
+class Foo<T>: Sub<T> {
+    fun foo(): Super<T> {
+        return <!TYPE_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>Foo<!>()
+    }
+}

compiler/testData/diagnostics/tests/inference/immutableArrayList.txt

@@ -0,0 +1,9 @@
+package
+
+internal final class Foo</*0*/ T> : p.J.Sub<T> {
+    public constructor Foo</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal final fun foo(): p.J.Super<T>
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/testData/diagnostics/tests/platformTypes/commonSupertype/typeOfElvis.kt

@@ -0,0 +1,20 @@
+// FILE: p/J.java
+
+package p;
+
+public class J {
+    public static J j() { return null; }
+}
+
+// FILE: k.kt
+
+import p.*
+
+fun foo(): J? = null
+
+fun main(args: Array<String>) {
+    val v = foo() ?: J.j()
+    if (v != null) {
+
+    }
+}

compiler/testData/diagnostics/tests/platformTypes/commonSupertype/typeOfElvis.txt

@@ -0,0 +1,4 @@
+package
+
+internal fun foo(): p.J?
+internal fun main(/*0*/ args: kotlin.Array<kotlin.String>): kotlin.Unit

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

@@ -4865,6 +4865,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
             
+            @TestMetadata("immutableArrayList.kt")
+            public void testImmutableArrayList() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/immutableArrayList.kt");
+                doTest(fileName);
+            }
+            
             @TestMetadata("inferInFunctionLiterals.kt")
             public void testInferInFunctionLiterals() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/inference/inferInFunctionLiterals.kt");
@@ -7799,6 +7805,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                     doTest(fileName);
                 }
                 
+                @TestMetadata("typeOfElvis.kt")
+                public void testTypeOfElvis() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/platformTypes/commonSupertype/typeOfElvis.kt");
+                    doTest(fileName);
+                }
+                
             }
             
             @TestMetadata("compiler/testData/diagnostics/tests/platformTypes/methodCall")

core/descriptors/src/org/jetbrains/jet/lang/resolve/DescriptorUtils.java

@@ -31,6 +31,7 @@ import org.jetbrains.jet.lang.types.ErrorUtils;
 import org.jetbrains.jet.lang.types.JetType;
 import org.jetbrains.jet.lang.types.LazyType;
 import org.jetbrains.jet.lang.types.TypeConstructor;
+import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
 
 import java.util.ArrayList;
@@ -397,9 +398,9 @@ public class DescriptorUtils {
 
         KotlinBuiltIns builtIns = KotlinBuiltIns.getInstance();
         return builtIns.isPrimitiveType(type) ||
-               builtIns.getStringType().equals(type) ||
-               builtIns.getNumber().getDefaultType().equals(type) ||
-               builtIns.getAnyType().equals(type);
+               JetTypeChecker.DEFAULT.equalTypes(builtIns.getStringType(), type) ||
+               JetTypeChecker.DEFAULT.equalTypes(builtIns.getNumber().getDefaultType(), type) ||
+               JetTypeChecker.DEFAULT.equalTypes(builtIns.getAnyType(), type);
     }
 
     public static boolean classCanHaveAbstractMembers(@NotNull ClassDescriptor classDescriptor) {

core/descriptors/src/org/jetbrains/jet/lang/resolve/calls/inference/ConstraintSystemImpl.java

@@ -23,6 +23,7 @@ import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.descriptors.ClassifierDescriptor;
 import org.jetbrains.jet.lang.descriptors.TypeParameterDescriptor;
 import org.jetbrains.jet.lang.types.*;
+import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
 import org.jetbrains.jet.lang.types.checker.TypeCheckingProcedure;
 import org.jetbrains.jet.lang.types.checker.TypingConstraints;
 import org.jetbrains.jet.lang.types.lang.KotlinBuiltIns;
@@ -388,7 +389,7 @@ public class ConstraintSystemImpl implements ConstraintSystem {
 
         // can be equal for the recursive invocations:
         // fun <T> foo(i: Int) : T { ... return foo(i); } => T <: T
-        if (subType.equals(superType)) return;
+        if (JetTypeChecker.DEFAULT.equalTypes(subType, superType)) return;
 
         assert !isMyTypeVariable(subType) || !isMyTypeVariable(superType) :
                 "The constraint shouldn't contain different type variables on both sides: " + subType + " <: " + superType;

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

@@ -49,7 +49,7 @@ public abstract class AbstractJetType implements JetType {
 
         JetType type = (JetType) obj;
 
-        return isNullable() == type.isNullable() && JetTypeChecker.DEFAULT.equalTypes(this, type);
+        return isNullable() == type.isNullable() && JetTypeChecker.FLEXIBLE_UNEQUAL_TO_INFLEXIBLE.equalTypes(this, type);
     }
 
     @Override

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

@@ -20,6 +20,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.jet.lang.descriptors.annotations.Annotations;
 import org.jetbrains.jet.lang.resolve.scopes.JetScope;
+import org.jetbrains.jet.lang.types.checker.JetTypeChecker;
 
 import java.util.List;
 
@@ -77,7 +78,11 @@ public abstract class DelegatingType implements JetType {
 
     @Override
     public boolean equals(Object obj) {
-        return getDelegate().equals(obj);
+        if (this == obj) return true;
+        if (!(obj instanceof JetType)) return false;
+
+        JetType type = (JetType) obj;
+        return JetTypeChecker.FLEXIBLE_UNEQUAL_TO_INFLEXIBLE.equalTypes(this, type);
     }
 
     @Override

core/descriptors/src/org/jetbrains/jet/lang/types/checker/JetTypeChecker.java

@@ -28,6 +28,13 @@ public class JetTypeChecker {
 
     public static final JetTypeChecker DEFAULT = new JetTypeChecker(new TypeCheckingProcedure(new TypeCheckerTypingConstraints()));
 
+    public static final JetTypeChecker FLEXIBLE_UNEQUAL_TO_INFLEXIBLE = new JetTypeChecker(new TypeCheckingProcedure(new TypeCheckerTypingConstraints()) {
+        @Override
+        protected boolean heterogeneousEquivalence(JetType inflexibleType, JetType flexibleType) {
+            return false;
+        }
+    });
+
     @NotNull
     public static JetTypeChecker withAxioms(@NotNull final TypeConstructorEquality equalityAxioms) {
         return new JetTypeChecker(new TypeCheckingProcedure(new TypeCheckerTypingConstraints() {

core/descriptors/src/org/jetbrains/jet/lang/types/checker/TypeCheckingProcedure.java

@@ -118,7 +118,7 @@ public class TypeCheckingProcedure {
         return true;
     }
 
-    private boolean heterogeneousEquivalence(JetType inflexibleType, JetType flexibleType) {
+    protected boolean heterogeneousEquivalence(JetType inflexibleType, JetType flexibleType) {
         // This is to account for the case when we have Collection<X> vs (Mutable)Collection<X>! or K(java.util.Collection<? extends X>)
         assert !TypesPackage.isFlexible(inflexibleType) : "Only inflexible types are allowed here: " + inflexibleType;
         return isSubtypeOf(TypesPackage.flexibility(flexibleType).getLowerBound(), inflexibleType)