Supported variance propagation.

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritVariance.java

@@ -0,0 +1,20 @@
+package test;
+
+import org.jetbrains.annotations.NotNull;
+import java.util.List;
+import java.util.Collection;
+
+import jet.runtime.typeinfo.KotlinSignature;
+
+public class InheritVariance {
+    @KotlinSignature("fun foo(): MutableCollection<out Number>")
+    public Collection<Number> foo() {
+        throw new UnsupportedOperationException();
+    }
+
+    public class Sub extends InheritVariance {
+        public List<Number> foo() {
+            throw new UnsupportedOperationException();
+        }
+    }
+}

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritVariance.kt

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+package test
+
+import org.jetbrains.annotations.NotNull
+
+public open class InheritVariance : java.lang.Object() {
+    public open fun foo(): MutableCollection<out Number> = throw UnsupportedOperationException()
+
+    public open class Sub: InheritVariance() {
+        override fun foo(): MutableList<out Number> = throw UnsupportedOperationException()
+    }
+}

compiler/testData/loadJava/kotlinSignature/propagation/return/InheritVariance.txt

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+namespace test
+
+public open class test.InheritVariance : java.lang.Object {
+    public final /*constructor*/ fun <init>(): test.InheritVariance
+    public open fun foo(): jet.MutableCollection<out jet.Number>
+    public open class test.InheritVariance.Sub : test.InheritVariance {
+        public final /*constructor*/ fun <init>(): test.InheritVariance.Sub
+        public open override /*1*/ fun foo(): jet.MutableList<out jet.Number>
+    }
+}