Use representative upper bound in JetTypeMapper instead of just the first

compiler/backend/src/org/jetbrains/kotlin/codegen/state/JetTypeMapper.java

@@ -509,10 +509,9 @@ public class JetTypeMapper {
         }
 
         if (descriptor instanceof TypeParameterDescriptor) {
-            TypeParameterDescriptor typeParameterDescriptor = (TypeParameterDescriptor) descriptor;
-            Type type = mapType(typeParameterDescriptor.getUpperBounds().iterator().next(), kind);
+            Type type = mapType(getRepresentativeUpperBound((TypeParameterDescriptor) descriptor), kind);
             if (signatureVisitor != null) {
-                signatureVisitor.writeTypeVariable(typeParameterDescriptor.getName(), type);
+                signatureVisitor.writeTypeVariable(descriptor.getName(), type);
             }
             return type;
         }
@@ -520,6 +519,18 @@ public class JetTypeMapper {
         throw new UnsupportedOperationException("Unknown type " + jetType);
     }
 
+    @NotNull
+    private static KotlinType getRepresentativeUpperBound(@NotNull TypeParameterDescriptor descriptor) {
+        List<KotlinType> upperBounds = descriptor.getUpperBounds();
+        assert !upperBounds.isEmpty() : "Upper bounds should not be empty: " + descriptor;
+        for (KotlinType upperBound : upperBounds) {
+            if (!isJvmInterface(upperBound)) {
+                return upperBound;
+            }
+        }
+        return CollectionsKt.first(upperBounds);
+    }
+
     @Nullable
     private static Type mapBuiltinType(@NotNull KotlinType type) {
         DeclarationDescriptor descriptor = type.getConstructor().getDeclarationDescriptor();

compiler/testData/codegen/boxWithStdlib/typeMapping/typeParameterMultipleBounds.kt

@@ -0,0 +1,29 @@
+interface I1
+interface I2
+open class C
+
+interface K {
+    // Erasure of a type parameter with multiple bounds should be the class bound, or the first bound if there's no class bound
+
+    fun <T> c1(t: T) where T : C, T : I1, T : I2
+    fun <T> c2(t: T) where T : I1, T : C, T : I2
+    fun <T> c3(t: T) where T : I2, T : C, T : I1
+    fun <T> c4(t: T) where T : I2, T : I1, T : C
+
+    fun <T> i1(t: T) where T : I1, T : I2
+    fun <T> i2(t: T) where T : I2, T : I1
+}
+
+fun box(): String {
+    val k = K::class.java
+
+    k.getDeclaredMethod("c1", C::class.java)
+    k.getDeclaredMethod("c2", C::class.java)
+    k.getDeclaredMethod("c3", C::class.java)
+    k.getDeclaredMethod("c4", C::class.java)
+
+    k.getDeclaredMethod("i1", I1::class.java)
+    k.getDeclaredMethod("i2", I2::class.java)
+
+    return "OK"
+}

compiler/tests/org/jetbrains/kotlin/codegen/generated/BlackBoxWithStdlibCodegenTestGenerated.java

@@ -4740,6 +4740,12 @@ public class BlackBoxWithStdlibCodegenTestGenerated extends AbstractBlackBoxCode
             String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/typeMapping/genericTypeWithNothing.kt");
             doTestWithStdlib(fileName);
         }
+
+        @TestMetadata("typeParameterMultipleBounds.kt")
+        public void testTypeParameterMultipleBounds() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("compiler/testData/codegen/boxWithStdlib/typeMapping/typeParameterMultipleBounds.kt");
+            doTestWithStdlib(fileName);
+        }
     }
 
     @TestMetadata("compiler/testData/codegen/boxWithStdlib/vararg")

core/descriptors/src/org/jetbrains/kotlin/resolve/DescriptorUtils.java

@@ -16,6 +16,7 @@
 
 package org.jetbrains.kotlin.resolve;
 
+import kotlin.CollectionsKt;
 import kotlin.jvm.functions.Function1;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;