Report errors for type parameters of properties that are not used in receiver types

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/Errors.java

@@ -269,6 +269,8 @@ public interface Errors {
     DiagnosticFactory0<JetDeclaration> TYPE_PARAMETERS_NOT_ALLOWED
             = DiagnosticFactory0.create(ERROR, TYPE_PARAMETERS_OR_DECLARATION_SIGNATURE);
 
+    DiagnosticFactory0<JetTypeParameter> TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER = DiagnosticFactory0.create(ERROR);
+
     DiagnosticFactory0<PsiElement> CYCLIC_GENERIC_UPPER_BOUND = DiagnosticFactory0.create(ERROR);
 
     DiagnosticFactory0<JetTypeParameter> MISPLACED_TYPE_PARAMETER_CONSTRAINTS = DiagnosticFactory0.create(WARNING);

compiler/frontend/src/org/jetbrains/kotlin/diagnostics/rendering/DefaultErrorMessages.java

@@ -629,6 +629,8 @@ public class DefaultErrorMessages {
         MAP.put(REIFIED_TYPE_FORBIDDEN_SUBSTITUTION, "Cannot use ''{0}'' as reified type parameter", RENDER_TYPE);
         MAP.put(TYPE_PARAMETERS_NOT_ALLOWED, "Type parameters are not allowed here");
 
+        MAP.put(TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER, "Type parameter of a property must be used in its receiver type");
+
         MAP.put(SUPERTYPES_FOR_ANNOTATION_CLASS, "Annotation class cannot have supertypes");
         MAP.put(MISSING_VAL_ON_ANNOTATION_PARAMETER, "'val' keyword is missing on annotation parameter");
         MAP.put(ANNOTATION_CLASS_CONSTRUCTOR_CALL, "Annotation class cannot be instantiated");

compiler/frontend/src/org/jetbrains/kotlin/resolve/DeclarationsChecker.java

@@ -20,6 +20,7 @@ import com.google.common.collect.ImmutableSet;
 import com.google.common.collect.Multimap;
 import com.google.common.collect.Sets;
 import com.intellij.psi.PsiElement;
+import kotlin.jvm.functions.Function1;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
@@ -471,6 +472,33 @@ public class DeclarationsChecker {
         checkAccessors(property, propertyDescriptor);
         checkTypeParameterConstraints(property);
         checkPropertyExposedType(property, propertyDescriptor);
+        checkPropertyTypeParametersAreUsedInReceiverType(propertyDescriptor);
+    }
+
+    private void checkPropertyTypeParametersAreUsedInReceiverType(@NotNull PropertyDescriptor descriptor) {
+        for (TypeParameterDescriptor typeParameter : descriptor.getTypeParameters()) {
+            if (isTypeParameterUsedInReceiverType(typeParameter, descriptor)) continue;
+
+            PsiElement typeParameterPsi = DescriptorToSourceUtils.getSourceFromDescriptor(typeParameter);
+            if (typeParameterPsi instanceof JetTypeParameter) {
+                trace.report(TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER.on((JetTypeParameter) typeParameterPsi));
+            }
+        }
+    }
+
+    private static boolean isTypeParameterUsedInReceiverType(
+            @NotNull final TypeParameterDescriptor parameter,
+            @NotNull PropertyDescriptor descriptor
+    ) {
+        ReceiverParameterDescriptor receiverParameter = descriptor.getExtensionReceiverParameter();
+        if (receiverParameter == null) return false;
+
+        return TypeUtils.containsSpecialType(receiverParameter.getType(), new Function1<JetType, Boolean>() {
+            @Override
+            public Boolean invoke(JetType type) {
+                return parameter.equals(type.getConstructor().getDeclarationDescriptor());
+            }
+        });
     }
 
     private void checkPropertyLateInit(@NotNull JetCallableDeclaration property, @NotNull PropertyDescriptor propertyDescriptor) {

compiler/testData/diagnostics/tests/typeParameters/propertyTypeParameters.kt

@@ -0,0 +1,33 @@
+// !DIAGNOSTICS: -REDUNDANT_PROJECTION -CONFLICTING_PROJECTION
+
+interface G
+
+val <T> T.a: Int
+    get() = 3
+
+val <T1, T2> Map<T1, T2>.b: String
+    get() = "asds"
+
+val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T : G<!>> G.c: Int get() = 5
+
+val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T1<!>, T2, T3> List<Map<T2, T3>>.d: Int get() = 6
+
+val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T: Any<!>> G.e: T?
+    get() = null
+
+val <T> List<Map<Int, Map<String, T>>>.f: Int get() = 7
+
+val <T> List<Map<Int, Map<String, out T>>>.g: Int get() = 7
+val <T> List<Map<Int, Map<String, in T>>>.h: Int get() = 7
+
+val <T> List<Map<T, Map<T, T>>>.i: Int get() = 7
+
+var <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T1<!>, <!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T2<!>, <!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T3<!>, <!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>T4<!>> p = 1
+
+class C<T1, T2> {
+    val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>E<!>> T1.a: Int get() = 3
+    val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>E<!>> T2.b: Int get() = 3
+    val <E> E.c: Int get() = 3
+    val <<!TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER!>E<!>> Map<T1, T2>.d: Int get() = 3
+    val <E> Map<T1, E>.e: Int get() = 3
+}

compiler/testData/diagnostics/tests/typeParameters/propertyTypeParameters.txt

@@ -0,0 +1,30 @@
+package
+
+public var </*0*/ T1, /*1*/ T2, /*2*/ T3, /*3*/ T4> p: kotlin.Int
+public val </*0*/ T> T.a: kotlin.Int
+public val </*0*/ T1, /*1*/ T2> kotlin.Map<T1, T2>.b: kotlin.String
+public val </*0*/ T : G> G.c: kotlin.Int
+public val </*0*/ T1, /*1*/ T2, /*2*/ T3> kotlin.List<kotlin.Map<T2, T3>>.d: kotlin.Int
+public val </*0*/ T : kotlin.Any> G.e: T?
+public val </*0*/ T> kotlin.List<kotlin.Map<kotlin.Int, kotlin.Map<kotlin.String, T>>>.f: kotlin.Int
+public val </*0*/ T> kotlin.List<kotlin.Map<kotlin.Int, kotlin.Map<kotlin.String, out T>>>.g: kotlin.Int
+public val </*0*/ T> kotlin.List<kotlin.Map<kotlin.Int, kotlin.Map<kotlin.String, in T>>>.h: kotlin.Int
+public val </*0*/ T> kotlin.List<kotlin.Map<T, kotlin.Map<T, T>>>.i: kotlin.Int
+
+public final class C</*0*/ T1, /*1*/ T2> {
+    public constructor C</*0*/ T1, /*1*/ T2>()
+    public final val </*0*/ E> T1.a: kotlin.Int
+    public final val </*0*/ E> T2.b: kotlin.Int
+    public final val </*0*/ E> E.c: kotlin.Int
+    public final val </*0*/ E> kotlin.Map<T1, T2>.d: kotlin.Int
+    public final val </*0*/ E> kotlin.Map<T1, E>.e: kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public interface G {
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -15805,6 +15805,12 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("propertyTypeParameters.kt")
+            public void testPropertyTypeParameters() throws Exception {
+                String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/typeParameters/propertyTypeParameters.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("upperBoundCannotBeArray.kt")
             public void testUpperBoundCannotBeArray() throws Exception {
                 String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/typeParameters/upperBoundCannotBeArray.kt");