Support generic type parameters in 'Specify return type explicitly'

So #KT-18074 Fixed

idea/src/org/jetbrains/kotlin/idea/intentions/SpecifyTypeExplicitlyIntention.kt

@@ -23,7 +23,9 @@ import com.intellij.openapi.util.TextRange
 import com.intellij.psi.PsiDocumentManager
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns
 import org.jetbrains.kotlin.descriptors.CallableDescriptor
+import org.jetbrains.kotlin.descriptors.FunctionDescriptor
 import org.jetbrains.kotlin.descriptors.PropertyDescriptor
+import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor
 import org.jetbrains.kotlin.idea.caches.resolve.analyze
 import org.jetbrains.kotlin.idea.caches.resolve.getResolutionFacade
 import org.jetbrains.kotlin.idea.caches.resolve.resolveToDescriptorIfAny
@@ -41,7 +43,6 @@ import org.jetbrains.kotlin.psi.psiUtil.startOffset
 import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.types.*
-import org.jetbrains.kotlin.types.typeUtil.containsTypeAliases
 import org.jetbrains.kotlin.utils.ifEmpty
 
 class SpecifyTypeExplicitlyIntention :
@@ -114,7 +115,17 @@ class SpecifyTypeExplicitlyIntention :
             val resolutionFacade = contextElement.getResolutionFacade()
             val bindingContext = resolutionFacade.analyze(contextElement, BodyResolveMode.PARTIAL)
             val scope = contextElement.getResolutionScope(bindingContext, resolutionFacade)
-            val types = with (exprType.getResolvableApproximations(scope, true).toList()) {
+
+            var checkTypeParameters = true
+            val descriptor = exprType.constructor.declarationDescriptor
+            if (descriptor != null && descriptor is TypeParameterDescriptor) {
+                val owner = descriptor.containingDeclaration
+                if (owner is FunctionDescriptor && owner.typeParameters.contains(descriptor)) {
+                    checkTypeParameters = false
+                }
+            }
+
+            val types = with (exprType.getResolvableApproximations(scope, checkTypeParameters).toList()) {
                 when {
                     exprType.isNullabilityFlexible() -> flatMap {
                         listOf(TypeUtils.makeNotNullable(it), TypeUtils.makeNullable(it))

idea/testData/intentions/specifyTypeExplicitly/genericClass.kt

@@ -0,0 +1,5 @@
+fun <T> generic1(): T = null!!
+
+class My<T> {
+    fun <caret>foo() = generic1<T>()
+}

idea/testData/intentions/specifyTypeExplicitly/genericClass.kt.after

@@ -0,0 +1,5 @@
+fun <T> generic1(): T = null!!
+
+class My<T> {
+    fun foo(): T = generic1<T>()
+}

idea/testData/intentions/specifyTypeExplicitly/genericFunction.kt

@@ -0,0 +1,2 @@
+fun <T> generic1(): T? = null
+fun <T> <caret>foo() = generic1<T>()

idea/testData/intentions/specifyTypeExplicitly/genericFunction.kt.after

@@ -0,0 +1,2 @@
+fun <T> generic1(): T? = null
+fun <T> foo(): T? = generic1<T>()

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -14609,6 +14609,18 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("genericClass.kt")
+        public void testGenericClass() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/specifyTypeExplicitly/genericClass.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("genericFunction.kt")
+        public void testGenericFunction() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/specifyTypeExplicitly/genericFunction.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("lambdaParam.kt")
         public void testLambdaParam() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/intentions/specifyTypeExplicitly/lambdaParam.kt");