Remove explicit type specification: don't propose for ext function type

#KT-8875 Fixed

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

@@ -77,6 +77,7 @@ class RemoveExplicitTypeIntention : SelfTargetingRangeIntention<KtCallableDeclar
             if (initializer == null) return true
             if (initializer !is KtLambdaExpression && initializer !is KtNamedFunction) return true
             val functionType = element.typeReference?.typeElement as? KtFunctionType ?: return true
+            if (functionType.receiver != null) return false
             if (functionType.parameters.isEmpty()) return true
             val valueParameters = when (initializer) {
                 is KtLambdaExpression -> initializer.valueParameters

idea/testData/intentions/removeExplicitType/extensionFunction.kt

@@ -0,0 +1,4 @@
+// IS_APPLICABLE: false
+val foo: <caret>Int.() -> String = {
+    toString() + hashCode()
+}

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

@@ -13316,6 +13316,11 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             runTest("idea/testData/intentions/removeExplicitType/anonymousFunctionInitializer3.kt");
         }
 
+        @TestMetadata("extensionFunction.kt")
+        public void testExtensionFunction() throws Exception {
+            runTest("idea/testData/intentions/removeExplicitType/extensionFunction.kt");
+        }
+
         @TestMetadata("funNoBody.kt")
         public void testFunNoBody() throws Exception {
             runTest("idea/testData/intentions/removeExplicitType/funNoBody.kt");