Do not report "unused receiver" on operator and infix functions

So #KT-16340 Fixed

idea/src/org/jetbrains/kotlin/idea/inspections/UnusedReceiverParameterInspection.kt

@@ -36,6 +36,7 @@ import org.jetbrains.kotlin.idea.util.getThisReceiverOwner
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.resolve.BindingContext
+import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.model.VariableAsFunctionResolvedCall
@@ -48,7 +49,11 @@ class UnusedReceiverParameterInspection : AbstractKotlinInspection() {
             private fun check(callableDeclaration: KtCallableDeclaration) {
                 val receiverTypeReference = callableDeclaration.receiverTypeReference
                 if (receiverTypeReference == null || receiverTypeReference.textRange.isEmpty) return
-                if (callableDeclaration.isOverridable() || callableDeclaration.hasModifier(KtTokens.OVERRIDE_KEYWORD)) return
+
+                if (callableDeclaration.isOverridable() ||
+                    callableDeclaration.hasModifier(KtTokens.OVERRIDE_KEYWORD) ||
+                    callableDeclaration.hasModifier(KtTokens.OPERATOR_KEYWORD) ||
+                    callableDeclaration.hasModifier(KtTokens.INFIX_KEYWORD)) return
 
                 if (callableDeclaration is KtProperty && callableDeclaration.accessors.isEmpty()) return
                 if (callableDeclaration is KtNamedFunction && !callableDeclaration.hasBody()) return

idea/testData/inspectionsLocal/unusedReceiverParameter/.inspection

@@ -0,0 +1 @@
+org.jetbrains.kotlin.idea.inspections.UnusedReceiverParameterInspection

idea/testData/inspectionsLocal/unusedReceiverParameter/companion.kt

@@ -0,0 +1,16 @@
+// PROBLEM: none
+
+class Test(val test: Int) {
+    companion object
+
+    fun foo() = test
+}
+
+// Used
+operator fun Test.<caret>Companion.invoke() = Test(1)
+
+
+fun main(args: Array<String>) {
+    val x = Test()
+    x.foo()
+}

idea/testData/inspectionsLocal/unusedReceiverParameter/infix.kt

@@ -0,0 +1,14 @@
+// PROBLEM: none
+
+class Test(val test: Int) {
+    fun foo() = test
+}
+
+// Receiver unused but still inapplicable (infix)
+infix fun <caret>Test.build(x: Int) = Test(x * x)
+
+
+fun main(args: Array<String>) {
+    val x = Test(0) build 7
+    x.foo()
+}

idea/testData/inspectionsLocal/unusedReceiverParameter/operator.kt

@@ -0,0 +1,14 @@
+// PROBLEM: none
+
+class Test(val test: Int) {
+    fun foo() = test
+}
+
+// Receiver unused but still inapplicable (operator!)
+operator fun <caret>Test.invoke(x: Int, y: Int) = Test(x + y)
+
+
+fun main(args: Array<String>) {
+    val x = Test(0)(1, 2)
+    x.foo()
+}

idea/tests/org/jetbrains/kotlin/idea/inspections/LocalInspectionTestGenerated.java

@@ -1920,6 +1920,33 @@ public class LocalInspectionTestGenerated extends AbstractLocalInspectionTest {
         }
     }
 
+    @TestMetadata("idea/testData/inspectionsLocal/unusedReceiverParameter")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class UnusedReceiverParameter extends AbstractLocalInspectionTest {
+        public void testAllFilesPresentInUnusedReceiverParameter() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/inspectionsLocal/unusedReceiverParameter"), Pattern.compile("^([\\w\\-_]+)\\.kt$"), TargetBackend.ANY, true);
+        }
+
+        @TestMetadata("companion.kt")
+        public void testCompanion() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/unusedReceiverParameter/companion.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("infix.kt")
+        public void testInfix() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/unusedReceiverParameter/infix.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("operator.kt")
+        public void testOperator() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/inspectionsLocal/unusedReceiverParameter/operator.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("idea/testData/inspectionsLocal/unusedSymbol")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)