Fix search usages for invoke() extension operator (KT-18269)

#KT-18269 Fixed

idea/idea-analysis/src/org/jetbrains/kotlin/idea/search/usagesSearch/operators/InvokeOperatorReferenceSearcher.kt

@@ -27,8 +27,11 @@ import org.jetbrains.kotlin.idea.search.ideaExtensions.KotlinReferencesSearchOpt
 import org.jetbrains.kotlin.psi.KtCallExpression
 import org.jetbrains.kotlin.psi.KtElement
 import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.kotlin.psi.psiUtil.isExtensionDeclaration
 import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstance
-import org.jetbrains.uast.*
+import org.jetbrains.uast.UMethod
+import org.jetbrains.uast.UastContext
+import org.jetbrains.uast.convertOpt
 
 class InvokeOperatorReferenceSearcher(
         targetFunction: PsiElement,
@@ -44,7 +47,14 @@ class InvokeOperatorReferenceSearcher(
         val uMethod = uastContext.convertOpt<UMethod>(targetDeclaration, null)
         val uastParameters = uMethod?.uastParameters
 
-        callArgumentsSize = if (uastParameters != null && uastParameters.none { it.uastInitializer != null }) uastParameters.size else null
+        val isStableNumberOfArguments = uastParameters != null && uastParameters.none { it.uastInitializer != null }
+        callArgumentsSize = if (isStableNumberOfArguments) {
+            val numberOfArguments = uastParameters!!.size
+            when {
+                targetFunction.isExtensionDeclaration() -> numberOfArguments - 1
+                else -> numberOfArguments
+            }
+        } else null
     }
 
     override fun processPossibleReceiverExpression(expression: KtExpression) {

idea/testData/findUsages/kotlin/conventions/invokeExtension.0.kt

@@ -0,0 +1,11 @@
+// PSI_ELEMENT: org.jetbrains.kotlin.psi.KtNamedFunction
+// OPTIONS: usages
+package pack
+
+class P
+operator fun P.<caret>invoke() = 1
+
+fun f(p: P) {
+    p()
+    p.invoke()
+}

idea/testData/findUsages/kotlin/conventions/invokeExtension.log

@@ -0,0 +1,6 @@
+Resolved p()
+Searched references to pack.P
+Searched references to parameter p of pack.f(p: P) in non-Java files
+Used plain search of pack.invoke() in LocalSearchScope:
+    CLASS:P
+    FUN:invoke

idea/testData/findUsages/kotlin/conventions/invokeExtension.results.txt

@@ -0,0 +1,2 @@
+Function call 10 p.invoke()
+Implicit 'invoke' 9 p()

idea/tests/org/jetbrains/kotlin/findUsages/FindUsagesTestGenerated.java

@@ -133,6 +133,12 @@ public class FindUsagesTestGenerated extends AbstractFindUsagesTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("invokeExtension.0.kt")
+            public void testInvokeExtension() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/findUsages/kotlin/conventions/invokeExtension.0.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("plus.0.kt")
             public void testPlus() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/findUsages/kotlin/conventions/plus.0.kt");