correctly find usages of overridden Java method through synthetic accessors

#KT-12869 Fixed

idea/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinOverridingMethodReferenceSearcher.kt

@@ -25,6 +25,7 @@ import com.intellij.psi.search.searches.MethodReferencesSearch
 import com.intellij.util.Processor
 import org.jetbrains.kotlin.asJava.toLightMethods
 import org.jetbrains.kotlin.idea.references.KtSimpleNameReference
+import org.jetbrains.kotlin.idea.references.SyntheticPropertyAccessorReference
 import org.jetbrains.kotlin.idea.references.readWriteAccess
 import org.jetbrains.kotlin.idea.search.restrictToKotlinSources
 import org.jetbrains.kotlin.idea.util.runReadActionInSmartMode
@@ -67,17 +68,29 @@ class KotlinOverridingMethodReferenceSearcher : MethodUsagesSearcher() {
                                             strictSignatureSearch: Boolean): MethodTextOccurrenceProcessor {
         return object: MethodTextOccurrenceProcessor(aClass, strictSignatureSearch, *methods) {
             override fun processInexactReference(ref: PsiReference, refElement: PsiElement?, method: PsiMethod, consumer: Processor<PsiReference>): Boolean {
-                if (refElement !is KtCallableDeclaration) return true
+                val isGetter = JvmAbi.isGetterName(method.name)
+
+                fun isWrongAccessorReference(): Boolean {
+                    if (ref is KtSimpleNameReference) {
+                        val readWriteAccess = ref.expression.readWriteAccess(true)
+                        return readWriteAccess.isRead != isGetter && readWriteAccess.isWrite == isGetter
+                    }
+                    if (ref is SyntheticPropertyAccessorReference) {
+                        return (ref is SyntheticPropertyAccessorReference.Getter) != isGetter
+                    }
+                    return false
+                }
+
+                if (refElement !is KtCallableDeclaration) {
+                    if (isWrongAccessorReference()) return true
+                    return super.processInexactReference(ref, refElement, method, consumer)
+                }
 
                 var lightMethods = refElement.toLightMethods()
                         .filterNot { it.hasModifierProperty(PsiModifier.FINAL) }
                         .ifEmpty { return true }
                 if (refElement is KtProperty || refElement is KtParameter) {
-                    val isGetter = JvmAbi.isGetterName(method.name)
-                    if (ref is KtSimpleNameReference) {
-                        val readWriteAccess = ref.expression.readWriteAccess(true)
-                        if (readWriteAccess.isRead != isGetter && readWriteAccess.isWrite == isGetter) return true
-                    }
+                    if (isWrongAccessorReference()) return true
                     lightMethods = lightMethods.filter { JvmAbi.isGetterName(it.name) == isGetter }
                 }
 

idea/testData/findUsages/java/findJavaMethodUsages/OverriddenMethodSyntheticAccessor.0.java

@@ -0,0 +1,10 @@
+// PSI_ELEMENT: com.intellij.psi.PsiMethod
+// OPTIONS: usages
+public interface AI {
+    String <caret>getFoo();
+
+    public class A implements AI {
+        @Override
+        public String getFoo() {return "";}
+    }
+}

idea/testData/findUsages/java/findJavaMethodUsages/OverriddenMethodSyntheticAccessor.1.kt

@@ -0,0 +1,4 @@
+fun AI.A.bar() {
+    getFoo() // Found
+    foo // Not found
+}

idea/testData/findUsages/java/findJavaMethodUsages/OverriddenMethodSyntheticAccessor.results.txt

@@ -0,0 +1,2 @@
+Function call 2 getFoo() // Found
+Value read 3 foo // Not found

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

@@ -1452,6 +1452,12 @@ public class FindUsagesTestGenerated extends AbstractFindUsagesTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("OverriddenMethodSyntheticAccessor.0.java")
+            public void testOverriddenMethodSyntheticAccessor() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/findUsages/java/findJavaMethodUsages/OverriddenMethodSyntheticAccessor.0.java");
+                doTest(fileName);
+            }
+
             @TestMetadata("SyntheticProperties.0.java")
             public void testSyntheticProperties() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/findUsages/java/findJavaMethodUsages/SyntheticProperties.0.java");