[light classes] Improve isEquivalence checks

^KTIJ-25412

Update equivalence checks for light accessor methods and light fields
 to make them equivalent if they share the same underlying property.
 Follow the `kotlinOrigin` declaration:
 even if there is a property accessor,
 use property declaration.

analysis/symbol-light-classes/src/org/jetbrains/kotlin/light/classes/symbol/fields/SymbolLightFieldForProperty.kt

@@ -89,7 +89,9 @@ internal class SymbolLightFieldForProperty private constructor(
     }
 
     override fun isEquivalentTo(another: PsiElement?): Boolean {
-        return super.isEquivalentTo(another) || isOriginEquivalentTo(another)
+        return super.isEquivalentTo(another) ||
+                basicIsEquivalentTo(this, another as? PsiMethod) ||
+                isOriginEquivalentTo(another)
     }
 
     override fun isDeprecated(): Boolean = _isDeprecated

analysis/symbol-light-classes/src/org/jetbrains/kotlin/light/classes/symbol/methods/SymbolLightAccessorMethod.kt

@@ -262,6 +262,10 @@ internal class SymbolLightAccessorMethod private constructor(
 
     override fun getReturnType(): PsiType = _returnedType
 
+    override fun isEquivalentTo(another: PsiElement?): Boolean {
+        return super.isEquivalentTo(another) || basicIsEquivalentTo(this, another as? PsiField)
+    }
+
     override fun equals(other: Any?): Boolean {
         if (this === other) return true
         if (other !is SymbolLightAccessorMethod ||

analysis/symbol-light-classes/testData/equivalentTo/ClassPropertyWithAccessor.kt

@@ -0,0 +1,6 @@
+// org.jetbrains.kotlin.light.classes.symbol.fields.SymbolLightFieldForProperty
+class FooBar {
+    var f<caret>oo : String = "42"
+            get() = "42"
+    
+}

analysis/symbol-light-classes/tests/org/jetbrains/kotlin/light/classes/symbol/base/AbstractSymbolLightClassesEquivalentTest.kt

@@ -24,6 +24,15 @@ abstract class AbstractSymbolLightClassesEquivalentTest : AbstractAnalysisApiBas
         val declaration = testServices.expressionMarkerProvider.getElementOfTypeAtCaret<KtDeclaration>(ktFile)
         val lightElements = declaration.toLightElements()
         testServices.assertions.assertFalse(lightElements.isEmpty())
+        if (lightElements.size > 1) {
+            for (lightElement in lightElements) {
+                for (other in lightElements) {
+                    testServices.assertions.assertTrue(lightElement.isEquivalentTo(other)) {
+                        "Light elements are not equivalent: $lightElement and $other"
+                    }
+                }
+            }
+        }
         val lightElement = lightElements.find { it.javaClass.name == lightQName }
         testServices.assertions.assertNotNull(lightElement) { "Expected $lightQName, got: " + lightElements.joinToString { it::class.java.name } }
         testServices.assertions.assertTrue(lightElement!!.isEquivalentTo(declaration)) { "Light element is not equivalent to the corresponding ktElement" }

analysis/symbol-light-classes/tests/org/jetbrains/kotlin/light/classes/symbol/base/SymbolLightClassesEquivalentTestGenerated.java

@@ -36,6 +36,12 @@ public class SymbolLightClassesEquivalentTestGenerated extends AbstractSymbolLig
         runTest("analysis/symbol-light-classes/testData/equivalentTo/AnonymousClass.kt");
     }
 
+    @Test
+    @TestMetadata("ClassPropertyWithAccessor.kt")
+    public void testClassPropertyWithAccessor() throws Exception {
+        runTest("analysis/symbol-light-classes/testData/equivalentTo/ClassPropertyWithAccessor.kt");
+    }
+
     @Test
     @TestMetadata("CompanionProperty.kt")
     public void testCompanionProperty() throws Exception {