Refactor getDeprecation() -> getDeprecations()

In subsequent commits, another kind of deprecation is introduced which should
be reported alongside with deprecation by the `@Deprecated` annotation

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/checkers/DeprecatedCallChecker.kt

@@ -31,7 +31,7 @@ import org.jetbrains.kotlin.resolve.BindingTrace
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall
 import org.jetbrains.kotlin.resolve.calls.util.FakeCallableDescriptorForObject
 import org.jetbrains.kotlin.resolve.createDeprecationDiagnostic
-import org.jetbrains.kotlin.resolve.getDeprecation
+import org.jetbrains.kotlin.resolve.getDeprecations
 
 object DeprecatedCallChecker : CallChecker {
     override fun check(resolvedCall: ResolvedCall<*>, reportOn: PsiElement, context: CallCheckerContext) {
@@ -42,13 +42,17 @@ object DeprecatedCallChecker : CallChecker {
         // Objects will be checked by DeprecatedClassifierUsageChecker
         if (targetDescriptor is FakeCallableDescriptorForObject) return
 
-        val deprecation = targetDescriptor.getDeprecation()
+        val deprecations = targetDescriptor.getDeprecations().toMutableList()
 
         // avoid duplicating diagnostic when deprecation for property effectively deprecates setter
-        if (targetDescriptor is PropertySetterDescriptor && targetDescriptor.correspondingProperty.getDeprecation() == deprecation) return
+        if (targetDescriptor is PropertySetterDescriptor) {
+            deprecations -= targetDescriptor.correspondingProperty.getDeprecations()
+        }
 
-        if (deprecation != null) {
-            trace.report(createDeprecationDiagnostic(element, deprecation))
+        if (deprecations.isNotEmpty()) {
+            for (deprecation in deprecations) {
+                trace.report(createDeprecationDiagnostic(element, deprecation))
+            }
         }
         else if (targetDescriptor is PropertyDescriptor && shouldCheckPropertyGetter(element)) {
             targetDescriptor.getter?.let { check(it, trace, element) }

compiler/frontend/src/org/jetbrains/kotlin/resolve/checkers/DeprecatedClassifierUsageChecker.kt

@@ -21,7 +21,7 @@ import org.jetbrains.kotlin.config.LanguageVersionSettings
 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor
 import org.jetbrains.kotlin.resolve.BindingTrace
 import org.jetbrains.kotlin.resolve.createDeprecationDiagnostic
-import org.jetbrains.kotlin.resolve.getDeprecation
+import org.jetbrains.kotlin.resolve.getDeprecations
 
 class DeprecatedClassifierUsageChecker : ClassifierUsageChecker {
     override fun check(
@@ -30,8 +30,8 @@ class DeprecatedClassifierUsageChecker : ClassifierUsageChecker {
             element: PsiElement,
             languageVersionSettings: LanguageVersionSettings
     ) {
-        val deprecation = targetDescriptor.getDeprecation()
-        if (deprecation != null) {
+        val deprecations = targetDescriptor.getDeprecations()
+        for (deprecation in deprecations) {
             trace.report(createDeprecationDiagnostic(element, deprecation))
         }
     }

compiler/frontend/src/org/jetbrains/kotlin/resolve/deprecationUtil.kt

@@ -89,17 +89,17 @@ private data class DeprecatedByOverridden(private val deprecations: Collection<D
     internal fun additionalMessage() = "Overrides deprecated member in '${DescriptorUtils.getContainingClass(target)!!.fqNameSafe.asString()}'"
 }
 
-fun DeclarationDescriptor.getDeprecation(): Deprecation? {
+fun DeclarationDescriptor.getDeprecations(): List<Deprecation> {
     val deprecation = this.getDeprecationByAnnotation()
     if (deprecation != null) {
-        return deprecation
+        return listOf(deprecation)
     }
 
     if (this is CallableMemberDescriptor) {
-        return deprecationByOverridden(this)
+        return listOfNotNull(deprecationByOverridden(this))
     }
 
-    return null
+    return emptyList()
 }
 
 private fun deprecationByOverridden(root: CallableMemberDescriptor): Deprecation? {
@@ -200,9 +200,8 @@ enum class DeprecationLevelValue {
     WARNING, ERROR, HIDDEN
 }
 
-fun DeclarationDescriptor.isDeprecatedHidden(): Boolean {
-    return getDeprecation()?.deprecationLevel == HIDDEN
-}
+fun DeclarationDescriptor.isDeprecatedHidden(): Boolean =
+        getDeprecations().any { it.deprecationLevel == HIDDEN }
 
 @JvmOverloads
 fun DeclarationDescriptor.isHiddenInResolution(languageVersionSettings: LanguageVersionSettings, isSuperCall: Boolean = false): Boolean {