FIR/UAST: move multi resolve utils/APIs to the base module/service

plugins/uast-kotlin-base/src/org/jetbrains/uast/kotlin/BaseKotlinUastResolveProviderService.kt

@@ -19,6 +19,8 @@ interface BaseKotlinUastResolveProviderService {
 
     fun convertParent(uElement: UElement): UElement?
 
+    fun getReferenceVariants(ktExpression: KtExpression, nameHint: String): Sequence<PsiElement>
+
     fun resolveToDeclaration(ktExpression: KtExpression): PsiElement?
 
     fun resolveToType(ktTypeReference: KtTypeReference, source: UElement): PsiType?

plugins/uast-kotlin-base/src/org/jetbrains/uast/kotlin/internal/multiResolveUtils.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.uast.kotlin.internal
+
+import com.intellij.psi.PsiSubstitutor
+import com.intellij.psi.ResolveResult
+import com.intellij.psi.infos.CandidateInfo
+import org.jetbrains.kotlin.psi.KtExpression
+import org.jetbrains.uast.kotlin.BaseKotlinUastResolveProviderService
+
+fun getResolveResultVariants(
+    baseKotlinUastResolveProviderService: BaseKotlinUastResolveProviderService,
+    ktExpression: KtExpression?
+): Iterable<ResolveResult> {
+    ktExpression ?: return emptyList()
+
+    val referenceVariants = baseKotlinUastResolveProviderService.getReferenceVariants(ktExpression, ktExpression.name ?: ktExpression.text)
+
+    return referenceVariants.mapNotNull { CandidateInfo(it, PsiSubstitutor.EMPTY) }.asIterable()
+}
+