KT UAST: always preserve receiver expression of callable reference

It seems like qualifier type and qualifier expression did not co-exist,
but that only made users (like Lint detector) deal with inconsistent
examination of both information that are sometimes available or not.

Java UAST counterpart has both information always, so no good reason to
keep such contract in Kotlin UAST.

GitOrigin-RevId: 69f96325910cf8eea056449c984151925dffcf10

java/java-tests/testData/inspection/jvm/deadCode/usagesInCallableReceiver/expected.xml

@@ -1,8 +1,3 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <problems>
-  <problem>
-    <file>TC.kt</file>
-    <line>6</line>
-    <description>Parameter &lt;code&gt;s&lt;/code&gt; is not used</description>
-  </problem>
 </problems>

java/java-tests/testData/inspection/jvm/deadCode/usagesInCallableReceiver/src/TC.kt

@@ -3,7 +3,7 @@ fun main() {
 }
 
 fun foo(i: Int,
-        s: String //todo wrongly marked as unused, because simple references in callables are treated as class references
+        s: String
 ) {
   println("Foo $i"::toString)
   println(s::toString)

plugins/kotlin/uast/uast-kotlin-base/src/org/jetbrains/uast/kotlin/expressions/KotlinUCallableReferenceExpression.kt

@@ -8,8 +8,6 @@ import com.intellij.psi.PsiType
 import com.intellij.psi.ResolveResult
 import org.jetbrains.annotations.ApiStatus
 import org.jetbrains.kotlin.psi.KtCallableReferenceExpression
-import org.jetbrains.kotlin.psi.KtDotQualifiedExpression
-import org.jetbrains.kotlin.psi.KtNameReferenceExpression
 import org.jetbrains.uast.*
 import org.jetbrains.uast.kotlin.internal.getResolveResultVariants
 
@@ -19,21 +17,18 @@ class KotlinUCallableReferenceExpression(
     givenParent: UElement?
 ) : KotlinAbstractUExpression(givenParent), UCallableReferenceExpression, UMultiResolvable, KotlinUElementWithType {
 
+    private val qualifierExpressionPart = UastLazyPart<UExpression?>()
     private val qualifierTypePart = UastLazyPart<PsiType?>()
 
     override val qualifierExpression: UExpression?
-        get() {
-            if (qualifierType != null) return null
-            val receiverExpression = sourcePsi.receiverExpression ?: return null
-            return baseResolveProviderService.baseKotlinConverter.convertExpression(receiverExpression, this, DEFAULT_EXPRESSION_TYPES_LIST)
+        get() = qualifierExpressionPart.getOrBuild {
+            val receiverExpression = sourcePsi.receiverExpression ?: return@getOrBuild null
+            baseResolveProviderService.baseKotlinConverter.convertExpression(receiverExpression, this, DEFAULT_EXPRESSION_TYPES_LIST)
         }
 
     override val qualifierType: PsiType?
         get() = qualifierTypePart.getOrBuild {
-            if (sourcePsi.receiverExpression !is KtNameReferenceExpression && sourcePsi.receiverExpression !is KtDotQualifiedExpression) {
-                null
-            } else
-                baseResolveProviderService.getDoubleColonReceiverType(sourcePsi, this)
+            baseResolveProviderService.getDoubleColonReceiverType(sourcePsi, this)
         }
 
     override val callableName: String

plugins/kotlin/uast/uast-kotlin-fir/src/org/jetbrains/uast/kotlin/FirKotlinUastResolveProviderService.kt

@@ -618,9 +618,10 @@ interface FirKotlinUastResolveProviderService : BaseKotlinUastResolveProviderSer
             // Again, Analysis API returns [Unit] for statements, so we need to filter out
             // some cases that are not actually expression's return type.
             if (ktType.isUnit) {
+                val parent = ktExpression.parent
                 // E.g., AnnotationTarget.FIELD, reference to enum class is resolved to the constructor call,
                 // and then returned as Unit expression type. Same for path segments in a fully qualified name
-                if (ktExpression.parent is KtQualifiedExpression &&
+                if ((parent is KtQualifiedExpression || parent is KtDoubleColonExpression) &&
                     (ktExpression is KtQualifiedExpression || ktExpression is KtNameReferenceExpression)
                 ) {
                     return null

plugins/kotlin/uast/uast-kotlin-fir/tests/testData/legacyRenderLog/MethodReference.log.txt

@@ -3,6 +3,7 @@ UFile (package = )
         UField (name = x)
             UAnnotation (fqName = org.jetbrains.annotations.NotNull)
             UCallableReferenceExpression (name = bar)
+                USimpleNameReferenceExpression (identifier = Foo)
         UMethod (name = getX)
     UClass (name = Foo)
         UMethod (name = bar)

plugins/kotlin/uast/uast-kotlin-fir/tests/testData/legacyTypes/MethodReference.types.txt

@@ -3,6 +3,7 @@ UFile (package = ) [public final class MethodReferenceKt {...]
         UField (name = x) [@org.jetbrains.annotations.NotNull private static final var x: kotlin.reflect.KFunction<kotlin.Unit> = Foo::bar]
             UAnnotation (fqName = org.jetbrains.annotations.NotNull) [@org.jetbrains.annotations.NotNull]
             UCallableReferenceExpression (name = bar) [Foo::bar] : PsiType:KFunction<? extends Unit>
+                USimpleNameReferenceExpression (identifier = Foo) [Foo]
         UMethod (name = getX) [public static final fun getX() : kotlin.reflect.KFunction<kotlin.Unit> = UastEmptyExpression]
     UClass (name = Foo) [public final class Foo {...}]
         UMethod (name = bar) [public final fun bar() : void {...}]

plugins/kotlin/uast/uast-kotlin-fir/tests/testData/legacyValues/MethodReference.values.txt

@@ -3,6 +3,7 @@ UFile (package = ) [public final class MethodReferenceKt {...]
         UField (name = x) [@org.jetbrains.annotations.NotNull private static final var x: kotlin.reflect.KFunction<kotlin.Unit> = Foo::bar]
             UAnnotation (fqName = org.jetbrains.annotations.NotNull) [@org.jetbrains.annotations.NotNull]
             UCallableReferenceExpression (name = bar) [Foo::bar] = external Foo::bar()
+                USimpleNameReferenceExpression (identifier = Foo) [Foo] = external Foo()
         UMethod (name = getX) [public static final fun getX() : kotlin.reflect.KFunction<kotlin.Unit> = UastEmptyExpression]
     UClass (name = Foo) [public final class Foo {...}]
         UMethod (name = bar) [public final fun bar() : void {...}]

uast/uast-common/src/org/jetbrains/uast/expressions/UCallableReferenceExpression.kt

@@ -14,13 +14,11 @@ import org.jetbrains.uast.visitor.UastVisitor
 interface UCallableReferenceExpression : UReferenceExpression {
   /**
    * Returns the qualifier expression.
-   * Can be null if the [qualifierType] is known.
    */
   val qualifierExpression: UExpression?
 
   /**
    * Returns the qualifier type.
-   * Can be null if the qualifier is an expression.
    */
   val qualifierType: PsiType?