Support nullable callable references in raw FIR

compiler/fir/lightTree/src/org/jetbrains/kotlin/fir/lightTree/converter/ExpressionsConverter.kt

@@ -378,11 +378,13 @@ class ExpressionsConverter(
      */
     private fun convertCallableReferenceExpression(callableReferenceExpression: LighterASTNode): FirExpression {
         var isReceiver = true
+        var safe = false
         var firReceiverExpression: FirExpression? = null
         lateinit var firCallableReference: FirQualifiedAccess
         callableReferenceExpression.forEachChildren {
             when (it.tokenType) {
                 COLONCOLON -> isReceiver = false
+                QUEST -> safe = true
                 else -> if (it.isExpression()) {
                     if (isReceiver) {
                         firReceiverExpression = getAsFirExpression(it, "Incorrect receiver expression")
@@ -396,6 +398,7 @@ class ExpressionsConverter(
         return FirCallableReferenceAccessImpl(null).apply {
             calleeReference = firCallableReference.calleeReference as FirNamedReference
             explicitReceiver = firReceiverExpression
+            this.safe = safe
         }
     }
 

compiler/fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/RawFirBuilder.kt

@@ -1467,6 +1467,7 @@ class RawFirBuilder(session: FirSession, val scopeProvider: FirScopeProvider, va
                     expression.callableReference.toFirSourceElement(), expression.callableReference.getReferencedNameAsName(), null
                 )
                 explicitReceiver = expression.receiverExpression?.toFirExpression("Incorrect receiver expression")
+                safe = expression.hasQuestionMarks
             }
         }
 

compiler/fir/psi2fir/testData/rawBuilder/expressions/callableReferences.kt

@@ -20,3 +20,5 @@ val test5 = A::bar
 val test6 = A::qux
 
 val test7 = ::baz
+
+val test8 = A?::foo

compiler/fir/psi2fir/testData/rawBuilder/expressions/callableReferences.txt

@@ -29,3 +29,5 @@ FILE: callableReferences.kt
         public? get(): <implicit>
     public? final? val test7: <implicit> = ::baz#
         public? get(): <implicit>
+    public? final? val test8: <implicit> = A#?::foo#
+        public? get(): <implicit>

compiler/fir/resolve/testData/resolve/stdlib/getOnKProperty.txt

@@ -4,7 +4,7 @@ FILE: getOnKProperty.kt
             ^ Int(42)
         }
     public final fun test(): R|kotlin/Unit| {
-        lval f: R|kotlin/reflect/KProperty1<kotlin/Any, kotlin/Int>| = Q|kotlin/Any|::R|/meaning|
+        lval f: R|kotlin/reflect/KProperty1<kotlin/Any, kotlin/Int>| = Q|kotlin/Any|?::R|/meaning|
         R|<local>/f|.<Inapplicable(INAPPLICABLE): [kotlin/reflect/KProperty1.get]>#(Null(null))
         R|<local>/f|.R|FakeOverride<kotlin/reflect/KProperty1.get: R|kotlin/Int|>|(String())
     }

compiler/fir/tree/src/org/jetbrains/kotlin/fir/FirRenderer.kt

@@ -944,6 +944,9 @@ class FirRenderer(builder: StringBuilder) : FirVisitorVoid() {
     override fun visitCallableReferenceAccess(callableReferenceAccess: FirCallableReferenceAccess) {
         callableReferenceAccess.annotations.renderAnnotations()
         callableReferenceAccess.explicitReceiver?.accept(this)
+        if (callableReferenceAccess.safe) {
+            print("?")
+        }
         print("::")
         callableReferenceAccess.calleeReference.accept(this)
     }