[FIR] Remove FirNamedArgumentExpressions during completion

They are mostly necessary for argument mapping during resolution.
To support a couple checkers, we transform named args for varargs
into "fake" spread expressions.

Other than that, named arguments aren't needed for anything and often
lead to bugs where we forget to unwrap them for something, so it's
better to get rid of them.

#KT-66124

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/expressions/FirSpreadArgumentExpression.kt

@@ -24,6 +24,8 @@ abstract class FirSpreadArgumentExpression : FirWrappedArgumentExpression() {
     abstract override val annotations: List<FirAnnotation>
     abstract override val expression: FirExpression
     abstract override val isSpread: Boolean
+    abstract val isNamed: Boolean
+    abstract val isFakeSpread: Boolean
 
     override fun <R, D> accept(visitor: FirVisitor<R, D>, data: D): R =
         visitor.visitSpreadArgumentExpression(this, data)

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/expressions/builder/FirSpreadArgumentExpressionBuilder.kt

@@ -26,12 +26,16 @@ class FirSpreadArgumentExpressionBuilder : FirAnnotationContainerBuilder, FirExp
     override var source: KtSourceElement? = null
     override val annotations: MutableList<FirAnnotation> = mutableListOf()
     lateinit var expression: FirExpression
+    var isNamed: Boolean = false
+    var isFakeSpread: Boolean = false
 
     override fun build(): FirSpreadArgumentExpression {
         return FirSpreadArgumentExpressionImpl(
             source,
             annotations.toMutableOrEmpty(),
             expression,
+            isNamed,
+            isFakeSpread,
         )
     }
 

compiler/fir/tree/gen/org/jetbrains/kotlin/fir/expressions/impl/FirSpreadArgumentExpressionImpl.kt

@@ -26,6 +26,8 @@ internal class FirSpreadArgumentExpressionImpl(
     override val source: KtSourceElement?,
     override var annotations: MutableOrEmptyList<FirAnnotation>,
     override var expression: FirExpression,
+    override val isNamed: Boolean,
+    override val isFakeSpread: Boolean,
 ) : FirSpreadArgumentExpression() {
     @OptIn(UnresolvedExpressionTypeAccess::class)
     override val coneTypeOrNull: ConeKotlinType?

compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/FirArgumentUtil.kt

@@ -22,18 +22,19 @@ fun buildBinaryArgumentList(left: FirExpression, right: FirExpression): FirArgum
 }
 
 fun buildResolvedArgumentList(
-    mapping: LinkedHashMap<FirExpression, FirValueParameter>,
-    source: KtSourceElement? = null
-): FirResolvedArgumentList =
-    FirResolvedArgumentListImpl(source, mapping)
+    original: FirArgumentList?,
+    mapping: LinkedHashMap<FirExpression, FirValueParameter>
+): FirResolvedArgumentList {
+    return FirResolvedArgumentListImpl(original, mapping)
+}
 
 fun buildArgumentListForErrorCall(
     original: FirArgumentList,
-    mapping: Map<FirExpression, FirValueParameter?>
+    mapping: LinkedHashMap<FirExpression, FirValueParameter>
 ): FirArgumentList {
     return FirResolvedArgumentListForErrorCall(
-        original.source,
-        original.arguments.map { key -> key to mapping[key] }.toMap(LinkedHashMap())
+        original,
+        original.arguments.associateWithTo(LinkedHashMap()) { key -> mapping[key] },
     )
 }
 

compiler/fir/tree/src/org/jetbrains/kotlin/fir/expressions/impl/FirResolvedArgumentList.kt

@@ -11,14 +11,22 @@ import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.expressions.FirAbstractArgumentList
 import org.jetbrains.kotlin.fir.expressions.FirArgumentList
 import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirNamedArgumentExpression
 import org.jetbrains.kotlin.fir.visitors.FirTransformer
 import org.jetbrains.kotlin.fir.visitors.FirVisitor
 import org.jetbrains.kotlin.fir.visitors.transformSingle
 
 abstract class FirResolvedArgumentList : FirAbstractArgumentList() {
-    abstract override val source: KtSourceElement?
+    /**
+     * Contains the original, unresolved [FirArgumentList] which contains [FirNamedArgumentExpression]s,
+     * whereas [FirNamedArgumentExpression]s are removed from `this` resolved argument list.
+     */
+    abstract val originalArgumentList: FirArgumentList?
     abstract val mapping: LinkedHashMap<FirExpression, FirValueParameter>
 
+    final override val source: KtSourceElement?
+        get() = originalArgumentList?.source
+
     override val arguments: List<FirExpression>
         get() = mapping.keys.toList()
 
@@ -38,10 +46,9 @@ abstract class FirResolvedArgumentList : FirAbstractArgumentList() {
 
 
 internal class FirResolvedArgumentListImpl(
-    override val source: KtSourceElement?,
-    mapping: LinkedHashMap<FirExpression, FirValueParameter>
+    override val originalArgumentList: FirArgumentList?,
+    mapping: LinkedHashMap<FirExpression, FirValueParameter>,
 ) : FirResolvedArgumentList() {
-
     override var mapping: LinkedHashMap<FirExpression, FirValueParameter> = mapping
         private set
 
@@ -52,8 +59,8 @@ internal class FirResolvedArgumentListImpl(
 }
 
 internal class FirResolvedArgumentListForErrorCall(
-    override var source: KtSourceElement?,
-    private var _mapping: LinkedHashMap<FirExpression, FirValueParameter?>
+    override val originalArgumentList: FirArgumentList?,
+    private var _mapping: LinkedHashMap<FirExpression, FirValueParameter?>,
 ) : FirResolvedArgumentList() {
 
     override var mapping: LinkedHashMap<FirExpression, FirValueParameter> = computeMapping()

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/BuilderConfigurator.kt

@@ -377,6 +377,10 @@ object BuilderConfigurator : AbstractFirBuilderConfigurator<FirTreeBuilder>(FirT
             default("symbol", "FirAnonymousInitializerSymbol()")
         }
 
+        builder(spreadArgumentExpression) {
+            defaultFalse("isNamed", "isFakeSpread")
+        }
+
         val abstractResolvedQualifierBuilder by builder {
             fields from resolvedQualifier
         }

compiler/fir/tree/tree-generator/src/org/jetbrains/kotlin/fir/tree/generator/NodeConfigurator.kt

@@ -610,6 +610,11 @@ object NodeConfigurator : AbstractFieldConfigurator<FirTreeBuilder>(FirTreeBuild
             +booleanField("isSpread")
         }
 
+        spreadArgumentExpression.configure {
+            +booleanField("isNamed")
+            +booleanField("isFakeSpread")
+        }
+
         namedArgumentExpression.configure {
             +name
         }