diff --git a/compiler/fir/analysis-tests/testData/resolve/diagnostics/upperBoundViolated.kt b/compiler/fir/analysis-tests/testData/resolve/diagnostics/upperBoundViolated.kt
index 1249a552db8..ec716b05c42 100644
--- a/compiler/fir/analysis-tests/testData/resolve/diagnostics/upperBoundViolated.kt
+++ b/compiler/fir/analysis-tests/testData/resolve/diagnostics/upperBoundViolated.kt
@@ -1,4 +1,3 @@
-// COMPARE_WITH_LIGHT_TREE
 interface A
 
 class B<T> where T : A
@@ -15,7 +14,7 @@ fun test() {
     val b1 = B<<!UPPER_BOUND_VIOLATED!>Int<!>>()
     val b2 = B<C>()
     val b3 = B<<!UPPER_BOUND_VIOLATED!>Any?<!>>()
-    val b4 = B<<!UNRESOLVED_REFERENCE!>UnexistingType<!>>()<!UNRESOLVED_REFERENCE!>NL<!><!SYNTAX!><<!>Int<!SYNTAX{LT}!><!SYNTAX!>><!>()<!>NumberPhile<!SYNTAX!><!>
+    val b4 = B<<!UNRESOLVED_REFERENCE!>UnexistingType<!>>()<!UNRESOLVED_REFERENCE!>NL<!><!SYNTAX!><<!>Int<!SYNTAX!><!SYNTAX!>><!>()<!>NumberPhile<!SYNTAX!><!>
     val b5 = B<<!UPPER_BOUND_VIOLATED!>B<<!UNRESOLVED_REFERENCE!>UnexistingType<!>><!>>()
     fest<<!UPPER_BOUND_VIOLATED!>Boolean<!>>()
     fest<C>()
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
index c772984c47c..ed0b8825c08 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/components/ErrorNodeDiagnosticCollectorComponent.kt
@@ -13,14 +13,8 @@ import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fakeElement
 import org.jetbrains.kotlin.fir.analysis.diagnostics.toFirDiagnostics
-import org.jetbrains.kotlin.fir.declarations.FirErrorFunction
-import org.jetbrains.kotlin.fir.declarations.FirErrorImport
-import org.jetbrains.kotlin.fir.declarations.FirErrorProperty
-import org.jetbrains.kotlin.fir.declarations.FirProperty
-import org.jetbrains.kotlin.fir.diagnostics.ConeAmbiguousSuper
-import org.jetbrains.kotlin.fir.diagnostics.ConeDiagnostic
-import org.jetbrains.kotlin.fir.diagnostics.ConeSimpleDiagnostic
-import org.jetbrains.kotlin.fir.diagnostics.DiagnosticKind
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.diagnostics.*
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.references.FirErrorNamedReference
 import org.jetbrains.kotlin.fir.references.FirNamedReference
@@ -33,12 +27,12 @@ class ErrorNodeDiagnosticCollectorComponent(
     reporter: DiagnosticReporter,
 ) : AbstractDiagnosticCollectorComponent(session, reporter) {
     override fun visitErrorLoop(errorLoop: FirErrorLoop, data: CheckerContext) {
-        val source = errorLoop.source ?: return
+        val source = errorLoop.source
         reportFirDiagnostic(errorLoop.diagnostic, source, data)
     }
 
     override fun visitErrorTypeRef(errorTypeRef: FirErrorTypeRef, data: CheckerContext) {
-        val source = errorTypeRef.source ?: return
+        val source = errorTypeRef.source
         reportFirDiagnostic(errorTypeRef.diagnostic, source, data)
     }
 
@@ -49,7 +43,7 @@ class ErrorNodeDiagnosticCollectorComponent(
     }
 
     override fun visitErrorAnnotationCall(errorAnnotationCall: FirErrorAnnotationCall, data: CheckerContext) {
-        val source = errorAnnotationCall.source ?: return
+        val source = errorAnnotationCall.source
         reportFirDiagnostic(errorAnnotationCall.diagnostic, source, data)
     }
 
@@ -62,15 +56,15 @@ class ErrorNodeDiagnosticCollectorComponent(
     }
 
     private fun processErrorReference(reference: FirNamedReference, diagnostic: ConeDiagnostic, context: CheckerContext) {
-        var source = reference.source ?: return
+        var source = reference.source
         val callOrAssignment = context.callsOrAssignments.lastOrNull()?.takeIf {
             // Use the source of the enclosing FirQualifiedAccess if it is exactly the call to the erroneous callee.
             it.calleeReference == reference
         }
         // Don't report duplicated unresolved reference on annotation entry (already reported on its type)
-        if (source.elementType == KtNodeTypes.ANNOTATION_ENTRY && diagnostic is ConeUnresolvedNameError) return
+        if (source?.elementType == KtNodeTypes.ANNOTATION_ENTRY && diagnostic is ConeUnresolvedNameError) return
         // Already reported in FirConventionFunctionCallChecker
-        if (source.kind == KtFakeSourceElementKind.ArrayAccessNameReference &&
+        if (source?.kind == KtFakeSourceElementKind.ArrayAccessNameReference &&
             diagnostic is ConeUnresolvedNameError
         ) return
 
@@ -82,7 +76,7 @@ class ErrorNodeDiagnosticCollectorComponent(
             ) return
         }
 
-        if (source.kind == KtFakeSourceElementKind.DelegatedPropertyAccessor) {
+        if (source?.kind == KtFakeSourceElementKind.DelegatedPropertyAccessor) {
             val property = context.containingDeclarations.lastOrNull { it is FirProperty } as? FirProperty ?: return
             source = property.delegate?.source?.fakeElement(KtFakeSourceElementKind.DelegatedPropertyAccessor) ?: return
         }
@@ -101,55 +95,62 @@ class ErrorNodeDiagnosticCollectorComponent(
     }
 
     override fun visitErrorExpression(errorExpression: FirErrorExpression, data: CheckerContext) {
-        val source = errorExpression.source ?: return
-        reportFirDiagnostic(errorExpression.diagnostic, source, data)
+        val source = errorExpression.source
+        val diagnostic = errorExpression.diagnostic
+        if (source == null) {
+            // ConeSyntaxDiagnostic and DiagnosticKind.ExpressionExpected with no source (see check above) are typically symptoms of some
+            // syntax error that was already reported during parsing.
+            if (diagnostic is ConeSyntaxDiagnostic) return
+            if (diagnostic is ConeSimpleDiagnostic && diagnostic.kind == DiagnosticKind.ExpressionExpected) return
+        }
+        reportFirDiagnostic(diagnostic, source, data)
     }
 
     override fun visitErrorFunction(errorFunction: FirErrorFunction, data: CheckerContext) {
-        val source = errorFunction.source ?: return
+        val source = errorFunction.source
         reportFirDiagnostic(errorFunction.diagnostic, source, data)
     }
 
     override fun visitErrorProperty(errorProperty: FirErrorProperty, data: CheckerContext) {
-        val source = errorProperty.source ?: return
+        val source = errorProperty.source
         reportFirDiagnostic(errorProperty.diagnostic, source, data)
     }
 
     override fun visitErrorResolvedQualifier(errorResolvedQualifier: FirErrorResolvedQualifier, data: CheckerContext) {
-        val source = errorResolvedQualifier.source ?: return
+        val source = errorResolvedQualifier.source
         reportFirDiagnostic(errorResolvedQualifier.diagnostic, source, data)
     }
 
     override fun visitErrorImport(errorImport: FirErrorImport, data: CheckerContext) {
-        val source = errorImport.source ?: return
+        val source = errorImport.source
         reportFirDiagnostic(errorImport.diagnostic, source, data)
     }
 
     private fun reportFirDiagnostic(
         diagnostic: ConeDiagnostic,
-        source: KtSourceElement,
+        source: KtSourceElement?,
         context: CheckerContext,
         callOrAssignmentSource: KtSourceElement? = null
     ) {
         // Will be handled by [FirDestructuringDeclarationChecker]
-        if (source.elementType == KtNodeTypes.DESTRUCTURING_DECLARATION_ENTRY) {
+        if (source?.elementType == KtNodeTypes.DESTRUCTURING_DECLARATION_ENTRY) {
             return
         }
 
         // Will be handled by [FirDelegatedPropertyChecker]
-        if (source.kind == KtFakeSourceElementKind.DelegatedPropertyAccessor &&
+        if (source?.kind == KtFakeSourceElementKind.DelegatedPropertyAccessor &&
             (diagnostic is ConeUnresolvedNameError || diagnostic is ConeAmbiguityError || diagnostic is ConeInapplicableWrongReceiver || diagnostic is ConeInapplicableCandidateError)
         ) {
             return
         }
 
-        if (source.kind == KtFakeSourceElementKind.ImplicitConstructor || source.kind == KtFakeSourceElementKind.DesugaredForLoop) {
+        if (source?.kind == KtFakeSourceElementKind.ImplicitConstructor || source?.kind == KtFakeSourceElementKind.DesugaredForLoop) {
             // See FirForLoopChecker
             return
         }
 
         // Prefix inc/dec on array access will have two calls to .get(...), don't report for the second one.
-        if (source.kind == KtFakeSourceElementKind.DesugaredPrefixSecondGetReference) {
+        if (source?.kind == KtFakeSourceElementKind.DesugaredPrefixSecondGetReference) {
             return
         }
 
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt
index 491945a02d5..797f1c64895 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/coneDiagnosticToFirDiagnostic.kt
@@ -45,7 +45,7 @@ import org.jetbrains.kotlin.utils.addToStdlib.runIf
 import org.jetbrains.kotlin.utils.addToStdlib.shouldNotBeCalled
 
 private fun ConeDiagnostic.toKtDiagnostic(
-    source: KtSourceElement,
+    source: KtSourceElement?,
     callOrAssignmentSource: KtSourceElement?
 ): KtDiagnostic? = when (this) {
     is ConeUnresolvedReferenceError -> FirErrors.UNRESOLVED_REFERENCE.createOn(
@@ -118,7 +118,7 @@ private fun ConeDiagnostic.toKtDiagnostic(
     is ConeSyntaxDiagnostic -> FirSyntaxErrors.SYNTAX.createOn(callOrAssignmentSource ?: source, reason)
 
     is ConeSimpleDiagnostic -> when {
-        source.kind is KtFakeSourceElementKind && source.kind != KtFakeSourceElementKind.ReferenceInAtomicQualifiedAccess -> null
+        source?.kind is KtFakeSourceElementKind && source.kind != KtFakeSourceElementKind.ReferenceInAtomicQualifiedAccess -> null
         else -> this.getFactory(source).createOn(callOrAssignmentSource ?: source)
     }
 
@@ -162,7 +162,7 @@ fun FirBasedSymbol<*>.toInvisibleReferenceDiagnostic(source: KtSourceElement?):
 
 fun ConeDiagnostic.toFirDiagnostics(
     session: FirSession,
-    source: KtSourceElement,
+    source: KtSourceElement?,
     callOrAssignmentSource: KtSourceElement?
 ): List<KtDiagnostic> {
     return when (this) {
@@ -175,9 +175,9 @@ fun ConeDiagnostic.toFirDiagnostics(
 private fun mapUnsafeCallError(
     candidate: AbstractCandidate,
     rootCause: UnsafeCall,
-    source: KtSourceElement,
+    source: KtSourceElement?,
     qualifiedAccessSource: KtSourceElement?,
-): KtDiagnostic? {
+): KtDiagnostic {
     if (candidate.callInfo.isImplicitInvoke) {
         return FirErrors.UNSAFE_IMPLICIT_INVOKE_CALL.createOn(source, rootCause.actualType)
     }
@@ -187,14 +187,14 @@ private fun mapUnsafeCallError(
     val receiverExpression = candidate.callInfo.explicitReceiver
     val singleArgument = candidate.callInfo.argumentList.arguments.singleOrNull()
     if (receiverExpression != null && singleArgument != null &&
-        (source.elementType == KtNodeTypes.OPERATION_REFERENCE || source.elementType == KtNodeTypes.BINARY_EXPRESSION) &&
+        (source?.elementType == KtNodeTypes.OPERATION_REFERENCE || source?.elementType == KtNodeTypes.BINARY_EXPRESSION) &&
         (candidateFunctionSymbol?.isOperator == true || candidateFunctionSymbol?.isInfix == true)
     ) {
         // For augmented assignment operations (e.g., `a += b`), the source is the entire binary expression (BINARY_EXPRESSION).
         // TODO, KT-59809: No need to check for source.elementType == BINARY_EXPRESSION if we use operator as callee reference source
         //  (see FirExpressionsResolveTransformer.transformAssignmentOperatorStatement)
-        val operationSource = if (source.elementType == KtNodeTypes.BINARY_EXPRESSION) {
-            source.getChild(KtNodeTypes.OPERATION_REFERENCE)
+        val operationSource = if (source?.elementType == KtNodeTypes.BINARY_EXPRESSION) {
+            source?.getChild(KtNodeTypes.OPERATION_REFERENCE)
         } else {
             source
         }
@@ -216,7 +216,7 @@ private fun mapUnsafeCallError(
             )
         }
     }
-    return if (source.kind == KtFakeSourceElementKind.ArrayAccessNameReference) {
+    return if (source?.kind == KtFakeSourceElementKind.ArrayAccessNameReference) {
         FirErrors.UNSAFE_CALL.createOn(source, rootCause.actualType, receiverExpression)
     } else {
         FirErrors.UNSAFE_CALL.createOn(qualifiedAccessSource ?: source, rootCause.actualType, receiverExpression)
@@ -226,7 +226,7 @@ private fun mapUnsafeCallError(
 private fun mapInapplicableCandidateError(
     session: FirSession,
     diagnostic: ConeInapplicableCandidateError,
-    source: KtSourceElement,
+    source: KtSourceElement?,
     qualifiedAccessSource: KtSourceElement?,
 ): List<KtDiagnostic> {
     val typeContext = session.typeContext
@@ -341,7 +341,7 @@ private fun mapInapplicableCandidateError(
 private fun mapSystemHasContradictionError(
     session: FirSession,
     diagnostic: ConeConstraintSystemHasContradiction,
-    source: KtSourceElement,
+    source: KtSourceElement?,
     qualifiedAccessSource: KtSourceElement?,
 ): List<KtDiagnostic> {
     return buildList {
@@ -380,7 +380,7 @@ private fun mapSystemHasContradictionError(
 }
 
 private fun ConstraintSystemError.toDiagnostic(
-    source: KtSourceElement,
+    source: KtSourceElement?,
     qualifiedAccessSource: KtSourceElement?,
     typeContext: ConeTypeContext,
     candidate: AbstractCandidate,
@@ -507,7 +507,7 @@ private fun findInferredEmptyIntersectionNarrowedSource(
 }
 
 private fun reportInferredIntoEmptyIntersection(
-    source: KtSourceElement,
+    source: KtSourceElement?,
     typeVariable: ConeTypeVariable,
     incompatibleTypes: Collection<ConeKotlinType>,
     causingTypes: Collection<ConeKotlinType>,
@@ -531,7 +531,7 @@ private fun reportInferredIntoEmptyIntersection(
 private val NewConstraintError.lowerConeType: ConeKotlinType get() = lowerType as ConeKotlinType
 private val NewConstraintError.upperConeType: ConeKotlinType get() = upperType as ConeKotlinType
 
-private fun ConeSimpleDiagnostic.getFactory(source: KtSourceElement): KtDiagnosticFactory0 {
+private fun ConeSimpleDiagnostic.getFactory(source: KtSourceElement?): KtDiagnosticFactory0 {
     return when (kind) {
         DiagnosticKind.ReturnNotAllowed -> FirErrors.RETURN_NOT_ALLOWED
         DiagnosticKind.NotAFunctionLabel -> FirErrors.NOT_A_FUNCTION_LABEL
@@ -544,7 +544,7 @@ private fun ConeSimpleDiagnostic.getFactory(source: KtSourceElement): KtDiagnost
         DiagnosticKind.RecursionInImplicitTypes -> FirErrors.RECURSION_IN_IMPLICIT_TYPES
         DiagnosticKind.Java -> FirErrors.ERROR_FROM_JAVA_RESOLUTION
         DiagnosticKind.SuperNotAllowed -> FirErrors.SUPER_IS_NOT_AN_EXPRESSION
-        DiagnosticKind.ExpressionExpected -> when (source.elementType) {
+        DiagnosticKind.ExpressionExpected -> when (source?.elementType) {
             KtNodeTypes.BINARY_EXPRESSION -> FirErrors.ASSIGNMENT_IN_EXPRESSION_CONTEXT
             KtNodeTypes.FUN -> FirErrors.ANONYMOUS_FUNCTION_WITH_NAME
             KtNodeTypes.WHEN_CONDITION_IN_RANGE, KtNodeTypes.WHEN_CONDITION_IS_PATTERN, KtNodeTypes.WHEN_CONDITION_EXPRESSION ->
@@ -586,16 +586,16 @@ private fun ConeSimpleDiagnostic.getFactory(source: KtSourceElement): KtDiagnost
 @OptIn(InternalDiagnosticFactoryMethod::class)
 private fun KtDiagnosticFactory0.createOn(
     element: KtSourceElement?
-): KtSimpleDiagnostic? {
-    return element?.let { on(it, positioningStrategy = null) }
+): KtSimpleDiagnostic {
+    return on(element.requireNotNull(), positioningStrategy = null)
 }
 
 @OptIn(InternalDiagnosticFactoryMethod::class)
 private fun <A> KtDiagnosticFactory1<A>.createOn(
     element: KtSourceElement?,
     a: A
-): KtDiagnosticWithParameters1<A>? {
-    return element?.let { on(it, a, positioningStrategy = null) }
+): KtDiagnosticWithParameters1<A> {
+    return on(element.requireNotNull(), a, positioningStrategy = null)
 }
 
 @OptIn(InternalDiagnosticFactoryMethod::class)
@@ -603,8 +603,8 @@ private fun <A, B> KtDiagnosticFactory2<A, B>.createOn(
     element: KtSourceElement?,
     a: A,
     b: B
-): KtDiagnosticWithParameters2<A, B>? {
-    return element?.let { on(it, a, b, positioningStrategy = null) }
+): KtDiagnosticWithParameters2<A, B> {
+    return on(element.requireNotNull(), a, b, positioningStrategy = null)
 }
 
 @OptIn(InternalDiagnosticFactoryMethod::class)
@@ -613,8 +613,8 @@ private fun <A, B, C> KtDiagnosticFactory3<A, B, C>.createOn(
     a: A,
     b: B,
     c: C
-): KtDiagnosticWithParameters3<A, B, C>? {
-    return element?.let { on(it, a, b, c, positioningStrategy = null) }
+): KtDiagnosticWithParameters3<A, B, C> {
+    return on(element.requireNotNull(), a, b, c, positioningStrategy = null)
 }
 
 @OptIn(InternalDiagnosticFactoryMethod::class)
@@ -624,6 +624,6 @@ private fun <A, B, C, D> KtDiagnosticFactory4<A, B, C, D>.createOn(
     b: B,
     c: C,
     d: D
-): KtDiagnosticWithParameters4<A, B, C, D>? {
-    return element?.let { on(it, a, b, c, d, positioningStrategy = null) }
+): KtDiagnosticWithParameters4<A, B, C, D> {
+    return on(element.requireNotNull(), a, b, c, d, positioningStrategy = null)
 }
diff --git a/compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirExpressionBuilder.kt b/compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirExpressionBuilder.kt
index 24d163b76c5..13dca77f72e 100644
--- a/compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirExpressionBuilder.kt
+++ b/compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirExpressionBuilder.kt
@@ -66,7 +66,8 @@ class LightTreeRawFirExpressionBuilder(
         return converted as? R
             ?: buildErrorExpression(
                 expression?.toFirSourceElement(),
-                ConeSimpleDiagnostic(errorReason, DiagnosticKind.ExpressionExpected),
+                if (expression == null) ConeSyntaxDiagnostic(errorReason)
+                else ConeSimpleDiagnostic(errorReason, DiagnosticKind.ExpressionExpected),
                 converted,
             ) as R
     }
@@ -116,7 +117,7 @@ class LightTreeRawFirExpressionBuilder(
             OBJECT_LITERAL -> declarationBuilder.convertObjectLiteral(expression)
             FUN -> declarationBuilder.convertFunctionDeclaration(expression)
             DESTRUCTURING_DECLARATION -> declarationBuilder.convertDestructingDeclaration(expression).toFirDestructingDeclaration(baseModuleData)
-            else -> buildErrorExpression(null, ConeSimpleDiagnostic(errorReason, DiagnosticKind.ExpressionExpected))
+            else -> buildErrorExpression(expression.toFirSourceElement(KtFakeSourceElementKind.ErrorTypeRef), ConeSimpleDiagnostic(errorReason, DiagnosticKind.ExpressionExpected))
         }
     }
 
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
index dc329df1d06..691e93b5619 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirSyntheticCallGenerator.kt
@@ -50,7 +50,7 @@ import org.jetbrains.kotlin.name.CallableId
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.resolve.ArrayFqNames
 import org.jetbrains.kotlin.resolve.calls.tasks.ExplicitReceiverKind
-import org.jetbrains.kotlin.resolve.calls.tower.CandidateApplicability
+import org.jetbrains.kotlin.resolve.calls.tower.isSuccess
 import org.jetbrains.kotlin.types.Variance
 
 class FirSyntheticCallGenerator(
@@ -259,17 +259,18 @@ class FirSyntheticCallGenerator(
         val callInfo = generateCallInfo(callSite, name, argumentList, callKind)
         val candidate = generateCandidate(callInfo, function, context)
         val applicability = components.resolutionStageRunner.processCandidate(candidate, context)
-        if (applicability <= CandidateApplicability.INAPPLICABLE) {
+        val source = callSite.source?.fakeElement(KtFakeSourceElementKind.SyntheticCall)
+        if (!applicability.isSuccess) {
             return createErrorReferenceWithExistingCandidate(
                 candidate,
                 ConeInapplicableCandidateError(applicability, candidate),
-                source = null,
+                source,
                 context,
                 components.resolutionStageRunner
             )
         }
 
-        return FirNamedReferenceWithCandidate(callSite.source?.fakeElement(KtFakeSourceElementKind.SyntheticCall), name, candidate)
+        return FirNamedReferenceWithCandidate(source, name, candidate)
     }
 
     private fun generateCandidate(callInfo: CallInfo, function: FirSimpleFunction, context: ResolutionContext): Candidate {
diff --git a/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/KtDiagnosticReportHelpers.kt b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/KtDiagnosticReportHelpers.kt
index 610fbfdbb9b..d09844e0beb 100644
--- a/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/KtDiagnosticReportHelpers.kt
+++ b/compiler/frontend.common/src/org/jetbrains/kotlin/diagnostics/KtDiagnosticReportHelpers.kt
@@ -15,7 +15,7 @@ fun DiagnosticReporter.reportOn(
     context: DiagnosticContext,
     positioningStrategy: AbstractSourceElementPositioningStrategy? = null
 ) {
-    report(factory.on(requireSourceNotNull(source), positioningStrategy), context)
+    report(factory.on(source.requireNotNull(), positioningStrategy), context)
 }
 
 fun <A : Any> DiagnosticReporter.reportOn(
@@ -25,7 +25,7 @@ fun <A : Any> DiagnosticReporter.reportOn(
     context: DiagnosticContext,
     positioningStrategy: AbstractSourceElementPositioningStrategy? = null
 ) {
-    report(factory.on(requireSourceNotNull(source), a, positioningStrategy), context)
+    report(factory.on(source.requireNotNull(), a, positioningStrategy), context)
 }
 
 fun <A : Any, B : Any> DiagnosticReporter.reportOn(
@@ -36,7 +36,7 @@ fun <A : Any, B : Any> DiagnosticReporter.reportOn(
     context: DiagnosticContext,
     positioningStrategy: AbstractSourceElementPositioningStrategy? = null
 ) {
-    report(factory.on(requireSourceNotNull(source), a, b, positioningStrategy), context)
+    report(factory.on(source.requireNotNull(), a, b, positioningStrategy), context)
 }
 
 fun <A : Any, B : Any, C : Any> DiagnosticReporter.reportOn(
@@ -48,7 +48,7 @@ fun <A : Any, B : Any, C : Any> DiagnosticReporter.reportOn(
     context: DiagnosticContext,
     positioningStrategy: AbstractSourceElementPositioningStrategy? = null
 ) {
-    report(factory.on(requireSourceNotNull(source), a, b, c, positioningStrategy), context)
+    report(factory.on(source.requireNotNull(), a, b, c, positioningStrategy), context)
 }
 
 fun <A : Any, B : Any, C : Any, D : Any> DiagnosticReporter.reportOn(
@@ -61,11 +61,11 @@ fun <A : Any, B : Any, C : Any, D : Any> DiagnosticReporter.reportOn(
     context: DiagnosticContext,
     positioningStrategy: AbstractSourceElementPositioningStrategy? = null
 ) {
-    report(factory.on(requireSourceNotNull(source), a, b, c, d, positioningStrategy), context)
+    report(factory.on(source.requireNotNull(), a, b, c, d, positioningStrategy), context)
 }
 
-private fun requireSourceNotNull(source: AbstractKtSourceElement?): AbstractKtSourceElement =
-    requireNotNull(source) { "source must not be null" }
+fun AbstractKtSourceElement?.requireNotNull(): AbstractKtSourceElement =
+    requireNotNull(this) { "source must not be null" }
 
 fun DiagnosticReporter.reportOn(
     source: AbstractKtSourceElement?,
diff --git a/compiler/testData/diagnostics/tests/incompleteCode/kt59041.fir.kt b/compiler/testData/diagnostics/tests/incompleteCode/kt59041.fir.kt
index 5fcbf3f1bd3..6c17d5958d9 100644
--- a/compiler/testData/diagnostics/tests/incompleteCode/kt59041.fir.kt
+++ b/compiler/testData/diagnostics/tests/incompleteCode/kt59041.fir.kt
@@ -1,6 +1,5 @@
-// COMPARE_WITH_LIGHT_TREE
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 
 fun main() {
-     val list = <!UNRESOLVED_REFERENCE!>mutable<!> ListOf<!SYNTAX!><<!>Int<!SYNTAX{LT}!><!SYNTAX!>><!>(1) {}<!>
+     val list = <!UNRESOLVED_REFERENCE!>mutable<!> ListOf<!SYNTAX!><<!>Int<!SYNTAX!><!SYNTAX!>><!>(1) {}<!>
 }
diff --git a/compiler/testData/diagnostics/tests/incompleteCode/kt59041.kt b/compiler/testData/diagnostics/tests/incompleteCode/kt59041.kt
index 87860776cb2..8d29c5c0d3c 100644
--- a/compiler/testData/diagnostics/tests/incompleteCode/kt59041.kt
+++ b/compiler/testData/diagnostics/tests/incompleteCode/kt59041.kt
@@ -1,4 +1,3 @@
-// COMPARE_WITH_LIGHT_TREE
 // !DIAGNOSTICS: -UNUSED_VARIABLE
 
 fun main() {
diff --git a/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.fir.kt b/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.fir.kt
index 6be207023bd..548220ab308 100644
--- a/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.fir.kt
+++ b/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.fir.kt
@@ -1,4 +1,3 @@
 // NI_EXPECTED_FILE
-// COMPARE_WITH_LIGHT_TREE
 
-val unwrapped = <!UNRESOLVED_REFERENCE!>some<!>.<!SYNTAX!><<!><!UNRESOLVED_REFERENCE!>cabc<!><!SYNTAX{LT}!><!SYNTAX!>$Wrapper<!><<!PROJECTION_ON_NON_CLASS_TYPE_ARGUMENT!>out Any<!>><!>::<!UNRESOLVED_REFERENCE!>unwrap<!>
+val unwrapped = <!UNRESOLVED_REFERENCE!>some<!>.<!SYNTAX!><<!><!UNRESOLVED_REFERENCE!>cabc<!><!SYNTAX!><!SYNTAX!>$Wrapper<!><<!PROJECTION_ON_NON_CLASS_TYPE_ARGUMENT!>out Any<!>><!>::<!UNRESOLVED_REFERENCE!>unwrap<!>
diff --git a/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.kt b/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.kt
index 63460a80e07..3e1d5fce80b 100644
--- a/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.kt
+++ b/compiler/testData/diagnostics/tests/qualifiedExpression/nullCalleeExpression.kt
@@ -1,4 +1,3 @@
 // NI_EXPECTED_FILE
-// COMPARE_WITH_LIGHT_TREE
 
 val unwrapped = <!UNRESOLVED_REFERENCE!>some<!>.<!SYNTAX!><<!><!DEBUG_INFO_MISSING_UNRESOLVED!>cabc<!><!SYNTAX!>$Wrapper<!><out <!DEBUG_INFO_MISSING_UNRESOLVED!>Any<!>>::<!DEBUG_INFO_MISSING_UNRESOLVED!>unwrap<!>