diff --git a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
index 0295c7f5624..97d3ce9e651 100644
--- a/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
+++ b/compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt
@@ -245,10 +245,10 @@ val DIAGNOSTICS_LIST = DiagnosticListBuilder.buildDiagnosticList {
     group("Redeclarations") {
         val MANY_COMPANION_OBJECTS by error<FirSourceElement, PsiElement>()
         val CONFLICTING_OVERLOADS by error<FirSourceElement, PsiElement>(PositioningStrategy.DECLARATION_SIGNATURE_OR_DEFAULT) {
-            parameter<String>("conflictingOverloads") // TODO use Collection<Symbol> instead of String
+            parameter<Collection<AbstractFirBasedSymbol<*>>>("conflictingOverloads")
         }
         val REDECLARATION by error<FirSourceElement, PsiElement>() {
-            parameter<String>("conflictingDeclaration") // TODO use Collection<Symbol> instead of String
+            parameter<Collection<AbstractFirBasedSymbol<*>>>("conflictingDeclarations")
         }
         val ANY_METHOD_IMPLEMENTED_IN_INTERFACE by error<FirSourceElement, PsiElement>()
     }
diff --git a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
index 3c2f2f618f8..43d304be839 100644
--- a/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
+++ b/compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt
@@ -178,8 +178,8 @@ object FirErrors {
 
     // Redeclarations
     val MANY_COMPANION_OBJECTS by error0<FirSourceElement, PsiElement>()
-    val CONFLICTING_OVERLOADS by error1<FirSourceElement, PsiElement, String>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
-    val REDECLARATION by error1<FirSourceElement, PsiElement, String>()
+    val CONFLICTING_OVERLOADS by error1<FirSourceElement, PsiElement, Collection<AbstractFirBasedSymbol<*>>>(SourceElementPositioningStrategies.DECLARATION_SIGNATURE_OR_DEFAULT)
+    val REDECLARATION by error1<FirSourceElement, PsiElement, Collection<AbstractFirBasedSymbol<*>>>()
     val ANY_METHOD_IMPLEMENTED_IN_INTERFACE by error0<FirSourceElement, PsiElement>()
 
     // Invalid local declarations
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictsChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictsChecker.kt
index 4613251a767..76b4cd225ee 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictsChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictsChecker.kt
@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
+import org.jetbrains.kotlin.fir.FirSymbolOwner
 import org.jetbrains.kotlin.fir.analysis.checkers.FirDeclarationInspector
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
@@ -13,6 +14,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.declarations.FirDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 
 object FirConflictsChecker : FirBasicDeclarationChecker() {
     override fun check(declaration: FirDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
@@ -24,22 +26,22 @@ object FirConflictsChecker : FirBasicDeclarationChecker() {
             else -> return
         }
 
-        inspector.functionDeclarations.forEachNonSingle { it, hint ->
-            reporter.reportOn(it.source, FirErrors.CONFLICTING_OVERLOADS, hint, context)
+        inspector.functionDeclarations.forEachNonSingle { it, symbols ->
+            reporter.reportOn(it.source, FirErrors.CONFLICTING_OVERLOADS, symbols, context)
         }
 
-        inspector.otherDeclarations.forEachNonSingle { it, hint ->
-            reporter.reportOn(it.source, FirErrors.REDECLARATION, hint, context)
+        inspector.otherDeclarations.forEachNonSingle { it, symbols ->
+            reporter.reportOn(it.source, FirErrors.REDECLARATION, symbols, context)
         }
     }
 
-    private fun Map<String, List<FirDeclaration>>.forEachNonSingle(action: (FirDeclaration, String) -> Unit) {
+    private fun Map<String, List<FirDeclaration>>.forEachNonSingle(action: (FirDeclaration, Collection<AbstractFirBasedSymbol<*>>) -> Unit) {
         for (value in values) {
             if (value.size > 1) {
-                val hint = value.joinToString { that -> that.toString() }
+                val symbols = value.mapNotNull { (it as? FirSymbolOwner<*>)?.symbol }
 
                 value.forEach {
-                    action(it, hint)
+                    action(it, symbols)
                 }
             }
         }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt
index e2bcc0e751c..02a7a799985 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt
@@ -402,8 +402,8 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
 
             // Redeclarations
             map.put(MANY_COMPANION_OBJECTS, "Only one companion object is allowed per class")
-            map.put(CONFLICTING_OVERLOADS, "Conflicting overloads: {0}", TO_STRING) // *
-            map.put(REDECLARATION, "Conflicting declarations: {0}", TO_STRING) // *
+            map.put(CONFLICTING_OVERLOADS, "Conflicting overloads: {0}", SYMBOLS) // *
+            map.put(REDECLARATION, "Conflicting declarations: {0}", SYMBOLS) // *
             map.put(ANY_METHOD_IMPLEMENTED_IN_INTERFACE, "An interface may not implement a method of 'Any'") // &
 
             // Invalid local declarations
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderers.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderers.kt
index b0627cd5e12..4f8c8b6b190 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderers.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDiagnosticRenderers.kt
@@ -32,7 +32,7 @@ object FirDiagnosticRenderers {
     }
 
     val SYMBOLS = Renderer { symbols: Collection<AbstractFirBasedSymbol<*>> ->
-        symbols.joinToString(prefix = "[", postfix = "]", separator = ",", limit = 3, truncated = "...") { symbol ->
+        symbols.joinToString(prefix = "[", postfix = "]", separator = ", ", limit = 3, truncated = "...") { symbol ->
             SYMBOL.render(symbol)
         }
     }
diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt
index 31da6df9c5a..12e35474fc9 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt
@@ -731,14 +731,18 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
     }
     add(FirErrors.CONFLICTING_OVERLOADS) { firDiagnostic ->
         ConflictingOverloadsImpl(
-            firDiagnostic.a,
+            firDiagnostic.a.map { abstractFirBasedSymbol ->
+                firSymbolBuilder.buildSymbol(abstractFirBasedSymbol.fir as FirDeclaration)
+            },
             firDiagnostic as FirPsiDiagnostic<*>,
             token,
         )
     }
     add(FirErrors.REDECLARATION) { firDiagnostic ->
         RedeclarationImpl(
-            firDiagnostic.a,
+            firDiagnostic.a.map { abstractFirBasedSymbol ->
+                firSymbolBuilder.buildSymbol(abstractFirBasedSymbol.fir as FirDeclaration)
+            },
             firDiagnostic as FirPsiDiagnostic<*>,
             token,
         )
diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt
index 7a6b74440a1..1a7aca65037 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt
@@ -521,12 +521,12 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
 
     abstract class ConflictingOverloads : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = ConflictingOverloads::class
-        abstract val conflictingOverloads: String
+        abstract val conflictingOverloads: List<KtSymbol>
     }
 
     abstract class Redeclaration : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = Redeclaration::class
-        abstract val conflictingDeclaration: String
+        abstract val conflictingDeclarations: List<KtSymbol>
     }
 
     abstract class AnyMethodImplementedInInterface : KtFirDiagnostic<PsiElement>() {
diff --git a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
index cef054dea64..15b225a8cd3 100644
--- a/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
+++ b/idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt
@@ -830,7 +830,7 @@ internal class ManyCompanionObjectsImpl(
 }
 
 internal class ConflictingOverloadsImpl(
-    override val conflictingOverloads: String,
+    override val conflictingOverloads: List<KtSymbol>,
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
 ) : KtFirDiagnostic.ConflictingOverloads(), KtAbstractFirDiagnostic<PsiElement> {
@@ -838,7 +838,7 @@ internal class ConflictingOverloadsImpl(
 }
 
 internal class RedeclarationImpl(
-    override val conflictingDeclaration: String,
+    override val conflictingDeclarations: List<KtSymbol>,
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
 ) : KtFirDiagnostic.Redeclaration(), KtAbstractFirDiagnostic<PsiElement> {