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 5b94460a634..61d01694a98 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
@@ -327,7 +327,7 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
         val ILLEGAL_PROJECTION_USAGE by error<PsiElement>()
         val TYPE_PARAMETERS_IN_ENUM by error<PsiElement>()
         val CONFLICTING_PROJECTION by error<PsiElement> {
-            parameter<String>("type") // TODO use ConeType instead of String
+            parameter<ConeKotlinType>("type")
         }
         val VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED by error<KtTypeParameter>(PositioningStrategy.VARIANCE_MODIFIER)
 
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 cb4caa201f6..9c5fb9f0cd3 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
@@ -249,7 +249,7 @@ object FirErrors {
     val TYPE_PARAMETERS_IN_OBJECT by error0<PsiElement>()
     val ILLEGAL_PROJECTION_USAGE by error0<PsiElement>()
     val TYPE_PARAMETERS_IN_ENUM by error0<PsiElement>()
-    val CONFLICTING_PROJECTION by error1<PsiElement, String>()
+    val CONFLICTING_PROJECTION by error1<PsiElement, ConeKotlinType>()
     val VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED by error0<KtTypeParameter>(SourceElementPositioningStrategies.VARIANCE_MODIFIER)
     val CATCH_PARAMETER_WITH_DEFAULT_VALUE by error0<PsiElement>()
     val REIFIED_TYPE_IN_CATCH_CLAUSE by error0<PsiElement>()
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictingProjectionChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictingProjectionChecker.kt
index 3133ce79eff..52250e2eeba 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictingProjectionChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirConflictingProjectionChecker.kt
@@ -66,7 +66,7 @@ object FirConflictingProjectionChecker : FirBasicDeclarationChecker() {
                 actual is ConeKotlinTypeProjectionIn && protoVariance == Variance.OUT_VARIANCE ||
                 actual is ConeKotlinTypeProjectionOut && protoVariance == Variance.IN_VARIANCE
             ) {
-                reporter.reportOn(typeRef.source, FirErrors.CONFLICTING_PROJECTION, typeRef.coneType.toString(), context)
+                reporter.reportOn(typeRef.source, FirErrors.CONFLICTING_PROJECTION, typeRef.coneType, context)
                 return
             }
         }
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 6959c4c705f..ba16937106f 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
@@ -559,7 +559,7 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
             map.put(
                 CONFLICTING_PROJECTION,
                 "Projection is conflicting with variance of the corresponding type parameter of {0}. Remove the projection or replace it with ''*''",
-                TO_STRING
+                RENDER_TYPE
             )
             map.put(
                 VARIANCE_ON_TYPE_PARAMETER_NOT_ALLOWED,
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 7124b2675e2..05955fde1d5 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
@@ -1050,7 +1050,7 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
     }
     add(FirErrors.CONFLICTING_PROJECTION) { firDiagnostic ->
         ConflictingProjectionImpl(
-            firDiagnostic.a,
+            firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.a),
             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 4afd290dc32..f944e769343 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
@@ -743,7 +743,7 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
 
     abstract class ConflictingProjection : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = ConflictingProjection::class
-        abstract val type: String
+        abstract val type: KtType
     }
 
     abstract class VarianceOnTypeParameterNotAllowed : KtFirDiagnostic<KtTypeParameter>() {
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 3aa67f8c6e0..4c35aa692b9 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
@@ -1196,7 +1196,7 @@ internal class TypeParametersInEnumImpl(
 }
 
 internal class ConflictingProjectionImpl(
-    override val type: String,
+    override val type: KtType,
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
 ) : KtFirDiagnostic.ConflictingProjection(), KtAbstractFirDiagnostic<PsiElement> {