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 c766777b82d..6c21410b410 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
@@ -13,6 +13,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.declarations.impl.FirOuterClassTypeParameterRef
 import org.jetbrains.kotlin.fir.resolve.firProvider
 import org.jetbrains.kotlin.fir.resolve.getOuterClass
 import org.jetbrains.kotlin.fir.scopes.PACKAGE_MEMBER
@@ -26,7 +27,6 @@ import org.jetbrains.kotlin.fir.util.ListMultimap
 import org.jetbrains.kotlin.fir.visitors.FirVisitorVoid
 import org.jetbrains.kotlin.name.ClassId
 import org.jetbrains.kotlin.name.Name
-import org.jetbrains.kotlin.name.SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
 import org.jetbrains.kotlin.utils.SmartSet
 
 object FirConflictsChecker : FirBasicDeclarationChecker() {
@@ -217,11 +217,8 @@ object FirConflictsChecker : FirBasicDeclarationChecker() {
         when (declaration) {
             is FirFile -> checkFile(declaration, inspector, context)
             is FirRegularClass -> checkRegularClass(declaration, inspector)
-            is FirFunction -> {
-                checkConflictingValueParameters(declaration, context, reporter)
-                return
+            else -> {
             }
-            else -> return
         }
 
         inspector.declarationConflictingSymbols.forEach { (conflictingDeclaration, symbols) ->
@@ -246,24 +243,61 @@ object FirConflictsChecker : FirBasicDeclarationChecker() {
                 }
             }
         }
+
+        if (declaration.source?.kind !is FirFakeSourceElementKind) {
+            when (declaration) {
+                is FirMemberDeclaration -> {
+                    if (declaration is FirFunction) {
+                        checkConflictingParameters(declaration.valueParameters, context, reporter)
+                    }
+                    checkConflictingParameters(declaration.typeParameters, context, reporter)
+                }
+                is FirTypeParametersOwner -> {
+                    checkConflictingParameters(declaration.typeParameters, context, reporter)
+                }
+                else -> {
+                }
+            }
+        }
     }
 
-    private fun checkConflictingValueParameters(function: FirFunction, context: CheckerContext, reporter: DiagnosticReporter) {
-        val multimap = ListMultimap<Name, FirValueParameter>()
-        for (parameter in function.valueParameters) {
-            if (!parameter.name.isSpecial) {
-                multimap.put(parameter.name, parameter)
+    private fun checkConflictingParameters(parameters: List<FirElement>, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (parameters.size <= 1) return
+
+        val multimap = ListMultimap<Name, FirBasedSymbol<*>>()
+        for (parameter in parameters) {
+            val name: Name
+            val symbol: FirBasedSymbol<*>
+            when (parameter) {
+                is FirValueParameter -> {
+                    symbol = parameter.symbol
+                    name = parameter.name
+                }
+                is FirOuterClassTypeParameterRef -> {
+                    continue
+                }
+                is FirTypeParameterRef -> {
+                    symbol = parameter.symbol
+                    name = symbol.name
+                }
+                is FirTypeParameter -> {
+                    symbol = parameter.symbol
+                    name = parameter.name
+                }
+                else -> throw AssertionError("Invalid parameter type")
+            }
+            if (!name.isSpecial) {
+                multimap.put(name, symbol)
             }
         }
         for (key in multimap.keys) {
-            val parameters = multimap[key]
-            if (parameters.size > 1) {
-                val symbols = parameters.map { it.symbol }
-                for (parameter in parameters) {
+            val conflictingParameters = multimap[key]
+            if (conflictingParameters.size > 1) {
+                for (parameter in conflictingParameters) {
                     reporter.reportOn(
                         parameter.source,
                         FirErrors.REDECLARATION,
-                        symbols,
+                        conflictingParameters,
                         context
                     )
                 }
diff --git a/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.fir.kt b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.fir.kt
new file mode 100644
index 00000000000..9e4927535c8
--- /dev/null
+++ b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.fir.kt
@@ -0,0 +1,9 @@
+data class A1(val <!REDECLARATION, REDECLARATION!>x<!>: Int, val y: String, val <!REDECLARATION, REDECLARATION!>x<!>: Int) {
+    val z = ""
+}
+
+data class A2(val <!REDECLARATION!>x<!>: Int, val y: String) {
+    val <!REDECLARATION!>x<!> = ""
+}
+
+data class A3(<!REDECLARATION!>val<!SYNTAX!><!> :Int<!>, <!REDECLARATION!>val<!SYNTAX!><!> : Int<!>)
diff --git a/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt
index 62ddb6226aa..5713d718dcf 100644
--- a/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt
+++ b/compiler/testData/diagnostics/tests/dataClasses/repeatedProperties.kt
@@ -1,4 +1,3 @@
-// FIR_IDENTICAL
 data class A1(val <!REDECLARATION, REDECLARATION, REDECLARATION!>x<!>: Int, val y: String, val <!REDECLARATION, REDECLARATION, REDECLARATION!>x<!>: Int) {
     val z = ""
 }
diff --git a/compiler/testData/diagnostics/tests/redeclarations/RedeclaredTypeParameters.fir.kt b/compiler/testData/diagnostics/tests/redeclarations/RedeclaredTypeParameters.fir.kt
index ed1cc72fc2a..0199df540d7 100644
--- a/compiler/testData/diagnostics/tests/redeclarations/RedeclaredTypeParameters.fir.kt
+++ b/compiler/testData/diagnostics/tests/redeclarations/RedeclaredTypeParameters.fir.kt
@@ -1,6 +1,6 @@
-fun <T, T> Pair() {}
+fun <<!REDECLARATION!>T<!>, <!REDECLARATION!>T<!>> Pair() {}
 
-class P<T, T> {}
+class P<<!REDECLARATION!>T<!>, <!REDECLARATION!>T<!>> {}
 
-val <T, T> T.foo : Int
-    get() = 1
\ No newline at end of file
+val <<!REDECLARATION!>T<!>, <!REDECLARATION!>T<!>> T.foo : Int
+    get() = 1
diff --git a/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.fir.kt b/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.fir.kt
deleted file mode 100644
index 774f0c684ca..00000000000
--- a/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.fir.kt
+++ /dev/null
@@ -1,6 +0,0 @@
-interface Test1<T, T>
-interface Test2<X, Y, X>
-
-class Outer<T> {
-    interface TestNested<T>
-}
diff --git a/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.kt b/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.kt
index 25c3a42c108..7ff8c020b58 100644
--- a/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.kt
+++ b/compiler/testData/diagnostics/tests/redeclarations/interfaceTypeParameters.kt
@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 interface Test1<<!REDECLARATION!>T<!>, <!REDECLARATION!>T<!>>
 interface Test2<<!REDECLARATION!>X<!>, Y, <!REDECLARATION!>X<!>>