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 3687b9ffbe1..9aee94349c8 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
@@ -124,6 +124,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.LOCAL_INTERFACE_N
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.LOCAL_OBJECT_NOT_ALLOWED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_COMPANION_OBJECTS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_IMPL_MEMBER_NOT_IMPLEMENTED
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.METHOD_OF_ANY_IMPLEMENTED_IN_INTERFACE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MISSING_VAL_ON_ANNOTATION_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.MULTIPLE_VARARG_PARAMETERS
@@ -401,7 +402,7 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
                 WRONG_NUMBER_OF_TYPE_ARGUMENTS,
                 "{0,choice,0#No type arguments|1#One type argument|1<{0,number,integer} type arguments} expected for {1}",
                 null,
-                TO_STRING
+                SYMBOL
             )
             map.put(TYPE_PARAMETERS_IN_OBJECT, "Type parameters are not allowed for objects")
 //            map.put(ILLEGAL_PROJECTION_USAGE, ...) // &
@@ -485,44 +486,44 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
                 ABSTRACT_MEMBER_NOT_IMPLEMENTED,
                 "{0} is not abstract and does not implement abstract member {1}",
                 RENDER_CLASS_OR_OBJECT,
-                FQ_NAMES_IN_TYPES
+                NAME
             )
             map.put(
                 ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED,
                 "{0} is not abstract and does not implement abstract base class member {1}",
                 RENDER_CLASS_OR_OBJECT,
-                FQ_NAMES_IN_TYPES
+                NAME
             )
             map.put(
                 MANY_IMPL_MEMBER_NOT_IMPLEMENTED,
                 "{0} must override {1} because it inherits many implementations of it",
                 RENDER_CLASS_OR_OBJECT,
-                FQ_NAMES_IN_TYPES
+                NAME
             )
             map.put(
-                MANY_IMPL_MEMBER_NOT_IMPLEMENTED,
+                MANY_INTERFACES_MEMBER_NOT_IMPLEMENTED,
                 "{0} must override {1} because it inherits multiple interface methods of it",
                 RENDER_CLASS_OR_OBJECT,
-                FQ_NAMES_IN_TYPES
+                NAME
             )
 
             map.put(
                 RETURN_TYPE_MISMATCH_ON_OVERRIDE,
                 "Return type of ''{0}'' is not a subtype of the return type of the overridden member ''{1}''",
                 DECLARATION_NAME,
-                FQ_NAMES_IN_TYPES
+                DECLARATION_NAME
             )
             map.put(
                 PROPERTY_TYPE_MISMATCH_ON_OVERRIDE,
                 "Type of ''{0}'' is not a subtype of the overridden property ''{1}''",
                 DECLARATION_NAME,
-                FQ_NAMES_IN_TYPES
+                DECLARATION_NAME
             )
             map.put(
                 VAR_TYPE_MISMATCH_ON_OVERRIDE,
                 "Type of ''{0}'' doesn''t match the type of the overridden var-property ''{1}''",
                 DECLARATION_NAME,
-                FQ_NAMES_IN_TYPES
+                DECLARATION_NAME
             )
 
             map.put(
diff --git a/idea/testData/checker/ObjectLiteralInDelegate.fir.kt b/idea/testData/checker/ObjectLiteralInDelegate.fir.kt
index 33c19fee094..c4ff14021b3 100644
--- a/idea/testData/checker/ObjectLiteralInDelegate.fir.kt
+++ b/idea/testData/checker/ObjectLiteralInDelegate.fir.kt
@@ -3,16 +3,12 @@ interface A {
     fun get(x: Int)
 }
 
-class B : A by <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@181a2e4a: public abstract fun /A.get(x: R|kotlin/Int|): R|kotlin/Unit|
-">object</error> : A {}
+class B : A by <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member get">object</error> : A {}
 
-class C : A by (<error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@181a2e4a: public abstract fun /A.get(x: R|kotlin/Int|): R|kotlin/Unit|
-">object</error> : A {})
+class C : A by (<error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member get">object</error> : A {})
 
-class D : A by 1 <error descr="[NONE_APPLICABLE] None of the following functions are applicable: [kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, ...]">+</error> (<error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@181a2e4a: public abstract fun /A.get(x: R|kotlin/Int|): R|kotlin/Unit|
-">object</error> : A {})
+class D : A by 1 <error descr="[NONE_APPLICABLE] None of the following functions are applicable: [kotlin/Int.plus, kotlin/Int.plus, kotlin/Int.plus, ...]">+</error> (<error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member get">object</error> : A {})
 
 fun bar() {
-    val e = object : A by <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@181a2e4a: public abstract fun /A.get(x: R|kotlin/Int|): R|kotlin/Unit|
-">object</error> : A {} {}
+    val e = object : A by <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Object <anonymous> is not abstract and does not implement abstract member get">object</error> : A {} {}
 }
diff --git a/idea/testData/checker/Override.fir.kt b/idea/testData/checker/Override.fir.kt
index c90c0f43c11..427574a8206 100644
--- a/idea/testData/checker/Override.fir.kt
+++ b/idea/testData/checker/Override.fir.kt
@@ -15,21 +15,17 @@ package override
 
     class MyChildClass : MyClass() {}
 
-    <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@dae9e3: public abstract fun override/MyTrait.foo(): R|kotlin/Unit|
-">class MyIllegalClass</error> : MyTrait, MyAbstractClass() {}
+    <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass is not abstract and does not implement abstract member foo">class MyIllegalClass</error> : MyTrait, MyAbstractClass() {}
 
-    <error descr="[ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass2 is not abstract and does not implement abstract base class member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@62434f8c: public abstract fun override/MyAbstractClass.bar(): R|kotlin/Unit|
-">class MyIllegalClass2</error> : MyTrait, MyAbstractClass() {
+    <error descr="[ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass2 is not abstract and does not implement abstract base class member bar">class MyIllegalClass2</error> : MyTrait, MyAbstractClass() {
         override fun foo() {}
     }
 
-    <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass3 is not abstract and does not implement abstract member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@dae9e3: public abstract fun override/MyTrait.foo(): R|kotlin/Unit|
-">class MyIllegalClass3</error> : MyTrait, MyAbstractClass() {
+    <error descr="[ABSTRACT_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass3 is not abstract and does not implement abstract member foo">class MyIllegalClass3</error> : MyTrait, MyAbstractClass() {
         override fun bar() {}
     }
 
-    <error descr="[ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass4 is not abstract and does not implement abstract base class member org.jetbrains.kotlin.fir.declarations.impl.FirSimpleFunctionImpl@62434f8c: public abstract fun override/MyAbstractClass.bar(): R|kotlin/Unit|
-">class MyIllegalClass4</error> : MyTrait, MyAbstractClass() {
+    <error descr="[ABSTRACT_CLASS_MEMBER_NOT_IMPLEMENTED] Class MyIllegalClass4 is not abstract and does not implement abstract base class member bar">class MyIllegalClass4</error> : MyTrait, MyAbstractClass() {
         fun foo() {}
         override fun other() {}
     }
diff --git a/idea/testData/checker/ReturnTypeMismatchOnOverride.fir.kt b/idea/testData/checker/ReturnTypeMismatchOnOverride.fir.kt
index 03aec79470b..4608345f49b 100644
--- a/idea/testData/checker/ReturnTypeMismatchOnOverride.fir.kt
+++ b/idea/testData/checker/ReturnTypeMismatchOnOverride.fir.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 interface Base {
     fun foo(): Int
     var bar: Int
@@ -7,7 +5,7 @@ interface Base {
 }
 
 class Derived : Base {
-    override fun foo(): <error descr="[RETURN_TYPE_MISMATCH_ON_OVERRIDE] Return type of 'foo' is not a subtype of the return type of the overridden member 'public abstract fun foo(): Int defined in Base'">String</error> = ""
-    override var bar: <error descr="[VAR_TYPE_MISMATCH_ON_OVERRIDE] Type of 'bar' doesn't match the type of the overridden var-property 'public abstract var bar: Int defined in Base'">String</error> = ""
-    override val qux: <error descr="[PROPERTY_TYPE_MISMATCH_ON_OVERRIDE] Type of 'qux' is not a subtype of the overridden property 'public abstract val qux: Int defined in Base'">String</error> = ""
+    override fun foo(): <error descr="[RETURN_TYPE_MISMATCH_ON_OVERRIDE] Return type of 'foo' is not a subtype of the return type of the overridden member 'foo'">String</error> = ""
+    override var bar: <error descr="[VAR_TYPE_MISMATCH_ON_OVERRIDE] Type of 'bar' doesn't match the type of the overridden var-property 'bar'">String</error> = ""
+    override val qux: <error descr="[PROPERTY_TYPE_MISMATCH_ON_OVERRIDE] Type of 'qux' is not a subtype of the overridden property 'qux'">String</error> = ""
 }
diff --git a/idea/testData/checker/ReturnTypeMismatchOnOverride.kt b/idea/testData/checker/ReturnTypeMismatchOnOverride.kt
index 03aec79470b..550f21dd5b1 100644
--- a/idea/testData/checker/ReturnTypeMismatchOnOverride.kt
+++ b/idea/testData/checker/ReturnTypeMismatchOnOverride.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 interface Base {
     fun foo(): Int
     var bar: Int
diff --git a/idea/testData/checker/TypeArgumentsNotAllowed.fir.kt b/idea/testData/checker/TypeArgumentsNotAllowed.fir.kt
index 707f40d8d57..63f96384601 100644
--- a/idea/testData/checker/TypeArgumentsNotAllowed.fir.kt
+++ b/idea/testData/checker/TypeArgumentsNotAllowed.fir.kt
@@ -1,9 +1,7 @@
-// IGNORE_FIR
-
 package foo
 
 open class A<T>
 
-fun <T> f(<warning descr="[UNUSED_PARAMETER] Parameter 't' is never used">t</warning>: T<error descr="[TYPE_ARGUMENTS_NOT_ALLOWED] Type arguments are not allowed for type parameters"><T></error>) {}
+fun <T> f(t: <error descr="[TYPE_ARGUMENTS_NOT_ALLOWED] Type arguments are not allowed for type parameters">T<T></error>) {}
 
-fun <T> use(<warning descr="[UNUSED_PARAMETER] Parameter 'b' is never used">b</warning>: foo<error descr="[TYPE_ARGUMENTS_NOT_ALLOWED] Type arguments are not allowed here"><T></error>.A<T>) {}
+fun <T> use(b: <error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] One type argument expected for foo/A">foo<T>.A<T></error>) {}
diff --git a/idea/testData/checker/TypeArgumentsNotAllowed.kt b/idea/testData/checker/TypeArgumentsNotAllowed.kt
index 707f40d8d57..b6ba2b892af 100644
--- a/idea/testData/checker/TypeArgumentsNotAllowed.kt
+++ b/idea/testData/checker/TypeArgumentsNotAllowed.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 package foo
 
 open class A<T>
diff --git a/idea/testData/checker/Unresolved.fir.kt b/idea/testData/checker/Unresolved.fir.kt
index 62f5b5de57a..9a089ddb090 100644
--- a/idea/testData/checker/Unresolved.fir.kt
+++ b/idea/testData/checker/Unresolved.fir.kt
@@ -1,43 +1,33 @@
-// IGNORE_FIR
-
 package unresolved
 
-class Pair<A, B>(<warning>a</warning>: A, <warning>b</warning>: B)
+class Pair<A, B>(a: A, b: B)
 
 fun testGenericArgumentsCount() {
-    val <warning>p1</warning>: Pair<error><Int></error> = Pair(2, 2)
-    val <warning>p2</warning>: <error>Pair</error> = Pair(2, 2)
+    val p1: <error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] 2 type arguments expected for unresolved/Pair">Pair<Int></error> = Pair(2, 2)
+    val p2: <error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] 2 type arguments expected for unresolved/Pair">Pair</error> = Pair(2, 2)
 }
 
 fun testUnresolved() {
-    if (<error>a</error> is String) {
-        val <warning>s</warning> = <error>a</error>
+    if (<error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error> is String) {
+        val s = <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>
     }
-    <error>foo</error>(<error>a</error>)
+    <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: foo">foo</error>(<error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>)
     val s = "s"
-    <error>foo</error>(s)
-    foo1(<error>i</error>)
-    s.<error>foo</error>()
+    <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: foo">foo</error>(s)
+    foo1(<error descr="[UNRESOLVED_REFERENCE] Unresolved reference: i">i</error>)
+    s.<error descr="[UNRESOLVED_REFERENCE] Unresolved reference: foo">foo</error>()
 
-    when(<error>a</error>) {
-        is Int -> <error>a</error>
-        is String -> <error>a</error>
-        else -> <error>a</error>
+    when(<error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>) {
+        is Int -> <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>
+        is String -> <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>
+        else -> <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: a">a</error>
     }
 
-<<<<<<< Updated upstream
-    for (j in <error>collection</error>) {
-       var i: Int = <error>j</error>
-       i += 1
-       foo1(<error>j</error>)
-    }
-=======
-    <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: hasNext"><error descr="[UNRESOLVED_REFERENCE] Unresolved reference: next">for (j in <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: collection">collection</error>) {
+    <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: hasNext"><error descr="[UNRESOLVED_REFERENCE] Unresolved reference: iterator"><error descr="[UNRESOLVED_REFERENCE] Unresolved reference: next">for (j in <error descr="[UNRESOLVED_REFERENCE] Unresolved reference: collection">collection</error>) {
        var i: Int = j
        i += 1
        foo1(j)
-    }</error></error>
->>>>>>> Stashed changes
+    }</error></error></error>
 }
 
-fun foo1(<warning>i</warning>: Int) {}
+fun foo1(i: Int) {}
diff --git a/idea/testData/checker/Unresolved.kt b/idea/testData/checker/Unresolved.kt
index 866e2430bce..7d384ad75e1 100644
--- a/idea/testData/checker/Unresolved.kt
+++ b/idea/testData/checker/Unresolved.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 package unresolved
 
 class Pair<A, B>(<warning>a</warning>: A, <warning>b</warning>: B)
diff --git a/idea/testData/checker/diagnosticsMessage/incompleteTypeArgumentList.kt b/idea/testData/checker/diagnosticsMessage/incompleteTypeArgumentList.kt
index 6db81da7b18..c5948365e5a 100644
--- a/idea/testData/checker/diagnosticsMessage/incompleteTypeArgumentList.kt
+++ b/idea/testData/checker/diagnosticsMessage/incompleteTypeArgumentList.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 interface ApplicationFeature<in P : Pipeline<*>, B : Any, V>
 open class Pipeline<TSubject : Any>()
 fun <A : Pipeline<*>, T : Any, V> A.feature(<warning>feature</warning>: ApplicationFeature<error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] 3 type arguments expected for interface ApplicationFeature<in P : Pipeline<*>, B : Any, V>"><A, T></error>) : Unit {}
diff --git a/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.fir.kt b/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.fir.kt
index 0d07188bb82..03fcca7195f 100644
--- a/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.fir.kt
+++ b/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.fir.kt
@@ -1,9 +1,7 @@
-// IGNORE_FIR
-
 package name.that.may.be.very.long
 
 import java.io.Serializable
 
 interface Foo<T> : Comparable<Foo<T>>, Serializable, Cloneable
 
-fun test(<warning>f</warning>: <error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] One type argument expected for interface Foo<T>">Foo</error>) {}
+fun test(f: <error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] One type argument expected for name/that/may/be/very/long/Foo">Foo</error>) {}
diff --git a/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.kt b/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.kt
index 0d07188bb82..2373ef7828d 100644
--- a/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.kt
+++ b/idea/testData/checker/diagnosticsMessage/nArgumentsExpectedMessage.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 package name.that.may.be.very.long
 
 import java.io.Serializable
diff --git a/idea/testData/checker/regression/kt9887.fir.kt b/idea/testData/checker/regression/kt9887.fir.kt
index 8ae32fa024c..fceaf741f8d 100644
--- a/idea/testData/checker/regression/kt9887.fir.kt
+++ b/idea/testData/checker/regression/kt9887.fir.kt
@@ -1,7 +1,5 @@
-// IGNORE_FIR
-
 open class A<T>()
 class G<T>()
 
 
-class B : A<<error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] One type argument expected for class G<T>">G</error>>()
+class B : A<<error descr="[WRONG_NUMBER_OF_TYPE_ARGUMENTS] One type argument expected for G">G</error>>()
diff --git a/idea/testData/checker/regression/kt9887.kt b/idea/testData/checker/regression/kt9887.kt
index 8ae32fa024c..5ff49fbc44f 100644
--- a/idea/testData/checker/regression/kt9887.kt
+++ b/idea/testData/checker/regression/kt9887.kt
@@ -1,5 +1,3 @@
-// IGNORE_FIR
-
 open class A<T>()
 class G<T>()