diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
index 817cc45f796..64ac1407b3f 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
@@ -370,6 +370,7 @@ open class FirExpressionsResolveTransformer(transformer: FirBodyResolveTransform
                 this.name = name
                 candidateSymbol = null
             }
+            origin = FirFunctionCallOrigin.OPERATOR
         }
 
         // x.plusAssign(y)
diff --git a/compiler/testData/diagnostics/tests/Operators.fir.kt b/compiler/testData/diagnostics/tests/Operators.fir.kt
index c916a2e5261..6a3cfcde7eb 100644
--- a/compiler/testData/diagnostics/tests/Operators.fir.kt
+++ b/compiler/testData/diagnostics/tests/Operators.fir.kt
@@ -64,7 +64,7 @@ fun test() {
     a.get(1)
     a.get("str")
 
-    c += d
+    <!OPERATOR_MODIFIER_REQUIRED!>c += d<!>
     c -= d
 
     a<!OPERATOR_MODIFIER_REQUIRED!>..<!>b
diff --git a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.fir.kt
deleted file mode 100644
index 6bfb0d8bf7b..00000000000
--- a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.fir.kt
+++ /dev/null
@@ -1,193 +0,0 @@
-// !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION -EXTENSION_SHADOWED_BY_MEMBER
-// SKIP_TXT
-
-/*
- * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
- *
- * SPEC VERSION: 0.1-268
- * MAIN LINK: overload-resolution, building-the-overload-candidate-set-ocs, operator-call -> paragraph 2 -> sentence 3
- * PRIMARY LINKS: overload-resolution, building-the-overload-candidate-set-ocs, call-with-an-explicit-receiver -> paragraph 6 -> sentence 3
- * overload-resolution, building-the-overload-candidate-set-ocs, operator-call -> paragraph 4 -> sentence 1
- * NUMBER: 3
- * DESCRIPTION: Explicitly imported extension callables
- */
-
-
-// FILE: LibCase11.kt
-// TESTCASE NUMBER: 1
-package libPackage1
-import testPackCase1.Case
-import testPackCase1.Case.Inv
-import testPackCase1.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-// FILE: LibCase12.kt
-// TESTCASE NUMBER: 1
-package libPackage2
-import testPackCase1.Case
-import testPackCase1.Case.Inv
-import testPackCase1.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-
-// FILE: TestCase1.kt
-// TESTCASE NUMBER: 1
-package testPackCase1
-import libPackage1.plus
-import libPackage1.invoke
-import libPackage2.*
-class Case() {
-
-    class E(val plus: Inv? = null) {
-        /*operator*/ fun plus(value: Int) = Case()
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) = Case()
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plus(value: Int) = Case()
-
-        run {
-            <!DEBUG_INFO_CALL("fqName: libPackage1.plus; typeCall: operator extension function")!>e + 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: libPackage1.plus; typeCall: operator extension function")!>e + 1<!>
-
-    }
-}
-
-// FILE: LibCase21.kt
-// TESTCASE NUMBER: 2
-package libPackage1
-import testPackCase2.Case
-import testPackCase2.Case.Inv
-import testPackCase2.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-// FILE: LibCase22.kt
-// TESTCASE NUMBER: 2
-package libPackage2
-import testPackCase2.Case
-import testPackCase2.Case.Inv
-import testPackCase2.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-
-// FILE: TestCase2.kt
-// TESTCASE NUMBER: 2
-package testPackCase2
-import libPackage1.plus
-import libPackage1.invoke
-import libPackage2.*
-class Case() {
-
-    class E(val plus: Inv? = null) {
-        /*operator*/ fun plus(value: Int) = Case()
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) = Case()
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plus(value: Int) = Case()
-
-        run {
-            /*operator*/ fun E.plus(value: Int) = Case()
-
-            <!DEBUG_INFO_CALL("fqName: libPackage1.plus; typeCall: operator extension function")!>e + 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: libPackage1.plus; typeCall: operator extension function")!>e + 1<!>
-    }
-}
-
-// FILE: LibCase3.kt
-// TESTCASE NUMBER: 3
-package libPackage
-import testPackCase3.Case
-import testPackCase3.Case.Inv
-import testPackCase3.Case.E
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-
-// FILE: TestCase3.kt
-// TESTCASE NUMBER:  3
-package testPackCase3
-import libPackage.plusAssign
-import libPackage.invoke
-import libPackage.*
-class Case() {
-
-    class E(val plusAssign: Inv? = null) {
-        /*operator*/ fun plusAssign(value: Int) {}
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) {}
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plusAssign(value: Int) {}
-
-        run {
-            <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-
-    }
-}
-
-
-// FILE: LibCase4.kt
-// TESTCASE NUMBER: 4
-package libPackage
-import testPackCase4.Case
-import testPackCase4.Case.Inv
-import testPackCase4.Case.E
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-
-// FILE: TestCase4.kt
-// TESTCASE NUMBER: 4
-package testPackCase4
-import libPackage.plusAssign
-import libPackage.*
-import libPackage.invoke
-
-operator fun Case.E.plusAssign(value: Int) {}
-
-class Case() {
-
-    class E(val plusAssign: Inv? = null) {
-        /*operator*/ fun plusAssign(value: Int) {}
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) {}
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plusAssign(value: Int) {}
-
-        run {
-            /*operator*/ fun E.plusAssign(value: Int) {}
-
-            <!DEBUG_INFO_CALL("fqName: testPackCase4.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase4.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-    }
-}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.kt b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.kt
index 9b2188007ea..bd6de85aadb 100644
--- a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.kt
+++ b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.3.kt
@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION -EXTENSION_SHADOWED_BY_MEMBER
 // SKIP_TXT
diff --git a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.fir.kt
deleted file mode 100644
index f0fe20740d3..00000000000
--- a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.fir.kt
+++ /dev/null
@@ -1,194 +0,0 @@
-// !LANGUAGE: +NewInference
-// !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION -EXTENSION_SHADOWED_BY_MEMBER
-// SKIP_TXT
-
-/*
- * KOTLIN DIAGNOSTICS SPEC TEST (POSITIVE)
- *
- * SPEC VERSION: 0.1-268
- * MAIN LINK: overload-resolution, building-the-overload-candidate-set-ocs, operator-call -> paragraph 2 -> sentence 3
- * PRIMARY LINKS: overload-resolution, building-the-overload-candidate-set-ocs, call-with-an-explicit-receiver -> paragraph 6 -> sentence 4
- * overload-resolution, building-the-overload-candidate-set-ocs, operator-call -> paragraph 4 -> sentence 1
- * NUMBER: 4
- * DESCRIPTION: Extension callables declared in the package scope
- */
-
-
-// FILE: LibCase1.kt
-// TESTCASE NUMBER: 1
-package libPackage
-import testPackCase1.Case
-import testPackCase1.Case.Inv
-import testPackCase1.Case.E
-
-operator fun Case.E.plus(value: Int) =  Case().Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-
-// FILE: TestCase11.kt
-// TESTCASE NUMBER: 1
-package testPackCase1
-import libPackage.*
-
-operator fun Case.E.plus(value: Int) =  Case().Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-class Case() {
-    class E(val plus: Inv? = null) {
-        /*operator*/ fun plus(value: Int) = Case()
-    }
-
-    inner class Inv() {
-        /*operator*/ fun invoke(value: Int) = Case()
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plus(value: Int) = Case()
-
-        run {
-            <!DEBUG_INFO_CALL("fqName: testPackCase1.plus; typeCall: operator extension function")!>e + 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase1.plus; typeCall: operator extension function")!>e + 1<!>
-
-    }
-}
-
-// FILE: Lib11.kt
-// TESTCASE NUMBER: 2
-package libPackage1
-import testPackCase2.Case
-import testPackCase2.Case.Inv
-import testPackCase2.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-
-// FILE: Lib21.kt
-// TESTCASE NUMBER: 2
-package testPackCase2
-import testPackCase2.Case
-import testPackCase2.Case.Inv
-import testPackCase2.Case.E
-
-operator fun Case.E.plus(value: Int) =  Inv()
-operator fun Case.Inv.invoke(i: Int) = 1
-
-
-// FILE: TestCase12.kt
-// TESTCASE NUMBER: 2
-package testPackCase2
-import libPackage1.*
-class Case() {
-
-    operator fun plus(value: Int) = Case()
-
-    class E(val plus: Inv? = null) {
-        /*operator*/ fun plus(value: Int) = Case()
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) = Case()
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plus(value: Int) = Case()
-
-        run {
-            /*operator*/ fun E.plus(value: Int) = Case()
-
-            <!DEBUG_INFO_CALL("fqName: testPackCase2.plus; typeCall: operator extension function")!>e + 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase2.plus; typeCall: operator extension function")!>e + 1<!>
-    }
-}
-
-
-// FILE: LibCase3.kt
-// TESTCASE NUMBER: 3
-package libPackage
-import testPackCase3.Case
-import testPackCase3.Case.Inv
-import testPackCase3.Case.E
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-
-// FILE: TestCase3.kt
-// TESTCASE NUMBER: 3
-package testPackCase3
-import libPackage.*
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-class Case() {
-    class E(val plusAssign: Inv? = null) {
-        /*operator*/ fun plusAssign(value: Int) {}
-    }
-
-    inner class Inv() {
-        /*operator*/ fun invoke(value: Int) {}
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plusAssign(value: Int) {}
-
-        run {
-            <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-
-    }
-}
-
-// FILE: Lib12.kt
-// TESTCASE NUMBER: 4
-package libPackage1
-import testPackCase4.Case
-import testPackCase4.Case.Inv
-import testPackCase4.Case.E
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-
-// FILE: Lib22.kt
-// TESTCASE NUMBER: 4
-package testPackCase4
-import testPackCase4.Case
-import testPackCase4.Case.Inv
-import testPackCase4.Case.E
-
-operator fun Case.E.plusAssign(value: Int) {}
-operator fun Case.Inv.invoke(i: Int) {}
-
-
-// FILE: TestCase4.kt
-// TESTCASE NUMBER: 4
-package testPackCase4
-import libPackage1.*
-class Case() {
-
-    operator fun plusAssign(value: Int) {}
-
-    class E(val plusAssign: Inv? = null) {
-        /*operator*/ fun plusAssign(value: Int) {}
-    }
-
-    class Inv() {
-        /*operator*/ fun invoke(value: Int) {}
-    }
-
-    fun foo(e: E) {
-        /*operator*/ fun E.plusAssign(value: Int) {}
-
-        run {
-            /*operator*/ fun E.plusAssign(value: Int) {}
-
-            <!DEBUG_INFO_CALL("fqName: testPackCase4.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-        }
-        <!DEBUG_INFO_CALL("fqName: testPackCase4.Case.E.plusAssign; typeCall: function")!>e += 1<!>
-    }
-}
diff --git a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.kt b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.kt
index b498ba9dbbf..1e643abfc97 100644
--- a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.kt
+++ b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.4.kt
@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +NewInference
 // !DIAGNOSTICS: -UNUSED_VARIABLE -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_VALUE -UNUSED_PARAMETER -UNUSED_EXPRESSION -EXTENSION_SHADOWED_BY_MEMBER
 // SKIP_TXT
diff --git a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.5.fir.kt b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.5.fir.kt
index 95e9ea5f1e4..a7e01e8619a 100644
--- a/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.5.fir.kt
+++ b/compiler/tests-spec/testData/diagnostics/linked/overload-resolution/building-the-overload-candidate-set-ocs/operator-call/p-2/pos/3.5.fir.kt
@@ -96,8 +96,8 @@ class Case() {
         /*operator*/ fun E.plusAssign(value: Int) {}
 
         run {
-            <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
+            <!DEBUG_INFO_CALL("fqName: libPackage.plusAssign; typeCall: operator extension function")!>e += 1<!>
         }
-        <!DEBUG_INFO_CALL("fqName: testPackCase3.Case.E.plusAssign; typeCall: function")!>e += 1<!>
+        <!DEBUG_INFO_CALL("fqName: libPackage.plusAssign; typeCall: operator extension function")!>e += 1<!>
     }
 }