diff --git a/idea/idea-completion/testData/handlers/basic/EA70229.kt b/idea/idea-completion/testData/handlers/basic/EA70229.kt
index 2654d511dc4..70084ebeb11 100644
--- a/idea/idea-completion/testData/handlers/basic/EA70229.kt
+++ b/idea/idea-completion/testData/handlers/basic/EA70229.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 // ELEMENT: foo
 // CHAR: '\t'
 
diff --git a/idea/idea-completion/testData/handlers/basic/EA70229.kt.after b/idea/idea-completion/testData/handlers/basic/EA70229.kt.after
index 21fbbc5d12c..a0e5bd1330c 100644
--- a/idea/idea-completion/testData/handlers/basic/EA70229.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/EA70229.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 // ELEMENT: foo
 // CHAR: '\t'
 
diff --git a/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt b/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt
index be1703aeee5..1b2a31db312 100644
--- a/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt
+++ b/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class Cn<T>
 
 fun <T, C: Cn<T>> C.some(arg: (T) -> Unit): C {
diff --git a/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt.after b/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt.after
index 7a28ebbad82..dfdebcdd0ea 100644
--- a/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/TypeInferedFromWrapperType.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class Cn<T>
 
 fun <T, C: Cn<T>> C.some(arg: (T) -> Unit): C {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt
index 81db3d13f7c..4da2d0cb691 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class Some
 
 fun <T> Some.filter(predicate : (T) -> Boolean) = throw UnsupportedOperationException()
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt.after b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt.after
index c50c669fc66..eca918842f9 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertOnSpace.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 class Some
 
 fun <T> Some.filter(predicate : (T) -> Boolean) = throw UnsupportedOperationException()
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt
index 18447995318..7b6ee42f6f4 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt
@@ -1,4 +1,3 @@
-// FIR_COMPARISON
 // CODE_STYLE_SETTING: INSERT_WHITESPACES_IN_SIMPLE_ONE_LINE_METHOD = false
 
 fun main(args: Array<String>) {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt.after b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt.after
index c17ec99e2e0..c2441ce4a61 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/FunctionLiteralInsertWhenNoSpacesForBraces.kt.after
@@ -1,4 +1,3 @@
-// FIR_COMPARISON
 // CODE_STYLE_SETTING: INSERT_WHITESPACES_IN_SIMPLE_ONE_LINE_METHOD = false
 
 fun main(args: Array<String>) {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt
index 61dff845b2c..bc7b0726b68 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun <T> Array<T>.filter(predicate : (T) -> Boolean) : java.util.List<T> = throw UnsupportedOperationException()
 
 fun main(args: Array<String>) {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt.after b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt.after
index 8b7a93a5302..5420dffb436 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/HigherOrderFunction.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun <T> Array<T>.filter(predicate : (T) -> Boolean) : java.util.List<T> = throw UnsupportedOperationException()
 
 fun main(args: Array<String>) {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionLiteralForLocalFunction.kt.after b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionLiteralForLocalFunction.kt.after
index b30dbe55f1f..802785c8333 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionLiteralForLocalFunction.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionLiteralForLocalFunction.kt.after
@@ -2,7 +2,7 @@
 fun usage() {
     fun myLocalFun(action: () -> Unit) {}
 
-    myLocalFun {<caret>}
+    myLocalFun { <caret> }
 }
 
 // ELEMENT: myLocalFun
\ No newline at end of file
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt
index a1a8166d780..2be751f893c 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun some(f: () -> Unit) { f() }
 
 fun test() {
diff --git a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt.after b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt.after
index 357d8e93bdc..27c6963bbf4 100644
--- a/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/highOrderFunctions/InsertFunctionWithSingleParameterWithBrace.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun some(f: () -> Unit) { f() }
 
 fun test() {
diff --git a/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt b/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt
index a53f9975bf9..22b0fbbba65 100644
--- a/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt
+++ b/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt
@@ -1,4 +1,3 @@
-// FIR_COMPARISON
 package p
 
 val vvv = 1
diff --git a/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt.after b/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt.after
index c5af602c636..01f13022e12 100644
--- a/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/stringTemplate/GlobalVal.kt.after
@@ -1,4 +1,3 @@
-// FIR_COMPARISON
 package p
 
 val vvv = 1
diff --git a/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt b/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt
index ee18858ffe3..63eba43eb33 100644
--- a/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt
+++ b/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun f(list: List<String>) {
     list.<caret>
 }
diff --git a/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt.after b/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt.after
index 186bae9f9d3..b3554bf3bbe 100644
--- a/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt.after
+++ b/idea/idea-completion/testData/handlers/basic/typeArgsForCall/FunctionTypeParameter2.kt.after
@@ -1,3 +1,4 @@
+// FIR_COMPARISON
 fun f(list: List<String>) {
     list.map { <caret> }
 }
diff --git a/idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirLookupElementFactory.kt b/idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirLookupElementFactory.kt
index c8cee5647f7..3ceba7d35c8 100644
--- a/idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirLookupElementFactory.kt
+++ b/idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirLookupElementFactory.kt
@@ -247,6 +247,7 @@ private object FunctionInsertionHandler : QuotedNamesAwareInsertionHandler() {
 
         var openingBracketOffset = chars.indexOfSkippingSpace(openingBracket, offset)
         var closeBracketOffset = openingBracketOffset?.let { chars.indexOfSkippingSpace(closingBracket, it + 1) }
+        var inBracketsShift = 0
 
         if (openingBracketOffset == null) {
             if (lookupObject.insertEmptyLambda) {
@@ -254,7 +255,12 @@ private object FunctionInsertionHandler : QuotedNamesAwareInsertionHandler() {
                     context.setAddCompletionChar(false)
                 }
 
-                document.insertString(offset, " {}")
+                if (isInsertSpacesInOneLineFunctionEnabled(context.file)) {
+                    document.insertString(offset, " {  }")
+                    inBracketsShift = 1
+                } else {
+                    document.insertString(offset, " {}")
+                }
             } else {
                 if (isSmartEnterCompletion) {
                     document.insertString(offset, "(")
@@ -269,7 +275,7 @@ private object FunctionInsertionHandler : QuotedNamesAwareInsertionHandler() {
         }
 
         if (shouldPlaceCaretInBrackets(completionChar, lookupObject) || closeBracketOffset == null) {
-            editor.caretModel.moveToOffset(openingBracketOffset + 1)
+            editor.caretModel.moveToOffset(openingBracketOffset + 1 + inBracketsShift)
             AutoPopupController.getInstance(project)?.autoPopupParameterInfo(editor, offsetElement)
         } else {
             editor.caretModel.moveToOffset(closeBracketOffset + 1)
@@ -282,6 +288,9 @@ private object FunctionInsertionHandler : QuotedNamesAwareInsertionHandler() {
         return lookupObject.inputValueArguments || lookupObject.insertEmptyLambda
     }
 
+    // FIXME Should be fetched from language settings (INSERT_WHITESPACES_IN_SIMPLE_ONE_LINE_METHOD), but we do not have them right now
+    private fun isInsertSpacesInOneLineFunctionEnabled(file: PsiElement) = true
+
     override fun handleInsert(context: InsertionContext, item: LookupElement) {
         val targetFile = context.file as? KtFile ?: return
         val lookupObject = item.`object` as FunctionLookupObject
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 4e8b148ec0e..ab1feebc84c 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
@@ -536,6 +536,14 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.WRONG_MODIFIER_TARGET) { firDiagnostic ->
+        WrongModifierTargetImpl(
+            firDiagnostic.a,
+            firDiagnostic.b,
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.INLINE_CLASS_NOT_TOP_LEVEL) { firDiagnostic ->
         InlineClassNotTopLevelImpl(
             firDiagnostic as FirPsiDiagnostic<*>,
@@ -628,14 +636,6 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
-    add(FirErrors.WRONG_MODIFIER_TARGET) { firDiagnostic ->
-        WrongModifierTargetImpl(
-            firDiagnostic.a,
-            firDiagnostic.b,
-            firDiagnostic as FirPsiDiagnostic<*>,
-            token,
-        )
-    }
     add(FirErrors.NONE_APPLICABLE) { firDiagnostic ->
         NoneApplicableImpl(
             firDiagnostic.a.map { abstractFirBasedSymbol ->
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 97aa8bf0812..2cd04548b8e 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
@@ -389,6 +389,12 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = RedundantOpenInInterface::class
     }
 
+    abstract class WrongModifierTarget : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = WrongModifierTarget::class
+        abstract val modifier: KtModifierKeywordToken
+        abstract val target: String
+    }
+
     abstract class InlineClassNotTopLevel : KtFirDiagnostic<KtDeclaration>() {
         override val diagnosticClass get() = InlineClassNotTopLevel::class
     }
@@ -451,12 +457,6 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = ValueClassCannotBeCloneable::class
     }
 
-    abstract class WrongModifierTarget : KtFirDiagnostic<PsiElement>() {
-        override val diagnosticClass get() = WrongModifierTarget::class
-        abstract val modifier: KtModifierKeywordToken
-        abstract val target: String
-    }
-
     abstract class NoneApplicable : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = NoneApplicable::class
         abstract val candidates: List<KtSymbol>
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 db92907416d..0afd391bf5b 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
@@ -618,6 +618,15 @@ internal class RedundantOpenInInterfaceImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class WrongModifierTargetImpl(
+    override val modifier: KtModifierKeywordToken,
+    override val target: String,
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.WrongModifierTarget(), KtAbstractFirDiagnostic<PsiElement> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class InlineClassNotTopLevelImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,
@@ -725,15 +734,6 @@ internal class ValueClassCannotBeCloneableImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
-internal class WrongModifierTargetImpl(
-    override val modifier: KtModifierKeywordToken,
-    override val target: String,
-    firDiagnostic: FirPsiDiagnostic<*>,
-    override val token: ValidityToken,
-) : KtFirDiagnostic.WrongModifierTarget(), KtAbstractFirDiagnostic<PsiElement> {
-    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
-}
-
 internal class NoneApplicableImpl(
     override val candidates: List<KtSymbol>,
     firDiagnostic: FirPsiDiagnostic<*>,