From e8f5e35a86695efb8c402a6a8d1ad0de41d333b5 Mon Sep 17 00:00:00 2001
From: Dmitriy Novozhilov <dmitriy.novozhilov@jetbrains.com>
Date: Wed, 10 Jan 2024 14:08:54 +0200
Subject: [PATCH] [FIR] Consider expect declarations in defaults arguments
 inheritance checker

Actual functions cannot declare default values for parameters
Corresponding expect function should be checked instead
---
 ...MultipleDefaultsInheritedFromSupertypesChecker.kt | 12 ++++++++++--
 .../scopes/multipleDefaultsInhereted.fir.kt          |  8 ++++----
 2 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
index 96e04382da8..be6ab080668 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirMultipleDefaultsInheritedFromSupertypesChecker.kt
@@ -11,11 +11,14 @@ import org.jetbrains.kotlin.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.analysis.checkers.MppCheckerKind
 import org.jetbrains.kotlin.fir.analysis.checkers.collectOverriddenFunctionsWhere
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.processOverriddenFunctions
 import org.jetbrains.kotlin.fir.analysis.checkers.unsubstitutedScope
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.containingClassLookupTag
 import org.jetbrains.kotlin.fir.declarations.FirDeclarationOrigin
 import org.jetbrains.kotlin.fir.declarations.FirRegularClass
+import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
+import org.jetbrains.kotlin.fir.declarations.getSingleMatchedExpectForActualOrNull
 import org.jetbrains.kotlin.fir.declarations.utils.isExpect
 import org.jetbrains.kotlin.fir.declarations.utils.superConeTypes
 import org.jetbrains.kotlin.fir.isSubstitutionOverride
@@ -58,9 +61,14 @@ sealed class FirMultipleDefaultsInheritedFromSupertypesChecker(mppKind: MppCheck
         context: CheckerContext,
         reporter: DiagnosticReporter,
     ) {
-        val overriddenFunctions = function.collectOverriddenFunctionsWhere(mutableSetOf(), context) { overridden ->
+        val overriddenFunctions = mutableSetOf<FirNamedFunctionSymbol>()
+        function.processOverriddenFunctions(context) { overridden ->
+            // default values of actual functions are located in corresponding expect functions
+            val overriddenWithDefaults = overridden.getSingleMatchedExpectForActualOrNull() as? FirNamedFunctionSymbol ?: overridden
             // Substitution overrides copy default values from originals
-            !overridden.isSubstitutionOverride && overridden.valueParameterSymbols.any { it.hasDefaultValue }
+            if (!overriddenWithDefaults.isSubstitutionOverride && overriddenWithDefaults.valueParameterSymbols.any { it.hasDefaultValue }) {
+                overriddenFunctions += overriddenWithDefaults
+            }
         }
         val isExplicitOverride = function.origin == FirDeclarationOrigin.Source
 
diff --git a/compiler/testData/diagnostics/tests/multiplatform/scopes/multipleDefaultsInhereted.fir.kt b/compiler/testData/diagnostics/tests/multiplatform/scopes/multipleDefaultsInhereted.fir.kt
index 9256b1aad85..b88b91af964 100644
--- a/compiler/testData/diagnostics/tests/multiplatform/scopes/multipleDefaultsInhereted.fir.kt
+++ b/compiler/testData/diagnostics/tests/multiplatform/scopes/multipleDefaultsInhereted.fir.kt
@@ -16,8 +16,8 @@ expect interface I2 {
     override fun foo(<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES!>x: Int<!>)
 }
 
-interface CommonInterface : I1, I2 {
-    override fun foo(x: Int)
+<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE!>interface CommonInterface<!> : I1, I2 {
+    override fun foo(<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES!>x: Int<!>)
 }
 
 // MODULE: m1-jvm()()(m1-common)
@@ -33,6 +33,6 @@ actual interface I2 {
     actual fun bar(x: Int)
 }
 
-actual interface ExpectInterface : I1, I2 {
-    actual override fun foo(x: Int)
+<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES_WHEN_NO_EXPLICIT_OVERRIDE!>actual interface ExpectInterface<!> : I1, I2 {
+    actual override fun foo(<!MULTIPLE_DEFAULTS_INHERITED_FROM_SUPERTYPES!>x: Int<!>)
 }