From cf1bd9837a59754eba34696dc087f60575d39b56 Mon Sep 17 00:00:00 2001
From: Ivan Kochurkin <ivan.kochurkin@jetbrains.com>
Date: Thu, 16 Feb 2023 22:39:13 +0100
Subject: [PATCH] [FIR] Support of
 ACTUAL_TYPE_ALIAS_TO_CLASS_WITH_DECLARATION_SITE_VARIANCE diagnostic

---
 .../declaration/FirActualTypeAliasChecker.kt   | 18 ++++++++++--------
 .../genericClassImplTypeAlias.fir.kt           |  4 ++--
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirActualTypeAliasChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirActualTypeAliasChecker.kt
index 6045d5fcc8b..725267a4ea0 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirActualTypeAliasChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirActualTypeAliasChecker.kt
@@ -13,21 +13,23 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.declarations.FirTypeAlias
 import org.jetbrains.kotlin.fir.declarations.utils.isActual
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeAliasSymbol
+import org.jetbrains.kotlin.types.Variance
 
 object FirActualTypeAliasChecker : FirTypeAliasChecker() {
     override fun check(declaration: FirTypeAlias, context: CheckerContext, reporter: DiagnosticReporter) {
         if (!declaration.isActual) return
 
-        checkActualTypeAliasNotToClass(declaration, context, reporter)
-    }
+        val expandedTypeSymbol = declaration.expandedTypeRef.toClassLikeSymbol(context.session) ?: return
 
-    private fun checkActualTypeAliasNotToClass(
-        declaration: FirTypeAlias,
-        context: CheckerContext,
-        reporter: DiagnosticReporter
-    ) {
-        if (declaration.expandedTypeRef.toClassLikeSymbol(context.session) is FirTypeAliasSymbol) {
+        if (expandedTypeSymbol is FirTypeAliasSymbol) {
             reporter.reportOn(declaration.source, FirErrors.ACTUAL_TYPE_ALIAS_NOT_TO_CLASS, context)
         }
+
+        for (typeParameterSymbol in expandedTypeSymbol.typeParameterSymbols) {
+            if (typeParameterSymbol.variance != Variance.INVARIANT) {
+                reporter.reportOn(declaration.source, FirErrors.ACTUAL_TYPE_ALIAS_TO_CLASS_WITH_DECLARATION_SITE_VARIANCE, context)
+                break
+            }
+        }
     }
 }
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/multiplatform/headerClass/genericClassImplTypeAlias.fir.kt b/compiler/testData/diagnostics/tests/multiplatform/headerClass/genericClassImplTypeAlias.fir.kt
index 3ac0caca28a..2aca589ffb6 100644
--- a/compiler/testData/diagnostics/tests/multiplatform/headerClass/genericClassImplTypeAlias.fir.kt
+++ b/compiler/testData/diagnostics/tests/multiplatform/headerClass/genericClassImplTypeAlias.fir.kt
@@ -17,8 +17,8 @@ expect interface C10<L>
 // FILE: jvm.kt
 
 actual typealias C1 = String
-actual typealias C2<A> = List<String>
-actual typealias C3<B> = List<B>
+<!ACTUAL_TYPE_ALIAS_TO_CLASS_WITH_DECLARATION_SITE_VARIANCE!>actual typealias C2<A> = List<String><!>
+<!ACTUAL_TYPE_ALIAS_TO_CLASS_WITH_DECLARATION_SITE_VARIANCE!>actual typealias C3<B> = List<B><!>
 actual typealias C4<D, E> = MutableMap<D, E>
 actual typealias C5<F, G> = MutableMap<G, F>
 actual typealias C6<H> = MutableList<H>