From 36c0c2c76b74e3a01c5415df36e8894398477bbb Mon Sep 17 00:00:00 2001
From: Kirill Rakhman <kirill.rakhman@jetbrains.com>
Date: Thu, 14 Sep 2023 10:25:50 +0200
Subject: [PATCH] [FIR] Fix false negative TYPE_PARAMETER_AS_REIFIED_ARRAY

... in presence of typealiases.

#KT-61921
---
 .../checkers/expression/FirReifiedChecker.kt       | 14 ++++++++++----
 .../tpAsReified/GenericArrayAsReifiedArgument.kt   |  6 ++++++
 .../tpAsReified/GenericArrayAsReifiedArgument.txt  |  5 -----
 3 files changed, 16 insertions(+), 9 deletions(-)
 delete mode 100644 compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.txt

diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirReifiedChecker.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirReifiedChecker.kt
index e28cf0b1c0d..43115ee744c 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirReifiedChecker.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirReifiedChecker.kt
@@ -11,9 +11,11 @@ import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.diagnostics.chooseFactory
 import org.jetbrains.kotlin.diagnostics.reportOn
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.fullyExpandedClassId
 import org.jetbrains.kotlin.fir.analysis.diagnostics.*
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
 import org.jetbrains.kotlin.fir.references.toResolvedCallableSymbol
+import org.jetbrains.kotlin.fir.resolve.fullyExpandedType
 import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
 import org.jetbrains.kotlin.fir.types.*
@@ -58,11 +60,15 @@ object FirReifiedChecker : FirQualifiedAccessExpressionChecker() {
         isExplicit: Boolean,
         isArray: Boolean,
         context: CheckerContext,
-        reporter: DiagnosticReporter
+        reporter: DiagnosticReporter,
     ) {
-        if (typeArgument.classId == StandardClassIds.Array) {
-            val nestedTypeArgument = typeArgument.typeArguments[0].type ?: return
-            checkArgumentAndReport(nestedTypeArgument, source, isExplicit, isArray = true, context, reporter)
+        val fullyExpandedType = typeArgument.fullyExpandedType(context.session)
+        if (fullyExpandedType.classId == StandardClassIds.Array) {
+            // Type aliases can transform type arguments arbitrarily (drop, nest, etc...).
+            // Therefore, we check the arguments of the expanded type, not the ones that went into the type alias.
+            fullyExpandedType.typeArguments.forEach {
+                if (it is ConeKotlinType) checkArgumentAndReport(it, source, isExplicit, isArray = true, context, reporter)
+            }
             return
         }
 
diff --git a/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.kt b/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.kt
index da4d103de70..267e234ad65 100644
--- a/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.kt
+++ b/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.kt
@@ -4,10 +4,16 @@
 
 inline fun <reified T> foo() {}
 
+typealias TA<T, R> = Array<R>
+
 fun <T> bar() {
     foo<<!TYPE_PARAMETER_AS_REIFIED!>T<!>>()
     foo<<!TYPE_PARAMETER_AS_REIFIED_ARRAY_ERROR!>Array<T><!>>()
     foo<<!TYPE_PARAMETER_AS_REIFIED_ARRAY_ERROR!>Array<Array<T>><!>>()
+    foo<TA<T, String>>()
+    foo<<!TYPE_PARAMETER_AS_REIFIED_ARRAY_ERROR!>TA<String, T><!>>()
+    foo<TA<TA<String, T>, String>>()
+    foo<<!TYPE_PARAMETER_AS_REIFIED_ARRAY_ERROR!>TA<String, TA<String, T>><!>>()
     foo<Array<Int>>()
     foo<Array<Array<Int>>>()
     foo<IntArray>()
diff --git a/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.txt b/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.txt
deleted file mode 100644
index ca3e0fed575..00000000000
--- a/compiler/testData/diagnostics/tests/generics/tpAsReified/GenericArrayAsReifiedArgument.txt
+++ /dev/null
@@ -1,5 +0,0 @@
-package
-
-public fun </*0*/ T> bar(): kotlin.Unit
-public inline fun </*0*/ reified T> foo(): kotlin.Unit
-public fun test(/*0*/ x: kotlin.Array<kotlin.String>, /*1*/ y: kotlin.Array<*>): kotlin.Unit