[FIR] Improve TYPE_PARAMETER_AS_REIFIED detecting, implement TYPE_PARAMETER_AS_REIFIED_ARRAY, TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING

compiler/fir/checkers/checkers-component-generator/src/org/jetbrains/kotlin/fir/checkers/generator/diagnostics/FirDiagnosticsList.kt

@@ -483,6 +483,14 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<FirTypeParameterSymbol>("typeParameter")
         }
 
+        val TYPE_PARAMETER_AS_REIFIED_ARRAY by error<PsiElement> {
+            parameter<FirTypeParameterSymbol>("typeParameter")
+        }
+
+        val TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING by warning<PsiElement> {
+            parameter<FirTypeParameterSymbol>("typeParameter")
+        }
+
         val FINAL_UPPER_BOUND by warning<KtTypeReference> {
             parameter<ConeKotlinType>("type")
         }

compiler/fir/checkers/gen/org/jetbrains/kotlin/fir/analysis/diagnostics/FirErrors.kt

@@ -319,6 +319,8 @@ object FirErrors {
     val INNER_CLASS_OF_GENERIC_THROWABLE_SUBCLASS by error0<KtClassOrObject>(SourceElementPositioningStrategies.DECLARATION_NAME)
     val KCLASS_WITH_NULLABLE_TYPE_PARAMETER_IN_SIGNATURE by error1<KtNamedDeclaration, FirTypeParameterSymbol>(SourceElementPositioningStrategies.DECLARATION_NAME)
     val TYPE_PARAMETER_AS_REIFIED by error1<PsiElement, FirTypeParameterSymbol>()
+    val TYPE_PARAMETER_AS_REIFIED_ARRAY by error1<PsiElement, FirTypeParameterSymbol>()
+    val TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING by warning1<PsiElement, FirTypeParameterSymbol>()
     val FINAL_UPPER_BOUND by warning1<KtTypeReference, ConeKotlinType>()
     val UPPER_BOUND_IS_EXTENSION_FUNCTION_TYPE by error0<KtTypeReference>()
     val BOUNDS_NOT_ALLOWED_IF_BOUNDED_BY_TYPE_PARAMETER by error0<KtElement>()

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonExpressionCheckers.kt

@@ -42,7 +42,8 @@ object CommonExpressionCheckers : ExpressionCheckers() {
             FirTypeParameterInQualifiedAccessChecker,
             FirSealedClassConstructorCallChecker,
             FirUninitializedEnumChecker,
-            FirFunInterfaceConstructorReferenceChecker
+            FirFunInterfaceConstructorReferenceChecker,
+            FirTypeParameterAsReifiedChecker
         )
 
     override val functionCallCheckers: Set<FirFunctionCallChecker>

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/FirHelpers.kt

@@ -601,24 +601,20 @@ fun extractArgumentTypeRefAndSource(typeRef: FirTypeRef?, index: Int): FirTypeRe
     if (typeRef is FirResolvedTypeRef) {
         val delegatedTypeRef = typeRef.delegatedTypeRef
         if (delegatedTypeRef is FirUserTypeRef) {
-            var currentTypeArguments: List<FirTypeProjection>? = null
             var currentIndex = index
             val qualifier = delegatedTypeRef.qualifier
 
             for (i in qualifier.size - 1 downTo 0) {
                 val typeArguments = qualifier[i].typeArgumentList.typeArguments
                 if (currentIndex < typeArguments.size) {
-                    currentTypeArguments = typeArguments
-                    break
+                    val typeArgument = typeArguments.elementAtOrNull(currentIndex)
+                    return if (typeArgument is FirTypeProjection)
+                        FirTypeRefSource((typeArgument as? FirTypeProjectionWithVariance)?.typeRef, typeArgument.source)
+                    else null
                 } else {
                     currentIndex -= typeArguments.size
                 }
             }
-
-            val typeArgument = currentTypeArguments?.elementAtOrNull(currentIndex)
-            if (typeArgument is FirTypeProjection) {
-                return FirTypeRefSource((typeArgument as? FirTypeProjectionWithVariance)?.typeRef, typeArgument.source)
-            }
         } else if (delegatedTypeRef is FirFunctionTypeRef) {
             val valueParameters = delegatedTypeRef.valueParameters
             if (index < valueParameters.size) {

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/expression/FirTypeParameterAsReifiedChecker.kt

@@ -0,0 +1,78 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.checkers.expression
+
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticFactory1
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
+import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
+import org.jetbrains.kotlin.fir.expressions.toResolvedCallableSymbol
+import org.jetbrains.kotlin.fir.languageVersionSettings
+import org.jetbrains.kotlin.fir.symbols.impl.FirRegularClassSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.name.StandardClassIds
+
+object FirTypeParameterAsReifiedChecker : FirQualifiedAccessExpressionChecker() {
+    override fun check(expression: FirQualifiedAccessExpression, context: CheckerContext, reporter: DiagnosticReporter) {
+        val calleReference = expression.calleeReference
+        val typeArguments = expression.typeArguments
+        val typeParameters = calleReference.toResolvedCallableSymbol()?.typeParameterSymbols ?: return
+
+        val count = minOf(typeArguments.size, typeParameters.size)
+        for (index in 0 until count) {
+            val typeArgumentProjection = typeArguments.elementAt(index)
+            val source = typeArgumentProjection.source ?: calleReference.source
+            val typeArgument = typeArgumentProjection.toConeTypeProjection().type
+            val typeParameter = typeParameters[index]
+
+            if (source != null && (typeParameter.isTypeParameterOfKotlinArray())) {
+                checkArgumentAndReport(typeArgument, source, false, context, reporter)
+            }
+        }
+    }
+
+    private fun FirTypeParameterSymbol.isTypeParameterOfKotlinArray(): Boolean {
+        val containingDeclaration = containingDeclarationSymbol
+        return isReified ||
+                containingDeclaration is FirRegularClassSymbol && containingDeclaration.classId == StandardClassIds.Array
+    }
+
+    private fun checkArgumentAndReport(
+        typeArgument: ConeKotlinType?,
+        source: FirSourceElement,
+        isArray: Boolean,
+        context: CheckerContext,
+        reporter: DiagnosticReporter
+    ) {
+        if (typeArgument?.classId == StandardClassIds.Array) {
+            checkArgumentAndReport(typeArgument.typeArguments[0].type, source, true, context, reporter)
+            return
+        }
+
+        var factory: FirDiagnosticFactory1<FirTypeParameterSymbol>? = null
+
+        lateinit var symbol: FirTypeParameterSymbol
+        if (typeArgument is ConeTypeParameterType) {
+            factory = if (isArray) {
+                if (context.session.languageVersionSettings.supportsFeature(LanguageFeature.ProhibitNonReifiedArraysAsReifiedTypeArguments))
+                    FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY else
+                    FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING
+            } else {
+                FirErrors.TYPE_PARAMETER_AS_REIFIED
+            }
+            symbol = typeArgument.toSymbol(context.session) as FirTypeParameterSymbol
+        }
+
+        if (factory != null && !symbol.isReified) {
+            reporter.reportOn(source, factory, symbol, context)
+        }
+    }
+}

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/components/ExpressionCheckersDiagnosticComponent.kt

@@ -41,6 +41,10 @@ class ExpressionCheckersDiagnosticComponent(
         checkers.allFunctionCallCheckers.check(functionCall, data, reporter)
     }
 
+    override fun visitImplicitInvokeCall(implicitInvokeCall: FirImplicitInvokeCall, data: CheckerContext) {
+        checkers.allFunctionCallCheckers.check(implicitInvokeCall, data, reporter)
+    }
+
     override fun visitCallableReferenceAccess(callableReferenceAccess: FirCallableReferenceAccess, data: CheckerContext) {
         checkers.allCallableReferenceAccessCheckers.check(callableReferenceAccess, data, reporter)
     }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/diagnostics/FirDefaultErrorMessages.kt

@@ -365,6 +365,8 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETERS_I
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETERS_IN_OBJECT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETERS_NOT_ALLOWED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_AS_REIFIED
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_IN_CATCH_CLAUSE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_IS_NOT_AN_EXPRESSION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.TYPE_PARAMETER_OF_PROPERTY_NOT_USED_IN_RECEIVER
@@ -782,6 +784,16 @@ class FirDefaultErrorMessages {
             )
 
             map.put(TYPE_PARAMETER_AS_REIFIED, "Cannot use ''{0}'' as reified type parameter. Use a class instead", SYMBOL)
+            map.put(
+                TYPE_PARAMETER_AS_REIFIED_ARRAY,
+                "Cannot use ''{0}'' as reified type parameter, since the array type parameter is not reified.",
+                SYMBOL
+            )
+            map.put(
+                TYPE_PARAMETER_AS_REIFIED_ARRAY_WARNING,
+                "Cannot use ''{0}'' as reified type parameter, since the array type parameter is not reified.",
+                SYMBOL
+            )
             map.put(
                 FINAL_UPPER_BOUND,
                 "''{0}'' is a final type, and thus a value of the type parameter is predetermined",