[FIR] Implement DEFINITELY_NON_NULLABLE_AS_REIFIED diagnostic

#KT-55646 Fixed

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -2074,6 +2074,12 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.DEFINITELY_NON_NULLABLE_AS_REIFIED) { firDiagnostic ->
+        DefinitelyNonNullableAsReifiedImpl(
+            firDiagnostic as KtPsiDiagnostic,
+            token,
+        )
+    }
     add(FirErrors.FINAL_UPPER_BOUND) { firDiagnostic ->
         FinalUpperBoundImpl(
             firSymbolBuilder.typeBuilder.buildKtType(firDiagnostic.a),

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -1474,6 +1474,10 @@ sealed class KtFirDiagnostic<PSI : PsiElement> : KtDiagnosticWithPsi<PSI> {
         abstract val type: KtType
     }
 
+    abstract class DefinitelyNonNullableAsReified : KtFirDiagnostic<PsiElement>() {
+        override val diagnosticClass get() = DefinitelyNonNullableAsReified::class
+    }
+
     abstract class FinalUpperBound : KtFirDiagnostic<KtTypeReference>() {
         override val diagnosticClass get() = FinalUpperBound::class
         abstract val type: KtType

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -1772,6 +1772,11 @@ internal class ReifiedTypeForbiddenSubstitutionImpl(
     override val token: KtLifetimeToken,
 ) : KtFirDiagnostic.ReifiedTypeForbiddenSubstitution(), KtAbstractFirDiagnostic<PsiElement>
 
+internal class DefinitelyNonNullableAsReifiedImpl(
+    override val firDiagnostic: KtPsiDiagnostic,
+    override val token: KtLifetimeToken,
+) : KtFirDiagnostic.DefinitelyNonNullableAsReified(), KtAbstractFirDiagnostic<PsiElement>
+
 internal class FinalUpperBoundImpl(
     override val type: KtType,
     override val firDiagnostic: KtPsiDiagnostic,

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

@@ -666,6 +666,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val REIFIED_TYPE_FORBIDDEN_SUBSTITUTION by error<PsiElement> {
             parameter<ConeKotlinType>("type")
         }
+        val DEFINITELY_NON_NULLABLE_AS_REIFIED by error<PsiElement>()
 
         val FINAL_UPPER_BOUND by warning<KtTypeReference> {
             parameter<ConeKotlinType>("type")

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

@@ -413,6 +413,7 @@ object FirErrors {
     val TYPE_PARAMETER_AS_REIFIED by error1<PsiElement, FirTypeParameterSymbol>()
     val TYPE_PARAMETER_AS_REIFIED_ARRAY by deprecationError1<PsiElement, FirTypeParameterSymbol>(ProhibitNonReifiedArraysAsReifiedTypeArguments)
     val REIFIED_TYPE_FORBIDDEN_SUBSTITUTION by error1<PsiElement, ConeKotlinType>()
+    val DEFINITELY_NON_NULLABLE_AS_REIFIED by error0<PsiElement>()
     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/expression/FirReifiedChecker.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.expression
 
+import org.jetbrains.kotlin.KtRealSourceElementKind
 import org.jetbrains.kotlin.KtSourceElement
 import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.diagnostics.chooseFactory
@@ -20,19 +21,27 @@ import org.jetbrains.kotlin.name.StandardClassIds
 
 object FirReifiedChecker : FirQualifiedAccessExpressionChecker() {
     override fun check(expression: FirQualifiedAccessExpression, context: CheckerContext, reporter: DiagnosticReporter) {
-        val calleReference = expression.calleeReference
+        val calleeReference = expression.calleeReference
         val typeArguments = expression.typeArguments
-        val typeParameters = calleReference.toResolvedCallableSymbol()?.typeParameterSymbols ?: return
+        val typeParameters = calleeReference.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 source = typeArgumentProjection.source ?: calleeReference.source ?: continue
-            val typeArgument = typeArgumentProjection.toConeTypeProjection().type
+
+            val typeArgument = typeArgumentProjection.toConeTypeProjection().type ?: continue
             val typeParameter = typeParameters[index]
 
-            if (source != null && typeParameter.isReifiedTypeParameterOrFromKotlinArray()) {
+            if (typeParameter.isReifiedTypeParameterOrFromKotlinArray()) {
-                checkArgumentAndReport(typeArgument, source, false, context, reporter)
+                checkArgumentAndReport(
+                    typeArgument,
+                    source,
+                    isExplicit = typeArgumentProjection.source?.kind == KtRealSourceElementKind,
+                    isArray = false,
+                    context,
+                    reporter
+                )
             }
         }
     }
@@ -44,34 +53,35 @@ object FirReifiedChecker : FirQualifiedAccessExpressionChecker() {
     }
 
     private fun checkArgumentAndReport(
-        typeArgument: ConeKotlinType?,
+        typeArgument: ConeKotlinType,
         source: KtSourceElement,
+        isExplicit: Boolean,
         isArray: Boolean,
         context: CheckerContext,
         reporter: DiagnosticReporter
     ) {
-        if (typeArgument?.classId == StandardClassIds.Array) {
+        if (typeArgument.classId == StandardClassIds.Array) {
-            checkArgumentAndReport(typeArgument.typeArguments[0].type, source, true, context, reporter)
+            val nestedTypeArgument = typeArgument.typeArguments[0].type ?: return
+            checkArgumentAndReport(nestedTypeArgument, source, isExplicit, isArray = true, context, reporter)
             return
         }
 
         if (typeArgument is ConeTypeParameterType) {
-            val factory = if (isArray) {
-                FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY.chooseFactory(context)
-            } else {
-                FirErrors.TYPE_PARAMETER_AS_REIFIED
-            }
             val symbol = typeArgument.lookupTag.typeParameterSymbol
             if (!symbol.isReified) {
-                reporter.reportOn(source, factory, symbol, context)
+                reporter.reportOn(
+                    source,
+                    if (isArray) FirErrors.TYPE_PARAMETER_AS_REIFIED_ARRAY.chooseFactory(context) else FirErrors.TYPE_PARAMETER_AS_REIFIED,
+                    symbol,
+                    context
+                )
             }
-        } else if (typeArgument != null && typeArgument.cannotBeReified()) {
+        } else if (typeArgument is ConeDefinitelyNotNullType && isExplicit) {
+            // We sometimes infer type arguments to DNN types, which seems to be ok. Only report explicit DNN types written by user.
+            reporter.reportOn(source, FirErrors.DEFINITELY_NON_NULLABLE_AS_REIFIED, context)
+        } else if (typeArgument.isNothing || typeArgument.isNullableNothing || typeArgument is ConeCapturedType) {
             reporter.reportOn(source, FirErrors.REIFIED_TYPE_FORBIDDEN_SUBSTITUTION, typeArgument, context)
-            return
         }
     }
 
-    private fun ConeKotlinType.cannotBeReified(): Boolean {
-        return this.isNothing || this.isNullableNothing || this is ConeCapturedType
-    }
 }

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

@@ -147,6 +147,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DATA_CLASS_VARARG
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DATA_CLASS_WITHOUT_PARAMETERS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DATA_OBJECT_CUSTOM_EQUALS_OR_HASH_CODE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DECLARATION_CANT_BE_INLINED
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DEFINITELY_NON_NULLABLE_AS_REIFIED
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DELEGATED_PROPERTY_INSIDE_VALUE_CLASS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.DELEGATED_PROPERTY_IN_INTERFACE
@@ -1219,6 +1220,10 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             "Cannot use ''{0}'' as reified type parameter",
             RENDER_TYPE
         )
+        map.put(
+            DEFINITELY_NON_NULLABLE_AS_REIFIED,
+            "Cannot use definitely-non-nullable type as reified type argument",
+        )
         map.put(
             FINAL_UPPER_BOUND,
             "''{0}'' is a final type, and thus a value of the type parameter is predetermined",

compiler/testData/diagnostics/tests/explicitDefinitelyNotNullableViaIntersection/reifiedArguments.fir.kt

@@ -1,8 +0,0 @@
-// SKIP_TXT
-// !LANGUAGE: +DefinitelyNonNullableTypes
-
-inline fun <reified T : Any> foo() {}
-
-inline fun <reified F> bar() {
-    foo<F & Any>()
-}

compiler/testData/diagnostics/tests/explicitDefinitelyNotNullableViaIntersection/reifiedArguments.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // SKIP_TXT
 // !LANGUAGE: +DefinitelyNonNullableTypes
 
@@ -6,3 +7,12 @@ inline fun <reified T : Any> foo() {}
 inline fun <reified F> bar() {
     foo<<!DEFINITELY_NON_NULLABLE_AS_REIFIED!>F & Any<!>>()
 }
+
+class KAnnotatedElement(val annotations: List<Any>)
+
+inline fun <reified T : Any> Iterable<*>.firstIsInstanceOrNull(): T? {
+    return null
+}
+
+private inline fun <reified T> KAnnotatedElement.findAnnotation(): T? =
+    annotations.firstIsInstanceOrNull()