[FIR] Add DNN checks

Merge-request: KT-MR-7000
Merged-by: Nikolay Lunyak <lunyak.kolya@mail.ru>

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

@@ -705,6 +705,10 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
             parameter<String>("description")
             parameter<String>("causingTypes")
         }
+
+        val INCORRECT_LEFT_COMPONENT_OF_INTERSECTION by error<KtTypeReference>()
+        val INCORRECT_RIGHT_COMPONENT_OF_INTERSECTION by error<KtTypeReference>()
+        val NULLABLE_ON_DEFINITELY_NOT_NULLABLE by error<KtTypeReference>()
     }
 
     val REFLECTION by object : DiagnosticGroup("Reflection") {

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

@@ -417,6 +417,9 @@ object FirErrors {
     val PLATFORM_CLASS_MAPPED_TO_KOTLIN by warning1<PsiElement, FqName>(SourceElementPositioningStrategies.REFERENCED_NAME_BY_QUALIFIED)
     val INFERRED_TYPE_VARIABLE_INTO_EMPTY_INTERSECTION by error4<PsiElement, String, Collection<ConeKotlinType>, String, String>()
     val INFERRED_TYPE_VARIABLE_INTO_POSSIBLE_EMPTY_INTERSECTION by warning4<PsiElement, String, Collection<ConeKotlinType>, String, String>()
+    val INCORRECT_LEFT_COMPONENT_OF_INTERSECTION by error0<KtTypeReference>()
+    val INCORRECT_RIGHT_COMPONENT_OF_INTERSECTION by error0<KtTypeReference>()
+    val NULLABLE_ON_DEFINITELY_NOT_NULLABLE by error0<KtTypeReference>()
 
     // Reflection
     val EXTENSION_IN_CLASS_REFERENCE_NOT_ALLOWED by error1<KtExpression, FirCallableSymbol<*>>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)

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

@@ -12,6 +12,7 @@ object CommonTypeCheckers : TypeCheckers() {
         FirTypeAnnotationChecker,
         FirSuspendModifierChecker,
         FirDeprecatedTypeChecker,
-        FirOptInUsageTypeRefChecker
+        FirOptInUsageTypeRefChecker,
+        FirDefinitelyNotNullableChecker,
     )
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/type/FirDefinitelyNotNullableChecker.kt

@@ -0,0 +1,30 @@
+/*
+ * Copyright 2010-2022 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.type
+
+import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
+import org.jetbrains.kotlin.fir.types.*
+
+object FirDefinitelyNotNullableChecker : FirTypeRefChecker() {
+    override fun check(typeRef: FirTypeRef, context: CheckerContext, reporter: DiagnosticReporter) {
+        val intersection = (typeRef as? FirResolvedTypeRef)?.delegatedTypeRef as? FirIntersectionTypeRef ?: return
+
+        if (intersection.isMarkedNullable) {
+            reporter.reportOn(intersection.source, FirErrors.NULLABLE_ON_DEFINITELY_NOT_NULLABLE, context)
+        }
+
+        if (!intersection.isLeftValidForDefinitelyNotNullable) {
+            reporter.reportOn(intersection.leftType.source, FirErrors.INCORRECT_LEFT_COMPONENT_OF_INTERSECTION, context)
+        }
+
+        if (!intersection.isRightValidForDefinitelyNotNullable) {
+            reporter.reportOn(intersection.rightType.source, FirErrors.INCORRECT_RIGHT_COMPONENT_OF_INTERSECTION, context)
+        }
+    }
+}

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

@@ -252,6 +252,8 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCOMPATIBLE_TYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCONSISTENT_TYPE_PARAMETER_BOUNDS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCONSISTENT_TYPE_PARAMETER_VALUES
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCORRECT_CHARACTER_LITERAL
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCORRECT_LEFT_COMPONENT_OF_INTERSECTION
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INCORRECT_RIGHT_COMPONENT_OF_INTERSECTION
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INC_DEC_SHOULD_NOT_RETURN_UNIT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INFERENCE_ERROR
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.INFERENCE_UNSUCCESSFUL_FORK
@@ -359,6 +361,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NO_THIS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NO_TYPE_ARGUMENTS_ON_RHS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NO_VALUE_FOR_PARAMETER
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NULLABLE_INLINE_PARAMETER
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NULLABLE_ON_DEFINITELY_NOT_NULLABLE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NULLABLE_SUPERTYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NULLABLE_TYPE_IN_CLASS_LITERAL_LHS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.NULLABLE_TYPE_OF_ANNOTATION_MEMBER
@@ -982,6 +985,18 @@ object FirErrorsDefaultMessages : BaseDiagnosticRendererFactory() {
             TO_STRING,
             TO_STRING
         )
+        map.put(
+            NULLABLE_ON_DEFINITELY_NOT_NULLABLE,
+            "'!!' type cannot be marked as nullable"
+        )
+        map.put(
+            INCORRECT_LEFT_COMPONENT_OF_INTERSECTION,
+            "Intersection types are only supported for definitely non-nullable types: left part should be a type parameter with nullable bounds"
+        )
+        map.put(
+            INCORRECT_RIGHT_COMPONENT_OF_INTERSECTION,
+            "Intersection types are only supported for definitely non-nullable types: right part should be non-nullable Any"
+        )
 
         map.put(TYPE_MISMATCH, "Type mismatch: inferred type is {1} but {0} was expected", TO_STRING, TO_STRING, NOT_RENDERED)
         map.put(THROWABLE_TYPE_MISMATCH, "Throwable type mismatch: actual type is {0}", TO_STRING, NOT_RENDERED)

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

@@ -128,6 +128,7 @@ private fun ConeDiagnostic.toKtDiagnostic(
     is ConeLocalVariableNoTypeOrInitializer -> runIf(variable.isLocalMember) {
         FirErrors.VARIABLE_WITH_NO_TYPE_NO_INITIALIZER.createOn(source)
     }
+    is ConeForbiddenIntersection -> null // reported in FirDefinitelyNotNullableChecker
 
     is ConeUnderscoreIsReserved -> FirErrors.UNDERSCORE_IS_RESERVED.createOn(this.source)
     is ConeUnderscoreUsageWithoutBackticks -> FirErrors.UNDERSCORE_USAGE_WITHOUT_BACKTICKS.createOn(this.source)

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/providers/impl/FirTypeResolverImpl.kt

@@ -523,14 +523,11 @@ class FirTypeResolverImpl(private val session: FirSession) : FirTypeResolver() {
             is FirDynamicTypeRef -> ConeDynamicType.create(session) to null
             is FirIntersectionTypeRef -> {
                 val leftType = typeRef.leftType.coneType
-                val rightType = typeRef.rightType.coneType
-
-                if (rightType.isAny && leftType is ConeTypeParameterType) {
+                if (leftType is ConeTypeParameterType) {
                     ConeDefinitelyNotNullType(leftType) to null
                 } else {
-                    ConeErrorType(ConeUnsupported("Intersection types are not supported yet", typeRef.source)) to null
+                    ConeErrorType(ConeForbiddenIntersection) to null
                 }
-
             }
             else -> error(typeRef.render())
         }

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/diagnostics/ConeDiagnostics.kt

@@ -237,3 +237,7 @@ class ConeAmbiguousAlteredAssign(val altererNames: List<String?>) : ConeDiagnost
     override val reason: String
         get() = "Assign altered by multiple extensions"
 }
+
+object ConeForbiddenIntersection : ConeDiagnostic {
+    override val reason: String get() = "Such an intersection type is not allowed"
+}

compiler/fir/tree/src/org/jetbrains/kotlin/fir/types/FirTypeUtils.kt

@@ -191,3 +191,7 @@ val ConeKotlinType.canBeNull: Boolean
         }
     }
 
+val FirIntersectionTypeRef.isLeftValidForDefinitelyNotNullable
+    get() = leftType.coneType.let { it is ConeTypeParameterType && it.canBeNull && !it.isMarkedNullable }
+
+val FirIntersectionTypeRef.isRightValidForDefinitelyNotNullable get() = rightType.coneType.isAny