[FIR] Implement SPREAD_OF_NULLABLE

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

@@ -409,6 +409,8 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER by error<KtElement> {
             parameter<String>("name")
         }
+
+        val SPREAD_OF_NULLABLE by error<PsiElement>(PositioningStrategy.SPREAD_OPERATOR)
     }
 
     val AMBIGUITY by object : DiagnosticGroup("Ambiguity") {
@@ -570,7 +572,7 @@ object DIAGNOSTICS_LIST : DiagnosticList("FirErrors") {
         val NOTHING_TO_OVERRIDE by error<KtModifierListOwner>(PositioningStrategy.OVERRIDE_MODIFIER) {
             parameter<FirMemberDeclaration>("declaration")
         }
-        
+
         val CANNOT_OVERRIDE_INVISIBLE_MEMBER by error<KtNamedDeclaration>(PositioningStrategy.OVERRIDE_MODIFIER) {
             parameter<FirCallableDeclaration>("overridingMember")
             parameter<FirCallableDeclaration>("baseMember")

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

@@ -75,6 +75,7 @@ enum class PositioningStrategy(private val strategy: String? = null) {
     ASSIGNMENT_LHS,
     IMPORT_LAST_NAME,
     DATA_MODIFIER,
+    SPREAD_OPERATOR,
 
     ;
 

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

@@ -281,6 +281,7 @@ object FirErrors {
     val RESULT_TYPE_MISMATCH by error2<KtExpression, ConeKotlinType, ConeKotlinType>()
     val MANY_LAMBDA_EXPRESSION_ARGUMENTS by error0<KtValueArgument>()
     val NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER by error1<KtElement, String>()
+    val SPREAD_OF_NULLABLE by error0<PsiElement>(SourceElementPositioningStrategies.SPREAD_OPERATOR)
 
     // Ambiguity
     val OVERLOAD_RESOLUTION_AMBIGUITY by error1<PsiElement, Collection<FirBasedSymbol<*>>>(SourceElementPositioningStrategies.REFERENCE_BY_QUALIFIED)

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

@@ -45,6 +45,7 @@ object CommonExpressionCheckers : ExpressionCheckers() {
             FirConventionFunctionCallChecker,
             FirDivisionByZeroChecker,
             FirConstructorCallChecker,
+            FirSpreadOfNullableChecker
         )
 
     override val tryExpressionCheckers: Set<FirTryExpressionChecker>

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

@@ -0,0 +1,40 @@
+/*
+ * 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.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.FirErrors
+import org.jetbrains.kotlin.fir.analysis.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.expressions.FirExpression
+import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
+import org.jetbrains.kotlin.fir.expressions.FirSpreadArgumentExpression
+import org.jetbrains.kotlin.fir.expressions.FirVarargArgumentsExpression
+import org.jetbrains.kotlin.fir.types.ConeFlexibleType
+import org.jetbrains.kotlin.fir.types.canBeNull
+import org.jetbrains.kotlin.fir.types.coneType
+
+object FirSpreadOfNullableChecker : FirFunctionCallChecker() {
+    override fun check(expression: FirFunctionCall, context: CheckerContext, reporter: DiagnosticReporter) {
+        fun checkAndReport(argument: FirExpression, source: FirSourceElement?) {
+            val argumentTypeRef = argument.typeRef
+            if (argument is FirSpreadArgumentExpression && argumentTypeRef.coneType !is ConeFlexibleType && argumentTypeRef.canBeNull) {
+                reporter.reportOn(source, FirErrors.SPREAD_OF_NULLABLE, context)
+            }
+        }
+
+        for (argument in expression.argumentList.arguments) {
+            if (argument is FirVarargArgumentsExpression) {
+                for (subArgument in argument.arguments) {
+                    checkAndReport(subArgument, argument.source)
+                }
+            } else {
+                checkAndReport(argument, argument.source)
+            }
+        }
+    }
+}

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

@@ -316,6 +316,7 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SETTER_PROJECTED_
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SETTER_VISIBILITY_INCONSISTENT_WITH_PROPERTY_VISIBILITY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SINGLETON_IN_SUPERTYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SMARTCAST_IMPOSSIBLE
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SPREAD_OF_NULLABLE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SUPERCLASS_NOT_ACCESSIBLE_FROM_INTERFACE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SUPERTYPES_FOR_ANNOTATION_CLASS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.SUPERTYPE_APPEARS_TWICE
@@ -672,6 +673,7 @@ class FirDefaultErrorMessages {
             map.put(NO_VALUE_FOR_PARAMETER, "No value passed for parameter ''{0}''", NAME)
             map.put(NAMED_PARAMETER_NOT_FOUND, "Cannot find a parameter with this name: {0}", TO_STRING)
             map.put(MANY_LAMBDA_EXPRESSION_ARGUMENTS, "Only one lambda expression is allowed outside a parenthesized argument list")
+            map.put(SPREAD_OF_NULLABLE, "The spread operator (*foo) may not be applied to an argument of nullable type")
 
             map.put(TYPE_MISMATCH, "Type mismatch: inferred type is {1} but {0} was expected", TO_STRING, TO_STRING)
             map.put(THROWABLE_TYPE_MISMATCH, "Throwable type mismatch: actual type is {0}", TO_STRING)

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

@@ -20,6 +20,8 @@ import org.jetbrains.kotlin.lexer.KtTokens.VISIBILITY_MODIFIERS
 import org.jetbrains.kotlin.psi.KtParameter.VAL_VAR_TOKEN_SET
 import org.jetbrains.kotlin.psi.stubs.elements.KtConstantExpressionElementType
 import org.jetbrains.kotlin.psi.stubs.elements.KtStringTemplateExpressionElementType
+import org.jetbrains.kotlin.psi.stubs.elements.KtValueArgumentElementType
+import org.jetbrains.kotlin.psi.stubs.elements.KtValueArgumentListElementType
 
 object LightTreePositioningStrategies {
     val DEFAULT = object : LightTreePositioningStrategy() {
@@ -780,6 +782,17 @@ object LightTreePositioningStrategies {
             return markElement(nodeToMark, startOffset, endOffset, tree, node)
         }
     }
+
+    val SPREAD_OPERATOR: LightTreePositioningStrategy = object : LightTreePositioningStrategy() {
+        override fun mark(
+            node: LighterASTNode,
+            startOffset: Int,
+            endOffset: Int,
+            tree: FlyweightCapableTreeStructure<LighterASTNode>
+        ): List<TextRange> {
+            return super.mark(node, startOffset, startOffset + 1, tree)
+        }
+    }
 }
 
 fun FirSourceElement.hasValOrVar(): Boolean =

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

@@ -262,4 +262,9 @@ object SourceElementPositioningStrategies {
         LightTreePositioningStrategies.IMPORT_LAST_NAME,
         PositioningStrategies.IMPORT_LAST_NAME
     )
+
+    val SPREAD_OPERATOR = SourceElementPositioningStrategy(
+        LightTreePositioningStrategies.SPREAD_OPERATOR,
+        PositioningStrategies.SPREAD_OPERATOR
+    )
 }