[Analysis API FIR] fix KtSymbol creation for _ destructuring parameter

We need to have a corresponding declaration in the FIR tree,
so we can create a symbol for it

^KT-60904 fixed
^KT-60904 fixed

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirDestructuringDeclarationChecker.kt

@@ -26,11 +26,13 @@ import org.jetbrains.kotlin.fir.symbols.SymbolInternals
 import org.jetbrains.kotlin.fir.symbols.impl.FirNamedFunctionSymbol
 import org.jetbrains.kotlin.fir.symbols.lazyResolveToPhase
 import org.jetbrains.kotlin.fir.types.*
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.types.AbstractTypeChecker
 
 object FirDestructuringDeclarationChecker : FirPropertyChecker() {
     override fun check(declaration: FirProperty, context: CheckerContext, reporter: DiagnosticReporter) {
         val source = declaration.source ?: return
+        if (declaration.name == SpecialNames.UNDERSCORE_FOR_UNUSED_VAR) return
         // val (...) = `destructuring_declaration`
         if (source.elementType == KtNodeTypes.DESTRUCTURING_DECLARATION) {
             checkInitializer(source, declaration.initializer, reporter, context)

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirReservedUnderscoreDeclarationChecker.kt

@@ -17,6 +17,7 @@ import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.isCatchParameter
 import org.jetbrains.kotlin.fir.types.FirResolvedTypeRef
 import org.jetbrains.kotlin.fir.types.FirUserTypeRef
+import org.jetbrains.kotlin.name.SpecialNames
 
 object FirReservedUnderscoreDeclarationChecker : FirBasicDeclarationChecker() {
     override fun check(declaration: FirDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
@@ -55,7 +56,10 @@ object FirReservedUnderscoreDeclarationChecker : FirBasicDeclarationChecker() {
         isSingleUnderscoreAllowed: Boolean = false
     ) {
         val declarationSource = declaration.source
-        if (declarationSource != null && declarationSource.kind !is KtFakeSourceElementKind) {
+        if (declarationSource != null &&
+            declarationSource.kind !is KtFakeSourceElementKind &&
+            (declaration as? FirProperty)?.name != SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
+        ) {
             with(SourceNavigator.forElement(declaration)) {
                 val rawName = declaration.getRawName()
                 if (rawName?.isUnderscore == true && !(isSingleUnderscoreAllowed && rawName == "_")) {

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/extended/UnusedChecker.kt

@@ -29,6 +29,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.lazyResolveToPhase
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.fir.types.isBasicFunctionType
+import org.jetbrains.kotlin.name.SpecialNames
 
 object UnusedChecker : AbstractFirPropertyInitializationChecker() {
     override fun analyze(data: PropertyInitializationInfoData, reporter: DiagnosticReporter, context: CheckerContext) {
@@ -62,6 +63,7 @@ object UnusedChecker : AbstractFirPropertyInitializationChecker() {
             val variableSymbol = node.fir.symbol
             if (node.fir.source == null) return
             if (variableSymbol.isLoopIterator) return
+            if (variableSymbol.name == SpecialNames.UNDERSCORE_FOR_UNUSED_VAR) return
             val dataPerNode = data[node] ?: return
 
             val data = dataPerNode.values.mapNotNull { it[variableSymbol] }.reduceOrNull { acc, it -> acc.merge(it) }

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/Fir2IrVisitor.kt

@@ -251,6 +251,9 @@ class Fir2IrVisitor(
                 for (statement in script.statements) {
                     val irStatement = if (statement is FirDeclaration) {
                         when {
+                            statement is FirProperty && statement.name == SpecialNames.UNDERSCORE_FOR_UNUSED_VAR -> {
+                                continue
+                            }
                             statement is FirProperty && statement.origin == FirDeclarationOrigin.ScriptCustomization.ResultProperty -> {
                                 // Generating the result property only for expressions with a meaningful result type
                                 // otherwise skip the property and convert the expression into the statement
@@ -820,6 +823,7 @@ class Fir2IrVisitor(
         }
         if (this is FirContractCallBlock) return null
         if (this is FirBlock) return convertToIrExpression(this)
+        if (this is FirProperty && name == SpecialNames.UNDERSCORE_FOR_UNUSED_VAR) return null
         return accept(this@Fir2IrVisitor, null) as IrStatement
     }
 

compiler/fir/raw-fir/light-tree2fir/src/org/jetbrains/kotlin/fir/lightTree/converter/LightTreeRawFirDeclarationBuilder.kt

@@ -1390,8 +1390,11 @@ class LightTreeRawFirDeclarationBuilder(
             }
         }
 
-        if (identifier == "_") return null
-        val name = identifier.nameAsSafeName()
+        val name = if (identifier == "_") {
+            SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
+        } else {
+            identifier.nameAsSafeName()
+        }
         return buildProperty {
             source = entry.toFirSourceElement()
             moduleData = baseModuleData

compiler/fir/raw-fir/psi2fir/src/org/jetbrains/kotlin/fir/builder/PsiConversionUtils.kt

@@ -21,6 +21,7 @@ import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.types.FirTypeRef
 import org.jetbrains.kotlin.fir.types.impl.FirImplicitTypeRefImplWithoutSource
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.psi.*
 
 internal fun KtWhenCondition.toFirWhenCondition(
@@ -135,9 +136,12 @@ internal fun generateDestructuringBlock(
         }
         val isVar = multiDeclaration.isVar
         for ((index, entry) in multiDeclaration.entries.withIndex()) {
-            if (entry.nameIdentifier?.text == "_") continue
+            val name = if (entry.nameIdentifier?.text == "_") {
+                SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
+            } else {
+                entry.nameAsSafeName
+            }
             val entrySource = entry.toKtPsiSourceElement()
-            val name = entry.nameAsSafeName
             statements += buildProperty {
                 source = entrySource
                 this.moduleData = moduleData

compiler/fir/raw-fir/psi2fir/testData/rawBuilder/expressions/destructuring.txt

@@ -34,5 +34,6 @@ FILE: destructuring.kt
     public? final? fun bar(some: Some): R|kotlin/Unit| {
         lval <destruct>: <implicit> = some#
         lval a: <implicit> = R|<local>/<destruct>|.component1#()
+        lval <unused var>: <implicit> = R|<local>/<destruct>|.component2#()
         lval _: <implicit> = R|<local>/<destruct>|.component3#()
     }

compiler/testData/diagnostics/tests/redeclarations/RedeclaredValsAndVars.fir.txt

@@ -48,4 +48,5 @@ FILE: RedeclaredValsAndVars.fir.kt
 
         lval <destruct>: R|A| = R|/A.A|()
         lval _: R|kotlin/Int| = R|<local>/<destruct>|.R|/A.component1|()
+        lval <unused var>: R|kotlin/String| = R|<local>/<destruct>|.R|/A.component2|()
     }