[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

analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/symbols/psiBased/KtFe10PsiLocalVariableSymbol.kt

@@ -5,6 +5,7 @@
 
 package org.jetbrains.kotlin.analysis.api.descriptors.symbols.psiBased
 
+import com.intellij.extapi.psi.StubBasedPsiElementBase
 import org.jetbrains.kotlin.analysis.api.KtAnalysisSession
 import org.jetbrains.kotlin.analysis.api.descriptors.Fe10AnalysisContext
 import org.jetbrains.kotlin.analysis.api.descriptors.Fe10AnalysisFacade.AnalysisMode
@@ -23,6 +24,7 @@ import org.jetbrains.kotlin.analysis.api.symbols.pointers.KtSymbolPointer
 import org.jetbrains.kotlin.analysis.api.types.KtType
 import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.psi.KtVariableDeclaration
 import org.jetbrains.kotlin.resolve.BindingContext
 
@@ -36,8 +38,12 @@ internal class KtFe10PsiLocalVariableSymbol(
     }
 
     override val name: Name
-        get() = withValidityAssertion { psi.nameAsSafeName }
+        get() = withValidityAssertion {
-
+            when {
+                psi.nameIdentifier?.text == "_" -> SpecialNames.UNDERSCORE_FOR_UNUSED_VAR
+                else -> psi.nameAsSafeName
+            }
+        }
     override val returnType: KtType
         get() = withValidityAssertion { descriptor?.type?.toKtType(analysisContext) ?: createErrorType() }
 

analysis/analysis-api-fe10/src/org/jetbrains/kotlin/analysis/api/descriptors/symbols/psiBased/KtFe10PsiValueParameterSymbol.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.descriptors.VariableDescriptor
 import org.jetbrains.kotlin.descriptors.impl.PropertyDescriptorImpl
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.name.SpecialNames
 import org.jetbrains.kotlin.psi.KtParameter
 import org.jetbrains.kotlin.resolve.BindingContext
 
@@ -68,7 +69,10 @@ internal class KtFe10PsiValueParameterSymbol(
         }
 
     override val name: Name
-        get() = withValidityAssertion { psi.nameAsSafeName }
+        get() = withValidityAssertion {
+            if (psi.destructuringDeclaration != null) SpecialNames.DESTRUCT
+            else psi.nameAsSafeName
+        }
 
     context(KtAnalysisSession)
     override fun createPointer(): KtSymbolPointer<KtValueParameterSymbol> = withValidityAssertion {

analysis/analysis-api-fe10/tests-gen/org/jetbrains/kotlin/analysis/api/fe10/test/cases/generated/cases/symbols/Fe10IdeNormalAnalysisSourceModuleSingleSymbolByPsiGenerated.java

@@ -314,6 +314,46 @@ public class Fe10IdeNormalAnalysisSourceModuleSingleSymbolByPsiGenerated extends
         }
     }
 
+    @Nested
+    @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring")
+    @TestDataPath("$PROJECT_ROOT")
+    public class Destructuring {
+        @Test
+        public void testAllFilesPresentInDestructuring() throws Exception {
+            KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring"), Pattern.compile("^(.+)\\.kt$"), null, true);
+        }
+
+        @Test
+        @TestMetadata("destructuringDeclarationParameterInLambda.kt")
+        public void testDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclaration.kt")
+        public void testEntryInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclaration.kt")
+        public void testEntryUnderscoreInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryUnderscoreInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt");
+        }
+    }
+
     @Nested
     @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/errors")
     @TestDataPath("$PROJECT_ROOT")

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/components/KtFirImportOptimizer.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.analysis.low.level.api.fir.api.getOrBuildFirFile
 import org.jetbrains.kotlin.fir.FirElement
 import org.jetbrains.kotlin.fir.FirSession
 import org.jetbrains.kotlin.fir.declarations.FirFile
+import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
 import org.jetbrains.kotlin.fir.expressions.*
 import org.jetbrains.kotlin.fir.psi
@@ -130,6 +131,11 @@ internal class KtFirImportOptimizer(
                 super.visitImplicitInvokeCall(implicitInvokeCall)
             }
 
+            override fun visitProperty(property: FirProperty) {
+                if (property.name == SpecialNames.UNDERSCORE_FOR_UNUSED_VAR) return
+                super.visitProperty(property)
+            }
+
             override fun visitComponentCall(componentCall: FirComponentCall) {
                 processFunctionCall(componentCall)
                 super.visitComponentCall(componentCall)

analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/symbols/KtFirSymbolProvider.kt

@@ -10,6 +10,7 @@ import org.jetbrains.kotlin.analysis.api.fir.components.KtFirAnalysisSessionComp
 import org.jetbrains.kotlin.analysis.api.getModule
 import org.jetbrains.kotlin.analysis.api.symbols.*
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.getOrBuildFirFile
+import org.jetbrains.kotlin.analysis.low.level.api.fir.api.resolveToFirSymbol
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.resolveToFirSymbolOfType
 import org.jetbrains.kotlin.analysis.low.level.api.fir.api.throwUnexpectedFirElementError
 import org.jetbrains.kotlin.analysis.low.level.api.fir.util.errorWithFirSpecificEntries
@@ -25,6 +26,7 @@ import org.jetbrains.kotlin.name.FqName
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.isObjectLiteral
+import org.jetbrains.kotlin.resolve.calls.util.isSingleUnderscore
 
 internal class KtFirSymbolProvider(
     override val analysisSession: KtFirAnalysisSession,
@@ -186,11 +188,14 @@ internal class KtFirSymbolProvider(
 
     override val ROOT_PACKAGE_SYMBOL: KtPackageSymbol = KtFirPackageSymbol(FqName.ROOT, firResolveSession.project, token)
 
-    override fun getDestructuringDeclarationEntrySymbol(psi: KtDestructuringDeclarationEntry): KtFirLocalOrErrorVariableSymbol<*, *> {
+    override fun getDestructuringDeclarationEntrySymbol(psi: KtDestructuringDeclarationEntry): KtLocalVariableSymbol {
-        return when (val firSymbol = psi.resolveToFirSymbolOfType<FirVariableSymbol<*>>(firResolveSession)) {
+        return when (val firSymbol = psi.resolveToFirSymbol(firResolveSession)) {
             is FirPropertySymbol -> firSymbolBuilder.variableLikeBuilder.buildLocalVariableSymbol(firSymbol)
             is FirErrorPropertySymbol -> firSymbolBuilder.variableLikeBuilder.buildErrorVariableSymbol(firSymbol)
-            else -> throwUnexpectedFirElementError(firSymbol, psi, FirPropertySymbol::class, FirErrorPropertySymbol::class)
+            else -> throwUnexpectedFirElementError(
+                firSymbol, psi,
+                FirPropertySymbol::class, FirErrorPropertySymbol::class, FirValueParameterSymbol::class
+            )
         }
     }
 }

analysis/analysis-api-fir/tests-gen/org/jetbrains/kotlin/analysis/api/fir/test/cases/generated/cases/symbols/FirIdeNormalAnalysisSourceModuleSingleSymbolByPsiGenerated.java

@@ -314,6 +314,46 @@ public class FirIdeNormalAnalysisSourceModuleSingleSymbolByPsiGenerated extends
         }
     }
 
+    @Nested
+    @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring")
+    @TestDataPath("$PROJECT_ROOT")
+    public class Destructuring {
+        @Test
+        public void testAllFilesPresentInDestructuring() throws Exception {
+            KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring"), Pattern.compile("^(.+)\\.kt$"), null, true);
+        }
+
+        @Test
+        @TestMetadata("destructuringDeclarationParameterInLambda.kt")
+        public void testDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclaration.kt")
+        public void testEntryInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclaration.kt")
+        public void testEntryUnderscoreInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryUnderscoreInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt");
+        }
+    }
+
     @Nested
     @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/errors")
     @TestDataPath("$PROJECT_ROOT")

analysis/analysis-api-standalone/tests-gen/org/jetbrains/kotlin/analysis/api/standalone/fir/test/cases/generated/cases/symbols/FirStandaloneNormalAnalysisSourceModuleSingleSymbolByPsiGenerated.java

@@ -314,6 +314,46 @@ public class FirStandaloneNormalAnalysisSourceModuleSingleSymbolByPsiGenerated e
         }
     }
 
+    @Nested
+    @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring")
+    @TestDataPath("$PROJECT_ROOT")
+    public class Destructuring {
+        @Test
+        public void testAllFilesPresentInDestructuring() throws Exception {
+            KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring"), Pattern.compile("^(.+)\\.kt$"), null, true);
+        }
+
+        @Test
+        @TestMetadata("destructuringDeclarationParameterInLambda.kt")
+        public void testDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclaration.kt")
+        public void testEntryInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclaration.kt")
+        public void testEntryUnderscoreInDestructuringDeclaration() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryUnderscoreInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt");
+        }
+    }
+
     @Nested
     @TestMetadata("analysis/analysis-api/testData/symbols/singleSymbolByPsi/errors")
     @TestDataPath("$PROJECT_ROOT")

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.kt

@@ -0,0 +1,12 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: KtParameter
+// DO_NOT_CHECK_NON_PSI_SYMBOL_RESTORE
+
+data class X(val a: Int, val b: Int)
+
+fun x(action: (X, Int) -> Unit) {}
+
+fun main() {
+    x { <expr>(a, b)</expr>, i ->
+
+    }
+}

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.pretty.txt

@@ -0,0 +1 @@
+`<destruct>`: X

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/destructuringDeclarationParameterInLambda.txt

@@ -0,0 +1,22 @@
+KtValueParameterSymbol:
+  annotationsList: []
+  callableIdIfNonLocal: null
+  contextReceivers: []
+  generatedPrimaryConstructorProperty: null
+  hasDefaultValue: false
+  isCrossinline: false
+  isExtension: false
+  isImplicitLambdaParameter: false
+  isNoinline: false
+  isVararg: false
+  name: <destruct>
+  origin: SOURCE
+  receiverParameter: null
+  returnType: KtUsualClassType:
+    annotationsList: []
+    ownTypeArguments: []
+    type: X
+  symbolKind: LOCAL
+  typeParameters: []
+  getContainingModule: KtSourceModule "Sources of main"
+  deprecationStatus: null

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.kt

@@ -0,0 +1,8 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: KtDestructuringDeclarationEntry
+// DO_NOT_CHECK_NON_PSI_SYMBOL_RESTORE
+
+data class X(val a: Int, val b: Int)
+
+fun main(x: X) {
+    val (<expr>a</expr>, b) = x
+}

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.pretty.txt

@@ -0,0 +1 @@
+val a: kotlin.Int

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclaration.txt

@@ -0,0 +1,17 @@
+KtLocalVariableSymbol:
+  annotationsList: []
+  callableIdIfNonLocal: null
+  contextReceivers: []
+  isExtension: false
+  isVal: true
+  name: a
+  origin: SOURCE
+  receiverParameter: null
+  returnType: KtUsualClassType:
+    annotationsList: []
+    ownTypeArguments: []
+    type: kotlin/Int
+  symbolKind: LOCAL
+  typeParameters: []
+  getContainingModule: KtSourceModule "Sources of main"
+  deprecationStatus: null

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.kt

@@ -0,0 +1,12 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: KtDestructuringDeclarationEntry
+// DO_NOT_CHECK_NON_PSI_SYMBOL_RESTORE
+
+data class X(val a: Int, val b: Int)
+
+fun x(action: (X) -> Unit) {}
+
+fun main() {
+    x { (<expr>a</expr>, b) ->
+
+    }
+}

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.pretty.txt

@@ -0,0 +1 @@
+val a: kotlin.Int

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryInDestructuringDeclarationParameterInLambda.txt

@@ -0,0 +1,17 @@
+KtLocalVariableSymbol:
+  annotationsList: []
+  callableIdIfNonLocal: null
+  contextReceivers: []
+  isExtension: false
+  isVal: true
+  name: a
+  origin: SOURCE
+  receiverParameter: null
+  returnType: KtUsualClassType:
+    annotationsList: []
+    ownTypeArguments: []
+    type: kotlin/Int
+  symbolKind: LOCAL
+  typeParameters: []
+  getContainingModule: KtSourceModule "Sources of main"
+  deprecationStatus: null

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.kt

@@ -0,0 +1,8 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: KtDestructuringDeclarationEntry
+// DO_NOT_CHECK_NON_PSI_SYMBOL_RESTORE
+
+data class X(val a: Int, val b: Int)
+
+fun main(x: X) {
+    val (<expr>_</expr>, b) = x
+}

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.pretty.txt

@@ -0,0 +1 @@
+val `<unused var>`: kotlin.Int

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclaration.txt

@@ -0,0 +1,17 @@
+KtLocalVariableSymbol:
+  annotationsList: []
+  callableIdIfNonLocal: null
+  contextReceivers: []
+  isExtension: false
+  isVal: true
+  name: <unused var>
+  origin: SOURCE
+  receiverParameter: null
+  returnType: KtUsualClassType:
+    annotationsList: []
+    ownTypeArguments: []
+    type: kotlin/Int
+  symbolKind: LOCAL
+  typeParameters: []
+  getContainingModule: KtSourceModule "Sources of main"
+  deprecationStatus: null

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt

@@ -0,0 +1,12 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: KtDestructuringDeclarationEntry
+// DO_NOT_CHECK_NON_PSI_SYMBOL_RESTORE
+
+data class X(val a: Int, val b: Int)
+
+fun x(action: (X) -> Unit) {}
+
+fun main() {
+    x { (<expr>_</expr>, b) ->
+
+    }
+}

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.pretty.txt

@@ -0,0 +1 @@
+val `<unused var>`: kotlin.Int

analysis/analysis-api/testData/symbols/singleSymbolByPsi/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.txt

@@ -0,0 +1,17 @@
+KtLocalVariableSymbol:
+  annotationsList: []
+  callableIdIfNonLocal: null
+  contextReceivers: []
+  isExtension: false
+  isVal: true
+  name: <unused var>
+  origin: SOURCE
+  receiverParameter: null
+  returnType: KtUsualClassType:
+    annotationsList: []
+    ownTypeArguments: []
+    type: kotlin/Int
+  symbolKind: LOCAL
+  typeParameters: []
+  getContainingModule: KtSourceModule "Sources of main"
+  deprecationStatus: null

analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclaration.kt

@@ -0,0 +1,7 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: org.jetbrains.kotlin.psi.KtDestructuringDeclarationEntry
+
+data class X(val a: Int, val b: Int)
+
+fun main(x: X) {
+    val (<expr>_</expr>, b) = x
+}

analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclaration.txt

@@ -0,0 +1,32 @@
+KT element: KtDestructuringDeclarationEntry
+FIR element: FirPropertyImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+[ResolvedTo(BODY_RESOLVE)] lval <unused var>: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component1|()
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] entryUnderscoreInDestructuringDeclaration.kt
+    public final data [ResolvedTo(STATUS)] class X : R|kotlin/Any| {
+        public [ResolvedTo(STATUS)] [ContainingClassKey=X] constructor([ResolvedTo(STATUS)] [CorrespondingProperty=/X.a] a: R|kotlin/Int|, [ResolvedTo(STATUS)] [CorrespondingProperty=/X.b] b: R|kotlin/Int|): R|X| {
+            LAZY_super<R|kotlin/Any|>
+        }
+
+        public final [ResolvedTo(STATUS)] [ComponentFunctionSymbolKey=/X.component1, IsFromPrimaryConstructor=true] val a: R|kotlin/Int| = R|<local>/a|
+            public [ResolvedTo(STATUS)] [ContainingClassKey=X] get(): R|kotlin/Int|
+
+        public final [ResolvedTo(STATUS)] [ComponentFunctionSymbolKey=/X.component2, IsFromPrimaryConstructor=true] val b: R|kotlin/Int| = R|<local>/b|
+            public [ResolvedTo(STATUS)] [ContainingClassKey=X] get(): R|kotlin/Int|
+
+        public final operator [ResolvedTo(CONTRACTS)] fun component1(): R|kotlin/Int|
+
+        public final operator [ResolvedTo(CONTRACTS)] fun component2(): R|kotlin/Int|
+
+        public final [ResolvedTo(STATUS)] fun copy([ResolvedTo(STATUS)] a: R|kotlin/Int| = this@R|/X|.R|/X.a|, [ResolvedTo(STATUS)] b: R|kotlin/Int| = this@R|/X|.R|/X.b|): R|X|
+
+    }
+    public final [ResolvedTo(BODY_RESOLVE)] fun main([ResolvedTo(BODY_RESOLVE)] x: R|X|): R|kotlin/Unit| {
+        [ResolvedTo(BODY_RESOLVE)] lval <destruct>: R|X| = R|<local>/x|
+        [ResolvedTo(BODY_RESOLVE)] lval <unused var>: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component1|()
+        [ResolvedTo(BODY_RESOLVE)] lval b: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component2|()
+    }

analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt

@@ -0,0 +1,11 @@
+// LOOK_UP_FOR_ELEMENT_OF_TYPE: org.jetbrains.kotlin.psi.KtDestructuringDeclarationEntry
+
+data class X(val a: Int, val b: Int)
+
+fun x(action: (X) -> Unit) {}
+
+fun main() {
+    x { (<expr>_</expr>, b) ->
+
+    }
+}

analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.txt

@@ -0,0 +1,37 @@
+KT element: KtDestructuringDeclarationEntry
+FIR element: FirPropertyImpl
+FIR source kind: KtRealSourceElementKind
+
+FIR element rendered:
+[ResolvedTo(BODY_RESOLVE)] lval <unused var>: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component1|()
+
+FIR FILE:
+FILE: [ResolvedTo(IMPORTS)] entryUnderscoreInDestructuringDeclarationParameterInLambda.kt
+    public final data [ResolvedTo(STATUS)] class X : R|kotlin/Any| {
+        public [ResolvedTo(STATUS)] [ContainingClassKey=X] constructor([ResolvedTo(STATUS)] [CorrespondingProperty=/X.a] a: R|kotlin/Int|, [ResolvedTo(STATUS)] [CorrespondingProperty=/X.b] b: R|kotlin/Int|): R|X| {
+            LAZY_super<R|kotlin/Any|>
+        }
+
+        public final [ResolvedTo(STATUS)] [ComponentFunctionSymbolKey=/X.component1, IsFromPrimaryConstructor=true] val a: R|kotlin/Int| = R|<local>/a|
+            public [ResolvedTo(STATUS)] [ContainingClassKey=X] get(): R|kotlin/Int|
+
+        public final [ResolvedTo(STATUS)] [ComponentFunctionSymbolKey=/X.component2, IsFromPrimaryConstructor=true] val b: R|kotlin/Int| = R|<local>/b|
+            public [ResolvedTo(STATUS)] [ContainingClassKey=X] get(): R|kotlin/Int|
+
+        public final operator [ResolvedTo(CONTRACTS)] fun component1(): R|kotlin/Int|
+
+        public final operator [ResolvedTo(CONTRACTS)] fun component2(): R|kotlin/Int|
+
+        public final [ResolvedTo(STATUS)] fun copy([ResolvedTo(STATUS)] a: R|kotlin/Int| = this@R|/X|.R|/X.a|, [ResolvedTo(STATUS)] b: R|kotlin/Int| = this@R|/X|.R|/X.b|): R|X|
+
+    }
+    public final [ResolvedTo(CONTRACTS)] fun x([ResolvedTo(CONTRACTS)] action: R|(X) -> kotlin/Unit|): R|kotlin/Unit| {
+    }
+    public final [ResolvedTo(BODY_RESOLVE)] fun main(): R|kotlin/Unit| {
+        R|/x|(<L> = [ResolvedTo(BODY_RESOLVE)] [MatchingParameterFunctionTypeKey=kotlin/Function1<X, kotlin/Unit>] x@fun <anonymous>([ResolvedTo(BODY_RESOLVE)] <destruct>: R|X|): R|kotlin/Unit| <inline=NoInline>  {
+            [ResolvedTo(BODY_RESOLVE)] lval <unused var>: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component1|()
+            [ResolvedTo(BODY_RESOLVE)] lval b: R|kotlin/Int| = R|<local>/<destruct>|.R|/X.component2|()
+            ^@x Unit
+        }
+        )
+    }

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/OutOfContentRootGetOrBuildFirTestGenerated.java

@@ -606,6 +606,18 @@ public class OutOfContentRootGetOrBuildFirTestGenerated extends AbstractOutOfCon
         public void testEntryInDestructuringDeclarationParameterInLambda() throws Exception {
             runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryInDestructuringDeclarationParameterInLambda.kt");
         }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclaration.kt")
+        public void testEntryUnderscoreInDestructuringDeclaration() throws Exception {
+            runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryUnderscoreInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt");
+        }
     }
 
     @Nested

analysis/low-level-api-fir/tests/org/jetbrains/kotlin/analysis/low/level/api/fir/SourceGetOrBuildFirTestGenerated.java

@@ -606,6 +606,18 @@ public class SourceGetOrBuildFirTestGenerated extends AbstractSourceGetOrBuildFi
         public void testEntryInDestructuringDeclarationParameterInLambda() throws Exception {
             runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryInDestructuringDeclarationParameterInLambda.kt");
         }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclaration.kt")
+        public void testEntryUnderscoreInDestructuringDeclaration() throws Exception {
+            runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclaration.kt");
+        }
+
+        @Test
+        @TestMetadata("entryUnderscoreInDestructuringDeclarationParameterInLambda.kt")
+        public void testEntryUnderscoreInDestructuringDeclarationParameterInLambda() throws Exception {
+            runTest("analysis/low-level-api-fir/testdata/getOrBuildFir/destructuring/entryUnderscoreInDestructuringDeclarationParameterInLambda.kt");
+        }
     }
 
     @Nested

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 = if (identifier == "_") {
-        val name = identifier.nameAsSafeName()
+            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|()
     }