[FIR] Add lightTree support to extended checkers + minor refactorings

compiler/fir/analysis-tests/testData/extendedCheckers/RedundantVisibilityModifierChecker.kt

@@ -1,10 +1,9 @@
 fun f() {
-
+    <!REDUNDANT_VISIBILITY_MODIFIER!>public<!> <!CAN_BE_VAL!>var<!> baz = 0
     class LocalClass {
         <!REDUNDANT_VISIBILITY_MODIFIER!>internal<!> var foo = 0
     }
     LocalClass().foo = 1
-    <!REDUNDANT_VISIBILITY_MODIFIER!>public<!> <!CAN_BE_VAL!>var<!> baz = 0
 }
 
 internal inline fun internal() {

compiler/fir/analysis-tests/testData/extendedCheckers/RedundantVisibilityModifierChecker.txt

@@ -1,5 +1,6 @@
 FILE: RedundantVisibilityModifierChecker.kt
     public final fun f(): R|kotlin/Unit| {
+        lvar baz: R|kotlin/Int| = Int(0)
         local final class LocalClass : R|kotlin/Any| {
             public constructor(): R|LocalClass| {
                 super<R|kotlin/Any|>()
@@ -12,7 +13,6 @@ FILE: RedundantVisibilityModifierChecker.kt
         }
 
         R|/LocalClass.LocalClass|().R|/LocalClass.foo| = Int(1)
-        lvar baz: R|kotlin/Int| = Int(0)
     }
     internal final inline fun internal(): R|kotlin/Unit| {
         R|/f|()

compiler/fir/analysis-tests/tests/org/jetbrains/kotlin/fir/ExtendedFirWithLightTreeDiagnosticsTestGenerated.java

@@ -0,0 +1,314 @@
+/*
+ * Copyright 2010-2020 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;
+
+import com.intellij.testFramework.TestDataPath;
+import org.jetbrains.kotlin.test.JUnit3RunnerWithInners;
+import org.jetbrains.kotlin.test.KotlinTestUtils;
+import org.jetbrains.kotlin.test.TestMetadata;
+import org.junit.runner.RunWith;
+
+import java.io.File;
+import java.util.regex.Pattern;
+
+/** This class is generated by {@link org.jetbrains.kotlin.generators.tests.TestsPackage}. DO NOT MODIFY MANUALLY */
+@SuppressWarnings("all")
+@TestMetadata("compiler/fir/analysis-tests/testData/extendedCheckers")
+@TestDataPath("$PROJECT_ROOT")
+@RunWith(JUnit3RunnerWithInners.class)
+public class ExtendedFirWithLightTreeDiagnosticsTestGenerated extends AbstractExtendedFirWithLightTreeDiagnosticsTest {
+    private void runTest(String testDataFilePath) throws Exception {
+        KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
+    }
+
+    public void testAllFilesPresentInExtendedCheckers() throws Exception {
+        KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/fir/analysis-tests/testData/extendedCheckers"), Pattern.compile("^([^.]+)\\.kt$"), null, true);
+    }
+
+    @TestMetadata("ArrayEqualityCanBeReplacedWithEquals.kt")
+    public void testArrayEqualityCanBeReplacedWithEquals() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/ArrayEqualityCanBeReplacedWithEquals.kt");
+    }
+
+    @TestMetadata("RedundantExplicitTypeChecker.kt")
+    public void testRedundantExplicitTypeChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantExplicitTypeChecker.kt");
+    }
+
+    @TestMetadata("RedundantModalityModifierChecker.kt")
+    public void testRedundantModalityModifierChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantModalityModifierChecker.kt");
+    }
+
+    @TestMetadata("RedundantReturnUnitTypeChecker.kt")
+    public void testRedundantReturnUnitTypeChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantReturnUnitTypeChecker.kt");
+    }
+
+    @TestMetadata("RedundantSetterParameterTypeChecker.kt")
+    public void testRedundantSetterParameterTypeChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSetterParameterTypeChecker.kt");
+    }
+
+    @TestMetadata("RedundantSingleExpressionStringTemplateChecker.kt")
+    public void testRedundantSingleExpressionStringTemplateChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantSingleExpressionStringTemplateChecker.kt");
+    }
+
+    @TestMetadata("RedundantVisibilityModifierChecker.kt")
+    public void testRedundantVisibilityModifierChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantVisibilityModifierChecker.kt");
+    }
+
+    @TestMetadata("VariableAssignmentChecker.kt")
+    public void testVariableAssignmentChecker() throws Exception {
+        runTest("compiler/fir/analysis-tests/testData/extendedCheckers/VariableAssignmentChecker.kt");
+    }
+
+    @TestMetadata("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class CanBeReplacedWithOperatorAssignment extends AbstractExtendedFirWithLightTreeDiagnosticsTest {
+        private void runTest(String testDataFilePath) throws Exception {
+            KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
+        }
+
+        public void testAllFilesPresentInCanBeReplacedWithOperatorAssignment() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment"), Pattern.compile("^([^.]+)\\.kt$"), null, true);
+        }
+
+        @TestMetadata("BasicTest.kt")
+        public void testBasicTest() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/BasicTest.kt");
+        }
+
+        @TestMetadata("ComplexExpression.kt")
+        public void testComplexExpression() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/ComplexExpression.kt");
+        }
+
+        @TestMetadata("flexibleTypeBug.kt")
+        public void testFlexibleTypeBug() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/flexibleTypeBug.kt");
+        }
+
+        @TestMetadata("illegalMultipleOperators.kt")
+        public void testIllegalMultipleOperators() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/illegalMultipleOperators.kt");
+        }
+
+        @TestMetadata("illegalMultipleOperatorsMiddle.kt")
+        public void testIllegalMultipleOperatorsMiddle() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/illegalMultipleOperatorsMiddle.kt");
+        }
+
+        @TestMetadata("invalidSubtraction.kt")
+        public void testInvalidSubtraction() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/invalidSubtraction.kt");
+        }
+
+        @TestMetadata("list.kt")
+        public void testList() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/list.kt");
+        }
+
+        @TestMetadata("logicOperators.kt")
+        public void testLogicOperators() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/logicOperators.kt");
+        }
+
+        @TestMetadata("multipleOperators.kt")
+        public void testMultipleOperators() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/multipleOperators.kt");
+        }
+
+        @TestMetadata("multipleOperatorsRightSideRepeat.kt")
+        public void testMultipleOperatorsRightSideRepeat() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/multipleOperatorsRightSideRepeat.kt");
+        }
+
+        @TestMetadata("mutableList.kt")
+        public void testMutableList() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/mutableList.kt");
+        }
+
+        @TestMetadata("nonCommutativeRepeat.kt")
+        public void testNonCommutativeRepeat() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/nonCommutativeRepeat.kt");
+        }
+
+        @TestMetadata("nonRepeatingAssignment.kt")
+        public void testNonRepeatingAssignment() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/nonRepeatingAssignment.kt");
+        }
+
+        @TestMetadata("OperatorAssignment.kt")
+        public void testOperatorAssignment() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/OperatorAssignment.kt");
+        }
+
+        @TestMetadata("plusAssignConflict.kt")
+        public void testPlusAssignConflict() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/plusAssignConflict.kt");
+        }
+
+        @TestMetadata("rightSideRepeat.kt")
+        public void testRightSideRepeat() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/rightSideRepeat.kt");
+        }
+
+        @TestMetadata("simpleAssign.kt")
+        public void testSimpleAssign() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/simpleAssign.kt");
+        }
+
+        @TestMetadata("validAddition.kt")
+        public void testValidAddition() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/validAddition.kt");
+        }
+
+        @TestMetadata("validSubtraction.kt")
+        public void testValidSubtraction() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/canBeReplacedWithOperatorAssignment/validSubtraction.kt");
+        }
+    }
+
+    @TestMetadata("compiler/fir/analysis-tests/testData/extendedCheckers/emptyRangeChecker")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class EmptyRangeChecker extends AbstractExtendedFirWithLightTreeDiagnosticsTest {
+        private void runTest(String testDataFilePath) throws Exception {
+            KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
+        }
+
+        public void testAllFilesPresentInEmptyRangeChecker() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/fir/analysis-tests/testData/extendedCheckers/emptyRangeChecker"), Pattern.compile("^([^.]+)\\.kt$"), null, true);
+        }
+
+        @TestMetadata("NoWarning.kt")
+        public void testNoWarning() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/emptyRangeChecker/NoWarning.kt");
+        }
+
+        @TestMetadata("Warning.kt")
+        public void testWarning() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/emptyRangeChecker/Warning.kt");
+        }
+    }
+
+    @TestMetadata("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class RedundantCallOfConversionMethod extends AbstractExtendedFirWithLightTreeDiagnosticsTest {
+        private void runTest(String testDataFilePath) throws Exception {
+            KotlinTestUtils.runTest(this::doTest, this, testDataFilePath);
+        }
+
+        public void testAllFilesPresentInRedundantCallOfConversionMethod() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod"), Pattern.compile("^([^.]+)\\.kt$"), null, true);
+        }
+
+        @TestMetadata("booleanToInt.kt")
+        public void testBooleanToInt() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/booleanToInt.kt");
+        }
+
+        @TestMetadata("byte.kt")
+        public void testByte() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/byte.kt");
+        }
+
+        @TestMetadata("char.kt")
+        public void testChar() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/char.kt");
+        }
+
+        @TestMetadata("double.kt")
+        public void testDouble() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/double.kt");
+        }
+
+        @TestMetadata("float.kt")
+        public void testFloat() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/float.kt");
+        }
+
+        @TestMetadata("int.kt")
+        public void testInt() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/int.kt");
+        }
+
+        @TestMetadata("long.kt")
+        public void testLong() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/long.kt");
+        }
+
+        @TestMetadata("nullable.kt")
+        public void testNullable() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/nullable.kt");
+        }
+
+        @TestMetadata("nullable2.kt")
+        public void testNullable2() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/nullable2.kt");
+        }
+
+        @TestMetadata("safeString.kt")
+        public void testSafeString() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/safeString.kt");
+        }
+
+        @TestMetadata("safeString2.kt")
+        public void testSafeString2() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/safeString2.kt");
+        }
+
+        @TestMetadata("short.kt")
+        public void testShort() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/short.kt");
+        }
+
+        @TestMetadata("string.kt")
+        public void testString() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/string.kt");
+        }
+
+        @TestMetadata("StringTemplate.kt")
+        public void testStringTemplate() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/StringTemplate.kt");
+        }
+
+        @TestMetadata("toOtherType.kt")
+        public void testToOtherType() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/toOtherType.kt");
+        }
+
+        @TestMetadata("uByte.kt")
+        public void testUByte() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/uByte.kt");
+        }
+
+        @TestMetadata("uInt.kt")
+        public void testUInt() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/uInt.kt");
+        }
+
+        @TestMetadata("uLong.kt")
+        public void testULong() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/uLong.kt");
+        }
+
+        @TestMetadata("uShort.kt")
+        public void testUShort() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/uShort.kt");
+        }
+
+        @TestMetadata("variable.kt")
+        public void testVariable() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/extendedCheckers/RedundantCallOfConversionMethod/variable.kt");
+        }
+    }
+}

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

@@ -5,12 +5,11 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers
 
+import com.intellij.lang.LighterASTNode
+import com.intellij.openapi.util.Ref
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.FirSymbolOwner
-import org.jetbrains.kotlin.fir.Visibilities
-import org.jetbrains.kotlin.fir.Visibility
+import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.expressions.FirQualifiedAccessExpression
@@ -223,15 +222,18 @@ fun FirSimpleFunction.overriddenFunctions(
 /**
  * Returns the visibility by given KtModifierList
  */
-fun KtModifierList?.getVisibility() = this?.visibilityModifierType()?.toFirVisibility()
+fun KtModifierList?.getVisibility() = this?.visibilityModifierType()?.toVisibilityOrNull()
 
-fun KtModifierKeywordToken.toFirVisibility(): Visibility {
+/**
+ * Returns Visibility by token or null
+ */
+fun KtModifierKeywordToken.toVisibilityOrNull(): Visibility? {
     return when (this) {
         KtTokens.PUBLIC_KEYWORD -> Visibilities.Public
         KtTokens.PRIVATE_KEYWORD -> Visibilities.Private
         KtTokens.PROTECTED_KEYWORD -> Visibilities.Protected
         KtTokens.INTERNAL_KEYWORD -> Visibilities.Internal
-        else -> throw IllegalArgumentException("Unknown visibility modifier:$this")
+        else -> null
     }
 }
 
@@ -256,10 +258,10 @@ fun FirMemberDeclaration.implicitModality(context: CheckerContext): Modality {
 
     val klass = context.findClosestClassOrObject() ?: return Modality.FINAL
     val modifiers = this.modifierListOrNull() ?: return Modality.FINAL
-    if (modifiers.hasModifier(KtTokens.OVERRIDE_KEYWORD)) {
+    if (modifiers.contains(KtTokens.OVERRIDE_KEYWORD)) {
         val klassModifiers = klass.modifierListOrNull()
         if (klassModifiers != null && klassModifiers.run {
-                hasModifier(KtTokens.ABSTRACT_KEYWORD) || hasModifier(KtTokens.OPEN_KEYWORD) || hasModifier(KtTokens.SEALED_KEYWORD)
+                contains(KtTokens.ABSTRACT_KEYWORD) || contains(KtTokens.OPEN_KEYWORD) || contains(KtTokens.SEALED_KEYWORD)
             }) {
             return Modality.OPEN
         }
@@ -268,7 +270,7 @@ fun FirMemberDeclaration.implicitModality(context: CheckerContext): Modality {
     if (
         klass is FirRegularClass
         && klass.classKind == ClassKind.INTERFACE
-        && !modifiers.hasModifier(KtTokens.PRIVATE_KEYWORD)
+        && !modifiers.contains(KtTokens.PRIVATE_KEYWORD)
     ) {
         return if (this.hasBody()) Modality.OPEN else Modality.ABSTRACT
     }
@@ -276,7 +278,7 @@ fun FirMemberDeclaration.implicitModality(context: CheckerContext): Modality {
     return Modality.FINAL
 }
 
-private fun FirDeclaration.modifierListOrNull() = (this.source.getModifierList() as? FirPsiModifierList)?.modifierList
+private fun FirDeclaration.modifierListOrNull() = this.source.getModifierList()?.modifiers?.map { it.token }
 
 private fun FirDeclaration.hasBody(): Boolean = when (this) {
     is FirSimpleFunction -> this.body != null && this.body !is FirEmptyExpressionBlock
@@ -306,3 +308,23 @@ fun FirClass<*>.findNonInterfaceSupertype(context: CheckerContext): FirTypeRef?
 
     return null
 }
+
+/**
+ * Returns the source element of the eq operator in assignment statement
+ */
+fun FirSourceElement.eqOperatorSource(): FirSourceElement? {
+    return when (this) {
+        is FirLightSourceElement -> {
+            val children = Ref<Array<LighterASTNode>>()
+            val tree = tree
+            tree.getChildren(element, children)
+            val element = children.get().getOrNull(2) ?: return null
+            element.toFirLightSourceElement(element.startOffset, element.endOffset, tree)
+        }
+        is FirPsiSourceElement<*> -> {
+            val operator = psi.children.getOrNull(1)
+            operator?.toFirPsiSourceElement()
+        }
+        else -> null
+    }
+}

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

@@ -6,6 +6,7 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.eqOperatorSource
 import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirBasicExpresionChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.ARRAY_EQUALITY_OPERATOR_CAN_BE_REPLACED_WITH_EQUALS
@@ -13,9 +14,7 @@ import org.jetbrains.kotlin.fir.expressions.FirEqualityOperatorCall
 import org.jetbrains.kotlin.fir.expressions.FirOperation
 import org.jetbrains.kotlin.fir.expressions.FirStatement
 import org.jetbrains.kotlin.fir.expressions.arguments
-import org.jetbrains.kotlin.fir.psi
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
-import org.jetbrains.kotlin.fir.toFirPsiSourceElement
 import org.jetbrains.kotlin.fir.types.classId
 import org.jetbrains.kotlin.fir.types.coneType
 
@@ -29,6 +28,6 @@ object ArrayEqualityCanBeReplacedWithEquals : FirBasicExpresionChecker() {
         if (left.typeRef.coneType.classId != StandardClassIds.Array) return
         if (right.typeRef.coneType.classId != StandardClassIds.Array) return
 
-        reporter.report(expression.psi?.children?.get(1)?.toFirPsiSourceElement(), ARRAY_EQUALITY_OPERATOR_CAN_BE_REPLACED_WITH_EQUALS)
+        reporter.report(expression.source?.eqOperatorSource(), ARRAY_EQUALITY_OPERATOR_CAN_BE_REPLACED_WITH_EQUALS)
     }
 }

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

@@ -5,9 +5,16 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
+import com.intellij.lang.LighterASTNode
+import com.intellij.openapi.util.Ref
 import com.intellij.psi.tree.IElementType
+import org.jetbrains.kotlin.KtNodeTypes
+import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
+import org.jetbrains.kotlin.fir.FirLightSourceElement
+import org.jetbrains.kotlin.fir.FirPsiSourceElement
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
-import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirVariableAssignmentChecker
+import org.jetbrains.kotlin.fir.analysis.checkers.eqOperatorSource
+import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirExpressionChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.expressions.FirFunctionCall
@@ -16,39 +23,85 @@ import org.jetbrains.kotlin.fir.expressions.toResolvedCallableSymbol
 import org.jetbrains.kotlin.fir.psi
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
 import org.jetbrains.kotlin.fir.symbols.StandardClassIds
-import org.jetbrains.kotlin.fir.toFirPsiSourceElement
 import org.jetbrains.kotlin.fir.types.classId
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtNameReferenceExpression
-import org.jetbrains.kotlin.psi.KtOperationReferenceExpression
 
-object CanBeReplacedWithOperatorAssignmentChecker : FirVariableAssignmentChecker() {
+object CanBeReplacedWithOperatorAssignmentChecker : FirExpressionChecker<FirVariableAssignment>() {
     override fun check(expression: FirVariableAssignment, context: CheckerContext, reporter: DiagnosticReporter) {
         val lValue = expression.lValue
         if (lValue !is FirResolvedNamedReference) return
+        if (expression.source?.kind is FirFakeSourceElementKind) return
 
-        val operator = expression.psi?.children?.getOrNull(1) ?: return
-        val operationSign = (operator as? KtOperationReferenceExpression)?.operationSignTokenType
-        if (operationSign != KtTokens.EQ) return
-
-        val lValuePsi = lValue.psi as? KtNameReferenceExpression ?: return
         val rValue = expression.rValue as? FirFunctionCall ?: return
-        val rValuePsi = rValue.psi as? KtBinaryExpression ?: return
-        val rValueClassId = rValue.explicitReceiver?.typeRef?.coneType?.classId
+        if (rValue.source?.kind is FirFakeSourceElementKind) return
 
+        val rValueClassId = rValue.explicitReceiver?.typeRef?.coneType?.classId
         if (rValueClassId !in StandardClassIds.primitiveTypes) return
         val rValueResolvedSymbol = rValue.toResolvedCallableSymbol() ?: return
         if (rValueResolvedSymbol.callableId.classId !in StandardClassIds.primitiveTypes) return
 
-        if (rValuePsi.matcher(lValuePsi)) {
-            val operatorStatement = operator.toFirPsiSourceElement()
-            reporter.report(operatorStatement, FirErrors.CAN_BE_REPLACED_WITH_OPERATOR_ASSIGNMENT)
+        var needToReport = false
+        val assignmentSource = expression.source
+
+        if (assignmentSource is FirPsiSourceElement<*>) {
+            val lValuePsi = lValue.psi as? KtNameReferenceExpression ?: return
+            val rValuePsi = rValue.psi as? KtBinaryExpression ?: return
+
+            if (rValuePsi.matcher(lValuePsi)) {
+                needToReport = true
+            }
+        } else if (assignmentSource is FirLightSourceElement) {
+            val lValueLightTree = (lValue.source as FirLightSourceElement).element
+            val rValueLightTree = (rValue.source as FirLightSourceElement).element
+            if (lightTreeMatcher(lValueLightTree, rValueLightTree, assignmentSource)) {
+                needToReport = true
+            }
         }
+
+        if (needToReport) {
+            val reportSource = expression.source?.eqOperatorSource()
+            reporter.report(reportSource, FirErrors.CAN_BE_REPLACED_WITH_OPERATOR_ASSIGNMENT)
+        }
+
     }
 
-    fun KtBinaryExpression.matcher(variable: KtNameReferenceExpression): Boolean {
+    fun lightTreeMatcher(
+        variable: LighterASTNode,
+        expression: LighterASTNode,
+        source: FirLightSourceElement,
+        prevOperator: LighterASTNode? = null
+    ): Boolean {
+        val tree = source.tree
+        val childrenNullable = Ref<Array<LighterASTNode?>>()
+        tree.getChildren(expression, childrenNullable)
+        val children = childrenNullable.get().filterNotNull()
+
+        val operator = children.firstOrNull { it.tokenType == KtNodeTypes.OPERATION_REFERENCE }
+        if (prevOperator != null && !isLightNodesHierarchicallyTrue(prevOperator, operator)) return false
+        if (operator?.canBeAugmented() == false) return false
+
+        val commutative = operator != null && isCommutativeOperator(operator)
+        var afterOperatorNode = false
+        children.forEach {
+            when (it.tokenType) {
+                KtNodeTypes.REFERENCE_EXPRESSION -> {
+                    if ((commutative || !afterOperatorNode) && it.toString() == variable.toString()) return true
+                }
+                KtNodeTypes.BINARY_EXPRESSION -> {
+                    return lightTreeMatcher(variable, it, source, operator)
+                }
+                KtNodeTypes.OPERATION_REFERENCE -> {
+                    afterOperatorNode = true
+                }
+            }
+        }
+        return false
+    }
+
+    private fun KtBinaryExpression.matcher(variable: KtNameReferenceExpression): Boolean {
         if (!canBeAugmented()) return false
         if ((left as? KtNameReferenceExpression)?.getReferencedName() == variable.getReferencedName()) return true
         if ((right as? KtNameReferenceExpression)?.getReferencedName() == variable.getReferencedName() && isCommutative()) return true
@@ -60,9 +113,11 @@ object CanBeReplacedWithOperatorAssignmentChecker : FirVariableAssignmentChecker
             val isLeftMatch = isHierarchicallyTrue(operationToken, leftExpression?.operationToken)
                     && leftExpression?.matcher(variable) == true
             if (isLeftMatch) return true
+            val isRightMatch = isHierarchicallyTrue(operationToken, rightExpression?.operationToken)
+                    && rightExpression?.matcher(variable) == true
+            if (isRightMatch) return true
 
-            return (isHierarchicallyTrue(operationToken, rightExpression?.operationToken)
-                    && rightExpression?.matcher(variable) == true)
+            false
         } else {
             val leftExpression = left as? KtBinaryExpression
 
@@ -80,4 +135,13 @@ object CanBeReplacedWithOperatorAssignmentChecker : FirVariableAssignmentChecker
             || this.operationToken == KtTokens.PERC
 
     private fun isHierarchicallyTrue(currentOperation: IElementType, nextOperation: IElementType?) = currentOperation == nextOperation
+
+    private fun isCommutativeOperator(operator: LighterASTNode) = operator.toString().let { it == "+" || it == "*" }
+
+    private fun isLightNodesHierarchicallyTrue(first: LighterASTNode?, second: LighterASTNode?) =
+        first.toString() == second.toString()
+
+    private fun LighterASTNode.canBeAugmented() = this.toString().let {
+        it == "+" || it == "*" || it == "-" || it == "/" || it == "%"
+    }
 }

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

@@ -21,9 +21,7 @@ import org.jetbrains.kotlin.fir.types.classId
 import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.fir.types.isMarkedNullable
 import org.jetbrains.kotlin.name.ClassId
-import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtSafeQualifiedExpression
-import org.jetbrains.kotlin.types.expressions.OperatorConventions
 
 object RedundantCallOfConversionMethod : FirQualifiedAccessChecker() {
     override fun check(expression: FirQualifiedAccessExpression, context: CheckerContext, reporter: DiagnosticReporter) {
@@ -37,6 +35,21 @@ object RedundantCallOfConversionMethod : FirQualifiedAccessChecker() {
         }
     }
 
+    private fun FirExpression.isRedundant(qualifiedClassId: ClassId): Boolean {
+        val thisType = if (this is FirConstExpression<*>) {
+            this.typeRef.coneType.classId
+        } else {
+            when {
+                typeRef.coneType is ConeFlexibleType -> null
+                psi?.parent !is KtSafeQualifiedExpression
+                        && (psi is KtSafeQualifiedExpression || typeRef.coneType.isMarkedNullable) -> null
+                this.typeRef.coneType.isMarkedNullable -> null
+                else -> this.typeRef.coneType.classId
+            }
+        }
+        return thisType == qualifiedClassId
+    }
+
     private val targetClassMap = hashMapOf(
         "toString" to StandardClassIds.String,
         "toDouble" to StandardClassIds.Double,
@@ -51,26 +64,4 @@ object RedundantCallOfConversionMethod : FirQualifiedAccessChecker() {
         "toUShort" to StandardClassIds.UShort,
         "toUByte" to StandardClassIds.UByte
     )
-
-    private fun FirExpression.isRedundant(qualifiedClassId: ClassId): Boolean {
-        val thisType = if (this is FirConstExpression<*>) {
-            this.typeRef.coneType.classId
-        } else {
-            val binaryExpression = psi as? KtBinaryExpression
-            val operator = binaryExpression?.operationToken
-            if (operator in OperatorConventions.COMPARISON_OPERATIONS) {
-                // Special case here because compareTo returns Int
-                StandardClassIds.Boolean
-            } else {
-                when {
-                    typeRef.coneType is ConeFlexibleType -> null
-                    psi?.parent !is KtSafeQualifiedExpression
-                            && (psi is KtSafeQualifiedExpression || typeRef.coneType.isMarkedNullable) -> null
-                    this.typeRef.coneType.isMarkedNullable -> null
-                    else -> this.typeRef.coneType.classId
-                }
-            }
-        }
-        return thisType == qualifiedClassId
-    }
 }

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

@@ -6,7 +6,9 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 import org.jetbrains.kotlin.KtNodeTypes
-import org.jetbrains.kotlin.fir.FirFakeSourceElement
+import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
+import org.jetbrains.kotlin.fir.FirLightSourceElement
+import org.jetbrains.kotlin.fir.FirPsiSourceElement
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirMemberDeclarationChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
@@ -32,7 +34,7 @@ object RedundantExplicitTypeChecker : FirMemberDeclarationChecker() {
         val initializer = declaration.initializer ?: return
         val typeReference = declaration.returnTypeRef
 
-        if (typeReference.source is FirFakeSourceElement<*>) return
+        if (typeReference.source?.kind is FirFakeSourceElementKind) return
 
         val type = declaration.returnTypeRef.coneType
 
@@ -46,14 +48,14 @@ object RedundantExplicitTypeChecker : FirMemberDeclarationChecker() {
                         if (!type.isSame(StandardClassIds.Boolean)) return
                     }
                     KtNodeTypes.INTEGER_CONSTANT -> {
-                        if (initializer.text?.endsWith("L") == true) {
+                        if (initializer.kind == FirConstKind.Long) {
                             if (!type.isSame(StandardClassIds.Long)) return
                         } else {
                             if (!type.isSame(StandardClassIds.Int)) return
                         }
                     }
                     KtNodeTypes.FLOAT_CONSTANT -> {
-                        if (initializer.text?.endsWith("f", ignoreCase = true) == true) {
+                        if (initializer.kind == FirConstKind.Float) {
                             if (!type.isSame(StandardClassIds.Float)) return
                         } else {
                             if (!type.isSame(StandardClassIds.Double)) return
@@ -89,11 +91,18 @@ object RedundantExplicitTypeChecker : FirMemberDeclarationChecker() {
         reporter.report(declaration.returnTypeRef.source, FirErrors.REDUNDANT_EXPLICIT_TYPE)
     }
 
-    private val FirExpression.text
-        get() = this.source.psi?.text
-
-    private val FirTypeRef.text
-        get() = this.psi?.text
+    private val FirTypeRef.text: String?
+        get() {
+            return when (source) {
+                is FirPsiSourceElement<*> -> {
+                    source.psi?.text
+                }
+                is FirLightSourceElement -> {
+                    (source as FirLightSourceElement).element.toString()
+                }
+                else -> null
+            }
+        }
 
     private fun ConeKotlinType.isSame(other: ClassId?): Boolean {
         if (this.nullability.isNullable) return false

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

@@ -7,23 +7,24 @@ package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.fir.FirFakeSourceElement
+import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.analysis.checkers.FirModifier
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirMemberDeclarationChecker
+import org.jetbrains.kotlin.fir.analysis.checkers.getModifierList
 import org.jetbrains.kotlin.fir.analysis.checkers.implicitModality
+import org.jetbrains.kotlin.fir.analysis.checkers.source
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.REDUNDANT_MODALITY_MODIFIER
 import org.jetbrains.kotlin.fir.declarations.FirClass
 import org.jetbrains.kotlin.fir.declarations.FirMemberDeclaration
 import org.jetbrains.kotlin.fir.declarations.modality
-import org.jetbrains.kotlin.fir.psi
-import org.jetbrains.kotlin.fir.toFirPsiSourceElement
-import org.jetbrains.kotlin.psi.KtDeclaration
-import org.jetbrains.kotlin.psi.psiUtil.modalityModifier
+import org.jetbrains.kotlin.lexer.KtTokens
 
 object RedundantModalityModifierChecker : FirMemberDeclarationChecker() {
     override fun check(declaration: FirMemberDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
-        if (declaration.source is FirFakeSourceElement<*>) return
+        if (declaration.source?.kind is FirFakeSourceElementKind) return
 
         val modality = declaration.modality ?: return
         if (
@@ -35,7 +36,16 @@ object RedundantModalityModifierChecker : FirMemberDeclarationChecker() {
 
         if (modality != implicitModality) return
 
-        val modalityModifier = (declaration.psi as? KtDeclaration)?.modalityModifier() ?: return
-        reporter.report(modalityModifier.toFirPsiSourceElement(), REDUNDANT_MODALITY_MODIFIER)
+        val modalityModifierSource = declaration.source.getModifierList()?.modifiers?.modalitySource()
+        reporter.report(modalityModifierSource, REDUNDANT_MODALITY_MODIFIER)
+    }
+
+    private fun Collection<FirModifier<*>>.modalitySource(): FirSourceElement? {
+        return this.firstOrNull {
+            it.token == KtTokens.FINAL_KEYWORD
+                    || it.token == KtTokens.OPEN_KEYWORD
+                    || it.token == KtTokens.SEALED_KEYWORD
+                    || it.token == KtTokens.ABSTRACT_KEYWORD
+        }?.source
     }
 }

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

@@ -5,7 +5,7 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
-import org.jetbrains.kotlin.fir.FirFakeSourceElement
+import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirBasicDeclarationChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
@@ -21,7 +21,7 @@ object RedundantReturnUnitType : FirBasicDeclarationChecker() {
         if (declaration.body is FirSingleExpressionBlock) return
         val returnType = declaration.returnTypeRef
         if (returnType.source == null) return
-        if (declaration.source is FirFakeSourceElement<*>) return
+        if (declaration.source?.kind is FirFakeSourceElementKind) return
         if (returnType.annotations.isNotEmpty()) return
 
         if (returnType.isUnit) {

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

@@ -5,8 +5,14 @@
 
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
+import com.intellij.lang.LighterASTNode
+import com.intellij.lang.PsiBuilder
+import com.intellij.openapi.util.Ref
 import com.intellij.psi.PsiElement
+import org.jetbrains.kotlin.KtNodeTypes
 import org.jetbrains.kotlin.fir.FirFakeSourceElementKind
+import org.jetbrains.kotlin.fir.FirLightSourceElement
+import org.jetbrains.kotlin.fir.FirPsiSourceElement
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.expression.FirBasicExpresionChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
@@ -20,19 +26,42 @@ import org.jetbrains.kotlin.fir.types.coneType
 import org.jetbrains.kotlin.psi.KtStringTemplateExpression
 
 object RedundantSingleExpressionStringTemplateChecker : FirBasicExpresionChecker() {
-    override fun check(functionCall: FirStatement, context: CheckerContext, reporter: DiagnosticReporter) {
-        if (functionCall.source?.kind != FirFakeSourceElementKind.GeneratedToStringCallOnTemplateEntry) return
-        if (functionCall !is FirFunctionCall) return
+    override fun check(expression: FirStatement, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (expression.source?.kind != FirFakeSourceElementKind.GeneratedToStringCallOnTemplateEntry) return
+        if (expression !is FirFunctionCall) return
         if (
-            functionCall.explicitReceiver?.typeRef?.coneType?.classId == StandardClassIds.String
-            && functionCall.psi?.findStringParent()?.children?.size == 1 // there is no more children in original string template
+            expression.explicitReceiver?.typeRef?.coneType?.classId == StandardClassIds.String
+            && expression.stringParentChildrenCount() == 1 // there is no more children in original string template
         ) {
-            reporter.report(functionCall.source, REDUNDANT_SINGLE_EXPRESSION_STRING_TEMPLATE)
+            reporter.report(expression.source, REDUNDANT_SINGLE_EXPRESSION_STRING_TEMPLATE)
         }
     }
 
-    private fun PsiElement.findStringParent(): KtStringTemplateExpression? {
-        if (this is KtStringTemplateExpression) return this
-        return this.parent?.findStringParent()
+    private fun FirStatement.stringParentChildrenCount(): Int? {
+        return when (source) {
+            is FirPsiSourceElement<*> -> {
+                source.psi?.stringParentChildrenCount()
+            }
+            is FirLightSourceElement -> {
+                (source as FirLightSourceElement).element.stringParentChildrenCount(source as FirLightSourceElement)
+            }
+            else -> null
+        }
     }
-}
+
+    private fun PsiElement.stringParentChildrenCount(): Int? {
+        if (parent is KtStringTemplateExpression) return parent?.children?.size
+        return parent.stringParentChildrenCount()
+    }
+
+    private fun LighterASTNode.stringParentChildrenCount(source: FirLightSourceElement): Int? {
+        val parent = source.tree.getParent(this)
+        return if (parent?.tokenType == KtNodeTypes.STRING_TEMPLATE) {
+            val childrenOfParent = Ref<Array<LighterASTNode>>()
+            source.tree.getChildren(parent!!, childrenOfParent)
+            childrenOfParent.get().filter { it is PsiBuilder.Marker }.size
+        } else {
+            parent?.stringParentChildrenCount(source)
+        }
+    }
+}

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

@@ -7,54 +7,54 @@ package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 import org.jetbrains.kotlin.descriptors.ClassKind
 import org.jetbrains.kotlin.descriptors.Modality
-import org.jetbrains.kotlin.fir.FirFakeSourceElement
-import org.jetbrains.kotlin.fir.Visibilities
-import org.jetbrains.kotlin.fir.Visibility
+import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.analysis.checkers.*
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
 import org.jetbrains.kotlin.fir.analysis.checkers.declaration.FirBasicDeclarationChecker
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
 import org.jetbrains.kotlin.fir.declarations.*
-import org.jetbrains.kotlin.fir.toFirPsiSourceElement
+import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.psi.KtModifierListOwner
 import org.jetbrains.kotlin.psi.psiUtil.visibilityModifier
 
 object RedundantVisibilityModifierChecker : FirBasicDeclarationChecker() {
     override fun check(declaration: FirDeclaration, context: CheckerContext, reporter: DiagnosticReporter) {
-        if (declaration is FirConstructor && declaration.source is FirFakeSourceElement<*>) return
+        if (declaration is FirConstructor && declaration.source?.kind is FirFakeSourceElementKind) return
         if (declaration.source is FirFakeSourceElement<*>) return
         if (
             declaration !is FirMemberDeclaration
             && !(declaration is FirPropertyAccessor && declaration.visibility == context.containingPropertyVisibility)
         ) return
 
-        val modifierList = (declaration.source.getModifierList() as? FirPsiModifierList)?.modifierList ?: return
-        val visibilityModifier = modifierList.getVisibility() ?: return
+        val modifiers = declaration.source.getModifierList()
+        val visibilityModifier = when (modifiers) {
+            is FirPsiModifierList -> modifiers.modifierList.getVisibility()
+            is FirLightModifierList -> modifiers.modifiers.visibilityOrNull()
+            else -> null
+        } ?: return
         val implicitVisibility = declaration.implicitVisibility(context)
         val containingMemberDeclaration = context.findClosest<FirMemberDeclaration>()
 
         val redundantVisibility = when {
             visibilityModifier == implicitVisibility -> implicitVisibility
-
-            modifierList.hasModifier(KtTokens.INTERNAL_KEYWORD) &&
-                    containingMemberDeclaration.let {
-                        it != null && (it.isLocalMember || modifierList.hasModifier(KtTokens.PRIVATE_KEYWORD))
+            modifiers?.modifiers.hasModifier(KtTokens.INTERNAL_KEYWORD) &&
+                    containingMemberDeclaration.let { decl ->
+                        decl != null && (decl.isLocalMember || modifiers?.modifiers.hasModifier(KtTokens.PRIVATE_KEYWORD))
                     } -> Visibilities.Internal
-
-            else -> null
-        } ?: return
+            else -> return
+        }
 
         if (
             redundantVisibility == Visibilities.Public
             && declaration is FirProperty
-            && modifierList.hasModifier(KtTokens.OVERRIDE_KEYWORD)
+            && modifiers?.modifiers.hasModifier(KtTokens.OVERRIDE_KEYWORD)
             && declaration.isVar
             && declaration.setter?.visibility == Visibilities.Public
         ) return
 
-        val source = modifierList.visibilityModifier()?.toFirPsiSourceElement()
-        reporter.report(source, FirErrors.REDUNDANT_VISIBILITY_MODIFIER)
+        reporter.report(declaration.source.modifierSource, FirErrors.REDUNDANT_VISIBILITY_MODIFIER)
     }
 
     private fun FirDeclaration.implicitVisibility(context: CheckerContext): Visibility {
@@ -124,4 +124,23 @@ object RedundantVisibilityModifierChecker : FirBasicDeclarationChecker() {
 
     private val CheckerContext.containingPropertyVisibility
         get() = (this.containingDeclarations.last() as? FirProperty)?.visibility
+
+    private val FirSourceElement?.modifierSource: FirSourceElement?
+        get() = when (this) {
+            null -> null
+            is FirPsiSourceElement<*> -> (psi as? KtModifierListOwner)?.modifierList?.visibilityModifier()?.toFirPsiSourceElement()
+            is FirLightSourceElement -> {
+                val modifier = this.getModifierList()?.modifiers?.firstOrNull { it.isVisibilityModifier }
+                modifier?.source
+            }
+        }
+
+    private val FirModifier<*>.isVisibilityModifier
+        get() = this.token.toVisibilityOrNull() != null
+
+    private fun List<FirLightModifier>.visibilityOrNull() =
+        firstOrNull { it.token.toVisibilityOrNull() != null }?.token?.toVisibilityOrNull()
+
+    private fun List<FirModifier<*>>?.hasModifier(token: KtModifierKeywordToken) = this != null && any { it.token == token }
+
 }

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

@@ -6,20 +6,20 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.extended
 
 
+import com.intellij.lang.LighterASTNode
+import com.intellij.openapi.util.Ref
 import org.jetbrains.kotlin.contracts.description.EventOccurrencesRange
-import org.jetbrains.kotlin.fir.FirFakeSourceElement
-import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.analysis.cfa.AbstractFirPropertyInitializationChecker
 import org.jetbrains.kotlin.fir.analysis.cfa.PropertyInitializationInfo
 import org.jetbrains.kotlin.fir.analysis.cfa.TraverseDirection
 import org.jetbrains.kotlin.fir.analysis.cfa.traverse
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
-import org.jetbrains.kotlin.fir.psi
 import org.jetbrains.kotlin.fir.references.FirResolvedNamedReference
 import org.jetbrains.kotlin.fir.resolve.dfa.cfg.*
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
-import org.jetbrains.kotlin.fir.toFirPsiSourceElement
+import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.psi.KtProperty
 
 
@@ -50,8 +50,7 @@ object VariableAssignmentChecker : AbstractFirPropertyInitializationChecker() {
             val source = symbol.getValOrVarSource
             if (symbol.callableId.callableName.asString() == "<destruct>") {
                 lastDestructuringSource = symbol.getValOrVarSource
-                val childrenCount = symbol.fir.psi?.children?.size ?: continue
-                lastDestructuredVariables = childrenCount - 1 // -1 cuz we don't need expression node after equals operator
+                lastDestructuredVariables = symbol.getDestructuringChildrenCount() ?: continue
                 destructuringCanBeVal = true
                 continue
             }
@@ -65,7 +64,7 @@ object VariableAssignmentChecker : AbstractFirPropertyInitializationChecker() {
                     destructuringCanBeVal = false
                 }
                 lastDestructuredVariables--
-            } else if (canBeVal(symbol, value) && symbol.fir.delegate == null ) {
+            } else if (canBeVal(symbol, value) && symbol.fir.delegate == null) {
                 reporter.report(source, FirErrors.CAN_BE_VAL)
             }
         }
@@ -106,7 +105,32 @@ object VariableAssignmentChecker : AbstractFirPropertyInitializationChecker() {
     }
 
     private val FirPropertySymbol.getValOrVarSource
-        get() = (fir.psi as? KtProperty)?.valOrVarKeyword?.toFirPsiSourceElement()
-            ?: fir.psi?.firstChild?.toFirPsiSourceElement()
-            ?: fir.source
+        get() = when (fir.source) {
+            is FirSourceElement -> {
+                (fir.psi as? KtProperty)?.valOrVarKeyword?.toFirPsiSourceElement()
+                    ?: fir.psi?.firstChild?.toFirPsiSourceElement()
+                    ?: fir.source
+            }
+            is FirLightSourceElement -> {
+                val children = Ref<Array<LighterASTNode>>()
+                val tree = (fir.source as FirLightSourceElement).tree
+                tree.getChildren(tree.root, children)
+                children.get().first { it.tokenType == KtTokens.VAL_KEYWORD || it.tokenType == KtTokens.VAR_KEYWORD }.let {
+                    it.toFirLightSourceElement(it.startOffset, it.endOffset, tree)
+                }
+            }
+            else -> null
+        }
+
+    private fun FirPropertySymbol.getDestructuringChildrenCount(): Int? = when (fir.source) {
+        is FirPsiSourceElement<*> -> fir.psi?.children?.size?.minus(1) // -1 cuz we don't need expression node after equals operator
+        is FirLightSourceElement -> {
+            val source = fir.source as FirLightSourceElement
+            val tree = (fir.source as FirLightSourceElement).tree
+            val children = Ref<Array<LighterASTNode?>>()
+            tree.getChildren(source.element, children)
+            children.get().count { it != null }
+        }
+        else -> null
+    }
 }

compiler/tests-common/tests/org/jetbrains/kotlin/fir/AbstractExtendedFirWithLightTreeDiagnosticsTest.kt

@@ -0,0 +1,17 @@
+/*
+ * Copyright 2010-2020 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
+
+import org.jetbrains.kotlin.fir.analysis.checkers.declaration.ExtendedDeclarationCheckers
+import org.jetbrains.kotlin.fir.analysis.checkers.expression.ExtendedExpressionCheckers
+import org.jetbrains.kotlin.fir.analysis.checkersComponent
+
+abstract class AbstractExtendedFirWithLightTreeDiagnosticsTest : AbstractFirDiagnosticsWithLightTreeTest() {
+    override fun configureSession(session: FirSession) {
+        session.checkersComponent.register(ExtendedDeclarationCheckers)
+        session.checkersComponent.register(ExtendedExpressionCheckers)
+    }
+}

compiler/tests/org/jetbrains/kotlin/generators/tests/GenerateCompilerTests.kt

@@ -646,5 +646,11 @@ fun main(args: Array<String>) {
                 model("extendedCheckers", pattern = KT_WITHOUT_DOTS_IN_NAME)
             }
         }
+
+        testGroup("compiler/fir/analysis-tests/tests", "compiler/fir/analysis-tests/testData") {
+            testClass<AbstractExtendedFirWithLightTreeDiagnosticsTest> {
+                model("extendedCheckers", pattern = KT_WITHOUT_DOTS_IN_NAME)
+            }
+        }
     }
 }