FIR checkers: report VAL_REASSIGNMENT for assignment operators

Currently VAL_REASSIGNMENT are only reported on direct assignments.
Reassignments in the form of, for example, `+=` are reported as
`VARIABLE_EXPECTED`, which differs from FE1.0.

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

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.name.Name
@@ -483,13 +484,13 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
             parameter<FirPropertySymbol>("variable")
         }
         val VAL_REASSIGNMENT by error<FirSourceElement, KtExpression> {
-            parameter<FirPropertySymbol>("variable")
+            parameter<FirVariableSymbol<*>>("variable")
         }
         val VAL_REASSIGNMENT_VIA_BACKING_FIELD by warning<FirSourceElement, KtExpression> {
-            parameter<FirPropertySymbol>("variable")
+            parameter<FirPropertySymbol>("property")
         }
         val VAL_REASSIGNMENT_VIA_BACKING_FIELD_ERROR by error<FirSourceElement, KtExpression> {
-            parameter<FirPropertySymbol>("variable")
+            parameter<FirPropertySymbol>("property")
         }
         val WRONG_INVOCATION_KIND by warning<FirSourceElement, PsiElement> {
             parameter<AbstractFirBasedSymbol<*>>("declaration")

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

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
 import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.name.Name
@@ -296,7 +297,7 @@ object FirErrors {
 
     // Control flow diagnostics
     val UNINITIALIZED_VARIABLE by error1<FirSourceElement, KtSimpleNameExpression, FirPropertySymbol>()
-    val VAL_REASSIGNMENT by error1<FirSourceElement, KtExpression, FirPropertySymbol>()
+    val VAL_REASSIGNMENT by error1<FirSourceElement, KtExpression, FirVariableSymbol<*>>()
     val VAL_REASSIGNMENT_VIA_BACKING_FIELD by warning1<FirSourceElement, KtExpression, FirPropertySymbol>()
     val VAL_REASSIGNMENT_VIA_BACKING_FIELD_ERROR by error1<FirSourceElement, KtExpression, FirPropertySymbol>()
     val WRONG_INVOCATION_KIND by warning3<FirSourceElement, PsiElement, AbstractFirBasedSymbol<*>, EventOccurrencesRange, EventOccurrencesRange>()

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

@@ -14,12 +14,12 @@ import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.FIR
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.FQ_NAMES_IN_TYPES
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.NAME
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.NULLABLE_STRING
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.PROPERTY_NAME
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.RENDER_CLASS_OR_OBJECT
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.RENDER_TYPE
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.SYMBOL
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.SYMBOLS
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.TO_STRING
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.VARIABLE_NAME
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.VISIBILITY
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnosticRenderers.WHEN_MISSING_CASES
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors.ABSENCE_OF_PRIMARY_CONSTRUCTOR_FOR_INLINE_CLASS
@@ -646,10 +646,10 @@ class FirDefaultErrorMessages : DefaultErrorMessages.Extension {
             )
 
             // Control flow diagnostics
-            map.put(UNINITIALIZED_VARIABLE, "{0} must be initialized before access", PROPERTY_NAME)
-            map.put(VAL_REASSIGNMENT, "Val cannot be reassigned", PROPERTY_NAME)
-            map.put(VAL_REASSIGNMENT_VIA_BACKING_FIELD, "Reassignment of read-only property via backing field is deprecated", PROPERTY_NAME)
-            map.put(VAL_REASSIGNMENT_VIA_BACKING_FIELD_ERROR, "Reassignment of read-only property via backing field", PROPERTY_NAME)
+            map.put(UNINITIALIZED_VARIABLE, "{0} must be initialized before access", VARIABLE_NAME)
+            map.put(VAL_REASSIGNMENT, "Val cannot be reassigned", VARIABLE_NAME)
+            map.put(VAL_REASSIGNMENT_VIA_BACKING_FIELD, "Reassignment of read-only property via backing field is deprecated", VARIABLE_NAME)
+            map.put(VAL_REASSIGNMENT_VIA_BACKING_FIELD_ERROR, "Reassignment of read-only property via backing field", VARIABLE_NAME)
             map.put(
                 WRONG_INVOCATION_KIND,
                 "{2} wrong invocation kind: given {3} case, but {4} case is possible",

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

@@ -14,10 +14,7 @@ import org.jetbrains.kotlin.fir.declarations.*
 import org.jetbrains.kotlin.fir.render
 import org.jetbrains.kotlin.fir.renderWithType
 import org.jetbrains.kotlin.fir.symbols.AbstractFirBasedSymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirCallableSymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirClassLikeSymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirPropertySymbol
-import org.jetbrains.kotlin.fir.symbols.impl.FirTypeParameterSymbol
+import org.jetbrains.kotlin.fir.symbols.impl.*
 import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.fir.types.render
 
@@ -43,7 +40,7 @@ object FirDiagnosticRenderers {
         element.toString()
     }
 
-    val PROPERTY_NAME = Renderer { symbol: FirPropertySymbol ->
+    val VARIABLE_NAME = Renderer { symbol: FirVariableSymbol<*> ->
         symbol.fir.name.asString()
     }
 

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

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.fir.resolve.calls.NamedArgumentNotAllowed
 import org.jetbrains.kotlin.fir.resolve.calls.ResolutionDiagnostic
 import org.jetbrains.kotlin.fir.resolve.calls.VarargArgumentOutsideParentheses
 import org.jetbrains.kotlin.fir.resolve.diagnostics.*
+import org.jetbrains.kotlin.fir.symbols.impl.FirBackingFieldSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.lexer.KtTokens
 import org.jetbrains.kotlin.resolve.calls.tower.isSuccess
@@ -39,6 +40,10 @@ private fun ConeDiagnostic.toFirDiagnostic(
     }
     is ConeOperatorAmbiguityError -> FirErrors.ASSIGN_OPERATOR_AMBIGUITY.on(source, this.candidates)
     is ConeVariableExpectedError -> FirErrors.VARIABLE_EXPECTED.on(source)
+    is ConeValReassignmentError -> when (val symbol = this.variable) {
+        is FirBackingFieldSymbol -> FirErrors.VAL_REASSIGNMENT_VIA_BACKING_FIELD_ERROR.on(source, symbol.fir.symbol)
+        else -> FirErrors.VAL_REASSIGNMENT.on(source, symbol)
+    }
     is ConeTypeMismatchError -> FirErrors.TYPE_MISMATCH.on(qualifiedAccessSource ?: source, this.expectedType, this.actualType)
     is ConeUnexpectedTypeArgumentsError -> FirErrors.TYPE_ARGUMENTS_NOT_ALLOWED.on(this.source.safeAs() ?: source)
     is ConeIllegalAnnotationError -> FirErrors.NOT_AN_ANNOTATION_CLASS.on(source, this.name.asString())