FIR: support separate ASSIGNMENT_IN_EXPRESSION_CONTEXT

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

@@ -50,6 +50,7 @@ object DIAGNOSTICS_LIST : DiagnosticList() {
         val ILLEGAL_CONST_EXPRESSION by error<PsiElement>()
         val ILLEGAL_UNDERSCORE by error<PsiElement>()
         val EXPRESSION_EXPECTED by error<PsiElement>(PositioningStrategy.SELECTOR_BY_QUALIFIED)
+        val ASSIGNMENT_IN_EXPRESSION_CONTEXT by error<FirSourceElement, KtBinaryExpression>()
         val BREAK_OR_CONTINUE_OUTSIDE_A_LOOP by error<PsiElement>()
         val NOT_A_LOOP_LABEL by error<PsiElement>()
         val VARIABLE_EXPECTED by error<PsiElement>()

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

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.fir.types.ConeKotlinType
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtArrayAccessExpression
+import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtClass
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtDeclaration
@@ -76,6 +77,7 @@ object FirErrors {
     val ILLEGAL_CONST_EXPRESSION by error0<PsiElement>()
     val ILLEGAL_UNDERSCORE by error0<PsiElement>()
     val EXPRESSION_EXPECTED by error0<PsiElement>(SourceElementPositioningStrategies.SELECTOR_BY_QUALIFIED)
+    val ASSIGNMENT_IN_EXPRESSION_CONTEXT by error0<FirSourceElement, KtBinaryExpression>()
     val BREAK_OR_CONTINUE_OUTSIDE_A_LOOP by error0<PsiElement>()
     val NOT_A_LOOP_LABEL by error0<PsiElement>()
     val VARIABLE_EXPECTED by error0<PsiElement>()

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

@@ -48,9 +48,9 @@ private fun ConeDiagnostic.toFirDiagnostic(
         FirErrors.WRONG_NUMBER_OF_TYPE_ARGUMENTS.on(qualifiedAccessSource ?: source, this.desiredCount, this.type)
     is ConeNoTypeArgumentsOnRhsError ->
         FirErrors.NO_TYPE_ARGUMENTS_ON_RHS.on(qualifiedAccessSource ?: source, this.desiredCount, this.type)
-    is ConeSimpleDiagnostic -> when {
+    is ConeSimpleDiagnostic -> when (source.kind) {
-        source.kind is FirFakeSourceElementKind -> null
+        is FirFakeSourceElementKind -> null
-        else -> this.getFactory().on(qualifiedAccessSource ?: source)
+        else -> this.getFactory(source).on(qualifiedAccessSource ?: source)
     }
     is ConeInstanceAccessBeforeSuperCall -> FirErrors.INSTANCE_ACCESS_BEFORE_SUPER_CALL.on(source, this.target)
     is ConeStubDiagnostic -> null
@@ -158,7 +158,7 @@ private fun mapInapplicableCandidateError(
     }.ifEmpty { listOf(FirErrors.INAPPLICABLE_CANDIDATE.on(source, diagnostic.candidate.symbol)) }
 }
 
-private fun ConeSimpleDiagnostic.getFactory(): FirDiagnosticFactory0<*> {
+private fun ConeSimpleDiagnostic.getFactory(source: FirSourceElement): FirDiagnosticFactory0<*> {
     @Suppress("UNCHECKED_CAST")
     return when (kind) {
         DiagnosticKind.Syntax -> FirErrors.SYNTAX
@@ -174,7 +174,11 @@ private fun ConeSimpleDiagnostic.getFactory(): FirDiagnosticFactory0<*> {
         DiagnosticKind.RecursionInImplicitTypes -> FirErrors.RECURSION_IN_IMPLICIT_TYPES
         DiagnosticKind.Java -> FirErrors.ERROR_FROM_JAVA_RESOLUTION
         DiagnosticKind.SuperNotAllowed -> FirErrors.SUPER_IS_NOT_AN_EXPRESSION
-        DiagnosticKind.ExpressionExpected -> FirErrors.EXPRESSION_EXPECTED
+        DiagnosticKind.ExpressionExpected -> if (source.elementType == KtNodeTypes.BINARY_EXPRESSION) {
+            FirErrors.ASSIGNMENT_IN_EXPRESSION_CONTEXT
+        } else {
+            FirErrors.EXPRESSION_EXPECTED
+        }
         DiagnosticKind.JumpOutsideLoop -> FirErrors.BREAK_OR_CONTINUE_OUTSIDE_A_LOOP
         DiagnosticKind.NotLoopLabel -> FirErrors.NOT_A_LOOP_LABEL
         DiagnosticKind.VariableExpected -> FirErrors.VARIABLE_EXPECTED

compiler/testData/diagnostics/tests/controlStructures/kt770.kt351.kt735_StatementType.fir.kt

@@ -149,9 +149,9 @@ fun bar(a: Unit) {}
 
 fun testStatementInExpressionContext() {
     var z = 34
-    val a1: Unit = <!EXPRESSION_EXPECTED!>z = 334<!>
+    val a1: Unit = <!ASSIGNMENT_IN_EXPRESSION_CONTEXT!>z = 334<!>
     val f = for (i in 1..10) {}
-    if (true) return <!EXPRESSION_EXPECTED!>z = 34<!>
+    if (true) return <!ASSIGNMENT_IN_EXPRESSION_CONTEXT!>z = 34<!>
     return <!EXPRESSION_EXPECTED!>while (true) {}<!>
 }
 

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDataClassConverters.kt

@@ -19,6 +19,7 @@ import org.jetbrains.kotlin.fir.declarations.FirTypeParameter
 import org.jetbrains.kotlin.fir.declarations.FirVariable
 import org.jetbrains.kotlin.fir.psi
 import org.jetbrains.kotlin.psi.KtArrayAccessExpression
+import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtClass
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtDeclaration
@@ -94,6 +95,12 @@ internal val KT_DIAGNOSTIC_CONVERTER = KtDiagnosticConverterBuilder.buildConvert
             token,
         )
     }
+    add(FirErrors.ASSIGNMENT_IN_EXPRESSION_CONTEXT) { firDiagnostic ->
+        AssignmentInExpressionContextImpl(
+            firDiagnostic as FirPsiDiagnostic<*>,
+            token,
+        )
+    }
     add(FirErrors.BREAK_OR_CONTINUE_OUTSIDE_A_LOOP) { firDiagnostic ->
         BreakOrContinueOutsideALoopImpl(
             firDiagnostic as FirPsiDiagnostic<*>,

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnostics.kt

@@ -25,6 +25,7 @@ import org.jetbrains.kotlin.idea.frontend.api.types.KtType
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtArrayAccessExpression
+import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtClass
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtDeclaration
@@ -87,6 +88,10 @@ sealed class KtFirDiagnostic<PSI: PsiElement> : KtDiagnosticWithPsi<PSI> {
         override val diagnosticClass get() = ExpressionExpected::class
     }
 
+    abstract class AssignmentInExpressionContext : KtFirDiagnostic<KtBinaryExpression>() {
+        override val diagnosticClass get() = AssignmentInExpressionContext::class
+    }
+
     abstract class BreakOrContinueOutsideALoop : KtFirDiagnostic<PsiElement>() {
         override val diagnosticClass get() = BreakOrContinueOutsideALoop::class
     }

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/frontend/api/fir/diagnostics/KtFirDiagnosticsImpl.kt

@@ -27,6 +27,7 @@ import org.jetbrains.kotlin.idea.frontend.api.types.KtType
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.KtArrayAccessExpression
+import org.jetbrains.kotlin.psi.KtBinaryExpression
 import org.jetbrains.kotlin.psi.KtClass
 import org.jetbrains.kotlin.psi.KtClassOrObject
 import org.jetbrains.kotlin.psi.KtDeclaration
@@ -109,6 +110,13 @@ internal class ExpressionExpectedImpl(
     override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
 }
 
+internal class AssignmentInExpressionContextImpl(
+    firDiagnostic: FirPsiDiagnostic<*>,
+    override val token: ValidityToken,
+) : KtFirDiagnostic.AssignmentInExpressionContext(), KtAbstractFirDiagnostic<KtBinaryExpression> {
+    override val firDiagnostic: FirPsiDiagnostic<*> by weakRef(firDiagnostic)
+}
+
 internal class BreakOrContinueOutsideALoopImpl(
     firDiagnostic: FirPsiDiagnostic<*>,
     override val token: ValidityToken,